Effect of composition on the width of the calorimetric glass transition in polymer–solvent and solvent–solvent mixtures

Abstract

The calorimetric glass‐transition temperature (Tg) and transition width were measured over the full composition range for solvent–solvent mixtures of o‐terphenyl with tricresyl phosphate and with dibutyl phthalate and for polymer–solvent mixtures of polystyrene with three dialkyl phthalates. Tg shifted smoothly to higher temperatures with the addition of the component with the higher Tg for both sets of solvent–solvent mixtures. The superposition of the differential scanning calorimetry traces showed almost no composition dependence for the width of the transition region. In contrast, the composition dependence of Tg in polymer–solvent mixtures was different at high and low polymer concentrations, and two distinct Tg's were observed at intermediate compositions. These results were interpreted in terms of the local length scale and associated local composition variations affecting Tg. The possible implications of these results for the dynamics of miscible polymer blends were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1155–1163, 2004

Dynamics in glass-forming mixtures: Comparison of behavior of polymeric and non-polymeric components

“…In work reported recently, Savin et al presented differential scanning calorimetry data from polymer solutions and argued that the results were qualitatively consistent with self-concentration and the LM model [28]. In particular, two T g 's were observed at intermediate compositions for one phase polymer solutions.…”

Multiple glass transitions and local composition effects on polymer solvent mixtures

“…3 As a starting point we focused on recent experimental DSC results for PS and DBP. 4 We developed a simple tree lattice model as a means of computing the distribution of local environments around a segment in the mixture, which lead to the spread in T g as reflected in the DSC results. A lattice description with chain connectivity naturally incorporates the effects of self-concentration associated with the presence of a polymeric component.…”

“…We assume that each element of the distribution comprises the corresponding pure DSC trace for that component, shifted to its own local T g , and having an amplitude proportional to mass fraction. We applied this recipe to the data on PS/DBP mixtures of Savin et al 4 with good results. In generating the DSC traces we initially sidestepped the problem of predicting the dependence of T g on effective composition by fitting the data of Savin et al for T g of each component as a function of bulk composition.…”

“…'' In principle, therefore, at any given mixture composition one might expect two T g 's; however, only one is typically reported. For this reason a recent study by Savin et al 4 represents both an opportunity and a challenge. In their work Savin et al presented and analyzed results on mixtures across the composition range of polystyrene (PS) with each of three substituted phthalates.…”

From melt to solution: Scaling relations for concentrated polystyrene solutions

“…In the notation PS-x/DEP-y, x identifies the molar mass of the PS samples, while y indicates the solution concentration. DEP can be considered as a good solvent for PS at room temperature [Savin et al (2004)]. All experiments were conducted at constant strain rate using a filament stretching rheometer at ambient condition, i.e., 21.5 C [Acharya et al (2008)].…”