Structure and Molecular Motion of Polystirene Adsorbed on porous silica by the Spin label method

用自旋标记法研究了分子量为3 × 10 ~（^3）、9.6 × 10 ~（^4）和3.8 × 10 ~（^5）的聚苯乙烯（PS）分子链吸附在多孔SiO_2和接枝聚环氧乙烷（PEO）的SiO_2表面的结构和分子运动。（1）PS的吸附速率和吸附量取决于接枝率低于2%。（2）PS与SiO2之间的分子间相互作用以及PS链的分子运动依赖于其分子量。分子量为3 × 10 ~（^3）的PS与SiO_2的相互作用较强，而分子量为9.6 × 10 ~（^4）和3.8 × 10 ~（^5）的PS在短时间内以“尾段或环段”的形式快速移动，随着吸附时间的延长，其移动性降低，并转变为“链段”。（3）接枝的PEO链的分子迁移率高于吸附的PS链，Mw= 3.8 × 10 ~（-5）。这一事实表明，PS链伸展的接枝链和adsrbed在二氧化硅表面上的“火车段”，而PEO链突出的“尾段”。同时还发现，随着吸附时间的延长，分子链的结构发生了变化。PEO和PS的结构取决于PS的分子量和PEO的接枝率。

Spin-label method is used to study structure and molecular motion of polystirene (PS) chains having molecular weights, Mw=3X10^3,9.6X10^4, and 3.8X10^5, adsorbed in a pore of porous silica and the silica suface grafted with poly (ethylene oxide) (PEO).(1)The adsorption rate and the amount of the adsorbed PS depend on the grafting ratio lower than 2%.(2)The molecular interaction between PS and silica and the molecular motion of PS chain depend on its molecular weight. The adsorped PS having Mw=3X10^3 strongly interacts with silica, whereas PS having Mw=9.6X10^4 and 3.8X10^5 moves rapidly as "tail or loop segment" at a short adsorption decreases its mobility with increasing adsorption time, and change to "train segment".(3)Molecular mobility of the grafted PEO chain is higher than the adsoroed PS chain, having Mw=3.8X10^5. This fact suggests that the PS chains spread out the grafted chains and adsrbed on the silica surface as "train segments", whereas PEO chains protrude as "tail segmens". It was also found that the molecular structure of the chains change with adsorption time. Their structure of PEO and PS depend on molecular weight of PS and grafting ratio of PEO.