Stepwise stereocomplex assembly of isotactic poly(methyl methacrylate) andsyndiotactic poly(alkyl methacrylate)s on surfaces

Isotactic (it-) poly(methyl methacrylate) (PMMA) and syndiotactic (st-) pol y(ethyl methacrylate) (PEMA) and poly(propyl methacrylate) (PPMA) were synt hesized by anionic polymerization in toluene at -78 degreesC with t-C4H9MgB r and t-C4H9Li/(C2H5)(3)Al, respectively, as initiators/coordinators. Combi ned it- and st-polymers were assembled by the alternate immersion of a 9 MH z quartz-crystal microbalance (QCM) as a substrate into their acetonitrile solutions at ambient temperature. QCM analysis showed constant growth of th e assembly except in the first two steps. The assembled ratios between st-P EMA and st-PPMA with it-PMMA (st-/it-) were 2.5 x 0.4 and 1.8 x 0.5, respec tively, indicating stepwise stereocomplex formation. The static contact ang le of the assembly at each step and its reflection absorption spectrum also implied complex formation. The amount of stereocomplex assembled was signi ficantly affected by the st-polymer concentration and its molecular weight. Atomic force microscopy observation showed the assemblies to have a molecu larly smooth surface.