This invention relates to a magnetic nanocomposite material that is capable of polymerising an anaerobic adhesive or other monomeric materials in need thereof. Also disclosed herein is the use of the material in said polymerisation and its method of manufacture.
The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.
Many air-sensitive reactions or manufacturing processes for the production of polymers intrinsically require an anaerobic atmosphere to avoid interactions with reactive or unstable forms of oxygen, which can produce undesirable by-products. Anaerobic adhesives are intentionally designed for use under low oxygen or deoxygenated conditions that are found in sophisticated, complex, and tight spaces or surface irregularity. As such, anaerobic adhesives are often colloquially known as threadlockers or retaining compounds. These adhesives cure on active metal surfaces in the absence of oxygen in the bond line. Thus, anaerobic adhesives are often applied in locking, sealing, retaining, and bonding, which are crucial processes in the electronics, packaging, and automobile industries, and so may be useful in reducing maintenance and leakage and thereby help keep factories running efficiently (amongst other uses). Moreover, anaerobic adhesives have great accessibility, storage longevity, and are eco-friendly, as compared to the other types of adhesives.
Anaerobic adhesives are one-component and solvent-free adhesives that consist of dimethacrylate monomers. Cross-linking occurs in the absence of oxygen based on a redox radical polymerization. The speed of the redox radical initiation can be tailored by the decomposition of the peroxide species caused by the presence of appropriate transition metal ions in the polymerization system (P. Klemarczyk & J. Guthrie, in Advances in Structural Adhesive Bonding, (Ed: D. A. Dillard), Woodhead Publishing, 2010, 96). However, conventional activation approaches, such as thermal, chemical, photochemical, redox, and mechanical means, can only initiate the polymerization and have limited control on the polymerization over the desirable area during the curing process. In addition, the conditions used for these processes tend to be relatively severe, resulting in high energy consumption, substrate damage and high cost.
Thus, there remains a need to develop a process for anaerobic adhesive curing/polymerisation under mild, hazard-free conditions.
It is believed that magnetically controllable localized polymerization could overcome the challenges noted briefly above in relation to localized polymerization or adhesive formation.
Magnetically induced localized polymerization uses an external magnetic field to control localized initiation of polymerization toward the curing system in a sustainable, spontaneous, safe, eco-friendly, efficient manner that has a wide range of potential applications in both science and engineering.
It has been surprisingly found that a magnetic nanocomposite material disclosed herein can act as a co-initiator of polymerisation to provide localised polymerisation under mild reaction conditions. The invention will now be discussed by reference to the following numbered clauses.
where:
the wavy lines represent the point of attachment to the rest of the molecule;
each L independently represents NR1R2 or SR3
each R1 independently represents H or C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted;
each R2 independently represents —(CHR4)nNR5R6;
each R3 independently represents —(CHR4)nSR7;
each R5 and R6 independently represent H, C1 to C6 alkyl that is unsubstituted, —(CHR4)nNR8R9, or a point of attachment to a further constitutional repeating unit or an end group;
each n independently represents 2 to 6;
each R8 and R9 independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted, —(CHR4)nNR10R11, or a point of attachment to a further constitutional repeating unit or an end group;
each R10 and R11 independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted, or a point of attachment to a further constitutional repeating unit or an end group;
each R4 represents H, OH or OR12; and
each OR12 independently represents C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted; or
where:
each X independently represents S or NR13; and
each R13 independently represents H or C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted.
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit and the wavy lines b and, when present, c represent a point of attachment to the rest of the molecule.
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit and the wavy lines b and, when present, c represent a point of attachment to the rest of the molecule.
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit and the wavy line b represents a point of attachment to the rest of the molecule.
where:
the wavy line represents the point of attachment to the rest of the molecule;
each L′ independently represents an end group selected from NR1′R2′ or SR3′;
each R1′ independently represents H or C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted;
each R2′ independently represents —(CHR4′)nNR5′R6′;
each R3′ independently represents —(CHR4′)nSR7′;
each R5′ and R6′ independently represent H, C1 to C6 alkyl that is unsubstituted, —(CHR4′)nNR8′R9′;
each n independently represents 2 to 6;
each R8′ and R9′ independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted, —(CHR4)nNR10R11;
each R10′ and R11′ independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted;
each R4′ represents H, OH or OR12′; and
each OR12′ independently represents C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted; or
where:
the wavy line represents the point of attachment to the rest of the molecule;
each L″ independently represents an end group of formula 1c′:
where:
the wavy line represents the point of attachment to the rest of the molecule;
each X′ independently represents S or NR13;
each X″ independently represents SR14 or NR15′R16′; and
each R13′ to R16′ independently represents H or C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted.
where the wavy line a represents a point of attachment to the rest of the final generation constitutional repeating unit.
where the wavy line a represents a point of attachment to the rest of the final generation constitutional repeating unit.
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit.
It has been surprisingly found that the use of a magnetic nanocomposite material having a core of a magnetic nanoparticle that is covered with a shell bearing dendrons that chelate an initiating metal ion can be used in the formation of polymers/anaerobic adhesives in a localized manner under mild reaction conditions.
