Orientational ordering poly segmental

Since ordered structural orientation is believed to be a prerequisite for exhibiting alternation in physical properties in monolayer coverage, I have interpreted the alternation exhibited in the C data for the liquids that comprise Z(CH2)nH series to mean that such moleclules are fixed to the monomer unit of poly(styrene) segments in the liquid-saturated gel-state via the Z substituent, and that these adsorbed molecules are distributed around the adsorption sites (i.e, the monomer units) in a well-defined orientation with respect to each site, such that the established orientation relative to that monomer unit is maintained despite the freedom of rotation and serpentine movement of the polymer segments between crosslink junctions in the liquid-saturated gel domain. 

This molecular weight dependence of adsorption leads to fractionation, when the polymer is polydisperse, and exchange can take place freely. Hamori showed that there were significant differences in the adsorption behaviour of atactic and isotactic poly(methyl methacrylate) (PMMA) on silica from acetonitrile. Isotactic PMMA was adsorbed whereas atactic PMMA was not. Miyamoto et aV used this difference to separate isotactic and syndiotactic polymers. Botham and Thies found that isotactic poly(isopropyl acrylate) had a higher fraction of segments in direct contact with the surface than its syndiotactic or atactic equivalents. These experiments show the importance, even if second order, of the orientation and accessibility of the polymers adsorbing groups to the solid surface. 

---