胍基锌配合物催化丙交酯开环聚合研究

Study on Ring-opening Polymerization of Lactide Catalyzed by Guanidine Zinc Complexes

发展绿色、高效的催化剂技术替代目前广泛应用的锡类催化剂一直是聚乳酸(PLA)及其相关催化剂技术研究领域的热点.本研究设计合成了双核胍基锌配合物,该配合物以环氧化物作为共引发剂,可在模拟工业条件下以较高的活性(TOF=7.50×103~3.45×104 h-1)催化丙交酯开环聚合,且在极低的催化剂浓度条件仍可保持良好活性.聚合所得产物的凝胶渗透色谱(GPC)曲线呈单峰窄分布(1.25~1.49),分子量为6.2~34.3 kg/mol.通过对低分子量聚合产物进行基质辅助激光解吸/电离飞行时间质谱(MALDI-TOF-MS)表征分析,证实所得聚合产物以环状聚乳酸(c-PLA)为主,并提出可能的成环机理.此外,该双核胍基锌配合物具有较好的普适性,可实现ε-己内酯(ε-CL)和δ-戊内酯(δ-VL)等多种内酯单体的开环聚合.

Poly(lactic acid)(PLA)is one of the most important biodegradable polymers,which has attracted much attention due to its renewable raw materials and excellent biodegradation properties.The quest to develop sustainable and high-performance catalytic technologies as alternatives to the tin catalysts,which are prevalent currently,is a hot topic in this field.Cyclic PLA,contrasting with the extensively produced linear PLA,has garnered significant attention due to its superior crystallinity,thermal stability,and low intrinsic viscosity,and it has been reported that the mixture of cyclic poly(lactic acid)and linear poly(lactic acid)has better hydrolysis resistance and thermal stability.This study reports the design and synthesis of a binuclear guanidine zinc complex,exhibiting exceptional activity(TOF=7.50×103-3.45×104 h-1)in catalyzing lactide ring-opening polymerization for the efficient production of cyclic poly(lactic acid)under simulated industrial conditions.Gel permeation chromatography(GPC)analysis revealed a narrow,unimodal distribution(1.25-1.49)of the obtained products,with a molecular weight range of 6.2-34.3 kg/mol.Matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS)characterization of low molecular weight products confirmed the predominant presence of cyclic PLA,allowing for the proposal of a plausible ring formation mechanism.Moreover,the experiment demonstrated the binuclear guanidine zinc complex's effective catalytic action on a diverse range of lactone monomers,offering a novel avenue for the development of broad-spectrum catalytic systems within the realm of metal catalysis.