Surface energy and surface composition of end-fluorinated polystyrene

Contact angle analysis was applied to characterize the compositions, surfac e enrichment and surface energies for a homologous series of fluorosilane-t erminated polystyrenes (PS-F) ranging from 5300 to 148 000 g/mol in molecul ar weight. Surface enrichment of fluorinated end groups was found to decrea se with increasing molecular weight but the relative enrichment of end grou ps (the ratio of the surface to the bulk concentration) increased with incr easing molecular weight. Calculations showed that surface segregation great ly affected surface properties with a 3% concentration of end groups yieldi ng a 39% decrease in surface tension and a 0.1% concentration leading to an 8% decrease. The scaling of polymer surface tension with molecular weight for this system was compared with theory and was found to vary with molecul ar weight, the power law, dependence increasing with molecular weight. (C) 2001 Elsevier Science B.V. All rights reserved.