Solvent effects on the miscibility of poly(methyl methacrylate)/poly(vinyl acetate) blends I: Using differential scanning calorimetry and viscometry techniques

The influence of solvent and temperature on the miscibility of poly(methyl methacrylate)/poly(vinyl acetate) (PMMA/PVAc) was investigated. Experiments using differential scanning calorimetry (DSC) and viscometry were performed. LCST curve was determined by measurements of transmitted light intensity against temperature, at several compositions of PMMA/PVAc, 15/85, 25/75, 50/50, 75/25 and 85/15. It was observed that the miscibility of the PMMA/PVAc blends depends on the solvent. The blends are miscible in chloroform at 30 degrees C and 50 degrees C, whereas in N,N-dimethyl formamide (DMF) at the same temperatures, the blends are immiscible. In toluene the miscibility depends on the temperature: the blends are miscible at 30 degrees C and immiscible at 50 degrees C. Results from viscometry match very well those of DSC. The film of PMMA/PVAc 50/50 cast from chloroform presents only one T-g. If cast from DMF, the blend presents two T-g values, close to those for pure polymers. The thermogram of the opalescent film, cast from DMF, is similar to the one obtained after a transparent film, cast from chloroform, was heated above the LCST curve. (C) 1999 Elsevier Science Ltd. All rights reserved.