Patent Application
20080004415
The present invention relates in general to nonlinear optically active molecules and, more particularly to hyperpolarizable organic chromophores having useful electro-optical coefficients.
Electro-optic materials alter their physical properties in the presence of an electric field. Typically, when the material is subjected to an electric field, its polarization changes dramatically, resulting in an increase in the index of refraction of the material and an accompanying decrease in the velocity of light through the material. This electric field-dependent index of refraction can be used to encode electric signals onto optical signals. Uses include, for example, switching optical signals and steering light beams.
Many types of electro-optic materials have been utilized for use in electro-optic devices. Among these materials are, inter alia, inorganic materials such as lithium niobate, semiconductor materials such as gallium arsenide, organic crystalline materials, and electrically poled polymer films that include organic chromophores. A review of nonlinear optical materials is provided in L. Dalton, “Nonlinear Optical Materials”, Kirk-Othmer Encyclopedia of Chemical Technology, 4th Edition, Volume 17 (John Wiley & Sons, New York, 1995), pp. 288-302.
Electro-optic poled polymers have many advantages as modulating materials. Their advantages include their applicability to thin-film waveguiding structures, which are relatively easily fabricated and compatible with existing microelectronic processing. These polymers incorporate organic nonlinear optically active molecules to effect modulation. Because organic materials have low dielectric constants and satisfy the condition that n2=∈, where n is the index of refraction and ∈ is the dielectric constant, organic electro-optic will have wide bandwidths. The dielectric constant of these materials (∈=2.5-4) relatively closely matches the propagating electrical and optical waves, which provides for a bandwidth greater than 100 GHz.
In contrast to inorganic materials in which polar optical lattice vibrations diminish their effectiveness, the optical properties of organic nonlinear optical materials depend primarily on the hyperpolarizability of their electrons without a significant adverse contribution from the lattice polarizability Thus, organic nonlinear optical materials offer advantages for ultrafast electro-optic modulation and switching.
For an organic chromophore to be suitable for electro-optic applications, the chromophore should have a large molecular optical nonlinearity, referred to as the first hyperpolarizability (β), and a large dipole moment (μ). A common figure of merit used to compare materials is the value μβ/MW, where MW is the molecular weight of the chromophore. However, materials characterized as having such large μβ/MW values commonly suffer from large intermolecular electrostatic interactions that lead to intermolecular aggregation resulting in light scattering, unacceptably high values of optical loss, and low EO values. Many of these difficulties can be attributed to the electron acceptor, which induces a large molecular dipole moment, leading to the problems associated with chromophore aggregation.
Thus, the effectiveness of organic nonlinear optical materials having high hyperpolarizability and large dipole moments is limited by the tendency of these materials to aggregate when processed into polymers with low refractive index. Accordingly, there exists a need for improved nonlinear optically active materials having large hyperpolarizabilities and large dipole moments and that, when employed in electro-optic devices, exhibit large electro-optic coefficients. The present invention seeks to fulfill these needs and provides further related advantages.
In one aspect, the present invention provides a hyperpolarizable organic chromophore. The chromophore is a nonlinear optically active compound that includes a π-donor conjugated to a π-acceptor through a π-electron conjugated bridge. In other aspects of the invention, donor structures and acceptor structures are provided.
In another aspect of the invention, a chromophore-containing polymer is provided. In one embodiment, the chromophore is physically incorporated into the polymer to provide a composite. In another embodiment, the chromophore is covalently bonded to the polymer, either as a side chain polymer or through crosslinking into the polymer.
In other aspects, the present invention also provides a method for making the chromophore, a method for making the chromophore-containing polymer, and methods for using the chromophore and chromophore-containing polymer.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The drawings will be described in more detail below.
In one aspect, the present invention provides a hyperpolarizable organic chromophore. The chromophore is a nonlinear optically active compound that includes a π-donor conjugated to a π-acceptor through a π-electron conjugated bridge.
The chromophores of the invention are characterized as having high electro-optic coefficients; large hyperpolarizability; large dipole moments; chemical, thermal, electrochemical, and photochemical stability; low absorption at operating wavelengths (e.g., 1.3 and 1.55 μm); suitable solubility in solvents suitable for the host polymers detailed below; compatibility with host polymer; and low volatility.
Absorption Maximum (λmax).
The nonlinear optical properties of chromophores are strongly correlated with the absorption maximum of the chromophore. As λmax increases the NLO properties increase. The absorption maximum of the chromophores have been both computationally determined and experimentally measured.
Dipole Moment and Optical Hyperpolarizability (β)
Nonlinear optical effects of organic materials depend mainly on the compound's hyperpolarizability (β) and the magnitude of its intrinsic dipole moment (μ). The molecular first hyperpolarizabilities (β) were calculated from the experimentally determined absorption maximum using the expression log(β)=3.6118 log(λmax)−7.8324 (Harper). The dipole moments were calculated using ab initio electronic structure methods as implemented in JAGUAR™ (Jaguar 4.0, Schrodinger Inc., Portland, Oreg., 1991-2000). Ab initio methods have been shown to provide accurate descriptions of the dipole moments in organic molecules. All the chromophore geometries were optimized using DFT methods with the B3LYP functional and the 6/31G* basis set. These resulting geometries were used for the calculation of the dipole moments.
Chromophore Figure-of-Merit (FOM)
The chromophore figure-of-merit (FOM) is determined by the formula FOM=μβ/(molecular weight). This is an approximate measure of how good a chromophore is. Ideally, a chromophore would have a high FOM, while being soluble in the polymers of interest. In reality, increasing the chromophore FOM typically reduces the chromophore solubility and increases its tendency to aggregate, reducing the measurable EO response of the material. The best chromophores are those that have large FOM values while still remaining active in the polymers of interest.
Chromophore Solubility/Aggregation
Intermolecular attractive forces and limited chromophore solubility in the polymer matrix can cause chromophore aggregation, leading to diminished electro-optic coefficient. Improving chromophore design can reduce/eliminate aggregation by increasing chromophore solubility and reducing chromophore aggregation, leading to enhanced electro-optic coefficients.
Many molecules can be prepared having high hyperpolarizability values, however their utility in electro-optic devices often is diminished by the inability to incorporate these molecules into a host material with sufficient non-centrosymmetric molecular alignment to provide a device with acceptable electro-optic activity. Molecules with high hyperpolarizability typically exhibit strong dipole-dipole interactions in solution or other host material that makes it difficult, if not impossible, to achieve a high degree of non-centrosymmetric order unless undesirable spatially anisotropic intermolecular electrostatic interactions are minimized. In addition, molecules with high hyperpolarizability commonly have limited solubility in low refractive index polymers, which also leads to the aggregation and the reduction of the electro-optic activity.
