Patent Application
20250129219
Shape memory polymers are smart materials that can be shaped into temporary forms and recover the permanent shapes by external trigger on demand. The thermally triggered shape memory effect is particularly useful and widely studied because it is easy to achieve and no additional structures are needed. As for the two-way shape memory effect, its primary actuation feature is thermally opposite to common physics. Namely, two-way shape memory polymers expand upon cooling and contract upon heating. The two-way shape memory effect was first observed in liquid crystalline elastomers in 2001. Then, Mather et al. reported the two-way shape memory effect in a crosslinked semi-crystalline polymer network—poly(cyclooctene). After that, various two-way shape memory polymer systems with varying actuation strains and working temperature ranges were developed.
Polymer gels are soft and stretchable and are composed of polymer networks swollen with small molecules, such as water for hydrogels, ionic liquid for ionogels, and organic solvent for organogels. Compared to hydrogels and ionogels, organogels are more stable to thermal and moisture change due to the stability of organic solvents, which are more feasible in a wide variety of applications. Generally, organogels can be prepared by swelling crosslinked polymers in organic solvents. However, the obtained organogels are sometimes inhomogeneous because of a concentration gradient associated with depth.
Stimuli-responsive gels have attracted attention due to their unique properties and smart features. Tremendous efforts have been devoted to the development of various functional gels, such as hydrogels for drug release and ionogels for strain sensing. Indeed, some shape memory polymer gels have been reported recently. For example, Zhao et al. developed a highly stretchable, shape memory organohydrogel by utilizing phase-transition micro inclusions. Cai and coworkers demonstrated a high strength, recyclable, anti-swelling and shape-memory hydrogels based on crystal microphase crosslinking for flexible sensor applications. However, the two-way shape memory properties of polymer gels remain unexplored.
Previously, a thermally crosslinked poly(1,4-butadiene) material has been synthesized with reversible elongation upon cooling and contraction upon heating at temperatures below 0° C. Both entropy and enthalpy mechanisms were responsible for the reversible actuation of this system. However, the actuation strain was still not high enough for many common applications. Furthermore, the actuation reversibility of this polymer system was only 75%, which is quite low for long-term usage in practical applications.
Despite advances in shape-memory polymer and organogel research, there is still a scarcity of organogels having two-way shape-memory properties that are homogeneous, that exhibit a high actuation strain as well as actuation reversibility. Ideally, the organogels would be homogeneous and would not exhibit concentration gradients of their components associated with depth in the organogel structure. An ideal organogel could be easily and quickly crosslinked without requiring a large energy input. In one embodiment, the organogel and crosslinking rate could be modified to allow 3D printing of the organogel. In some embodiments, such an organogel would be recyclable. These needs and other needs are satisfied by the present disclosure.
In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, the disclosure, in one aspect, relates to two-way shape memory organogels including at least a crosslinked polymer and an organic free phase. In a further aspect, the un-crosslinked polymer or polymer precursor such as, for example, an oligomer, can be crosslinked by a photoinitiator through free-radical polymerization. In one aspect, the polymer can be cis-poly(1,4-butadiene), while the organic free phase can be a plasticizer such as, for example, bis(2-ethylhexyl) phthalate. The two-way shape memory organogels have excellent stability in high vacuum environments and at high temperatures, desirable mechanical properties, and reliable actuation reversibility. Also disclosed are methods of making the organogels and sensors and other devices that include the organogels.
Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. In addition, all optional and preferred features and modifications of the described embodiments are usable in all aspects of the disclosure taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.
Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Disclosed herein is the use of a common plasticizer as a free organic phase to develop polybutadiene (PBD)-based organogels. In one aspect, owing to the incorporation of a photo-initiator, the organogels can be crosslinked by UV light in several minutes. In another aspect, the organogels are ultrastable to high vacuum environments and high temperature. In a further aspect, and without wishing to be bound by theory, the PBD-based organogels exhibit a high two-way shape memory actuation strain due to the balanced melting/crystallization behavior and crosslinked molecular networks. In one aspect, the PBD-based organogels can be used in strain sensing applications.
In one aspect, in situ polymerization of monomer/oligomer in organic solvents is an effective method to fabricate homogeneous organogels such as those presently disclosed. In another aspect, among known polymerization methods, photo-induced polymerization and/or crosslinking is feasible in practical usage, is energy-saving, and can be achieved in minutes instead of hours or days. In a further aspect, photo-induced crosslinking can be easily modified for 3D printing.
