聚乳酸的ATRP引发剂的合成与表征

Synthesis and Characterization of Polylactic acid Macromolecular Initiator by ATRP

利用原子转移自由基聚合法向聚乳酸引入亲水性基团来改善其疏水性之前要合成聚乳酸大分子引发剂的原理,通过酸性降解高分子量聚乳酸得到数均分子量为8 000、分子量分布为1.26的低分子量聚乳酸,然后利用酯化反应,使其与2-溴异丁酰溴反应,得到聚乳酸引发剂,并利用核磁共振谱仪和红外光谱仪对样品进行了表征.此外,通过调节各反应物质的摩尔比,进一步研究了2-溴异丁酰溴与聚乳酸的摩尔比、反应时间和2-溴异丁酰溴转化率间的关系,当反应24 h、2-溴异丁酰溴和聚乳酸的摩尔比为2∶1时,2-溴异丁酰溴的转化率可达到最大为79%.

Introducing hydrophilic group onto polylactic acid （PLA） by atom transfer radical polymerization would facilitate changing the hydrophobieity of PLA to amphipathy, in which progress macromolecular initiator preparation is the first step. The synthesis strategy of polylactic acid macromolecular initiator （PLA-Br） consisted of a two-step procedure： （i） degradation of high molecular weight PLA to about 8000 g/mol and molecular weight distribution about 1.26, followed by （ii） quantitative conversion of the PLA hydroxyl end-groups with bromoisobutyryl bromide （BIBB）. The macromolecular parameters and structures of PLA-Br were determined by 1H-NMR spectroscopy and FT-IR. Dependences of conversion ratio of BIBB on the mole ratio of BIBB and PLA and the reaction time were discussed. The results showed that the highest esterification rate of PLA was 79% as the mole ratio of BIBB and PLA 1 ： 2 and reaction time 24 h.