In certain embodiments, the chromophores of the invention include substituents that enhance the solubility of the chromophore in low refractive index polymers. In one embodiment, the chromophore includes one or more substituents on the donor group portion of the chromophore. In another embodiment, the chromophore includes one or more substituents on the bridge portion of the chromophore. In a further embodiment, the chromophore includes one or more substituents on the acceptor portion of the chromophore. The chromophores of the invention can include combinations of donors, bridges, and acceptors, one or more of which can include substituents to enhance solubility. Thus, in certain embodiments, the invention provides chromophores having one or more substituents effective to reduce chromophore aggregation. In certain embodiments, the invention also provides for substituents on the donor, or bridge, or acceptor, which alter the chromophore shape that reduce the disadvantageous molecular interactions by sterically inhibiting the close approach of chromophores. In these embodiments, the active portion of the chromophore is embedded within the molecular structure that effectively insulates the chromophore dipole from interaction with other such dipoles. Thus, through the use of substitution and control of chromophore shape, the chromophores of the invention provide high electro-optic coefficients when incorporated into electro-optic devices
Film Quality
Films of the chromophores and polymer, at the specified chromophore weight percentage, were cast onto quartz blanks from dioxane solution. After drying, the films were judged for their optical clarity and homogeneity on a scale of 1-10, with 1 being a completely perfect film. Polymer/chromophore solutions were deemed to be of sufficient quality for further testing if the film scored higher than a 4 on this scale. A set of reference films was employed to ensure consistency in the film evaluation.
Refractive Index Measurement
For chromophore/polymer films of sufficient optical quality, the refractive indices of the materials will be measured at 1550 nm using the prism coupling method [H. Onodera, I. Awai, and J.-I. Ikenoue, “Refractive index measurement of bulk materials: prism coupling method”, Applied Optics, Vol. 22, 1194-1197, (1983)]. In this method, a thin film is formed on a prism face, and by measuring the power as a function of incidence angle for a 1550 nm laser beam, the refractive index of the film is measured.
Electro-Optic Coefficient (r33)
A chromophore's electro-optic coefficient (r33) can be measured in a polymer matrix using a transmission technique at telecommunication wavelength of 1.55 μm. A representative method for measuring the electro-optic coefficient is described in Nahata, et al., “Electro-optic Determination of the Nonlinear-Optical Properties of a Covalently Functionalized Disperse Red 1 Copolymer”, J. Opt. Soc. Am. B, Vol. 10, pp. 1553-1564 (1993).
Ideally, the electrooptic coefficient of a material is determined solely from the FOM of the chromophore and the loading of the chromophore in the host polymer. Thus the largest response would be obtained by placing as much of a high FOM chromophore as is possible within any refractive index constraints there may be. In reality, chromophores with higher FOM values have a stronger tendency to perform non-ideally. This invention, then, is concerned with chromophores that possess large FOM values, but also exhibit large electrooptic coefficients when placed in the polymers of interest.
The chromophores of the invention are characterized as having an electrooptic coefficient (r33) of at least about 5 pm/V at 100 V/m poling voltage measured at 1.55 μm in a fluoropolymer with a compound loading of about 5% to 20% by weight based on the total weight of fluoropolymer. The chromophore loading is determined by ensuring the refractive index of the composite system is approximately 1.475 or less at room temperature. This refractive index ensures the material can be used as cladding on silica waveguides when at elevated temperature. When there is no need to maintain low refractive index, the chromophores of this invention may also be incorporated into conventional polymers at higher concentrations, leading to correspondingly higher electrooptic coefficients.
Representative Chromophore Components and Structures
In addition to providing chromophores, the present invention provides donors, bridges, and acceptor components useful in the construction of chromophores for electro-optic device adaptation. As noted above, the chromophores of the invention include: (1) a π-donor conjugated to (2) a π-acceptor through (3) a π-electron conjugated bridge.
Donors
Representative donor structures from the prior art are illustrated below. The donor typically consists of an aromatic ring with an attached amino group. Other donors include, for example, cyclohexene, furan, or thiophene rings with an attached amino group.
In certain embodiments, the donor includes a bulky substituent to enhance chromophore solubility or inhibit chromophore aggregation. In other embodiments, the donor includes a functional group (e.g., trifluorovinyl ether) suitable for attachment as a polymer side chain, or for crosslinking to either a polymer matrix or other suitably functionalized chromophores. Inclusion of the bulky substituent or functional group tends to decrease the figure of merit for the chromophore, as the molecular weight is increased while the nonlinearity and dipole moment tend to remain unchanged. This decrease in the chromophore figure of merit can often be partially offset by including more chromophore in the chromophore/polymer blend, while remaining within whatever refractive index constraints may exist for the total material. [L. Dalton, Nonlinear Optical Polymeric Materials: From Chromophore Design to Commercial Applications, “Advances in Polymer Science” vol. 158, K.-S. Lee Editor, Polymers for Photonic Applications I, pages 1-86, Springer, N.Y., 2002]
Bridges
Representative bridge structures from the prior art are illustrated below. The bridge structure is a π-electron conjugated bridge. The bridge can include a variety of groups including, for example, a dihydrofuran group, a fused dithiophene group, a fused trithiophene group, a dithiophene group, and substituted versions of these groups.
[H. Singh Nalwa et. al., Organic Materials for Second-Order Nonlinear Optics in “Nonlinear Optics of Organic Molecules and Polymers”, edited by H. S. Singh Nalwa and S. Miyata, Chapter 4, pages 89-350, CRC Press, Boca Raton, Fla., 1997]
[A. Harper et al, J. Opt. Soc. Am. B, vol. 15, pages 329-339 (1998)]
[L. R. Dalton et al, J. Mater. Chem., vol. 9, pages 1905-1920 (1999)
In certain embodiments, the π-electron conjugated bridge includes a bulky substituent to inhibit chromophore aggregation. Included among these substituents are alkyl substituents.
It will be appreciated that chromophores of the invention can include any combination of donors, bridges, acceptors, substituted donors, substituted bridges, and substituted acceptors, described herein.
As used herein, the term “alkyl group” refers to branched or straight chain alkyl groups. Alkyl groups include from one to ten or more carbon atoms that are unsubstituted or substituted. The alkyl groups include substituents for coupling to a main chain polymer, substituents for coupling to a crosslinking group, or crosslinking substituents.
The following bridge structures may also be used for the chromophores of this invention.
Acceptors
Representative prior art acceptor structures are illustrated below. The acceptor consists of multiple electron withdrawing groups, typically cyano groups, joined to a conjugated linker or conjugated fused ring. The addition of the third cyano group greatly reduces the solubility of the chromophores in low-refractive index polymers, and increases the tendency of the chromophores to aggregate in all polymers. The solution in the prior art to the aggregation problem has been to include bulky groups either on the donor or the acceptor itself.
[A. W. Harper, Systematic Optimization of Second Order Optical Nonlinearities in Molecules and Polymers, Ph.D. Dissertation, 1997, Univ. of Southern California]
Chromophore-Containing Polymers
In another aspect of the invention, chromophore-containing polymers are provided. These polymers include any one of the chromophores described above, including the chromophore-containing macromolecular structures. In one embodiment, the chromophore is physically incorporated into a polymer to provide a composite. In another embodiment, the chromophore is covalently incorporated into the polymer by, for example, attachment as a side chain or crosslinking. In one embodiment, the chromophore is crosslinked to the polymer in more than one position, for example, a double-ended crosslinked chromophore.
