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Synthesis and characterization of biodegradable lactic acid‐based polymers by chain extension
Author(s) -
Gu ShuYing,
Yang Ming,
Yu Tao,
Ren TianBin,
Ren Jie
Publication year - 2008
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.2435
Subject(s) - gel permeation chromatography , prepolymer , differential scanning calorimetry , polymer , polymer chemistry , molar mass distribution , glass transition , lactic acid , monomer , materials science , biodegradable polymer , chemical engineering , polyurethane , composite material , physics , genetics , biology , bacteria , engineering , thermodynamics
BACKGROUND: Poly(lactic acid) (PLA), coming from renewable resources, can be used to solve environmental problems. However, PLA has to have a relatively high molecular weight in order to have acceptable mechanical properties as required in many applications. Chain‐extension reaction is an effective method to raise the molecular weight of PLA. RESULTS: A high molecular weight biodegradable lactic acid polymer was successfully synthesized in two steps. First, the lactic acid monomer was oligomerized to low molecular weight hydroxyl‐terminated prepolymer; the molecular weight was then increased by chain extension using 1,6‐hexamethylene diisocyanate as the chain extender. The polymer was characterized using 1 H NMR analysis, gel permeation chromatography, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the obtained polymer had a M n of 27 500 g mol −1 and a M w of 116 900 g mol −1 after 40 min of chain extension at 180 °C. The glass transition temperature ( T g ) of the low molecular weight prepolymer was 47.8 °C. After chain extension, T g increased to 53.2 °C. The mechanical and rheological properties of the obtained polymer were also investigated. CONCLUSION: The results suggest that high molecular weight PLA can be achieved by chain extension to meet conventional uses. Copyright © 2008 Society of Chemical Industry