Applications for this material relate to any know application of an anaerobic adhesive and include, but are not limited to the formation of polymers/adhesives in an enclosed and confined spaces. Thus, in a first aspect of the invention, there is provided a magnetic nanocomposite material, comprising:
In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components/features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of” or “consists essentially of”). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of” or the phrase “consists essentially of” or synonyms thereof and vice versa.
The phrase, “consists essentially of” and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.
It is to be understood the present invention is not limited to particular devices or methods, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include singular and plural referents unless the content clearly dictates otherwise. Furthermore, the word “may” is used throughout this application in a permissive sense (i.e., having the potential to, being able to), not in a mandatory sense (i.e., must). The term “include,” and derivations thereof, mean “including, but not limited to.” The term “coupled” means directly or indirectly connected.
As will be appreciated, the magnetic nanoparticle core may be formed from any suitable material that is magnetic. Suitable materials that are magnetic include, but are not limited to, Fe, Ni, Co, Nd, Mn, Gd, Sm, Dy, alloys thereof and metallic ceramics (e.g. ferrite) thereof. In particular embodiments that may be mentioned herein, the magnetic nanoparticle may comprise one or more metals selected from the group consisting of Ni, Co, Zn, Cu, Mn, and Fe. As such, alloys and ceramics of these metals are contemplated for use as the magnetic nanoparticle. In yet more particular embodiments of the invention, the magnetic nanoparticle may be formed from Fe.
The magnetic nanoparticles used as the core, around which a second material forms a shell, may have any suitable size. For example, the magnetic nanoparticles may have a size of from 5 to 50 nm, such as from 5 to 25 nm or they may have a size of from 100 to 600 nm, such as from 200 to 390 nm.
As will be appreciated, the resulting magnetic nanocomposite material will have a diameter larger than that of the core magnetic nanoparticles. This is because the magnetic nanocomposite material has a shell material surrounding the core and then a plurality of dendrons attached to this shell. Thus, the magnetic nanocomposite material may have a diameter of from:
Any suitable material that can be used to form a coating over the magnetic nanoparticles and is then capable of providing (or being adapted to provide) a plurality of anchoring elements can be used as the shell that surrounds the magnetic nanoparticle. In embodiments that may be mentioned herein, the shell may be a silica shell. Said silica shell may be made by any suitable starting material (e.g. tetraethyl orthosilicate, or tetraethoxysilane).
The shell material, no matter the material used, should be able to provide an anchoring element for the growth of a plurality of dendrons. The shell material may inherently contain suitable anchoring elements, or it may be reacted further to provide such elements. When used herein, the term “anchoring element” is used to refer to a moiety that is covalently bonded to both the shell material and at least one of the plurality of dendrons. An example of a suitable moiety that may be used as an anchoring element includes, a material that has a linear or branched C1 to C10 alkyl chain substituted by one or more amino groups. For example, the anchoring element may be a 3-propylamino group.
As stipulated by section “DH-1.17 dendron” of the “IUPAC nomenclature and terminology for dendrimers with regular dendrons and for hyperbranched polymers” (see https://iupac.org/recommendation/nomenclature-terminoloav-dendrimers-regular-dendrons-hyperbranched-polymers/), a Dendron is “part of a molecule with only one free valence, comprising exclusively dendritic and terminal constitutional repeating units and in which each path from the free valence to any end-group comprises the same number of constitutional repeating units”. When used herein, the “free valence” position of the Dendron refers to a first generation constitutional repeating unit's point of attachment of the Dendron to the shell material via the anchoring group.
Herein, a “first non-final generation constitutional repeating unit” refers to a constitutional repeating unit that is directly covalently bonded to the anchoring element. A “second non-final generation constitutional repeating unit” refers to a constitutional repeating unit that is attached covalently to the first non-final generation constitutional repeating unit. A “third non-final generation constitutional repeating unit” refers to a constitutional repeating unit that is attached covalently to the second non-final generation constitutional repeating unit. Further generations of non-final constitutional repeating unit may be interpreted accordingly. A “final generation constitutional repeating unit”, refers to the final portion of the dendron, which is capped by end groups. The final generation constitutional repeating unit may be any suitable generation of the constitutional repeating unit, though it cannot be the first generation constitutional repeating unit.
Any suitable number of generations of constitutional repeating units may be used in the current invention, provided that the resulting end groups can firmly chelate to the metal ions stably.
Thus, there may be from 1 to m generations of non-final constitutional repeating units, where m is from 2 to 5 (it will be appreciated that the total number of generations is m+1, as the final generation is not included in m). In embodiments that may be mentioned herein, m may be 1 to provide a plurality of G2 dendrons (dendrons having two generations of constitutional repeating units in total). Without wishing to be bound by theory, it is noted that G2-G6 (e.g. G2) dendrons disclosed herein may have a good chelation to copper (or other suitable metal) ions and function well as co-nanoinitiators for polymerisation reactions, as discussed in more detail below. Dendrons having a higher generation may not provide a strong chelation to copper (or other metal) ions because of an electrostatic repulsion cause either by the amine groups or the metal ions at the branches of the dendrons.
