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Effects of soft segments and hydrolysis on the crystallization behavior of degradable poly(oxyethylene)/poly( L ‐lactide) block copolymers
Author(s) -
Hu David ShiawGuang,
Liu HsinJiant
Publication year - 1994
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1994.021950409
Subject(s) - copolymer , crystallization , materials science , spherulite (polymer physics) , polymer chemistry , nucleation , peg ratio , differential scanning calorimetry , chemical engineering , avrami equation , isothermal process , hydrolysis , lactide , composite material , chemistry , polymer , thermodynamics , organic chemistry , crystallization of polymers , physics , finance , engineering , economics
Abstract The crystallization behavior of poly(oxyethylene) (PEG)/poly( L ‐lactide) (PLLA) block copolymers with PEG (number‐average molecular weights M n = 1000–6000) contents ≦ 18,3 wt.‐% has been studied under different isothermal temperature and linear cooling conditions. A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt state. The influence of copolymer composition and hydrolysis on radial growth rates of spherulites, G , in PEG/PLLA copolymer was investigated using polarized light video‐microscopy. The data were analyzed in terms of a model describing two processes, namely crystal nucleation and growth which were observed experimentally in a typical Avrami plot for the isothermal data. At a given crystallization temperature, G 's are increased with increasing PEG content and with decreasing PEG segment length in PEG/PLLA copolymer spherulites. The Avrami exponent n and rate coefficient k of PEG/PLLA copolymers decrease with increasing hydrolysis time up to 200 h. The spherulite morphology appeared to be a complex function of copolymer composition, hydrolysis time and crystallization temperature.