In one aspect, provided herein are two-way shape memory organogels including at least a crosslinked polymer, a photoinitiator, and an organic free phase. In an aspect, the polymer can be cis-poly(1,4-butadiene) (PBD). In an aspect, the PBD can have a molecular weight of from about 5000 to about 500,000 Da, or from about 10,000 Da to about 500,000 Da, or of about 5000; 10,000; 25,000; 50,000; 75,000; 100,000; 150,000; 200,000; 250,000; 300,000; 350,000; 400,000; 450,000; or about 500,000 Da, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values. In a further aspect, the polymer can be present at from about 10 wt % to about 100 wt %, or from about 20 wt % to about 60 wt %, or about 10, 20, 30, 40, 50, 60, 70, 80, 90, or about 100 wt %, or at about 37 wt % of the organogel. In some aspects, the polymer has a glass transition temperature (Tg) of from about −60° C. to about −110° C., or from about 100° C. to about −110° C., or of about −60, −65, −70, −75, −80, −85, −90, −95, −100, −105, or −110° C., or a combination of any of the foregoing values, or a range encompassing any of the foregoing values. In another aspect, the polymer has a viscosity (Mooney ML 1+4 at 100° C.) of from about 10 to about 100, from about 40 to about 50, or of about 10, 20, 30, 40, 50, 60, 70, 80, 90, or about 100, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values.
In an aspect, the photoinitiator can be 2-hydroxy-2-methylpropiophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, 2,2-bimethoxy-2-phenylacetophenone, 1-Hydroxycyclohexyl phenyl ketone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4-diethyl-9H-thioxanthen-9-one, a triarylsulfonium hexafluorophosphate salt, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, a triarylsulfonium hexafluoroantimonate salt, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate, 2-methyl-4′-(methylthio)-2-morpholinopropiophenone, 2-isopropylthioxanthone, benzophenone, 4-chlorobenzophenone, 4-benzoylbiphenyl, 2-benzyl-2-(dimethylamino)-4′-morpholino-butyrophenone, or any combination thereof. In one aspect, the photoinitiator is 2-hydroxy-2-methylpropiophenone. In some aspects, the photoinitiator is present at from about 0.5 wt % to about 5 wt %, or at about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or about 5 wt %, or is about 3 wt % of the organogel.
In some aspects, the organic free phase includes a plasticizer such as, for example, bis(2-ethylhexyl) phthalate, dioctyl phthalate, dibutyl phthalate, diisobutyl phthalate, tritolyl phosphate, trioctyl phosphate, butyl oleate, tributyl citrate, epoxidized soybean oil, dibutyl sebacate, dioctyl sebacate, bis(2-ethylhexyl) adipate, dioctyl adipate, tributyl O-acetylcitrate, Tri(ethylene glycol) bis(2-ethylhexanoate), butyl oleate, epoxidized linseed oil, butyl epoxy stearate, or any combination thereof. In one aspect, the plasticizer is bis(2-ethylhexyl) phthalate. In one aspect, the organic free phase is present at from about 40 wt % to about 80 wt % in the two-way shape memory organogel, or at about 40, 45, 50, 55, 60, 65, 70, 755, or about 80 wt %, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values. In one aspect, the organic free phase is present at 60 wt %.
In one aspect, the disclosed two-way shape memory organogels are stable in high vacuum. Further in this aspect, the two-way shape memory organogels can lose less than 5%, less than 4%, less than 3%, or less than 2% total weight after 48 hours in a high vacuum environment. In another aspect, the disclosed two-way shape memory organogels are stable at high temperatures. Further in this aspect, the two-way shape memory organogels lose less than about 5%, less than 4%, less than 3%, or less than 2% weight after 2 hours at 100° C.
In another aspect, the two-way shape memory organogels have a reversible elongation upon cooling (EUC) of from about 50% to about 200%, or of about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or about 200%, or of about 156% and a reversible contraction upon heating (CUH) of from about 50% to about 200%, or of about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or about 200%, or of about 151%. In another aspect, actuation reversibility of the two-way shape memory organogels is greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or is at least 97%.
