| 摘要 |
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.
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