Coating modulus and barnacle bioadhesion.

The effect of coating modulus on the strength of pseudobarnacle adhesive bonding was investigated. A radical polymerized poly(butylmethacrylate) coating cross-linked with allylmethacrylate was used as a model coating. The coating Tg was determined to be 18 degrees C by differential scanning calorimetry (DSC). Dynamic contact angle measurements (DCA) at different temperatures indicated that the surface chemistry was not significantly affected in the range investigated (5-50 degrees C). However, an increased noise level in the force vs. displacement curves indicated an increased molecular mobility with a fast reorganization of hydrophilic ester groups during the measurement. Dynamic mechanical analysis (DMA) as a function of temperature revealed a large drop in storage modulus (G') from 20 degrees C to 70 degrees C, as expected. A good correlation between the coating storage modulus and the detachment stress of pseudobarnacles was observed even though energy dissipation during the analysis was observed. The decreased adhesion might be a result of the increased molecular flexibility as determined by DCA and DMA at increased temperature. The increased molecular mobility might increase the tendency for interfacial slip, which ultimately results in decreased adhesion strength.