In embodiments of the invention that may be mentioned herein, each non-final generation constitutional repeating unit may have the fragment formula 1a or 1b:
where:
the wavy lines represent the point of attachment to the rest of the molecule;
each L independently represents NR1R2 or SR3
each R1 independently represents H or C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted;
each R2 independently represents —(CHR4)nNR5R6;
each R3 independently represents —(CHR4)nSR7;
each R5 and R6 independently represent H, C1 to C6 alkyl that is unsubstituted, —(CHR4)nNR8R9, or a point of attachment to a further constitutional repeating unit or an end group;
each n independently represents 2 to 6;
each R8 and R9 independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted, —(CHR4)nNR10R11, or a point of attachment to a further constitutional repeating unit or an end group;
each R10 and R11 independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted, or a point of attachment to a further constitutional repeating unit or an end group;
each R4 represents H, OH or OR12; and
each OR12 independently represents C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted; or
where:
each X independently represents S or NR13; and
each R13 independently represents H or C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted.
In particular embodiments of formula 1a and 1b that may be mentioned herein, each L may be selected from the list of:
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit and the wavy lines b and, when present, c represent a point of attachment to the rest of the molecule.
In more particular embodiments of formula 1a and 1b that may be mentioned herein, each L may be selected from the list of:
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit and the wavy lines b and, when present, c represent a point of attachment to the rest of the molecule.
For example, in formula 1a and 1b, each L may be selected from the list of:
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit and the wavy line b represents a point of attachment to the rest of the molecule.
In embodiments of the invention that may be mentioned herein, each final generation constitutional repeating unit comprising a plurality of end groups may have the fragment formula 1a′ or 1b′:
where:
the wavy line represents the point of attachment to the rest of the molecule;
each L′ independently represents an end group selected from NR1′R2′ or SR3;
each R1′ independently represents H or C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted;
each R2 independently represents —(CHR4′)nNR5′R6′;
each R3′ independently represents —(CHR4)nSR7′;
each R5′ and R6′ independently represent H, C1 to C6 alkyl that is unsubstituted, —(CHR4)nNR8′R9′;
each n independently represents 2 to 6;
each R8′ and R9′ independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted, —(CHR4′)nNR10R11;
each R10′ and R11′ independently represent H, C1 to C6 alkyl, which C1 to C6 alkyl is unsubstituted;
each R4′ represents H, OH or OR12′; and
each OR12′ independently represents C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted; or
where:
the wavy line represents the point of attachment to the rest of the molecule;
each L″ independently represents an end group of formula 1c′:
where:
the wavy line represents the point of attachment to the rest of the molecule;
each X′ independently represents S or NR13;
each X″ independently represents SR14 or NR15′R16′; and
each R13′ to R16′ independently represents H or C1 to C3 alkyl, which C1 to C3 alkyl is unsubstituted.
In particular embodiments of formula 1a′ and 1b′ that may be mentioned herein, each end group may be selected from the list of:
where the wavy line a represents a point of attachment to the rest of the final generation constitutional repeating unit.
In particular embodiments of formula 1a′ and 1b′ that may be mentioned herein, each end group may be selected from the list of:
where the wavy line a represents a point of attachment to the rest of the final generation constitutional repeating unit.
For example, in embodiments of formula 1a′ and 1b′ that may be mentioned herein, each end group may be selected from the list of:
where the wavy line a represents a point of attachment to the rest of the constitutional repeating unit.
As noted above, a plurality of metal ions also form part of the magnetic nanocomposite material, where each metal ion is chelated to at least one of the plurality of end groups. Said metal ions may be selected from one or more of the group consisting of Mn3+, Ce4+, Co3+, Cu2+, Fe3+, Cr3+, Mn3+, Ce4+, and Co3+. More particularly, the metal ions may be selected from one or more of the group consisting of Cu2+, Fe3+, Cr3+, Mn3+, Ce4+, and Co3+. Yet more particularly, the plurality of metal ions may be Cu2+.
The magnetic nanocomposite material many also be referred to herein as MNPs-GX@My+, where MNPs stands for magnetic nanoparticles, GX stands for the total number of generations of constitutional repeating units in the magnetic nanocomposite material, M stands for the metal ion chelated to the end groups and y+represents the charge of said metal ion. For example, MNPs-G2@Cu2+ refers to a magnetic nanocomposite material having two total generations of constitutional repeating units where a Cu2+ ion is chelated to the end groups.
Advantages associated with the magnetic nanocomposite material may include:
The magnetic nanocomposite material may be particularly useful in the formation of a polymeric material (e.g. as a co-initiator of polymerisation). As such, in a further aspect of the invention, there is provided a polymeric product comprising:
As will be appreciated, the magnetic nanocomposite material may be distributed within the polymeric matrix that it has been used to help generate. Details of how this may be achieved will be discussed in more detail in relation to the method of formation of the polymeric product below.