Generally, once a chromophore of appropriate optical nonlinearity (μβ), optical absorption, and stability has been identified, the material is processed into a polymeric material that contains acentrically-aligned chromophores.
To withstand processing conditions and operational conditions (optical power levels at 1.3 and 1.55 microns), chromophore-containing polymers are hardened subsequent to electric field poling to withstand temperatures of 90° C. or greater. As noted above, in certain embodiments, the chromophores include reactive functional groups (e.g., hydroxyl groups) that permit processing into hardened polymer matrices. When thermosetting chemical reactions are employed to lock-in electric field poling-induced acentric order, a stepped poling procedure can be used in which temperature and electric field strength is increased in successive steps to optimize material electro-optic activity.
The chromophores can be incorporated into a variety of host materials including, for example, poly(methyl methacrylate) (PMMA); or copolymers of methyl methacrylate with trifluoroethyl methacrylate.
In summary, suitable methods for incorporating a chromophore into a polymer include the steps of combining the chromophore with the polymer; electric field poling of the chromophore/polymer mixture to acentrically align chromophores; followed by crosslinking, curing, and hardening the chromophore-containing polymer.
Electro-Optic Devices
Components of optical communication systems that may be fabricated, in whole or part, with materials of the present invention include, without limitation, straight waveguides, bends, single-mode splitters, couplers (including directional couplers, MMI couplers, star couplers), routers, filters (including wavelength filters), switches, modulators (optical and electrooptical, e.g., birefringent modulator, the Mach-Zehnder interferometer, and directional and evanescent coupler), arrays (including long, high-density waveguide arrays), optical interconnects, optochips, single-mode DWDM components, and gratings.
The materials of the present invention may be used in telecommunication, data communication, signal processing, information processing, and radar system devices and thus may be used in communication methods relying, at least in part, on the optical transmission of information. Thus, the present invention provides a method of communication comprising transmitting information by light, the light transmitted at least in part through a material of the present invention.
In various embodiments, the present invention provides one or more of:
The following examples are provided for the purpose of illustrating, not limiting, the invention.
In the following examples, all analytical grade reagents and solvents were purchased from commercial sources including, inter alia, SigmaAldrich and VWR Scientific Products. The starting materials and solvents were used without further purification unless otherwise noted. When dry reaction conditions are indicated, the solvents used are Aldrich Sure Seal grade; transferred via dry syringe or cannula. All reactions involving moisture or oxygen sensitive materials were performed in flame-dried glassware under a positive pressure of argon. Silica gel used for column chromatography was obtained from Aldrich with a mesh of 70-230 ASTM. Thin layer chromatography was done using EMS Science Silicagel 60 F254. plates. All proton and carbon nuclear magnetic resonance spectra were recorded on a Bruker 600 MHz FTNMR spectrometer using CDCl3 and tetramethylsilane as an internal reference. Visible spectra were obtained using a Shimadzu UV160U, using CHCl3 as the solvent, and a nominal chromophore concentration of 1×10−5 on a weight basis.
Host Polymers
The chromophores of this invention were evaluated in one or more of the following low-refractive index polymers. The polymers were synthesized using standard procedures. Polymer A (SPIKE) is a terpolymer composed of 14.4 mol % trifluoroethyl methacrylate, 80.6 mol % tetrafluoropropyl methacrylate, and 5 mol % hydroxyethyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4181. Polymer B (Run 46) is a terpolymer composed of 21 mol % trifluoroethyl methacrylate, 52 mol % tetrafluoropropyl methacrylate, and 27 mol % hydroxyethyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4338. Polymer C(CP001) is a terpolymer composed of 21 mol % trifluoroethyl methacrylate, 25 mol % heptafluoroisopropyl methacrylate and 25 mol % hydroxyethyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4189. Polymer D (CP062) is a terpolymer composed of 35 mol % trifluoroethyl methacrylate, 60 mol % difluoroethyl methacrylate and 5 mol % hydroxyethyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4322. Polymer E (CP051) is a copolymer composed of 50 mol % trifluoroethyl methacrylate, and 50 mol % methyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4384. Polymer F (CP088) is a terpolymer composed of 65 mol % tetrafluoropropyl methacrylate, 30 mol % methyl methacrylate, and 5 mol % hydroxyethyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4368. Polymer G (CP087) is a copolymer composed of 85 mol % tetrafluoropropyl methacrylate and 15 mol % hydroxyethyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4266. Polymer H(CP089) is a copolymer composed of 50 mol % tetrafluoropropyl methacrylate and 50 mol % methyl methacrylate. The refractive index of this polymer at 1550 nm was measured to be n=1.4378. Polymer I (CP090) is a terpolymer composed of 65 mol % tetrafluoropropyl methacrylate, 20 mol % tetrafluorobutyl methacrylate, and 15 mol % hydroxyethyl methacrylate.
Other polymers that can be used in this invention may have either low (n<1.5) or high (n>1.5) refractive index values, and include the following:
Thermoplastic Polymers: fluorinated acrylics, polyesters, polyimides, nylons, polycarbonates, polysulfones, and non-fluorinated nylons, acrylics, polyesters, polyimides, polycarbonates, and polysulfones.
Crosslinked Polymers: acrylics, polyesters, unsaturated polymers, polymers substituted with reactive groups (—COOH, —OH, —NCO, —Si(OCH3)3, —OCF═CF2) polyethers.
Branched polymers, interpenetrating polymer networks, and dendrimers [Bosman et al, Chem. Rev. 99, 1665, (1999)].
Additionally, the chromophores of this invention may be attached as side chain groups to these polymers.
Silicon Polymers: silicon polymers can contain the following backbone structures
where R aliphatic, aromatic, or fluoro-hydrocarbon mixtures.
Examples of commercial silicon polymers and resins can be found in United Chemical Technologies (UCT) Product Catalog 2005 (1-800-541-0559) [www.unitedchem.com]
The chromophores of this invention can be either blended into silicon polymers directly, or can be incorporated by modification of the chromophore for direct reaction into the silicon polymer backbone
The silicon polymers can have refractive index values that range between 1.38 and 1.53.
General Synthetic Routes for Donors (D) and Bridge (B) Structures (D-B):
Where R is either of the following
and R1 and R2 are defined in Example 1.
(Org. React Vol. 15, Chapter 2, pp 204-599, 1967. Org. React. Vol. 1, Chapter 8, pp 210-265, 1942)
General Synthetic Routes for Donor-Bridge (D-B) Acceptor (A) Structures (D-B-A):
where R is either of
and R1 and R2 are defined in Example 1, and the X and Y of the active methylene acceptors are defined in the following (Org. React. Vol. 15, Chapter 2, pp 204-599, 1967)
New Fluorinated Fused Ring Acceptor Structures:
The asterisk denotes the active methylene, and XF is given by
and XH is given by
Also included as novel fluorinated fused ring acceptors are
Synthesis of barbituric and thiobarbituric acid derivatives can be found in J. March, Advanced Organic Chemistry, J. Wiley & Sons, New York, 1985, pp 379, while the pyrazolones are described on pp 804.
