Systems and methods of creating liquid crystal polymers using stepped reactions
Provided herein are systems and methods for polymerizing and programming a liquid crystal polymer, including a liquid crystal elastomer (LCE) with two-way shape-memory via a stepped or self-limiting reaction. In the described method, the reaction may be stepped to achieve different aspects of the two-way shape-memory effect in the produced LCE. In one embodiment, the method creates a polydomain LCE body with a completed thiol-acrylate Michael addition reaction polymerization. The method may further crosslink the polydomain LCE body under a stimulus, thereby locking a domain state in a portion of the polymer. A two-way shape-memory effect of the LCE may thereafter be programmed and locked into the LCE the second stage polymerization reaction. The self-limiting reaction allows for unprecedented control over LCE domain states and cross-linking densities, as well as the resultant mechanical and optical properties of the LCE formed.
1. A method comprising:
creating a monomeric solution with a non-stoichiometric ratio of acrylate functional groups to thiol functional groups in the monomeric solution, the non-stoichiometric ratio being greater than 1;
causing a first polymerization of the monomeric solution that is limited by the non-stoichiometric ratio, resulting in a LCE body with a surplus of unreacted acrylate functional groups; and
deforming with a first bias force the LCE body along at least one dimension of the LCE body into a first shape;
wherein the first shape aligns a plurality of polydomains in the LCE body into a temporary monodomain.
2. The method of claim 1 , further comprising:
activating reversible shape-memory actuation of the LCE body via exposing the LCE body to a second temperature and a second bias force.
3. The method of claim 1 , further comprising:
activating a reversible shape-memory actuation of the LCE body via exposing the LCE body to a second temperature while the LCE body is under a strain.
4. The method of claim 1 , wherein a monomer of the monomeric solution is di-functional and includes both acrylate functional groups and thiol functional groups.
5. The method of claim 1 , wherein the monomeric solution is a mixture, the method further comprising:
combining into the mixture a mesogenic monomer and a crosslinking agent in order to produces the non-stoichiometric ratio.
6. The method of claim 5 , wherein the mixture further includes a flexible linear builder with thiol functional groups on two ends.
7. The method of claim 5 , the method further for producing a permanent monodomain in the LCE body and thereby defining a programmed shape of a two-way shape-memory effect, and wherein, the non-stoichiometric ratio is further less than 2:1, the method further comprising:
creating a permanent monodomain in the LCE body from the temporary monodomain by causing a second polymerization of a portion of surplus unreacted acrylate functional groups in a portion of the LCE body, while the portion of the LCE body is in the second shape.
8. The method of claim 7 , wherein the two-way shape-memory effect of the liquid crystal elastomer is controlled by a change in temperature in the LCE body.
9. The method of claim 7 , wherein the two-way shape-memory effect of the liquid crystal elastomer is controlled by electromagnetic radiation on the LCE body.
10. The method of claim 7 , further comprising:
further combining into the mixture a photoinitiator.
11. The method of claim 10 , wherein the second polymerization of the portion of surplus unreacted acrylate functional groups is performed by irradiation of the LCE body.
12. The method of claim 7 , wherein the second polymerization of the portion of surplus unreacted acrylate functional groups is performed by changing a temperature of the LCE body.
13. The method of claim 7 , wherein the second polymerization leaves a remaining portion of surplus acrylate functional groups unreacted in a second portion of the LCE body.
14. The method of claim 7 , wherein the second polymerization is confined to a first spatially-limited portion of the LCE body.
15. The method of claim 14 , wherein the second polymerization is confined by a photomask controlling irradiation that controls the second polymerization of the LCE body.
16. The method of claim 14 , wherein the second polymerization is confined by a temperature gradient that controls the second polymerization of the LCE body.
17. The method of claim 7 , further comprising:
third crosslinking a second spatially-limited portion after stretching the different portion of the LCE body to a third shape.
18. The method of claim 17 , wherein the third crosslinking completes bonding all remaining unreacted acrylate functional groups in the LCE body.
19. A method comprising:
creating a monomeric solution with a non-stoichiometric ratio of acrylate functional groups to thiol functional groups in the monomeric solution, the non-stoichiometric ratio being greater than 1;
causing a first polymerization of the monomeric solution at a first temperature that is limited by the non-stoichiometric ratio, resulting in a liquid crystal elastomer (LCE) body with a surplus of unreacted acrylate functional groups; and
providing a stimulus to transition a portion of the LCE body to a different molecular domain configuration selected from the group consisting of: isotropic, polydomain, and monodomain.
20. The method of claim 19 , wherein the portion of the LCE body is a first portion of the LCE body, the method further comprising:
causing a second polymerization of a portion of surplus unreacted acrylate functional groups in a second portion of the LCE body and thereby producing in the second portion of the LCE body a permanent domain configuration selected from the group consisting of: isotropic, polydomain, and monodomain.