Quantifying Biodegradable Amphiphilic Poly(L-Lactide)-block- Poly(Ethylene Glycol)-block-Poly(L-Lactide) Composition by Thermogravimetric Analysis

摘要

The thermogravimetric analysis (TGA) of two series of tri-block copolymers based on poly(1,1-lactide) (PLLA) and poly(ethylene glycol) (PEG) segments, having molar mass of 4000 or 600 g.mol-1, respectively, is reported. The prepared block copolymers presented wide range of molecular weights (800 to 25,000 g.mol-1) and compositions (16 to 80 wt.% of PEG). The thermal stability increased with the PLLA segment size and the tri-block copolymers prepared from PEG 4000 started to decompose at higher temperatures compared to those copolymers from PEG 600. The copolymers compositions were determined by thermogravimetric analysis and the results were compared to other traditional quantitative spectroscopic methods, hydrogen nuclear magnetic resonance spectrometry (1HNMR) and Fourier transform infrared spectrometry (FTIR). The PEG 4000 copolymers compositions calculated by TGA and by 1HNMR, presented differences of 1%, demonstrating feasibility of using thermogravimetric analysis for quantitative purposes.