New Fluorinated Fused Ring Acceptor Structures:
Synthesis of these structures is described in Australian Journal of Chemistry, Vol. 52, pp 1029-1033 (1999).
New Active Amine Acceptor Structures:
The following structures are typical active amine acceptor structures
Modifications of Amine-Functional Active Methylene Acceptor Structures:
The following structures are typical amine-functional active methylene acceptor structures:
The modifications to the above molecular structures that were made as part of this invention were as follows. References for the reactions can be found in J. March, Advanced Organic Chemistry, J. Wiley & Sons, New York, 1985, pp 370, pp 445, and pp 802.
1) First react the active methylene acceptor with a model donor-bridge (D-B) intermediate molecule such as
2) The next reaction sequences for this invention involve the addition of fluorinated alkyl or aryl isocyanates, acid chlorides or sulfonyl chlorides to the amine-functional acceptor-bridge-donor (A-B-D) model compounds previously described. The results of these reactions are shown in the following:
The resulting new acceptor structures can then be characterized as
where R is the ligand resulting from the addition of fluorinated alkyl or aryl isocyanate, acid chloride or sulfonyl chloride to the amine-functional acceptor.
New Active Methylene Acceptor Structures:
The following new acceptor structures are considered part of this invention. References for the synthesis of these acceptor structures is J. Fluorine Chemistry, Vol. 66, pp 301-309 (1994) and J. Am. Chem. Soc., Vol. 81, pp 4882-4885 (1959).
The following is also a new active methylene acceptor structure
Spatial Donor Structures
Normal EO chromophores can be represented by the D-B-A structural form, or explicitly showing a common donor
Chromophores also can be synthesized according to the following scheme:
Molecular weights of the linear and branched spacers can range from 84 to 1000, and can be aliphatic, aromatic, heteroatomic, partially fluorinated or fully fluorinated structures with refractive indices above or below 1.50.
New Donor-Bridge Structures
where A is any of the active methylene structures shown above and R1 and R2 are prior art donor ligands or donor ligands of this invention, as shown in Example 1.
New Bridge Structures
The following may be used alone, or in conjunction with other groups to form the bridge structures for the chromophores of this invention (Syn. Comm. 33, 2487-2496 (2003); J. Am. Chem. Soc. 108, 452-461 (1986)).
The general reaction scheme for bridge structures having both ketone and aldehyde functionality is to convert the ketone functionality into the donor portion of the chromophore and convert the aldehyde functionality into the acceptor portion of the chromophore.
where the bridge is selected so as to maintain an aromatic or conjugated pathway between the aldehyde and ketone functionalities.
For bridge structures with dialdehyde functionality, the general reaction scheme is as follows:
where the bridge is selected so as to maintain an aromatic or conjugated pathway between the two aldehyde functionalities.
These novel bridge ketone-functional structures can be reacted with
to form the following novel donor-bridge structures, where R1 and R2 are either prior art substituents or the new substituents of this invention.
Prior art donor structures or the donor structures of this invention can also be used with these new bridge structures as can prior art acceptors or the new acceptors of this invention.
Similar reactions can occur with aromatic or aliphatic dialdehydes such as:
In addition to the above structures, the following also form novel bridge structures:
where M=S, O, and R1 and R2 are as defined previously.
The following may also be used alone or in conjunction with other groups to form bridge structures (Tetrahedron 54, 2161-2168 (1998); Synthesis, 921-925 (1986); Synthesis, 690-692 (1980); J. Heterocyclic Chem. 13, 253-256 (1976))
With these structures the ketone functionality can be used to attach the acceptor group while the active CH3 group can be used to create the donor portion of the chromophore
New Bridge Structures and Arrangement
The following may be used alone, or in conjunction with other groups to form the bridge structures for the chromophores of this invention.
Synthesis of the chromophores of this invention using these bridge structures differs from standard approaches in that the double bond emerging from the ring(s) is oriented in the direction of the donor portion of the chromophore. This chromophore design is also possible with the bridge structures described elsewhere in this invention, and those mentioned in the prior art.
The following examples of chromophores are presented to demonstrate possible donors and acceptors that can be used with these bridge structures.
Additional Donor-Bridge Structures
The following may be used in conjunction with the acceptors of this invention, or those from the prior art, to form chromophores of this invention.
where M1=O, S; M2=O, S, and M1=, ≠M2. Z=—H, —O—CH2—(CF2)n=1-5—CF3, CH2—(CF2)n=1-8—CF3, —(CF2)n=1-5—CF3, and RA independently are any perfluorinated, fluorinated, or non-fluorinated aliphatic or aromatic group with 1-30 carbon atoms functionalized with zero or more of the following functional groups: hydroxyl, ether, ester, amino, silyl, siloxy, or the RA are independently R1 and R2 as defined previously.
The characteristics of the chromophore are shown in Table 8 using —CH2(CN)2) as the acceptor.
Note:
The absorption maxima are estimated from related compounds and differences in the absorption maxima for the parent donor/bridge compounds.
Thus we see the trade-off between better NLO performance (larger λmax) and solubility of the chromophore.
The five-member rings may also be used as part of the donor structure, as in the following
where M1=O, S; M2=O, S, and M1=, ≠M2. RA independently are any perfluorinated, fluorinated, or non-fluorinated aliphatic or aromatic group with 1-30 carbon atoms functionalized with zero or more of the following functional groups: hydroxyl, ether, ester, amino, silyl, siloxy, or the RA are independently R1 and R2 as defined previously.
Additionally, the following may be used as bridge structures, in conjunction with donors, acceptors, and possibly other bridge components of this invention and/or the prior art.
where M=O, S, Z=—O—CH2—(CF2)n=1-5—CF3, —CH2—(CF2)n=1-8—CF3, —(CF2)n=1-5—CF3.
The following may be used as bridge/acceptor structures, in conjunction with donors, and possibly other bridge components of this invention and/or the prior art.
where M=O, S. Z=—O—CH2—(CF2)n=1,5—CF3, —CH2—(CF2)n=1,8—CF3, —(CF2)n=1,5—CF3.
Examples of complete chromophores using these components include the following:
where M=O, S, Z=—O—CH2—(CF2)n=1-5—CF3, —CH2—(CF2)n=1-8—CF3, —(CF2)n=1-5—CF3.
In this example, we show the preferred structure of the chromophores of this invention. The general structure of these chromophore is shown below, where B is the π-conjugated or aromatic bridge, and A is the π-acceptor. If R1 or R2 contain one or more fluorine atoms, or reactive groups, care must be taken to isolate these groups from the amine to minimize any averse impact on the absorption maximum or dipole moment of the chromophore.
