WORMLIKE POLYSTYRENE BRUSHES IN THIN-FILMS

Mono- and multilayer films were prepared on mica by solution casting o f a high molecular weight polymacromonomer, i.e., a polymethacrylate o f about 1000 repeating units each of which was substituted by a polyst yrene chain with a molecular weight of about 5000 Da. The films were s tudied by tapping scanning force microscopy. The material showed a rem arkable preference for forming well-defined monolayers of a thickness of 6.5 +/- 0.2 nm consistent with the hard core diameter of the collap sed cylindrical brush molecules. When the films were probed with high normal force, the single molecules were observed to organize in a dens e nematic-like packing as expected for inherently stiff molecules. In order to minimize the surface area, the polymacromonomers form hairpin s, i.e., rather tight folds parallel to the surface. The orientational order was shown to be highest in a monolayer, S = 0.74, and to decrea se for layers at a larger distance from the flat substrate to a value S = 0.65.