The polymeric product may be formed using any suitable monomer or combination of monomers where the magnetic nanocomposite material can be used as a co-initiator. For example, the monomers may be a material that includes a carbon-to-carbon double bond. Examples of such materials include, but are not limited to vinyl chloride, propylene, vinyl acetate, vinylidene chloride, styrene, acrylonitrile, tetrafluoroethylene, isoprene, butadiene, chloroprene, N-isopropylacrylamide, 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate, ethylene glycol dimethacrylate, vinyl methacrylate, allyl methacrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, a dimethacrylate monomer, triethylene glycol dimethacrylate, and combinations thereof. In particular embodiments of the invention that may be mentioned herein, the monomer may be triethylene glycol dimethacrylate.
The polymeric product formed using the magnetic nanocomposite material described herein may have one or more of the following properties:
As described in the experimental section below, a tensile test of anaerobic polymer initiated by MNPs-G2@Cu2+ was conducted to compare the mechanical properties with a control system. From this test, the following advantages for the polymeric system can be derived, and it is expected that similar results would be obtained using the other magnetic nanocomposite materials discussed herein.
In addition, the interfacial adhesion of cured TRIEGMA was carried out by using single lap shear strength test to evaluate the adhesive property (see examples). The MNPs-G2@Cu2+ and control adhesive systems were physically secured to a surface under deoxygenated reaction conditions (as discussed in the experimental section and further below). The adhesive strength of the control and the MNPs-G2@Cu2+ system were measured and analyzed from 15 samples.
It will be appreciated that the magnetic nanocomposite material disclosed herein may be pre-packaged for use with a suitable monomer (or mixture of monomers. As such, in a further aspect of the invention, there is provided a formulation comprising:
In this formulation, the monomer may be selected from one or more of the group consisting of vinyl chloride, propylene, vinyl acetate, vinylidene chloride, styrene, acrylonitrile, tetrafluoroethylene, isoprene, butadiene, chloroprene, N-isopropylacrylamide, 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate, ethylene glycol dimethacrylate, vinyl methacrylate, allyl methacrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, a dimethacrylate monomer, and triethylene glycol dimethacrylate. For example, the monomer may be triethylene glycol dimethacrylate.
As mentioned above, the magnetic nanocomposite materials disclosed hereinbefore may be particularly useful in the formation of a polymeric material. In particular, a localized formation of the polymeric material at a desired site.
In a further aspect of the invention, there is provided a method of forming a polymeric material, the method comprising:
It is believed that the localized redox-initiated radical polymerization was magnetically induced by the synergistic function of initiators between the magnetic nanocomposite material (e.g. MNPs-G2@Cu2+) and peroxide. It is noticeable that the polymerization was necessarily promoted in the presence of a metal ion (e.g. Cu2+) source. It is also noted that the redox reaction between the metal ions in the end groups (e.g. Cu(II) and Cu(I) of magnetic responsive MNPs-G2@Cu2+) locally enhanced the decomposition of radical species from peroxide species to achieve the successful polymerization. This is demonstrated most clearly when the reaction is conducted in the presence of one or more magnets, which attracts the magnetic nanocomposite material and sets up a concentration gradient of peroxide radicals in the reaction mixture, which is discussed in more detail below.
As will be appreciated, the localised polymerisation feature is optional and may, or may not be used. As such, the use of magnets may be optional. However, if there is a desire to control the site of formation of the polymeric material, then this may be accomplished through the use of one of more magnets, such that the polymerization occurs at one or more desired regions of the vessel.
The vessel referred to herein may be any suitable vessel. This may be an inanimate object (e.g. inside a pipe or other hand-to-reach location) or, in some cases, a living subject in need of formation of a polymeric material at a particular location due to a specific treatment need.
It is noted that formation of the mixture at ambient temperature may be sufficient to cause the polymerisation to occur. However, if initiation of the polymerisation does not occur, or is proceeding too slowly, then heat may be applied to the mixture. For example, the mixture may be subjected to an activation by the application of heat to the mixture. Any suitable temperature may be applied such as from 20 to 100° C., such as from 25 to 75° C., such as from 30 to 60° C., such as from 40 to 50° C.
For the avoidance of doubt, when a nested set of numerical ranges is disclosed herein it is explicitly contemplated that any combination of the values listed may be used as the upper and lower end of the range. Thus, for the temperature values listed above, the following ranges are explicitly contemplated:
When a magnet is used in the method, any suitable magnet may be used. For example, the magnet(s) employed herein may be made from the materials discussed hereinbefore for use in the magnetic nanoparticles or they may be an electromagnet.
When magnet(s) are used in the polymerisation method, the magnetic nanocomposite material dispersed within the mixture in the vessel will be attracted towards the magnet(s). This means that the magnetic nanocomposite material becomes concentrated in area(s) close to a magnet.