Some of these groups may be used to attach chromophores to the polymer backbone as a sidechain, either by first reacting the donor component onto the polymer, then completing the chromophore synthesis, or by reacting the complete chromophore onto the polymer.
It should be noted that fluorine substitution in close proximity to the donor nitrogen atom can reduce the overall efficiency (lowers λmax and/or the dipole moment) of the chromophore.
Thus one has to carefully balance the amount of fluorine and the placement of the fluorine groups in order to synthesize chromophores that have good efficiency (high λmax values and large dipole moments) and solubility in fluoropolymers as well as lower refractive index values for use in various waveguide applications.
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structure of these chromophores is shown below, where B is a π-conjugated or aromatic bridge, and A is a π-acceptor. If DC1 or DC2 contain one or more fluorine atoms, then A and B can optionally contain fluorine atoms. If neither DC1 nor DC2 contain fluorine, then at least one of A or B must contain fluorine atoms or groups
DC=Donor-connecting link to a polymer backbone
BC=Bridge-connecting link to a polymer backbone
AC=Acceptor-connecting link to a polymer backbone
DC1, DC2, BC, AC each are independently selected from the following:
DC, B, BC, A, AC can each independently be pure hydrocarbon or may contain fluorine atoms as long as at least one does contain fluorine atoms. At least one of the four groups, DC1, DC2, AC, BC must be present for this example. If AC and/or BC are present, then DC1 and DC2 may also be represented by any of the R1 and R2 groups presented in Example 1.
The polymer will contain one or more complementary linking sites on its side chains.
The polymer must have the functional groups complementary to the functional groups on the chromophore. Optionally, additional functional groups may be present on the polymer.
The polymer can be designed so the refractive index after inclusion of the chromophore as the side chain is either low (n<˜1.49) or high (n>˜1.49).
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structures of these chromophores are shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
In this example, we show the preferred structure of one class of chromophores of this invention. The general structure of this chromophore is shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structure of this chromophore is shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structure of this chromophore is shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
In this example, XA is a hydrocarbon alkane, which may optionally include fluorine, XA=—CH2—CnFmH2n+1−m, where n=1 to 5 and m=0 to 2n+1.
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structure of this chromophore is shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structure of this chromophore is shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
In this example, we show the preferred structure of one class of the chromophores of this invention. The general structure of these chromophore is shown below, where D is a π-conjugated or aromatic donor, and B is a π-conjugated or aromatic bridge.
The following examples illustrate synthesis of specific chromophores based on the previous examples. The syntheses were performed as outlined previously.
Where R1, R2, and X7 are described elsewhere, and where Z is an aliphatic, or partially or fully halogenated aliphatic.
The measured absorption maximum was 583 nm, the molecular weight was 400.48, and the dipole was calculated as 18.7 Debye, giving an FOM of 6.7. This chromophore was incorporated into Polymer A at 8.48 wt % (153-105-06), with a refractive index of 1.452. The electrooptic coefficient of the material was measured to be 5.73 pm/V at 50 V/μ poling field.
The measured absorption maximum was 490 nm, the molecular weight was 223.27, and the dipole was calculated as 12.86 Debye, giving an FOM of 4.41. This chromophore was incorporated into Polymer B at 4.5 wt % (153-005-11), which represented its solubility limit. The resulting film quality was determined to be 3, with a refractive index of ˜1.46. The electrooptic coefficient of the material was measured to be 2.31 pm/V at 50 V/μ poling field.
The measured absorption maximum was 519 nm, the molecular weight was 249.31, and the dipole was calculated as 14.75 Debye, giving an FOM of 5.58. This chromophore was incorporated into Polymer A at 5.83 wt %, (153-012-23) which represented its solubility limit. The resulting film quality was of acceptable quality, with a refractive index of 1.4654. The electrooptic coefficient of the material was measured to be 3.90 pm/V at 50 V/μ poling field.
The measured absorption maximum was 555 nm, the molecular weight was 539.52, and the dipole was calculated as 9.32 Debye, giving an FOM of 2.07. This chromophore was incorporated into a 60/40 copolymer of methyl methacrylate and heptafluoroisopropyl methacrylate (n=1.4197) at 9.1 wt % (133-142-31). The resulting film quality was determined to be 3, with a refractive index 1.4459.
The measured absorption maximum was 521 nm, the molecular weight as 359.4, and the dipole was calculated as 14.08 Debye, giving an FOM of 3.74. This chromophore was incorporated into Polymer A at 11 wt % (153-044-34). The resulting film quality was determined to be 3, with a refractive index of 1.4646. Comparison to the results of Example 13, a prior art chromophore with conventional donor, shows the partially fluorinated donor has only slightly impacted both the chromophore absorption maximum and dipole moment, while greatly increasing its solubility in the test polymer.
The measured absorption maximum was 548 nm, the molecular weight was 385.43, and the dipole was calculated as 14.43 Debye, giving an FOM of 4.29. This chromophore was incorporated into Polymer C at 12.23 wt % (153-065-23). The resulting film quality was determined to be 7, which precluded measurements of the refractive index or EO response.
The estimated absorption maximum was 585 nm, the molecular weight was 437.49, and the dipole was calculated as 10.6 Debye, giving an estimated FOM of 3.5.
The measured absorption maximum was 586.5 nm, the molecular weight was 383.52, and the dipole was calculated as 12.87 Debye, giving an FOM of 4.92. This chromophore was incorporated into Polymer A at 10.36 wt % (153-099-30). The resulting film quality was determined to be 5−.
The measured absorption maximum was 651 nm, the molecular weight was 569.49, and the dipole was calculated as 13.24 Debye, giving an FOM of 5.0. This chromophore was incorporated into Polymer A at 10.85 wt % (133-115-23). The resulting film quality was determined to be 2, with a refractive index of 1.4524. This chromophore was incorporated into Polymer B at 9.25 wt % (133-137-29), with a refractive index of 1.4591. The electrooptic coefficient of the material was measured to be 2.73 pm/V at 50 V/μ poling field.
The measured absorption maximum was 679 nm, the molecular weight was 511.45, and the dipole was calculated as 15.16 Debye, giving an FOM of 7.37. This chromophore was incorporated into Polymer A at 9.75 wt % (153-074-02). The resulting film quality was determined to be 3, with a refractive index of 1.4524. This chromophore was incorporated into Polymer A at 10.0 wt % (153-074-25). The electrooptic coefficient of the material was measured to be 5.12 pm/V at 50 V/μ poling field.
The measured absorption maximum was 535 nm, the molecular weight was 365.27, and the dipole was calculated as 12.99 Debye, giving an FOM of 3.74. This chromophore was incorporated into Polymer A at 12 wt % (153-009-22). The resulting film quality was determined to be 3+. This chromophore was incorporated into Polymer A at 12.13 wt % (153-018-07) with a refractive index of 1.454. The electrooptic coefficient of the material was measured to be 6.14 pm/V at 50 V/μ poling field.
