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

Abstract

A 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.

Preparation and characterization of composites using blends of divinylbenzene‐based hyperbranched and linear functionalized polymers

“…The viscosity of LP:HB blends were found to be highest (5.9 × 10 4 Pa.s) at 200°C at low shear rate (0.01 s −1 ). This behavior could be explained taking into account the crosslinking effect of the HB polymer at that temperature, which was confirmed from the previous rheological study performed as described in, 15 where both LP:HB 90–10 and 80–20 did not reach a flow state (storage modulus > loss modulus; G ″ > G ′) even at high temperature (~200°C). However, viscosity of LP:H‐HB 90–10 and 80–20 blends were found to be slightly lower (3.8 × 10 3 Pa.s and 3.1 × 10 3 Pa.s, respectively) in comparison to LP (4.0 × 10 3 Pa.s) at shear rate of 0.01 s −1 .…”

“…Although LF polymer had a lower molecular weight than for HB and H‐HB, the tensile modulus of LP:LF 90–10 and 80–20 was statistically significantly higher ~15% ( p < 0.05) in comparison to the LP:HB 90–10 and 80–20, respectively. At room temperature (in absence of crosslinking) both HB and H‐HB possessed a globular, three‐dimensional structure whereas LF possess a most likely linear structure like LP with few functional groups, since the monomer for LF was only 1% of divinyl benzene and 99% styrene 15 . So, it can be said that the highly branched structure at R.T may have been responsible for the statistically significantly ( p < 0.05) lower modulus value for LP:HB and LP:H‐HB in comparison to LP:LF.…”

“…Linear poly(styrene) (LP) (Grade 430,102) (M w ~ 192 KiloDalton [kDa]) was purchased from Sigma Aldrich, UK. The hyperbranched poly(divinyl benzene) ( HB ) of (M w 60 kDa, respectively) and hydrogenated hyperbranched poly(divinyl benzene) ( H‐HB ) (M w ~ 60 kDa) and the linear functional poly(divinyl benzene) ( LF ) (M w ~ 10 kDa) were synthesized using the methods described in prior literature 15 . Woven E‐glass fiber was purchased from Plastic Direct (UK), weave style: plain woven, thickness: 0.2 mm, overall weight: 200 g m −2 , sizing type: silane and chloroform (10% w/v) was purchased from Fisher Scientific (UK).…”

“…The films of LP and the blends (~0.3 mm thick) of linear poly(styrene) (LP) with hyperbranched (HB) (LP:HB), hydrogenated hyperbranched (H‐HB) (LP:H‐HB), and linear functional (LF) (LP:LF) poly(divinyl benzene) of two different compositions (90:10 and 80:20) were prepared using the methods described in our previous paper 15 . The LP film and the blends were prepared by dissolving specific amounts of the polymers in chloroform (4% w/v).…”

“…This study reports on the preparation and comparison of polymer composites containing E‐glass fibers as reinforcement materials using matrices of; (a) pure (linear polystyrene) LP, (b) blends of LP with HB polymers containing reactive vinyl (CHCH 2 ) chain end group, (c) hydrogenated hyperbranched (H‐HB) with non‐reactive ethyl (CH 2 CH 3 ) functional groups, and (d) linear functional (LF) with vinyl (CHCH 2 ) chain end 15 . The temperatures utilized in this study for composite manufacture were determined from a previous rheological study of pure LP and its blends.…”