LIQUID CRYSTALLINE POLYMERS

• US 20030228367A1
• Filed: 08/30/2002
• Published: 12/11/2003
• Est. Priority Date: 03/13/2000
• Status: Active Grant

• Current Assignee: Brown University
• Original Assignee: Brown University
• Inventors: Jacob, Jules S., Edwards, Edwin E., Chickering, Donald E. III, Mathiowitz, Edith, Jong, Yong S.
• Granted Patent: US 6,696,075 B2
• Time in Patent Office: Days
• US Class Current: 424/486
• CPC Class Codes: B29C 55/00 Shaping by stretching, e.g. drawing through a die; Apparatus therefor B29C61/08 takes precedence
• CPC Class Codes: B29C 55/18 by squeezing between surfaces, e.g. rollers
• CPC Class Codes: B29K 2105/0079 Liquid crystals
• CPC Class Codes: C09K 19/38 Polymers

Abstract

Methods for inducing a thermoplastic polymer, which can be non-mesogenic, to exhibit liquid crystalline properties have been developed. The method includes the steps of (a) heating the polymer from an initial temperature below its glass transition temperature (Tg) to a temperature greater than its Tg and below its melting temperature (Tm); (b) exposing the polymer to a pressure greater than about 2 metric tons/in², preferably between about 2 and 10 metric tons/in², preferably for at least about one minute, while maintaining the temperature greater than its Tg; and (c) cooling the polymer below the Tg while maintaining the elevated pressure. Unlike many prior art transition processes which are reversible, this process provides a liquid crystal state that can be maintained for years at ambient conditions. In a preferred embodiment, the plastics are bioerodible thermoplastic polymers, such as polyanhydrides, some polyesters, polyamides, and polyaromatics. The liquid crystalline polymers can be used in the controlled release or retention of substances encapsulated in the polymers. The polymer can be in a variety of forms including films, film laminants, and microparticles. In a preferred embodiment, the LC polymers are used to encapsulate therapeutic, diagnostic, or prophylactic agents for use in medical or pharmaceutical applications.

Claims

1. A method for inducing a liquid crystalline state in a polymer comprising the steps of:

(a) heating the polymer from an initial temperature below its glass transition temperature to a temperature greater than its glass transition temperature and below its melting temperature; and

(b) applying pressure to the polymer until a liquid crystalline state is induced in the polymer, while maintaining the temperature at greater than the glass transition temperature; and

(c) cooling the polymer below the glass transition temperature while maintaining the pressure.

2. The method of claim 1 wherein the pressure in step (b) and (c) is between about 28 and 140 MPa.

3. The method of claim 1 wherein the polymer is pressed in step (b) for greater than about one minute.

4. The method of claim 3 wherein the polymer is pressed in step (b) for between about 1 and 10 minutes.

5. The method of claim 1 wherein the polymer is a non-mesogenic polymer.

6. The method of claim 5 wherein the polymer is selected from the group consisting of celluloses, poly(acrylic acid)s, polyacrylonitriles, poly(L-analine)s, polyamides, polybutylene-terephthalate, poly(ε

-caprolactam), poly(ε

-caprolactone), polycarbonates, polyesters, polyhydroxybutyrate, polyimides, polylactams, polylactones, polymethacrylates, polynucleotides, polypropylenes, polystyrenes, polytetrafluoroethylene, polyurethanes, and vinyl polymers.

7. The method of claim 1 wherein the polymer is a polyethylene.

8. The method of claim 1 wherein the polymer is bioerodible.

9. The method of claim 8 wherein the polymer is selected from the group consisting of polycaprolactone, poly(fumaric acid-co-sebacic acid), poly(carboxyphenoxypropane-co-sebacic acid), poly(maleic acid), poly(hydroxy acids), copolymers of poly(hydroxy acids), and blends thereof.

10. The method of claim 1 wherein the polymer is non-bioerodible.

11. The method of claim 10 wherein the polymer is selected from the group consisting of polyethylene, polystyrene, polyvinylphenol, nylons, and polypropylene.