The measured absorption maximum was 490 nm, the molecular weight as 373.37, and the dipole was calculated as 8.52 Debye, giving an FOM of 3.98. This chromophore was incorporated into Polymer C at 14.32 wt % (133-115-35). The resulting film quality was determined to be 5.
The measured absorption maximum was 584 nm, the molecular weight was 469.37, and the dipole was calculated as 15.37 Debye, giving an FOM of 4.73. This chromophore was incorporated into a 50/50 copolymer of methyl methacrylate and heptafluoroisopropyl methacrylate at 14.05 wt % (153-069-21). The resulting film quality was determined to be 4.
The measured absorption maximum was 527.5 nm, the molecular weight was 295.34, and the dipole was calculated as 11.16 Debye, giving an FOM of 3.78. This chromophore was incorporated into Polymer A at 12.48 wt % (153-020-32). The resulting film quality was determined to be 2, with a refractive index of 1.4638. The electrooptic coefficient of the material was measured to be 3.37 pm/V at 50V/μ poling field. This chromophore was incorporated into Polymer A at 11.34 wt % (153-090-10) with a refractive index of 1.4627. The electrooptic coefficient of the material was measured to be 5.88 pm/V at 50 V/μ poling field.
The measured absorption maximum was 538 nm, the molecular weight was 349.31, and the dipole was calculated as 12.88 Debye, giving an FOM of 3.96. This chromophore was incorporated into Polymer A at 9.93 wt % (153-034-16). The resulting film quality was determined to be 3. This chromophore was incorporated into Polymer A at 15.0 wt % (153-049-02), with a refractive index of 1.4655. The electrooptic coefficient of the material was measured to be 4.41 pm/V at 50 V/μ poling field.
The measured absorption maximum was 585 nm, the molecular weight was 431.52, and the dipole was calculated as 15.36 Debye, giving an FOM of 5.17. This chromophore was incorporated into Polymer A at 8.62 wt % (153-069-06). The resulting film quality was determined to be 8−.
The measured absorption maximum was 535 nm, the molecular weight was 363.34, and the dipole was calculated as 12.44 Debye, giving an FOM of 3.60. This chromophore was incorporated into Polymer A at 12.0 wt % (153-110-02). The resulting film quality was determined to be 3, with a refractive index of 1.4568. The electrooptic coefficient of the material was measured to be 5.09 pm/V at 50 V/μ poling field.
The measured absorption maximum was 600 nm, the molecular weight was 350.43, and the dipole was calculated as 16.5 Debye, giving an FOM of 7.49. This chromophore was incorporated into Polymer D at 7.78 wt % (153-067-26), with a refractive index of 1.4816. The electrooptic coefficient of the material was measured to be 3.76 pm/V at 50 V/μ poling field.
The measured absorption maximum was 631 nm, the molecular weight was 446.48, and the dipole was calculated as 16.59 Debye, giving an FOM of 7.09. This chromophore was incorporated into Polymer A at 9.88 wt % (153-079-18), with a refractive index of 1.4489. The electrooptic coefficient of the material was measured to be 1.55 pm/V at 50 V/μ poling field.
The measured absorption maximum was 636 nm, the molecular weight was 452.58, and the dipole was calculated as 17.15 Debye, giving an FOM of 7.44. This chromophore was incorporated into Polymer A at 10.54 wt % (153-105-18). The resulting film quality was determined to be 3−, with a refractive index of 1.4536. The electrooptic coefficient of the material was measured to be 3.74 pm/V at 50 V/μ poling field.
The measured absorption maximum was 627 nm, the molecular weight was 707.00, and the dipole was calculated as 14.86 Debye, giving an FOM of 3.92. This chromophore was incorporated into Polymer A at 10.25 wt % (153-143-10). The resulting film quality was determined to be 5, with a refractive index of 1.4494. The electrooptic coefficient of the material was measured to be 3.20 pm/V at 50 V/μ poling field. The use of the massive donor groups did little to enhance chromophore performance or solubility in the low refractive index polymers.
The measured absorption maximum was 654 nm, the molecular weight was 563.61, and the dipole was calculated as 17.88 Debye, giving an FOM of 6.89. This chromophore was incorporated into Polymer A at 9.19 wt % (153-150-26). The resulting film quality was determined to be 7. This chromophore was incorporated into a 50/50 copolymer of methyl methacrylate and trifluoroethyl methacrylate at 9.03 wt % (153-150-29). The resulting film quality was determined to be 3−.
The measured absorption maximum was 625 nm, the molecular weight was 469.46, and the dipole was calculated as 16.9 Debye, giving an FOM of 6.64. This chromophore was incorporated into Polymer A at 9.13 wt % (153-143-26). The resulting film quality was determined to be 3−, with a refractive index of 1.4693. The electrooptic coefficient of the material was measured to be 9.83 pm/V at 50 V/μ poling field.
The measured absorption maximum was 583 nm, the molecular weight was 435.42, and the dipole was calculated as 14.41 Debye, giving an FOM of 4.75. This chromophore was incorporated into Polymer A at 11.03 wt % (153-099-02). The resulting film quality was determined to be 4−.
The measured absorption maximum was 582.5 nm, the molecular weight was 459.42, and the dipole was calculated as 15.94 Debye, giving an FOM of 4.96. This chromophore was incorporated into Polymer A at 11.33 wt % (153-127-31). The resulting film quality was determined to be 3−.
Three commercial, highly fluorinated polymers, Teflon AF (Dupont), CYTOP (Asahi Glass), and Lumiflon (Asahi Glass) were exposed to hot chromophore vapor (EC9, Example 21) over a 24-hour period.
CYTOP is soluble in perfluoro-t-butyl amine. The chromophore of Example 14 (EC12) was also somewhat soluble in this solvent. A saturated solution of the chromophore in perfluoro-t-butyl amine containing 9% by weight CYTOP was filtered through glass wool and a small amount was applied to an EO test cell then dried for 2 hours on a 70 C hot plate. A measurable EO response was obtained.
Optical quality waveguides were obtained (Japan Synthetic Rubber) or made according to the recipes and processes described in “Sol-Gel Technologies or Thin Films, Fibers, Preforms, Electronics, and Specialty Shapes”, Lisa C. Klein ed., Noyes Publications, Park Ridge, N.J., 1988.
The starting refractive index of the sol-gel waveguide was 1.4752. A 10% by weight solution of the chromophore of Example 24 (EC23) in dioxane (red colored solution) was placed on the surface of the sol-gel waveguide and allowed to soak into the waveguide over a 24 hour time period at room temperature. The sample was covered and a dioxane vapor was maintained over the sample for the entire period.
After 24 hours the sample was removed from the container and the remaining solvent/chromophore was wiped off the surface of the waveguide. A refractive index measurement was then made of the now red color-stained sol-gel waveguide. The waveguide no longer exhibited a single refractive index, but instead exhibited the behavior typical of diffusion-formed waveguides, where the refractive index varies due to a concentration gradient of the dopant.
