Inprakhon Pranee, Lalot Thierry
Department of Biotechnology, Faculty of Science, Mahidol University, Rama VI Rd, Phayathai, Bangkok, Thailand.
J Biotechnol. 2007 Sep 30;131(4):418-24. doi: 10.1016/j.jbiotec.2007.07.726. Epub 2007 Jul 21.
Enzymes are potentially useful catalysts for polymerization as well as modification of polymers. While lipases have been used previously for polymerization reactions, they have not been used for modification of polymers. In this report, lipases were used to determine regioselective modification of ester functions in a telomer of poly(methyl acrylate). The influence of chain length on the extent of transesterification of methyl acrylate telomers of DP(n) 6-50 was studied by examining the relationship between the extents of enzymic modification to other telomerization parameters. The regioselectivity was observed when the average DP(n) of telomers is in a range of 6-22. At a higher DP(n) (>22), however, the average number of reacting ester functions per telomer strongly deviated from the theoretically predicted value. This phenomenon was suspected as a result of steric hindrance caused by folding of longer telomer chains. To verify this hypothesis, acrylate telomers at a DP(n) ranging from 10 to 42 were synthesized using a shorter telogen, i.e., 2,2'-ethanedithiol. The transesterification of these telomers showed a deviation in a degree of conversion when DP(n) was greater than 10, possibly indicating the inhibition caused by steric hindrance. Therefore, regioselective modification of acrylic polymers, which is difficult to achieve by conventional chemical methods, may be accomplished enzymatically.
酶对于聚合物的聚合以及改性而言是潜在有用的催化剂。虽然脂肪酶此前已用于聚合反应，但尚未用于聚合物的改性。在本报告中，脂肪酶被用于确定聚（丙烯酸甲酯）端粒中酯官能团的区域选择性改性。通过研究酶促改性程度与其他端粒化参数之间的关系，研究了链长对聚合度（DP(n)）为6 - 50的丙烯酸甲酯端粒酯交换程度的影响。当端粒的平均DP(n)在6 - 22范围内时观察到区域选择性。然而，在较高的DP(n)（>22）时，每个端粒反应性酯官能团的平均数与理论预测值有很大偏差。这种现象被怀疑是由于较长端粒链折叠引起的空间位阻所致。为了验证这一假设，使用较短的调聚剂，即2,2'-乙二硫醇，合成了DP(n)范围为10至42的丙烯酸酯端粒。当DP(n)大于10时，这些端粒的酯交换在转化率上出现偏差，这可能表明存在空间位阻引起的抑制作用。因此，传统化学方法难以实现的丙烯酸聚合物的区域选择性改性可以通过酶促反应来完成。