Without wishing to be bound by theory, it is believed that, as the magnetic nanocomposite material interacts with the peroxide source to form peroxide radicals, the concentration of the magnetic nanocomposite material in area(s) close to a magnet results in a concentration gradient of peroxide radicals within the mixture, with the highest concentration of peroxide radicals being closest to the area(s) in the vessel close to a magnet and an increasingly lower concentration the further from a magnet that one travels. Given that the peroxide radicals initiate the polymerisation reaction, the highest concentration of polymers would be expected to occur closest to the area(s) affected by a magnet, while little or no polymer would be expected to be formed in areas that are not affected by a magnetic field. This effect may be seen, for instance, in
As noted previously, the method of polymerisation may be conducted in the absence of oxygen (e.g. under a suitable inert atmosphere, such as nitrogen or argon).
As will be appreciated, the magnets may be static or moving dynamically. As such, in embodiments where the one or more magnets are moved in a pattern, the resulting polymeric material may conform to the pattern provided by the one or more magnets. This is demonstrated in Examples 12-13 and
In embodiments where the one or more magnets are statically placed and the polymeric material may form at an area of the vessel corresponding to the location of the one or more magnets. In embodiments of the invention where a static pattern is desired to be formed the diameter of the magnetic nanocomposite material may be from 5 to 100 nm, such as from 6 to 50 nm, such as 8 to 30 nm.
Applications of the technology disclosed herein may relate to equipment that needs to be sealed (e.g. military and civilian personal protective equipment), in the electronics industry (e.g. to adhere a heat sink to a processing in need thereof), in medicine (e.g. to seal a wound), in the pipeline industry (e.g. to seal a leak), in the aerospace, automotive and rail industries (e.g. to act as a glass sealant in engine components; as a thread locking adhesive, and the like).
An example of a magnetic composite material that may be used herein is the core-shell is the second-generation magnetic nanoparticles carrying Cu2+ ions (MNPs-G2@Cu2+). As described in the examples below that was successfully formed and served as a magnetic responsive co-nanoinitiator and nanofiller.
The synthesis procedures and combination of anaerobic adhesive polymerization system are as following:
It will be appreciated that any other suitable fatty acid and solvents may be used in the above described process, which is intended as a guide to the manufacture of such materials.
It will be appreciated that this method may be adapted to suit the other products described herein.
It will be appreciated that the process above for the formation of the final product can be adapted to use the other metal ions as described hereinbefore that are suitable for this purpose.
As will be appreciated the monomer and peroxide source may be varied, as discussed hereinbefore.
Further aspects and embodiments of the invention will now be discussed by reference to the following non-limiting embodiments.
Materials
All chemicals were purchased from Sigma-Aldrich. No purification of the chemicals was carried out before use. The steel substrates (Q-Panel, RS-14) for single lap shear test that fulfilled the requirement of ASTM D1002, were purchased from Q-Lab.
Analytical Techniques
TEM-EDX
TEM (JEOL 2010 UHR, Japan) was equipped with EDX detector to image the morphology and investigate the elemental components of MNPs before and after surface modification. The dispersion of sample was drop-cast onto nickel grid for imaging and running EDX.
XRD analysis
XRD was performed by Pananalytical XRD (Cu-Kα radiation operated at 40 kV and 30 mA) to reveal the phase of MNPs compared with JCPDF database. Powder sample was prepared on the zero-background holder before the XRD experiment was run.
FTIR Spectroscopy
The FTIR spectra of the modified MNPs were obtained by PerkinElmer FTIR Frontier spectrometer. FTIR was performed to check the functional groups on the MNPs after each modification step.
XPS
XPS analysis was performed using an AXIS Supra spectrometer (Kratos Analytical, UK) equipped with a hemispherical analyzer (monochromatic Al K-alpha source (1487 eV) operated at 15 kV and 15 mA) to detect elemental components and the chemical environment on the surface of the materials. The samples were prepared by drop casting of the dispersion on indium tin oxide (ITO)-coated glass.
Inductively Coupled Plasma Mass Spectrometer (ICP-MS)
Perkin Elmer (model Elan-DRC-e) was employed to measure the concentration of elements in the sample dispersion.
TGA
TGA (Q500) was utilized to investigate the thermal stability of the sample, with a rate 10° C./min under N2 flow from 30-700° C.
Elemental Analysis (EA)
The organic moiety from carbon, nitrogen, hydrogen was analyzed by using EA (Elementar Vario EL Ill model, CHNS elemental analyzer).
VSM
The magnetization was measured at room temperature (RT) using a 8600 Series (Lake Shore Cryotronics) VSM.
Spherical MNPs (25-30 nm) were synthesized via a thermal decomposition method developed by Park et al. (J. Park et al., Nat. Mater. 2004, 3, 891-895).
Briefly, an iron-oleate precursor was prepared by refluxing a reaction of iron chloride (FeCl319 6H2O, 2.16 g) and sodium oleate (7.30 g) dissolved in ethanol (EtOH, 16 mL), deionized (DI) water (12 mL), and hexane (28 mL). The solution was heated to 70° C. for 4 h. The iron-oleate precursor was purified by extraction with DI water several times, and the solvents were removed in vacuo. The iron-oleate precursor was obtained as a waxy form.