These results show how one can infuse EO chromophores into sol-gel waveguides so that electrooptically active devices can be manufactured.
The chromophore was synthesized according to the following procedure. The diamine (CH3CH2—NH—CH2C8H16CH2—NH—CH2CH3) was prepared by reacting N-ethylaniline (Aldrich Chemical Company) with 1-iodibromodecane (Aldrich Chemical Company) to produce an aromatic linear spatial donor structure. Bromination of the aromatic groups followed by reaction with bridge and acceptor groups produced the final product
The measured absorption maximum was similar to that of the monomeric chromophore (Example 23). The chromophore formed poor films in low index fluorinated polymers, due to the extended hydrocarbon spacer.
The measured absorption maximum was 564 nm, the molecular weight was 298.34, and the dipole was calculated as 11.1 Debye, giving an FOM of 4.73. This chromophore was incorporated into Polymer A at 9.96 wt % (178-52-30). The resulting film quality was determined to be 3− with a refractive index of 1.4538. The electrooptic coefficient of the material was measured to be 5.47 pm/V at 50 V/μ poling field.
The measured absorption maximum was 559 nm, the molecular weight was 420.38, and the dipole was calculated as 12.97 Debye, giving an FOM of 3.80. This chromophore was incorporated into Polymer A at 10.23 wt % (153-150-10). The resulting film quality was determined to be 3 with a refractive index of 1.4578. The electrooptic coefficient of the material was measured to be 5.05 pm/V at 50 V/μ poling field.
The absorption maximum was estimated as 650 nm, the molecular weight was 537.63, and the dipole was calculated as 17.32 Debye, giving an FOM of 6.8. This chromophore was incorporated into Polymer A at 10.33 wt % (178-17-02). The resulting film quality was determined to be 3− with a refractive index of 1.4516. The electrooptic coefficient of the material was measured to be 2.59 pm/V at 50 V/μ poling field.
The measured absorption maximum was estimated as 640 nm, the molecular weight was 459.58, and the dipole was calculated as 14.78 Debye, giving an FOM of 6.5.
The measured absorption maximum was 465.5 nm, the molecular weight was 453.38, and the dipole was calculated as 10.47 Debye, giving an FOM of 1.47.
The measured absorption maximum was 487 nm, the molecular weight was 453.45, and the dipole was calculated as 8.68 Debye, giving an FOM of 1.43. This chromophore was incorporated into Polymer E at 9.93 wt % (133-145-17). The resulting film quality was determined to be 3 with a refractive index of 1.4637. The electrooptic coefficient of the material was measured to be 1.90 pm/V at 50 V/μ poling field.
The measured absorption maximum was 530 nm, the molecular weight was 250.31, and the dipole was calculated as 12.27 Debye, giving an FOM of 4.98. This chromophore was incorporated into Polymer A at 11.47 wt % (153-127-27). The resulting film quality was determined to be 6.
The measured absorption maximum was estimated at 565 nm, the molecular weight was 403.38, and the dipole was calculated as 10.49 Debye, giving an FOM of 3.33.
The measured absorption maximum was 515.5 nm, the molecular weight was 585.39, and the dipole was calculated as 11.83 Debye, giving an FOM of 1.86. This chromophore was incorporated into Polymer A at 15.82 wt % (178-52-26). The resulting film quality was determined to be 3− with a refractive index of 1.4423. The electrooptic coefficient of the material was measured to be 2.84 pm/V at 50 V/μ poling field.
The measured absorption maximum was 570 nm, the molecular weight was 453.46, and the dipole was calculated as 12.04 Debye, giving an FOM of 3.51. This chromophore was incorporated into Polymer F at 8.4 wt % (178-56-02). The resulting film quality was determined to be 3 with a refractive index of 1.4602. The electrooptic coefficient of the material was measured to be 3.68 pm/V at 50 V/μ poling field.
The measured absorption maximum was 530.5 nm, the molecular weight was 369.46, and the dipole was calculated as 11.38 Debye, giving an FOM of 3.14.
The estimated absorption maximum was 590 nm, the molecular weight was 513.46, and the dipole was calculated as 14.75 Debye, giving an FOM of 4.30.
The measured absorption maximum was 561.5 nm, the molecular weight was 408.33, and the dipole was calculated as 11.81 Debye, giving an FOM of 3.62. This chromophore was incorporated into Polymer H at 9.65 wt % (178-61-26). The resulting film quality was determined to be 4− with a refractive index of 1.4675. The electrooptic coefficient of the material was measured to be 2.28 pm/V at 50 V/μ poling field.
The measured absorption maximum was 483.5 nm, the molecular weight was 325.33, and the dipole was calculated as 12.85 Debye, giving an FOM of 2.88. This chromophore was found to be soluble in highly fluorinated commercial polymers with some carboxylic acid functionality (178-079-08).
The measured absorption maximum was 494 nm, the molecular weight was 469.40, and the dipole was calculated as 12.95 Debye, giving an FOM of 2.18. This chromophore was found to be soluble in highly fluorinated commercial Polymers with some carboxylic acid ester functionality (178-091-28). This chromophore was incorporated into Polymer I at 15.13 wt % (178-120-22). The resulting film had a refractive index of 1.45. The electrooptic coefficient of the material was measured to be 3.78 pm/V at 50 V/μ poling field.
The measured absorption maximum was 545 nm, the molecular weight was 493.34, and the dipole was calculated as 13.74 Debye, giving an FOM of 3.13. This chromophore was found to be soluble in highly fluorinated commercial polymers with some carboxylic acid ester functionality (178-097-30).
The measured absorption maximum was 475.5 nm, the molecular weight was 457.39, and the dipole was calculated as 6.03 Debye, giving an FOM of 0.91. This chromophore was found to be soluble in highly fluorinated commercial polymers with some carboxylic acid functionality (178-094-17).
The measured absorption maximum was 643 nm, the molecular weight was 713.45, and the dipole was calculated as 17.93 Debye, giving an FOM of 5.13.
U.S. Pat. No. 5,256,784 and U.S. Pat. No. 5,670,090 teach that barbituric and thiobarbituric acids can have the range of structures shown below
The prior art barbituric/thiobarbituric acid structures are acceptors and react with the donor-bridge intermediate materials to form NLO chromophores
All the NLO compounds derived using barbituric or thiobarbituric acid acceptors disclosed or anticipated/taught in these prior patents are not compatible with the fluoropolymers used in this invention. All these prior art NLO compounds, based on barbituric or thiobarbituric acid acceptors, have high melting points, tend to crystallize out of our polymer systems, and have high refractive index values. All of these properties detract from the ability to create total low refractive index systems (polymer plus NLO chromophore) from these NLO compounds that are compatible with standard silica waveguides, presently used as platforms by the telecommunications industry.