In one aspect, the two-way shape memory organogels have a storage modulus of from about 0.01 MPa to about 1,000 MPa, or of about 0.01, 0.1, 1, 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or about 1,000 MPa, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values. In an aspect, storage modulus can depend on temperature and frequency. In another aspect, the two-way shape memory organogels have a loss modulus of from about 0.001 MPa to about 1,000 MPa, or of about 0.001, 0.01, 0.1, 1, 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or about 1,000 MPa, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values. In an aspect, loss modulus can depend on temperature and frequency. In still another aspect, the two-way shape memory organogels have a complex viscosity of from about 10 Pas to about 1,000,000 Pa·s, or about 10; 100; 1000; 10,000; 100,000; 250,000; 500,000; 750,000; or about 1,000,000 Pa·s, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values. In one aspect, the complex viscosity can be dependent on temperature and frequency. In still another aspect, the two-way shape memory organogels have a melting point of form about 0° C. to about −40° C., or of from about −10° C. to about −25° C., or of about 0, −5, −10, −15, −20, −25 −30, −35, or about −40° C., or a combination of any of the foregoing values, or a range encompassing any of the foregoing values.
In one aspect, the two-way shape memory organogels can complete three or more actuation cycles without degradation. In still another aspect, creep strain of the two-way shape memory organogels is from about 5% to about 25% after three actuation cycles, or is about 5, 10, 15, 20, or about 25% after three actuation cycles. In still another aspect, the two-way shape memory organogels have an elongation at break of from about 100% to about 2000%, or of from about 400% to about 1000%, or of about 100, 250, 500, 750, 1000, 1250, 1500, 1750, or about 2000%, or a combination of any of the foregoing values, or a range encompassing any of the foregoing values.
In one aspect, provided herein is a method for making the disclosed two-way shape memory organogels, the method including at least the steps of:
In a further aspect, the organic solvent can be chloroform. In another aspect, step (a) is conducted for at least 3 days. In still another aspect, curing is accomplished using UV irradiation. In one aspect, the method further includes 3D printing the uncrosslinked organogel into a three-dimensional shape prior to performing step (d).
Also disclosed herein are devices including the disclosed two-way shape memory organogels. In one aspect, the devices can be sensors such as, for example, strain sensors or temperature sensors. In a further aspect, when the device is a strain sensor, the device further includes conductive particles such as, for example, metallic particles, carbon black, multiwalled carbon nanotubes (MWCNTs), graphene flakes, graphite flakes, MXene nanosheets, silver nanowires, or any combination thereof, embedded in a surface of the two-way shape memory organogel. In another aspect, the device can be an actuator. In one aspect, when the device is an actuator, it can be useful in wearable electronics, soft robotics, and structural health monitoring, among other applications.
Many modifications and other embodiments disclosed herein will come to mind to one skilled in the art to which the disclosed compositions and methods pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosures are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. The skilled artisan will recognize many variants and adaptations of the aspects described herein. These variants and adaptations are intended to be included in the teachings of this disclosure and to be encompassed by the claims herein.
Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure.
Any recited method can be carried out in the order of events recited or in any other order that is logically possible. That is, unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.
All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided herein can be different from the actual publication dates, which can require independent confirmation.
While aspects of the present disclosure can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present disclosure can be described and claimed in any statutory class.
It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed compositions and methods belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.
Prior to describing the various aspects of the present disclosure, the following definitions are provided and should be used unless otherwise indicated. Additional terms may be defined elsewhere in the present disclosure.
As used herein, “comprising” is to be interpreted as specifying the presence of the stated features, integers, steps, or components as referred to, but does not preclude the presence or addition of one or more features, integers, steps, or components, or groups thereof. Moreover, each of the terms “by”, “comprising,” “comprises”, “comprised of,” “including,” “includes,” “included,” “involving,” “involves,” “involved,” and “such as” are used in their open, non-limiting sense and may be used interchangeably. Further, the term “comprising” is intended to include examples and aspects encompassed by the terms “consisting essentially of” and “consisting of.” Similarly, the term “consisting essentially of” is intended to include examples encompassed by the term “consisting of.
As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a polymer,” “a photoinitiator,” or “an organogel,” include, but are not limited to, mixtures or combinations of two or more such polymers, photoinitiators, or organogels, and the like.
It should be noted that ratios, concentrations, amounts, and other numerical data can be expressed herein in a range format. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms a further aspect. For example, if the value “about 10” is disclosed, then “10” is also disclosed.
