Comparison of thermal, thermomechanical, and rheological properties of blends of divinylbenzene‐based hyperbranched and linear functionalized polymers

Abstract

ABSTRACTA range of polymer blends were prepared via a solvent‐based film casting process using highly/hyperbranched (HB) polydivinylbenzenes (PDVB) polymers of two different molecular weights, linear functionalized (LF), hydrogenated hyperbranched (H‐HB2) PDVB, and linear polystyrene (LP). The thermal, thermomechanical, and rheological properties of the pure polymers and blends were then investigated and the results related to the concentration of “branched” polymer in the blend and the level of branching/polymer end groups present in the “branched” polymers used. Differential scanning calorimetry (DSC) analysis revealed an increase of the glass transition temperature (Tg) for the blends containing the nonhydrogenated HBs (~108 °C compared to ~102 °C for LP), which was attributed to crosslinking via the unsaturated reactive chain end/pendant groups in the HB (CHCH2). In contrast at the blends, containing the hydrogenated polymers H‐HB2, exhibited the same Tg as LP (~102°C) due to absence of crosslinking from the (H‐HB2) polymer. As the unsaturated HBs were found to be thermally curable, curing temperature rheology measurements were carried out employing a temperature ramp. No specific Tgel (the temperature at which HB gets crosslinked) was identified for LP‐HB1 and LP‐HB2 blends, which might be suggested to be due to the fact that both chain entanglement from linear polystyrene. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48547.