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作 者:Li-Dong Feng Xin-Chao Bian Gao Li Xue-Si Chen
机构地区:[1]Key Laboratory of Polymer Ecomaterials,Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,Changchun 130022,China [2]Jilin Biomedical Polymers Engineering Laboratory,Changchun 130022,China
出 处:《Chinese Journal of Polymer Science》2021年第8期966-974,I0005,共10页高分子科学(英文版)
基 金:the National Key Research and Development Program of China(No.2016YFB0302500);the National Natural Science Foundation of China(Nos.51873209,51873210,51773194 and 51973219);Jilin Scientific and Technological Development Program,China(No.20200403022SF).
摘 要:The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose method.The kinetic models were also explored by the Malek method,and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)05]}versus 1/7for experimental data from TGA with model reactions.The pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg^(-1)but increased appreciably in the presence of extraneous Sn^(2+),-COOH/Sn^(2+),or-OH/Sn^(2+).The Ea values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn2+in different chemical environments because Sn^(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups,which were different in steric hindrance for the formation of activated complex between Sn^(2+) and PLLA.Under the catalysis of Sn^(2+),a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains,and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of lactide.However,it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol^(-1).
关 键 词:Poly(L-lactide) Pyrolysis mechanism Carboxyl group Hydroxyl group TIN
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