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Predictors of glass transition in the biodegradable poly‐lactide and poly‐lactide‐ co ‐glycolide polymers
Author(s) -
In Pyo Park Peter,
Jonnalagadda Sriramakamal
Publication year - 2006
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.22135
Subject(s) - glass transition , intrinsic viscosity , polymer , lactide , materials science , plga , polymer chemistry , viscosity , rheology , relaxation (psychology) , biodegradable polymer , copolymer , chemical engineering , composite material , nanotechnology , psychology , social psychology , nanoparticle , engineering
The biodegradable polylactide (PLA) and polylactide‐ co ‐glycolides (PLGAs) are being widely investigated for use as scaffolds in bone and ligament reconstruction. The glass transition temperatures ( T g ) for these polymers are generally greater than 37°C, causing PLA and PLGA devices to possess brittle characteristics in physiological conditions. To evaluate the possibility of obtaining PLGA polymers with T g values below 37°C, we evaluated the determinants of T g in PLA and PLGA copolymers. The T g , changes in specific heat capacity (Δ C p ), and enthalpic relaxation (Δ H g ) in two consecutive heating cycles were correlated with lactide/glycolide content and intrinsic viscosity [η] for PLA, PLGAs 90:10, 75:25, 65:35, and 50:50. A linear correlation was observed between T g and intrinsic viscosity, with 0.1 dL/g increase in viscosity resulting in an increase in T g by about 3.55°C. The selection of PLA and PLGA copolymers with [η] values <0.19 dL/g, corresponding to a viscosity average molecular weight of <70 kDa, will obtain PLA/PLGA polymers with T g values below 37°C. The lowest attainable T g values were found to be 28–30°C. Intrinsic viscosity also correlated with Δ C p differences between aged and rapidly cooled polymers, and is therefore important in predicting free volume changes within these polymers upon aging. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1983–1987, 2006