Then, a reaction mixture of iron-oleate precursor:oleic acid (OA):1-octadecene=36:5.7:200 by weight were mixed at RT. The reaction was heated to 320° C. with a constant rate of 3.3° C. min−1, and holding for 30 min under inert condition with the use of Schlenk technique. The reaction mixture began to boil and form particles, and turbid and brownish black solids were observed in the solution. After the resulting solution with MNPs was cooled down to RT, hexane and i-propanol were used to precipitate the MNPs. The MNPs were separated by centrifugation and re-dispersed in cyclohexane to give pristine MNPs.
MNPs-G2@Cu2+ NCs were designed according to the concept of core-shell structure, as illustrated in
MNPs@—SiO2
To improve the functionality of the pristine MNPs prepared in Example 1, silane modification was introduced to attach appropriate linkers onto the surface of the pristine MNPs. The pristine MNPs were coated with silane compounds using the following procedure.
Igepal CO-520 (9.88 g) and anhydrous cyclohexane (90 mL) were stirred together for 10 min. Basic ammonium hydroxide (1.50 mL, 25%, NH4OH) solution was gradually added to the reaction mixture and was mixed well. After that, pristine MNPs (90 mg) were added into the reaction mixture. Tetraethyl orthosilicate (TEOS, 600 mL) was added dropwise into the reaction mixture and it was stirred for 16 h at RT. The resulting core-shell MNPs@SiO2 NPs were purified by washing and centrifuging with EtOH, and re-dispersing in EtOH. By doing so, a silica shell with an approximate thickness of 5-6 nm was coated on MNPs.
MNPsDNH2
To modify amine group onto MNPs@SiO2 NPs, 3-aminopropyltriethoxysilane (APS) was used as the coupling agent. MNPs@SiO2 core-shell NPs (30 mg) were dispersed well in a mixture of water and EtOH (1:1) by sonication before adding APS (50 μL). The reaction mixture was stirred continuously for 8 h at RT. The resulting MNPs-APS NPs were purified with EtOH and separated by centrifugation. Then, MNPs@APS (MNPs@NH2) was re-dispersed and sonicated in tetrahydrofuran (THF) for modification in further steps.
To promote the surface functionality, dendrimer ligands were grafted onto MNPs-APS NPs.
MNPs-CC1
Cyanuric chloride (1.85 g, CC), and trimethylamine (1.40 mL) were dissolved in THF. Subsequently, MNPs-APS (2 g) was dispersed in the reaction mixture to initiate the amine coupling reaction. The reaction mixture was stirred for 10 h to give MNPs-CC1. The resulting MNPs-CC1 were centrifuged and purified with hot THF several times.
MNPs-Generation 1 (MNPs-G1)
A dispersion of MNPs-CC1 (1 g) in DMF (12 mL), ethylenediamine (en, 0.53 mL) and triethylamine (TEA, 1.1 mL) were mixed at 60° C. for 12 h to give MNPs-generation 1 (MNPs-G1). The resulting MNPs-G1 were centrifuged and purified with hot EtOH several times.
MNPs-CC2
MNPs-CC2 was prepared from MNPs-G1 (1 g) by following the protocol for MNPs-CC1 except CC (1.66 g) and TEA (1.2 mL) in THF (20 mL) were used, and the reaction mixture was stirred for 14 h.
MNPs-Generation 2 (MNPs-G2)
MNPs-G2 was prepared from MNPs-CC2 (1 g) by following the protocol for MNPs-G1 except en (0.63 mL) and TEA (1.3 mL) in DMF (20 mL) were used, and the reaction mixture was stirred for 60° C. for 14 h.
MNPs-G2(Cu2+
MNPs-G2 was covalently coordinated with copper(II) (Cu2+) through the addition of copper(II) acetate (Cu(OAc)2) at the end of the dendrimer branches. A dispersion of MNPs-G2 (0.5 g) in DMF (10 mL) was mixed with Cu(OAc)2 (0.09 g) and stirred for 6 h. The suspension of MNPs-G2@Cu2+ was subsequentially centrifuged and washed with acetone. Dark green MNPs-G2@Cu2+ was then obtained. The resulting MNPs-G2@Cu2+ was stored in the fridge. The copper content of MNPs-G2@Cu2+ was measured with ICP-MS prior to use.
The materials prepared in Examples 1 and 2 were taken for characterization studies.
Results and Discussion
The well-dispersed spherical and pristine MNPs with a diameter range of 15-21 nm were confirmed by the high-resolution TEM micrograph as depicted in
The surface of the pristine MNPs were modified with silane through selective coating of TEOS on the MNPs surface (MNPs@SiO2) to enhance the functionality and improve chemical stability.
