2,3,6,7-四氢-5氢-噻唑[3,2-a]嘧啶催化L-丙交酯开环聚合

Ring-opening polymerization of L-lactide catalyzed by 2,3,6,7-tetrahydro-5H-thiazolo [3,2-a] pyrimidine

以3,4,5,6-四氢-2-嘧啶硫醇、1,2-二溴乙烷和无水碳酸钠等为原料,采用一步法合成2,3,6,7-四氢-5氢-噻唑[3,2-a]嘧啶(ITU).以ITU为有机催化剂催化L-丙交酯(LLA)开环聚合反应,得到产物聚L-丙交酯(PLLA).反应的最佳条件:CH2Cl2作溶剂,cLLA=2.0 mol/L,n(LLA)/n(ITU)=20,n(LLA)/n(BnOH)=200,30℃下反应62 h,LLA单体转化率可达97.4%,数均分子质量为1.23×10^4 g/mol,分子质量分布为1.10.利用NMR和FTIR对聚合物进行表征,确定合成产物为PLLA,热分析结果得出PLLA的熔融温度为173℃,XRD图谱显示PLLA为α晶型的聚合物.通过NMR和FTIR对聚合物端基进行分析,推测聚合反应为"单体-活化"机理.

2,3,6,7-tetrahydro-5 H-thiazolo [3,2-a] pyrimidine(ITU)was synthesized by one step method using 3,4,5,6-tetrahydro-2-pyrimidinethiol,1,2-dibromoethane and anhydrous Na2 CO3 as raw materials. Ring-opening polymerization of L-lactide(LLA)catalyzed by ITU was explored and polylactide(PLLA)was obtained. The optimum condition of the ring-opening polymerization was as follows:cLLA= 2.0 mol/L,n(LLA)/n(ITU)= 20,n(LLA)/n(BnOH)= 200,T = 30 ℃,t = 62 h,and CH2 Cl2 was used as solvent. The conversion of LLA monomer reached 97.4%. The number average molecular weight of the polymer is 1.23 ×10^4 g/mol and the molecular weight distribution is 1.10. The polymer was charac-terized and the structure of PLLA was confirmed by NMR and FTIR techniques. The result of thermal analysis showed that the melting peak of PLLA was 173 ℃. The XRD spectrum confirmed PLLA was typical α-form crystal. The polymerization mechanism"monomer-activated process"was inferred through the analysis of end group of PLLA by NMR and FTIR.