Stimuli-responsive liquid crystalline networks

Patent metadata

Field	Value
Publication number	US-10253261-B2
Application number	US-201715409717-A
Country	US
Kind code	B2
Filing date	Jan 19, 2017
Priority date	Jan 19, 2016
Publication date	Apr 9, 2019
Grant date	Apr 9, 2019

Abstract

Liquid crystalline network compositions comprising azo-containing aromatic epoxy units cross-linked with alkylene diacid units having alkylene segments containing at least one methylene unit, wherein the azo-containing aromatic epoxy units and alkylene diacid units are connected by ester linkages resulting from ring-opening esterification between the epoxy units and alkylene diacids, and wherein the azo-containing aromatic epoxy units and alkylene diacid units are in a molar ratio that results in the liquid crystalline network composition exhibiting a glass transition temperature (T g ) of at least 25° C. Methods for producing these compositions and their use in light- or thermal-activated physical deformation, shape memory applications, and self-healing, as well as their ability to be recycled and used in additive manufacturing processes are also described.

First claim

What is claimed is:

1. A liquid crystalline network composition comprising azo-containing aromatic epoxy units cross-linked with alkylene diacid units having alkylene segments containing at least one methylene unit, wherein the azo-containing aromatic epoxy units and alkylene diacid units are connected by ester linkages resulting from ring-opening esterification between the epoxy units and alkylene diacids, and wherein the azo-containing aromatic epoxy units and alkylene diacid units are in a molar ratio that results in the liquid crystalline network composition exhibiting a glass transition temperature (T g ) of at least 25° C.

2. The composition of claim 1 , wherein the liquid crystalline network composition possesses a thermal stability of the liquid crystalline phase (T lc ) of at least 50° C.

3. The composition of claim 1 , wherein said azo-containing aromatic epoxy units possess at least two phenyl rings connected by an azo (—N═N—) linking group, and each of said at least two phenyl rings is connected directly, or indirectly via a linker, to at least one epoxy group.

4. The composition of claim 1 , wherein said alkylene diacid units have alkylene segments containing at least three methylene units.

5. The composition of claim 1 , wherein said alkylene diacid units have alkylene segments containing at least four methylene units.

6. The composition of claim 1 , wherein said alkylene diacid units have alkylene segments containing at least five methylene units.

7. The composition of claim 1 , wherein said molar ratio is a molar ratio of azo-containing aromatic epoxy units to alkylene diacid units of 0.5:1 to 1.5:1.

8. The composition of claim 1 , wherein said T g is at least 30° C. and up to 70° C.

9. The composition of claim 1 , wherein said liquid crystalline network composition further comprises 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

10. A method of producing a liquid crystalline network composition, the method comprising cross-linking azo-containing aromatic epoxy molecules with alkylene diacid molecules containing at least one methylene unit at a processing temperature of at least 120° C. to 250° C., wherein the azo-containing aromatic epoxy molecules and alkylene diacid molecules are in a molar ratio that results in the liquid crystalline network composition exhibiting a glass transition temperature (T g ) of at least 25° C., and said cross-linking comprises formation of ester linkages by ring-opening esterification between the epoxy units and alkylene diacids.

11. The method of claim 10 , wherein the liquid crystalline network composition possesses a thermal stability of the liquid crystalline phase (T lc ) of at least 50° C.

12. The method of claim 10 , wherein said azo-containing aromatic epoxy molecules possess at least two phenyl rings connected by an azo (—N═N—) linking group, and each of said at least two phenyl rings is connected directly, or indirectly via a linker, to at least one epoxy group.

13. The method of claim 10 , wherein said alkylene diacid molecules have alkylene segments containing at least three methylene units.

14. The method of claim 10 , wherein said alkylene diacid molecules have alkylene segments containing at least four methylene units.

15. The method of claim 10 , wherein said alkylene diacid molecules have alkylene segments containing at least five methylene units.

16. The method of claim 10 , wherein said molar ratio is a molar ratio of azo-containing aromatic epoxy molecules to alkylene diacid molecules of 0.5:1 to 1.5:1.

17. The method of claim 10 , wherein said T g is at least 30° C. and up to 70° C.

18. The method of claim 10 , wherein said azo-containing aromatic epoxy molecules and alkylene diacid molecules are cross-linked in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a ring-opening and transesterification catalyst, and the resulting liquid crystalline network composition further comprises 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

19. A method of light-activated mechanical deformation of a liquid crystalline network composition, the method comprising:
providing a liquid crystalline network composition comprising azo-containing aromatic epoxy units cross-linked with alkylene diacid units having alkylene segments containing at least one methylene unit, wherein the azo-containing aromatic epoxy units and alkylene diacid units are connected by ester linkages resulting from ring-opening esterification between the epoxy units and alkylene diacids, and wherein the azo-containing aromatic epoxy units and alkylene diacid units are in a molar ratio that results in the liquid crystalline network composition exhibiting a glass transition temperature (T g ) of at least 25° C.; and
exposing said liquid crystalline network composition to electromagnetic radiation having a wavelength of 300-500 nm at an intensity sufficient to result in a bulk physical deformation of the liquid crystalline network, wherein said physical deformation occurs at least primarily by light-stimulated trans-cis-trans or trans-cis isomeric conversion of the azo groups without thermal decomposition of the liquid crystalline network composition.

20. The method of claim 19 , wherein said bulk physical deformation is reversible.

21. The method of claim 19 , wherein said bulk physical deformation comprises bending of the liquid crystalline network composition.

22. The method of claim 19 , wherein said electromagnetic radiation is polarized, and the polarized electromagnetic radiation selectively elicits a trans-cis-trans or trans-cis reversal in only those azo groups oriented in a direction where said trans-cis-trans or trans-cis reversal can be effected by the polarized electromagnetic radiation while other azo groups oriented in other directions do not undergo a trans-cis-trans or trans-cis reversal.

23. The method of claim 19 , wherein said electromagnetic radiation has a wavelength of 300-400 nm and is at an intensity sufficient to result in a thermally-induced liquid crystalline phase transition, wherein said thermally-induced liquid crystalline phase transition occurs as a result of absorption of said electromagnetic radiation by azo groups and subsequent release of thermal energy by said azo groups.

24. The method of claim 23 , wherein said thermally-induced liquid crystalline phase transition imparts a shape memory ability to the liquid crystalline network composition.

25. The method of claim 23 , wherein said liquid crystalline network composition contains a physical defect, and said electromagnetic radiation induces self-healing of the liquid crystalline network composition to the extent that said physical defect is no longer observable.

26. The method of claim 19 , wherein said azo-containing aromatic epoxy units possess at least two phenyl rings connected by an azo (—N═N—) linking group, and each of said at least two phenyl rings is connected directly, or indirectly via a linker, to at least one epoxy group.

27. The method of claim 19 , wherein said alkylene diacid units have alkylene segments containing at least three methylene units.

28. The method of claim 19 , wherein said alkylene diacid units have alkylene segments containing at least four methylene units.

29. The method of claim 19 , wherein said alkylene diacid units have alkylene segments containing at least five methylene units.

30. The method of claim 19 ,

Assignees

• Ut Battelle Llc
• Univ Washington State

Inventors

• Li Yuzhan
• Rios Orlando
• Kessler Michael Richard

Classifications

• C08G59/686

  containing nitrogen · CPC title

• C08G59/28 Primary

  containing acyclic nitrogen atoms · CPC title

• C08G2280/00

  Compositions for creating shape memory · CPC title

• C09K19/3814 Primary

  Polyethers · CPC title

• C08G59/4207

  aliphatic · CPC title