Contact Angle Study on Polymer-Grafted Silicon Wafers

Surface wettability and hydrophilicity of terminally grafted PVP and PVAc on smooth silicon wafers were investigated by advancing and receding contact angle measurements. Surface wetting trends correlated with polymer graft yield. Contact angle hysteresis results did not reveal a clear dependence of surface wetting on surface roughness (determined by atomic force microscopy) at the nanoscale level. Surface roughness appeared decrease with increasing chain length for the present surfaces produced by free radical graft polymerization. Contact angle analysis in terms of surface tension components demonstrated that the degree of hydrophilicity of polymer-grafted smooth inorganic surfaces depends on both polymer functionality and polymer graft yield. It is postulated that reorientation of surface-grafted polymer chains could account for changes in surface wettability, similar to those observed for solid polymer films.