To examine the organic moieties from dendrimer modification at each generation, TGA and EA characterization were carried out. The TGA and EA characterization evidently supported the sequence of dendrimer growth from G1 to G2 (
To further prove the sequence of dendrimer growth on the MNPs surface, MNPs-APS, MNPs-G1, and MNPs-G2 samples were analyzed by XPS as illustrated in
XPS calculations:
The XPS peak area ratio of N/C (triazine) from MNPs-G1=437/1370=0.32 The XPS peak area ratio of N/C (triazine) from MNPs-G2=1084/1514=0.72
The XPS peak area ratio of N (triazine)/N (branch) from MNPs-G1=437/4291=0.10 The XPS peak area ratio of N (triazine)/N (branch) from MNPs-G2=1084/3837=0.28 According to the higher generation of dendrimer, the number of amino groups on the terminal branches increased exponentially with each generation of growth, which allowed multiple reactive sites for self-assembly with Cu(II) via electrostatic interaction (R. K. Sharma et al., Green Chem. 2016, 18, 3184; and V. V. Narayanan & G. R. Newkome, in Dendrimers, Springer Berlin Heidelberg, Berlin, Heidelberg 1998, 19-77).
The MNPs-G2@Cu2+ core-shell structure was investigated by TEM-EDX. The diameter obtained after copper immobilization on MNPs-G2 was 31 nm. The dendrimer growth was evidently shown by the thicker layer compared with core-shell MNPs@APS structure. From the TEM micrograph (
VSM revealed the magnetic properties of pristine MNPs and MNPs-G2@Cu2+ NCs (
Therefore, it is confirmed that MNPs-G2@Cu2+ NCs were successfully synthesized. The amino functional groups from dendrimer immobilized with copper content on MNPs@SiO2 (MNPs-G2@Cu2+ NCs) represent an advanced nano-architecture design of catalyst and filler with a unique advantage of being magnetic field responsive.
The preparation of the polymerization systems is described below. The same molar equivalent of each component was used in each system. Cu(OAc)2 was utilized as the copper source in the control systems.
TRIEGMA+tert-butyl peroxybenzoate
TRIEGMA (1.53 mmol) and tert-butyl peroxybenzoate (98% peroxide, 0.21 mmol) were mixed.
TRIEGMA+Cu(OAc)2
TRIEGMA (1.53 mmol) and Cu(OAc)2 (0.249 μmol) were mixed.
tert-butyl peroxybenzoate+Cu(OAc)2
Tert-butyl peroxybenzoate (98% peroxide, 0.21 mmol) and Cu(OAc)2 (0.249 μmol) were mixed.
TRIEGMA+tert-butyl peroxybenzoate+Cu(OAc)2 (anaerobic adhesive control)
TRIEGMA (1.53 mmol), tert-butyl peroxybenzoate (98% peroxide, 0.21 mmol) and Cu(OAc)2 (0.249 μmol, copper content) were mixed.
TRIEGMA+tert-butyl peroxybenzoate+MNPs-G2@Cu2+ (MNPs-G2(@Cu2+ adhesive)
MNPs-G2@Cu2+ adhesive was prepared from MNPs-G2@Cu2+ by following the protocol for 35 anaerobic adhesive control except MNPs-G2@Cu2+ NCs were used instead of Cu(OAc)2. The concentration of Cu(II) on MNPs-G2@Cu2+ NCs was analyzed using ICP-MS.
All the polymerization systems were cured under a deoxygenated environment (in glovebox) for 24 h.
The performance of MNPs-G2@Cu2+ NCs toward redox radical polymerization was evaluated using the polymerization systems prepared in Example 4.
Results and Discussion
The polymerization of TRIEGMA monomer was initiated in the presence of MNPs-G2@Cu2+ NCs with tert-butyl peroxybenzoate. The direct use of Cu(OAc)2 as the initiator was used for comparison.
The digital images of the cured polymers in vials are depicted in
The mechanical properties of the cured control and MNPs-G2@Cu2+ polymers were investigated.
Tensile Test
The MNPs-G2@Cu2+ and control polymerization systems in Example 4 were taken for post-cure heat treatment according to literature (D. Lascano et al., Polymers 2019, 11, 1354; and Y. H. Bagis & F. A. Rueggeberg, Dent. Mater. 2000, 16, 244-2477).
The reaction mixture of the anaerobic adhesive control and MNPs-G2@Cu2+ adhesive prepared in Example 4 was each cured in a rectangular-shaped Teflon mold. The polymerization occurred under deoxygenated environment (in glovebox) at RT. After that, the samples were taken for post-cure heat treatment. The samples were treated with a hot air gun (100° C.) until a freestanding form was obtained. Finally, specimens with 15 mm width, 1 mm thickness, and 10 mm initial nominal gauge length (the length between the grippers of the mechanical tester) were obtained.
The tensile stress-strain test was conducted using a mechanical tester (MTS Criterion, model 43) with a 1 kN load cell and a strain rate of 1.27 mm min−1 at RT. The data were monitored and recorded in real time by a connected computer. The stress was calculated using the equation, σ=F/A, where F is the load, and A is the bonding area of the adhesive.
The strain was calculated from ε=ΔL/L, where ΔL is the elongation of the sample compared with the initial length (L) of the sample. The Young's modulus was acquired from the slope at the beginning of the stress-stain curve (linear region).
