嵌段共聚水溶性高分子在空气/水界面吸附态的构象

对于用几种不同疏水／亲水单体比合成的聚(丙烯酸丁酯／丙烯酸)共聚物样品测定了其水溶液的表面张力,运用Gibbs吸附方程求得在样品溶液临界胶束浓度时样品在气／液界面的分子吸附面积,以此推测其吸附态构象。结果表明,亲水单体单元在共聚物中含量多时,样品分子趋于在水中溶解;疏水单体单元多时,样品分子趋于在表面吸附。其吸附态构象为分子链上相邻的数个丁酯侧基吸附于水面,形成“薄煎饼状”疏水微区。

Conformation of Soluble Block Copolymer in Adsorbed State at Air-water Interface

P(BA/AA) copolymers were prepared with varied BA monomer ratios. The surface tensions of the aqueous solution for the copolymers were determined. Then, the surface area per molecule A_0 at the surface was calculated by Gibbs adsorption equation for each copolymer solution at its cmc, and the conformation of the molecules was imaged using A_0 data. The results showed that when hydrophilic chains are much more than hydrophobic ones in a copolymer the molecules tend to dissolve in water. Otherwise, when the hydrophilic chains are much less than the hydrophobic chains, the molecules tend to be adsorbed at the surface, the conformation of which might be that several butyl side groups on the P (BA/AA) backbone are adsorbed one by one on the water surface, forming a hydrophobic domain like a "pancake".