When a range is expressed, a further aspect includes from the one particular value and/or to the other particular value. For example, where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g. the phrase “x to y” includes the range from ‘x’ to ‘y’ as well as the range greater than ‘x’ and less than ‘y’. The range can also be expressed as an upper limit, e.g. ‘about x, y, z, or less’ and should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘less than x’, less than y’, and ‘less than z’. Likewise, the phrase ‘about x, y, z, or greater’ should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘greater than x’, greater than y’, and ‘greater than z’. In addition, the phrase “about ‘x’ to ‘y”, where ‘x’ and ‘y’ are numerical values, includes “about ‘x’ to about ‘y’”.
It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of “about 0.1% to 5%” should be interpreted to include not only the explicitly recited values of about 0.1% to about 5%, but also include individual values (e.g., about 1%, about 2%, about 3%, and about 4%) and the sub-ranges (e.g., about 0.5% to about 1.1%; about 5% to about 2.4%; about 0.5% to about 3.2%, and about 0.5% to about 4.4%, and other possible sub-ranges) within the indicated range.
As used herein, the terms “about,” “approximate,” “at or about,” and “substantially” mean that the amount or value in question can be the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art such that equivalent results or effects are obtained. In some circumstances, the value that provides equivalent results or effects cannot be reasonably determined. In such cases, it is generally understood, as used herein, that “about” and “at or about” mean the nominal value indicated ±10% variation unless otherwise indicated or inferred. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about,” “approximate,” or “at or about” whether or not expressly stated to be such. It is understood that where “about,” “approximate,” or “at or about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.
As used herein, the term “effective amount” refers to an amount that is sufficient to achieve the desired modification of a physical property of the composition or material. For example, an “effective amount” of a free organic phase refers to an amount that is sufficient to achieve the desired improvement in the property modulated by the formulation component, e.g. achieving the desired two-way shape memory properties of the disclosed organogels. The specific level in terms of wt % in a composition required as an effective amount will depend upon a variety of factors including the amount and type of photoinitiator, amount and type of polymer, degree of crosslinking, and end use conditions (e.g., temperature, pressure, etc.) of the two-way shape memory organogel including the free organic phase.
As used herein, the terms “optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
A “shape memory polymer” as used herein is a smart material that can modify one or more properties (e.g. size, shape, stiffness, strain, stress, or the like) in response to an external stimulus (e.g. heat, light, pH, ion concentration, electric field, magnetic field, presence of a solvent, or the like). Shape memory polymers can return from these deformed states to their original state.
A “two-way shape memory polymer” as used herein is a smart material that can reversibly and repeatedly shift between its permanent shape and programmed temporary shape under external stimuli such as cycling temperatures. Depending on the training or programming, a two-way shape memory polymer can exhibit reversible actuation under external tension, under zero external load, or even under external compression.
As used herein, an “organogel” is a gel having an organic liquid phase within a three-dimensional, crosslinked network.
Unless otherwise specified, temperatures referred to herein are based on atmospheric pressure (i.e. one atmosphere).
Now having described the aspects of the present disclosure, in general, the following Examples describe some additional aspects of the present disclosure. While aspects of the present disclosure are described in connection with the following examples and the corresponding text and figures, there is no intent to limit aspects of the present disclosure to this description. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the present disclosure.
The present disclosure can be described in accordance with the following numbered aspects, which should not be confused with the claims.
Aspect 1. A two-way shape memory organogel comprising a crosslinked polymer, a photoinitiator, and an organic free phase.
Aspect 2. The two-way shape memory organogel of aspect 1, wherein the polymer comprises cis-poly(1,4-butadiene) (PBD) having a molecular weight of from about 5000 Da to about 500,000 Da
Aspect 3. The two-way shape memory organogel of aspect 1 or 2, wherein the polymer is present at from about 10 wt % to about 100 wt % of the organogel.
Aspect 4. The two-way shape memory organogel of any one of aspects 1-3, wherein the polymer has a glass transition temperature (Tg) of from about −60° C. to about −110° C.
Aspect 5. The two-way shape memory organogel of any one of aspects 1-4, wherein the polymer has a viscosity of from about 10 to about 100 (Mooney ML 1+4 at 100° C.).