Results and Discussion
The presence of the C═C signal (1637 cm−1) on the FT-IR spectra of the cured control and MNPs-G2@Cu2+ polymers (
A tensile test on the anaerobic polymer initiated by MNPs-G2@Cu2+ (
The interfacial adhesion of cured TRIEGMA was carried out by using single lap shear strength test to evaluate the adhesive property.
Single Lap Shear Adhesion Test
The surface of the stainless-steel substrates (25 mm width×102 mm length x 2 mm thickness) was cleaned with iso-propanol for surface pre-treatment. To control the thickness of the adhesive (160-170 μm) between the adherends, the stainless-steel substrate was framed by double-sided tape on the rough side. The reaction mixture of the anaerobic adhesive control and MNPs-G2@Cu2+ adhesive prepared in Example 4 was each applied onto the bonding area (20 mm width×13 mm length) which was secured with a clip. The panels were treated overnight under deoxygenated environment (in glovebox) without elevating temperature applied. The lap shear test was conducted by using a mechanical tester (MTS Criterion, model 43) with a 1 kN load cell and a strain rate of 1.27 mm min−1 at RT.
Results and Discussion
The bonding area between the adherends of both systems (MNPs-G2@Cu2+ and control) were physically secured under deoxygenated condition at 24 h polymerization time, without a trace of wet adhesive leftover. Typically, the inert species generated via redox-radical polymerization are suppressed by the active metal surface, resulting in better polymerization at RT under deoxygenated condition. According to
The magnetic field induced localized polymerization of the MNPs-G2@Cu2+ adhesive prepared in Example 4 was evaluated.
Magnetically Localized Polymerization
The polymerization of TRIEGMA monomer was magnetically initiated in the presence of MNPs-G2@Cu2+ with tert-butyl peroxybenzoate (
Results and Discussion
The localized redox-initiated radical polymerization was magnetically induced by the synergistic function of initiators between MNPs-G2@Cu2+ and peroxid, as depicted in
MMPs were prepared and developed from the original method by Zhao et al. (Zhao, Y. et al., Chem. Eng. J. 2014, 235, 275-283).
FeCl3·6H2O (1.35 g, 2.5 mmol) was fully dissolved in ethylene glycol (40 mL), followed by the addition of polyethylene glycol (PEG-4000, 1.0 g), sodium acetate (3.6 g), and trisodium citrate (0.72 g). The reaction mixture was stirred vigorously at 70° C. for 1-2 h until it was completely homogeneous. The resulting mixture was sealed in Teflon-lined stainless-steel autoclaves, and heated to 200° C. for 8 h in the oven. The resulting black reaction mixture was washed several times with DI water and EtOH, and dried at 60° C. in the vacuum oven to obtain bare MMPs as a black or brownish powder.
The surface of the bare MMPs prepared in Example 9 was modified by following the protocols in Example 2.
MMPs@SiO2
MMPs@SiO2 was prepared from bare MMPs by following the protocol for MNPs@SiO2.
MMPs-G2
MMPs-G2 was prepared from bare MMPs by following the protocol for MNPs-G2.
MMPs-G2@Cu2+
MMPs-G2@Cu2+ was prepared from MMPs-G2 by following the protocol for MNPs-G2@Cu2+.
The materials prepared in Examples 9 and 10 were taken for characterization studies.
Results and Discussion
The bigger size (250±23 nm) of MMPs was shown by TEM micrograph (
Magnetic patterning (static patterning) studies were carried out on a MMPs-G2@Cu2+ and TRIEGMA polymerization system.
MMPs-G2@Cu2++TRIEGMA
TRIEGMA (2.40 mL), tert-butyl peroxybenzoate (98% peroxide, 240 μL), and MMPs-G2@Cu2+ (prepared in Example 10, 0.249 μmol copper content) were mixed under inert condition in a glovebox.
Magnetic Patterning (Static Patterning)
The pattern was created by using a circular magnet under the petri dish/substrate, as shown in the setup design in
Results and Discussion
Magnetic patterning (dynamic patterning) studies were carried out on the MMPs-G2@Cu2+ and TRIEGMA polymerization system prepared in Example 12.
Magnetic Patterning (Dynamic Patterning)
The pattern was created by using a permanent magnet to draw the on-demand pattern under the petri dish/substrate, as shown in the setup design in
Results and Discussion
A prepolymer system was developed to be more viscous than the TRIEGMA monomer since we believe that a prepolymer with higher viscosity can secure the magnetic pattern better than TRIEGMA monomer which has lower viscosity. Magnetic static and dynamic patterning were carried out as described in Examples 12 and 13, respectively.
Prepolymer System
A prepolymer was prepared from HEMA (4000 μL), TRIEGMA (90 μL), peroxide (210 μL), copper(II) tetrafluoroborate (Cu(BF4)2, 2140 μL), and ethylene glycol (15 mL) under inert condition at 60-70° C. for 4 min.
Results and Discussion
A static pattern was seen after placing the substrate above circular magnet for 10 min under inert condition at 40-50° C. (
Number | Date | Country | Kind |
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10202011744P | Nov 2020 | SG | national |
Filing Document | Filing Date | Country | Kind |
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PCT/SG2021/050726 | 11/25/2021 | WO |