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

采用自旋标记法研究了分子量为Mw=3X10^3、9.6X10^4和3.8X10^5的聚苯乙烯（PS）链吸附在多孔二氧化硅孔中以及接枝聚环氧乙烷（PEO）的二氧化硅表面的结构和分子运动。(1)接枝率低于2%时，PS的吸附速率和吸附量取决于接枝率。(2) PS与二氧化硅的分子相互作用和PS链的分子运动取决于PS的分子量。而Mw=9.6X10^4和3.8X10^5的PS在较短的吸附时间内以“尾段”或“环段”的形式快速移动，随着吸附时间的增加迁移率降低，变为“列段”。(3)接枝的PEO链分子迁移率高于吸附的PS链，分子量为3.8X10^5。这一事实表明，PS链将接枝链展开，并以“列车段”的形式附着在二氧化硅表面上，而PEO链则以“尾部段”的形式突出。研究还发现，这些链的分子结构随吸附时间的变化而变化。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.