Aspect 6. The two-way shape memory organogel of any one of aspects 1-5, wherein the photoinitiator comprises 2-hydroxy-2-methylpropiophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, 2,2-bimethoxy-2-phenylacetophenone, 1-Hydroxycyclohexyl phenyl ketone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4-diethyl-9H-thioxanthen-9-one, a triarylsulfonium hexafluorophosphate salt, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, a triarylsulfonium hexafluoroantimonate salt, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate, 2-methyl-4′-(methylthio)-2-morpholinopropiophenone, 2-isopropylthioxanthone, benzophenone, 4-chlorobenzophenone, 4-benzoylbiphenyl, 2-benzyl-2-(dimethylamino)-4′-morpholino-butyrophenone, or any combination thereof.
Aspect 7. The two-way shape memory organogel of any one of aspects 1-6, wherein the photoinitiator is present at from about 0.5 wt % to about 5 wt % of the organogel.
Aspect 8. The two-way shape memory organogel of any one of aspects 1-7, wherein the organic free phase comprises a plasticizer.
Aspect 9. The two-way shape memory organogel of aspect 8, wherein the plasticizer comprises bis(2-ethylhexyl) phthalate, dioctyl Phthalate, dibutyl phthalate, diisobutyl phthalate, tritolyl phosphate, trioctyl phosphate, butyl oleate, tributyl citrate, epoxidized soybean oil, dibutyl sebacate, dioctyl sebacate, bis(2-ethylhexyl) adipate, dioctyl adipate, tributyl O-acetylcitrate, Tri(ethylene glycol) bis(2-ethylhexanoate), butyl oleate, epoxidized linseed oil, butyl epoxy stearate, or any combination thereof.
Aspect 10. The two-way shape memory organogel of any one of aspects 1-9, wherein the organic free phase is present at from about 40 wt % to about 80 wt % in the two-way shape memory organogel.
Aspect 11. The two-way shape memory organogel of aspect 10, wherein the organic free phase is present at about 60 wt % in the two-way shape memory organogel.
Aspect 12. The two-way shape memory organogel of any one of aspects 1-11, wherein the two-way shape memory organogel loses less than 5% total weight after 48 h in a high vacuum environment.
Aspect 13. The two-way shape memory organogel of any one of aspects 1-12, wherein the two-way shape memory organogel loses less than about 5% total weight after 2 h at 100° C.
Aspect 14. The two-way shape memory organogel of any one of aspects 1-13, wherein the two-way shape memory organogel has a reversible elongation upon cooling (EUC) of from about 50% to about 200%.
Aspect 15. The two-way shape memory organogel of any one of aspects 1-14, wherein the two-way shape memory organogel has a reversible contraction upon heating (CUH) of from about 50% to about 200%.
Aspect 16. The two-way shape memory organogel of any one of aspects 1-15, wherein actuation reversibility is greater than 50%.
Aspect 17. The two-way shape memory organogel of aspect 16, wherein the two-way shape memory organogel has an actuation reversibility of about 97%.
Aspect 18. The two-way shape memory organogel of any one of aspects 1-17, wherein the two-way shape memory organogel has a storage modulus of from about 0.01 MPa to about 1,000 MPa.
Aspect 19. The two-way shape memory organogel of any one of aspects 1-18, wherein the two-way shape memory organogel has a loss modulus of from about 0.001 MPa to about 1,000 MPa.
Aspect 20. The two-way shape memory organogel of any one of aspects 1-19, wherein the two-way shape memory organogel has a complex viscosity of from about 10 Pa·s to about 1,000,000 Pa·s.
Aspect 21. The two-way shape memory organogel of any one of aspects 1-20, wherein the two-way shape memory organogel has a melting point of from about 0° C. to about −40° C.
Aspect 22. The two-way shape memory organogel of any one of aspects 1-21, wherein the two-way shape memory organogel can complete three or more actuation cycles without degradation.
Aspect 23. The two-way shape memory organogel of any one of aspects 1-22, wherein creep strain of the two-way shape memory organogel is from about 5% to about 25% after three actuation cycles.
Aspect 24. The two-way shape memory organogel of any one of aspects 1-23, wherein creep strain of the two-way shape memory organogel is about 9% after three actuation cycles.
Aspect 25. The two-way shape memory organogel of any one of aspects 1-24, wherein the two-way shape memory organogel has an elongation at break of from about 100% to about 2000%.
Aspect 26. A method for making the two-way shape memory organogel of any one of aspects 1-25, the method comprising:
Aspect 27. The method of aspect 26, wherein the organic solvent comprises chloroform.