Our invention is based on the creation of completely new barbituric or thiobarbituric acid compounds that have unique combinations of lower melting points and lower refractive indices than the prior art. The current prior art NLO chromophores based on conventional barbituric or thiobarbituric acid structures are either not soluble or not stable/compatible with the fluoropolymers described in this invention. This invention describes new barbituric or thiobarbituric acid derivatives that can be used to create new NLO chromophores with lower melting points, lower refractive indices, and are more stable/soluble in the fluoropolymers described in this invention.
Control of Melting Points of Barbituric and Thiobarbituric Acids
Barbituric acids and thiobarbituric acids are easily derived from substituted urea or thiourea compounds
It can be shown that the melting points of the thiourea and urea starting materials greatly influence the melting points of the final barbituric or thiobarbituric acid compounds. Tables 20 and 21 contain the melting points and molecular weight information for a number of commercially available urea and thiourea compounds which are used to prepare prior art barbituric and thiobarbituric acid structures. Also Tables 20 and 21 contain two “McGinniss Equation” parameters XN (weight fraction of nitrogen in the urea or thiourea starting materials) and Z′ (π electron density fraction) which are used to correlate the melting points of the starting urea or thiourea with their chemical structures (reference). In both cases there is a good correlation between the melting points, the molecular weights and the “McGinniss Equation” variables.
There is also a direct correlation between the melting points of the substituted ureas and thioureas with the melting points of their associated barbituric or thiobarbituric acid compounds (Table 22). The melting point/chemical structure correlation results shown in Tables 20-22 are applicable to a wide variety of relatively simple prior art materials but do not hold for fluorinated or nitro derivatives of urea and thiourea compounds. Table 23 gives a listing of a variety of fluorinated or nitro-substituted phenyl urea and thiourea compounds along with their melting points and associated “McGinniss Equation” variables. There is no obvious correlation of the melting points of these compounds with their chemical structure. In general one can only make the following observations:
The control of the melting points of the barbituric (BBA) or thiobarbituric (TBBA) acid derivatives is critical for the overall design of the NLO chromophores that go into the fluoropolymer systems of this invention. The NLO chromophores of interest are generally made as shown previously.
Melting Point = 0.086*(Molecular Weight) + 106.224*(XN) + 1878*(Z′) + 61.76
Correlation coefficient R = 0.89
Melting Point = 0.336*(Molecular Weight) + 638.3*(XN) + 2190*(Z′) − 100.84
Correlation coefficient R = 0.89
Melting Point of Urea/Thiourea Derivatives = 0.53*(BBA/TBBA melt point) + 21.68
Correlation coefficient R = 0.89
No correlation between the melting points of fluorine/nitro-containing thioureas/ureas and their molecular parameters.
Thus, if the BBA or TBBA melting points are too high or too low than the overall melting point of the resultant NLO chromophore will reflect this trend. If the melting point of the resultant NLO chromophores are too high then extreme temperatures and pressures are required to apply and fill the polymer-NLO chromophore system into the fragile silica waveguide structures. High temperatures and pressures can damage the waveguides or create devices with high optical loss (Table 24). If the melting points of the NLO chromophores are too low then the polymer system could become plasticized at elevated temperatures which could lead to voltage breakdown or rapid thermal degradation of the total system (Table 24). These very practical constraints are not recognized by the prior art in that all of the prior art NLO chromophores are designed to be in all-hydrocarbon polymer waveguide structures and were not designed or will not function in a silica waveguide platform that requires a fluoropolymer as described in this invention.
Control of Solubility and Refractive Index of Barbituric Acids and Thiobarbituric Acids in Fluoropolymers of this Invention
In general fluorine-containing aromatic NLO chromophore derivatives of barbituric and thiobarbituric acids have marginal solubility in the polymers of this invention. All-hydrocarbon NLO chromophore barbituric or thiobarbituric acid derivatives have almost no solubility in the polymers of this invention (Table 25). Combinations of fluorinated aromatic and fluorinated alkyl substituted barbituric/thiobarbituric acid modified NLO chromophores can be made to be soluble in the polymers of this invention (Table 26). It should be noted, however, that too much fluorine or the wrong type of fluorine substitution on the barbituric/thiobarbituric acid functionality (acceptor) of the NLO chromophore will plasticize the polymer resulting in a system that will not withstand high temperature and voltage over any extended service lifetime. High concentrations of fluorine in a molecule increase its molecular weight and sometimes a greater weight percent of the NLO chromophore is required to match the electrooptic performance of its lower molecular weight all-hydrocarbon counterpart. Higher concentrations of certain types of fluorinated NLO chromophores can plasticize the fluoropolymer which can lead to poor performance.
The synthesis method by which all the fluorine-modified barbituric/thiobarbituric acid derivatives of this invention were made are shown in Table 27.
It was also discovered that NLO chromophores with mixed alkane (hydrocarbon and fluorocarbon) modification of barbituric/thiobarbituric acid acceptors were also soluble in the fluoropolymers of this invention (Table 28). These mixed fluorine-alkane/hydrocarbon-alkane barbituric or thiobarbituric acid acceptors can be synthesized as follows:
The other requirement for chromophores of this invention is that they do not adversely affect the overall refractive index of the total system. This means that the chromophores should contain functionalities, such as aliphatic carbon fluorine groups, to maintain a low refractive index (n). Table 29 shows a comparison of calculated refractive index values for prior art barbituric/thiobarbituric acid acceptors and the fluorine-modified barbituric/thiobarbituric acid acceptors of this invention.
Note: The refractive index values for all the acceptors in this table were calculated using the molar refractive index values contained in D. W. van Krevelen “Properties of Polymers” 2ndEdition, Elsevier, New York, 1980 pp 212-218.
Other novel structures envisioned in this invention include the modification of the aryl group on an amine-functional acceptor to contain fluorine groups.
An additional novel modification to these acceptors is as follows:
An alternate modification is:
The following reaction scheme describes how a prior art fluorinated active methylene acceptor is synthesized
The problem with this particular fluorinated acceptor is that it is not very soluble in our fluoropolymers and the aromatic group increases the overall refractive index of the chromophore and the total system (polymer+chromophore).
New fluorinated active methylene pyrazoline-5-one compounds were synthesized as follows
Other modifications could also include reacting the phenylhydrazines with:
The contribution of the aromatic groups to the refractive index are shown in Table 30.
Other acceptors of this invention are as follows:
These acceptors can be synthesized in the following manner
J. March, Advanced Organic Chemistry, J. Wiley, New York, 1985, pp 804.
These acceptors can be synthesized in the following manner
A. Quilico, “The Chemistry of Heterocyclic Compounds”, A. Weissberger editor, vol. 17, pp 6 (1962), J. Wiley, New York.
In summary, this invention distinguishes itself from prior art barbituric/thiobarbituric acid acceptors, pyrazoline-5-one acceptors and isoxazolene acceptors in the following manner:
While the invention has been described with reference to a preferred embodiment, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In this application all units are in the metric system and all amounts and percentages are by weight, unless otherwise expressly indicated. Also, all citations referred herein are expressly incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/US05/14418 | Apr 2005 | US | national |
