Topographical, chemical, thermal and electrostatic properties of latex films

Scanning probe microscopy (SPM) was used for studying the changes in topographical, chemical, thermal and electrostatic properties of a styrene-butadiene latex coating as a function of annealing time. Changes in local surface properties obtained with SPM were correlated with changes in surface chemistry measured by time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and contact angle measurements. The studied copolymer film goes through chemically and topographically meta-stable transition states during thermal annealing, reaching a steady state only after a significant annealing time (21 h). The differences in surface chemistry of the meta-stable states appeared as characteristic thermal and electrostatic properties of the latex coating. The results on film formation and drying are discussed in light of existing literature and theories. In this transition stage, the surface concentrations of polymeric components show unstable behavior, accordingly shifting the thermal transitions. Furthermore, the drying of the surface and desorption of surfactants is affecting the surface charge balance, changing from negative to positive. This was attributed to the change of balance of ionic components on the surface.