Influence of different alkyl side chains on solid surface tension of polymethacrylates

Low-rate dynamic contact angles on poly(t-butyl methacrylate) (PtBMA) were measured by an automated axisymmetric drop shape analysis profile (ADSA-P). The solid surface tension of PtBMA is calculated to be 18.1 mJ/m(2), with a 95% confidence limit of +/-0.6 mJ/m(2). This value was compared to previo us results with different homopolymeric polymethacrylates [poly(methyl meth acrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(n-butyl methacr ylate) (PnBMA)] and with copolymeric polymethacrylates {poly(methyl methacr ylate/ethyl methacrylate, 30/70) [P(MMA/EMA, 30/70)] and poly(methyl methac rylate/n-butyl methacrylate) [P(MMA/nBMA)]}. It was found that increasing l ength and size of the alkyl side chain decrease the solid surface tension, as expected. Comparison with pure alkyl surfaces suggests that the surface tension of PtBMA is dominated by the very hydrophobic t-butyl group. (C) 20 00 John Wiley & Sons, Inc.