New methodologies for separating glass transitions from energy of film formation in polystyrene latexes

Polystyrene latexes were synthesized to study water evaporation details and to separate the energy of film formation from the glass transition tempera ture. Three experimental techniques were employed in the present work to st udy the formation of polystyrene latex films: standard differential scannin g calorimetry (DSC), modulated DSC, and the Mahr method applied to modulate d DSC. High-resolution thermogravimetric analysis (TGA) was used to study t he water evaporation. The TGA experiments revealed evaporation curves consi stent with the notion of surface tension and tortuosity effects being the c ontrolling factors. The method of Mahr was combined with the new software p ackage for DSC to provide an improved method of separating the glass transi tion of polystyrene from its surface tension-based free energy of film form ation. The result was that the films formed under the extremely mild condit ions employed had 30-70% of their surfaces obliterated by interfacial adhes ion. (C) 1999 John Wiley & Sons, Inc.