Aspect 28. The method of aspect 26 or 27, wherein step (a) is conducted for at least 3 days.
Aspect 29. The method of any one of aspects 26-29, wherein curing is accomplished using UV irradiation.
Aspect 30. The method of any one of aspects 26-29, further comprising 3D printing the uncrosslinked organogel into a three-dimensional shape prior to performing step (d).
Aspect 31. A device comprising the two-way shape memory organogel of any one of aspects 1-25.
Aspect 32. The device of aspect 31, wherein the device comprises a sensor or an actuator.
Aspect 33. The device of aspect 32, wherein the sensor comprises a strain sensor or a temperature sensor.
Aspect 34. The device of aspect 33, wherein the strain sensor further comprises conductive particles selected from metallic particles, carbon black, multiwalled carbon nanotubes (MWCNTs), graphene flakes, graphite flakes, MXene nanosheets, silver nanowires, or any combination thereof embedded in a surface of the two-way shape memory organogel.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary of the disclosure and are not intended to limit the scope of what the inventors regard as their disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in° C. or is at ambient temperature, and pressure is at or near atmospheric.
Cis-poly(1,4-butadiene) (PBD) (Budene® 1208) was supplied by Goodyear Chemical (Akron, OH, USA). The viscosity is 46 (Mooney ML 1+4 @ 100° C.) and the onset glass transition temperature is −104° C. Chloroform, bis(2-ethylhexyl) phthalate, and 2-hydroxy-2-methylpropiophenone (97%) were purchased from Sigma-Aldrich and used as received.
First, 50 g of PBD were cut into small pieces and immersed into 950 g of chloroform for at least 3 days. The conical flask was fully sealed to avoid the evaporation of chloroform. After completely swelling, the mixture was vigorously stirred for 1 h to obtain a sticky homogeneous solution. Various amounts of plasticizer bis(2-ethylhexyl) phthalate and photoinitiator 2-hydroxy-2-methylpropiophenone were added into the solution upon further stirring. Chloroform was then removed by simple evaporation and overnight vacuum drying at room temperature. Three formulas with different amounts (40, 60, and 80 wt %) of plasticizer were prepared. The content of photoinitiator is constant (3 wt % of PBD) for all formulas. After completely removing the solvent, the obtained samples were named as PBD-40P, PBD-60P, and PBD-80P corresponding to the content of the plasticizer. As for UV curing, the obtained sticky samples were smeared into a plastic spacer with thickness of 1.2 mm clamped by two transparent plastic slides. The samples were maintained until the air bubbles disappeared. The samples were then cured in a UV chamber (IntelliRay 600, Uvitron International, USA) for 60 s under 80% irradiation intensity (232 nm, 45 mW/cm2). The crosslinked samples were abbreviated as c-PBD-40P, c-PBD-60P, and c-PBD-80P, respectively.
For demonstrating the strain sensing application, the organogel specimen was coated with multiwalled carbon nanotubes (20-40 nm of diameter, 5-15 μm of length) to increase the electrical conductivity. Specifically, the multiwalled carbon nanotube particles were homogeneously sprayed on the surface of the PBD-60P film. The obtained sample was wrapped by PTFE films and hot-pressed at 100° C. for 2 h. Finally, the sensor specimen was treated by ultrasonic cleaning in ethanol to remove the unbound carbon nanotubes.
Thermal behavior of the organogels was characterized by PerkinElmer 4000 differential scanning calorimeter (DSC) (MA, USA). About 5 mg of the samples was heated and cooled between −70 and 80° C. at a rate of 10° C. min−1; both the holding times at −70 and 80° C. were 2 min. The second heating-cooling cycle was conducted and profiled to remove the effect of thermal history. The purging rate of nitrogen gas was 30 mL min−1.
Storage modulus, loss modulus, and tan δ curves were collected by a Q800 dynamic mechanical analyzer (DMA) (TA Instruments, DE, United States) in multifrequency strain mode with a heating rate of 3° C./min and a frequency of 1 Hz. The temperature range was from −90° C. to 60° C.
Thermogravimetric analysis (TGA) was conducted by a Q5000 thermal analyzer (TA Co., USA). For non-isothermal test, the sample was heated from 25 to 800° C. at a heating rate of 10° C./min in nitrogen atmosphere. For isothermal test, the sample was rapidly heated from 25 to 100° C. at a heating rate of 100° C./min in nitrogen atmosphere, then isothermal at 100° C. for 120 min. The purging rate of nitrogen gas was 40 mL min−1.
