二乙醇胺改性聚乳酸的直接熔融聚合法合成及其表征

Direct Melt Polycondensation and Characterization of Polylactic acid Modified by Diethanolamine

以乳酸(LA)、二乙醇胺(DEA)为原料,采用熔融聚合法直接合成了二乙醇胺改性聚乳酸,并用特性粘数、FT-IR、1HNMR、GPC、DSC、XRD等手段进行表征,探讨了催化剂种类和用量、熔融聚合反应时间、反应温度以及不同投料比、不同构型乳酸对聚合物合成的影响。在单体投料摩尔比n(DEA)∶n(L-LA)=1∶200、160℃、70Pa、催化剂SnO用量0.7(wt)%、熔融聚合8h条件下,聚合物重均相对分子质量(Mw)可达8100。随着投料比中DEA的增加,产物特性粘数逐步降低,Mw逐渐减小,玻璃化温度(Tg)有降低的趋势。以L-LA聚合得到的聚合物的Mw、分散度(Mw/Mn)和结晶度均比由D,L-LA得到的产物的更高。因此,笔者认为,由于D,L-A与L-LA存在反应速率差异,因而二者有不同的反应历程。新合成方法有利于降低二乙醇胺改性聚乳酸作为药物缓释载体等生物医学材料的合成成本。

Polylactic acid modified by diethanolamine was synthesized via melt polycondensation by using lactic acid （LA） and diethanolamine（DEA） as starting monomer material directly and characterized with intrinsic viscosity, FT- IR, ^1 H NMR, GPC, DSC and XRD. The influences of different synthetic conditions including kinds and quantity of catalyst, time and temperature of melt copelycondensation, and different molar feed ratio, different LA conformation on the polymer were discussed in detail. Under the conditions of molar feed ratio of DEA to L-LA 1：200,amount of catalyst SnO 0.7（wt）%, polymerization temperature 160℃ and pressure 70Pa, polymerization time 8h the maximum Mw of the as-prepared polymer was 8100,which had met the requirement of drug delivery cartier material. With the increase of the molar feed ratio of DEA, its intrinsic viscosity, Mw and glass-transition temperature decreased gradually. Using L-LA as starting material, M,, polydispersity index and crystallinity of the polymer were larger than these of D, L-LA. Based on the above, it is proposed that the reaction mechanism of direct melt polycondensation was different by using D, L-LA and L-LA as monomer. The synthetic method is beneficial to reduce the synthesis cost of polytactic acid modified by diethanolamine as biomedical materials, including drug delivery cartier material.