Effect of Exogenous Carboxyl and Hydroxyl Groups on Pyrolysis Reaction of High Molecular Weight Poly(L-Lactide)under the Catalysis of Tin

• 作者: Li-Dong Feng Xin-Chao Bian Gao Li Xue-Si Chen
• 来源期刊: 高分子科学（英文版）
• 年，卷（期）: 2021,（8）
• 所属期刊栏目: ARTICLES
• 页码范围: 966-974
• 页数: 9页
• 语种: 英文

摘要

The effect of exogenous hydroxyl,carboxyl groups and/or Sn2+on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(Ea)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 In{-ln[1-(1-w)0.5]}versus 1/T for 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 Sn2+,-COOH/Sn2+,or-OH/Sn2+.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 Sn2+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 Sn2+and PLLA.Under the catalysis of Sn2+,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 144g·mol-1.