Tensile test of dumbbell-shaped samples (ASTM D412) was performed by an expert 2610 MTS (ADMET, Norwood, MA, United States). The stretching rate was 20, 100, and 500 mm/min, respectively. For loading-unloading cycle test, the stretching rate was 20 mm/min. At least three parallel samples were used for tensile test.
Two-way shape memory performance was acquired with control-force mode using the Q800 dynamic mechanical analyzer (DMA) (TA Instruments, DE, USA). The tensile load and temperature were preprogrammed, and the strain change can be precisely recorded. The heating and cooling rate was 5° C. min−1. The isothermal time at −40° C. and 60° C. was 5 min and 3 min, respectively.
The stability of organogels was tested by drying in a vacuum oven at room temperature for various periods. The weight change was recorded by a balance.
The rheological behaviors of uncrosslinked specimens and crosslinked organogels were characterized with an HR 30 Discovery Hybrid Rheometer (TA Instruments, DE, USA) in parallel plate geometry (25 mm diameter and 1000 μm gap). Frequency sweep measurements were performed at 25° C. from 0.01 Hz to 100 Hz in dynamic mode with a strain of 1%. Stain sweep tests were performed at 25° C. from 0.01% to 100% in dynamic mode with an angular frequency of 10 rad/s.
The strain sensing properties were tested by coupling DMA (TA Instruments, DE, USA) and SourceMeter 2400 (Fotronic Co., MA). The specimen was stretched by DMA in strain rate mode at a rate of 5.0%/min to 20% and 50%, respectively. The change of electrical resistance was recorded in I-V mode by the SourceMeter 2400.
The addition of plasticizer can obviously change the viscoelastic behaviors of polymers. The storage modulus, loss modulus, and complex viscosity for pure PBD and PBD with various amounts of plasticizer were characterized by rheometer. First, the effect of oscillation strain on viscoelastic behavior was studied to determine the linear viscoelastic region. With increasing the content of plasticizer, the linear viscoelastic region extended to higher oscillation stain. Within the linear region, the 1% oscillation strain was selected to conduct the frequency sweep test.
Thermal properties of crosslinked PBD based organogels were characterized by DSC, and the corresponding profiles were displayed in
For the purpose of durability, the stabilities of organogels are of great importance in practical applications. The environmental stability was characterized by placing PBD based organogels in a high vacuum environment. The weight change of the organogels under 6×10−4 Pa environment was recorded and shown in
Thermal stability is another critical property for thermally triggered shape memory polymer systems. The non-isothermal test in inert atmosphere was conducted first to evaluate the thermal decomposition behaviors of PBD based organogels, as shown in
The comparison of two-way shape memory properties has been made to further validate the better performance of cPBD-60P organogel. As shown in
The PBD based organogels are stretchable and their mechanical properties are highly tunable by adding various amounts of plasticizer. As displayed in
Due to the stretchability, one promising application of the cPBD-60P sample is to serve as a strain sensor. The electrical conductivity can be easily achieved by a simple dry coating and hot-pressing procedure. The conductive multiwalled carbon nanotubes were tightly embedded on the surface of the cPBD-60P organogel. As displayed in
In summary, herein is disclosed a new kind of PBD based organogels with excellent stability using a commercial plasticizer as the organic phase. Specifically, the dynamic mechanical properties remain unchanged after placing the PBD based organogels in a high vacuum environment for 72 h. Owing to the melting/crystallization transition and crosslinked molecular network, the newly designed organogels exhibited a promising two-way shape memory property, which can be actuated below 0° C. with giant actuation strain. In particular, the EUC and CUH are 156% and 151% respectively, in the working temperature range of −40 to 60° C., which are higher than those of the reported systems. Besides the high actuation strain, the reversibility of the actuation is calculated to be 97%, demonstrating high actuation stability in practice. The PBD based organogel systems can be applied outdoors as actuators that are triggered by natural temperature change.
It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.
This application claims priority to, and the benefit of, U.S. provisional application Ser. No. 63/592,253 filed Oct. 23, 2023, which is hereby incorporated by reference in its entirety.
This invention was made with government support under grant numbers GR-00002850 and GR-00007711, both awarded by the National Science Foundation. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63592253 | Oct 2023 | US |
