采用固体NMR研究MPEG-PLA双嵌段共聚物的固态相区结构

THE STRUCTURE OF A MPEG-b-PLA DIBLOCK COPOLYMER IN ITS SOLID PHASE STUDIED BY SOLID-STATE NMR

采用固体核磁共振方法 ,研究了AB型聚 (L 丙氨酸 ) 聚乙二醇嵌段共聚物 (MPEG b PLA)的固态微相结构 .1 3C核的交叉极化与直接极化实验表明 ,MPEG中存在晶态和非晶态两种相区结构 ,PLA则含有大量的α螺旋与少量的 β折叠二级结构 .由交叉极化过程下的1 3C自旋 晶格弛豫时间 (T1 )测定结果进一步表明 ,MPEG链段由于嵌段结构使结晶过程受抑制 ,结晶度明显下降 .PLA链段以结晶态形式存在 ,并由于大量α螺旋和β折叠有序结构的存在 ,链段非常刚性 ,运动严重受限 ,而β位甲基因为可以自由旋转 。

In this work, the structure of a poly(ethylene glycol) methyl ether b poly(L alanine) copolymer (MPEG b PLA) in its solid state was studied by 13 C CP/MAS, DP/MAS and spin lattice relaxation time T 1 NMR experiments. The results revealed that the PEG blocks are crystallizable in the solid state of the diblock polymer, but the degree of crystallinity is considerably lower in the diblock polymer state than that in pure PEG. It was found that the PLA blocks is rigid not only because of the formation of a large number of α helices and a small number of β sheets as secondary structures, but also owing to PLA crystallinity in the solid state. The results also implied that C\-β is more mobile than C\-α at room temperature, and the β methyl group rotates freely around its axis.