12. The method of claim 1 wherein the polymer is a mesogenic polymer.

13. The method of claim 1 wherein the polymer is water-insoluble.

14. The method of claim 13 wherein the polymer is selected from the group consisting of polyolefins and polyesters.

15. The method of claim 1 wherein the polymer is water-soluble.

16. The method of claim 1 wherein the polymer is in a shaped form selected from the group consisting of sheets, films, coatings, pellets, beads, artificial organs, prosthetic devices, sutures, and tissue engineering scaffolds.

17. A composition comprising a non-mesogenic polymer which exhibits liquid crystalline properties at a temperature below the glass transition temperature of the polymer.

18. The composition of claim 17 wherein the polymer is made by a method comprising the steps of

(a) heating the polymer from an initial temperature below its glass transition temperature to a temperature greater than its glass transition temperature and below its melting temperature;

and

(b) applying pressure to the polymer until a liquid crystalline state is induced in the polymer, while maintaining the temperature at greater than the glass transition temperature; and

(c) cooling the polymer below the glass transition temperature while maintaining the pressure.

19. The composition of claim 17 wherein the polymer is selected from the group consisting of polyethylene, celluloses, poly(acrylic acid)s, polyacrylonitriles, poly(L-analine)s, polyamides, polybutylene-terephthalate, poly(ε

-caprolactam), poly(ε

-caprolactone), polycarbonates, polyesters, polyhydroxybutyrate, polyimides, polylactams, polylactones, polymethacrylates, polynucleotides, polypropylenes, polystyrenes, polytetrafluoroethylene, polyurethanes, vinyl polymers, poly(lactic acid), polylactide-co-glycolide, copolymers thereof, and blends thereof.

20. The composition of claim 17 further comprising an encapsulated agent.

21. The composition of claim 20 wherein the encapsulated agent is an active agent for use in medical or pharmaceutical applications.

22. The composition of claim 20 wherein the encapsulated agent is selected from the group consisting of perfumes, flavoring agents, coloring agents, sunscreens, and pesticides.

23. A method for release of an encapsulated agent comprising

providing to a release site a composition comprising

a) a polymer which exhibits liquid crystalline properties at a temperature below the glass transition temperature of the polymer, and

b) an agent encapsulated in the polymer.

24. The method of claim 23 wherein the agent is an active agent for use in medical or pharmaceutical applications.

25. The method of claim 23 wherein the agent is selected from the group consisting of scents, flavoring agents, coloring agents, sunscreens, and pesticides.

26. An article for the release of an encapsulated agent comprising a polymer which exhibits liquid crystalline properties at a temperature below the glass transition temperature of the polymer, and the agent encapsulated in the polymer,

wherein the polymer is in a form selected from the group consisting of films, laminants, coatings, slabs, microparticles, containers for packaging of food or drugs, and orthopedic or prosthetic devices.

27. A monolithic composition for controlled delivery of an active agent comprising made using a process comprising

providing a polymer which contains substantially no liquid crystalline phase,

heating the polymer above its glass transition temperature and then subjecting the polymer to a pressure sufficient to induce a liquid crystalline phase in at least a portion of the polymer, and

combining the polymer with the active agent.

28. The composition of claim 27 wherein the polymer is water-insoluble.

29. The composition of claim 27 wherein the polymer is water-soluble.

30. The composition of claim 27 wherein the polymer is combined with the active agent to form a mixture before the step of inducing the liquid crystalline phase.

31. The composition of claim 27 wherein the polymer is combined with the active agent after the step of inducing the liquid crystalline phase.

32. The composition of claim 27 wherein the mixture of polymer and active agent is heated above the melting temperature of the active agent and then cooled before the step of inducing the liquid crystalline phase.

33. A barrier composition for use in packaging comprising

a non-mesogenic polymer which exhibits liquid crystalline properties at a temperature below the glass transition temperature of the polymer,

wherein the rate of diffusion of fluids through a layer of the polymer is reduced relative to the rate of diffusion of fluids through a layer of a form of the polymer which does not exhibit liquid crystalline properties.

35. The barrier composition of claim 33 wherein the fluid is selected from oxygen, water vapor, liquid water, and carbon dioxide.

34. A packaging article comprising the barrier composition of 33.