Department of Biobased Materials Science, Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan.
Biomacromolecules. 2012 Nov 12;13(11):3757-68. doi: 10.1021/bm301212a. Epub 2012 Oct 10.
For developing broader application of biobased polymers, graft copolymers and comb polymers having poly(lactic acid) (PLA) side chains have been synthesized by using a macromonomer technique. PLA macromonomers (MMm) having a methacryloyl polymerizable group with different PLA chain length with an average length m = 4, 6, 8, 12, 18, and 30 were prepared via ring-opening polymerization of l-lactide using hydroxyethyl methacrylate (HEMA) initiator catalyzed by Sn(Oct)(2). Radical polymerization behaviors of these macromonomers were examined. Radical copolymerization of MMm (m = 4, 6, and 8), with vinyl monomers like n-butyl methacrylate (BMA) and n-butyl acrylate (BA) in water as the reaction medium, gave stable miniemulsions of poly[n-butyl (meth)acrylate-graft-lactic acid]s [PB(M)A-g-PLAm]. MMm with m value higher than 12, however, gave aggregate products in a minor amount besides miniemulsions in a major amount, producing not a stable emulsion system of graft copolymers. The solution copolymerization, on the other hand, produced a wider variety of the graft copolymers, where a wider range of MMm (even m ≥ 12) can be employed. In a 1,4-dioxane solution, the radical copolymerization of MMm with BMA and methyl methacrylate (MMA) gave various graft copolymers [PB(M)MA-g-PLAm]. A new type of comb polymers (PMMm) having PLAm as pendant side chains were obtained by radical homopolymerization of MMm in a 1,4-dioxane solution. The graft copolymers and comb polymers obtained here are amorphous. Physical properties of the polymers from miniemulsions suggested them to be applicable for coatings or elastic materials which are environmentally desirable as a new class of biobased polymers. In addition, the present approach provided fundamental information on relationships between the length of PLA side chain and the bulk properties of the product polymers.
为了拓展生物基聚合物的应用范围，我们采用大分子单体技术合成了具有聚乳酸（PLA）侧链的接枝共聚物和梳状聚合物。通过使用羟乙基甲基丙烯酸酯（HEMA）引发剂，在辛酸亚锡（Sn(Oct)(2)）的催化作用下，开环聚合 L-丙交酯，制备了具有不同 PLA 链长的甲基丙烯酰基可聚合基团的 PLA 大分子单体（MMm），其平均长度 m = 4、6、8、12、18 和 30。研究了这些大分子单体的自由基聚合行为。在水作为反应介质的情况下，将 MMm（m = 4、6 和 8）与乙烯基单体如甲基丙烯酸正丁酯（BMA）和丙烯酸正丁酯（BA）进行自由基共聚，得到了聚[n-丁基（甲基）丙烯酸酯-接枝-乳酸]的稳定的细乳液[PB（M）A-g-PLAm]。然而，当 m 值高于 12 时，除了大量的细乳液之外，还会得到少量的聚集产物，从而不能形成接枝共聚物的稳定乳液体系。另一方面，溶液共聚可以得到更广泛的接枝共聚物，并且可以使用更广泛范围的 MMm（甚至 m≥12）。在 1,4-二氧六环溶液中，MMm 与 BMA 和甲基丙烯酸甲酯（MMA）的自由基共聚得到了各种接枝共聚物[PB（M）MA-g-PLAm]。通过 MMm 在 1,4-二氧六环溶液中的自由基均聚得到了具有 PLAm 作为侧挂支链的新型梳状聚合物（PMMm）。这里得到的接枝共聚物和梳状聚合物是无定形的。从细乳液得到的聚合物的物理性能表明，它们可应用于涂层或弹性材料，作为一类新型的生物基聚合物，它们具有环境友好的特点。此外，本研究提供了关于 PLA 侧链长度与产物聚合物的宏观性质之间关系的基本信息。
