DYNAMICALLY CROSS-LINKED THERMOPLASTIC ELASTOMERIC NETWORK BASED ON HAIRY NANOPARTICLES (HNP)

Abstract

Chain-end furan functionalized hairy nanoparticles (HNPs) with hard polystyrene (PS) cores and soft polydimethylsiloxane (PDMS) shells were synthesized by one-step anionic living polymerization. The synthesis of the functionalized HNPs was carried out by first preparing the living core through the copolymerization of styrene and divinylbenzene using sec-butyl lithium with tetrahydrofuran as the solvent, and next by adding the second monomer, hexamethylcyclotrisiloxane (D3) to the living polystyrene core. Following polymerization of the D3, the living polymer was terminated with dimethylchlorosilane to obtain the HNPs terminated with Si-H functional end group. The furan functionalized HNPs were synthesized by the hydrosilylation of the HNPs with 2-vinylfuran. Additionally, furan end functionalized poly(dimethylsiloxane) and poly(styrene) were synthesized by anionic living. 1H NMR and FT-IR spectra confirm the successful synthesis of the structure. Differential scanning calorimetry shows the presence of two thermal transitions indicative of the presence of a poly(dimethysiloxane) soft phase and a poly(styrene) hard phase suggesting that the HNPs are a thermoplastic elastomer. A proof of principle for the use of Diels−Alder chemistry as a thermoreversible cross-linking tool for the network polymers is demonstrated. The furan functionalized HNPs forms thermoreversible elastomeric networks on cross-linking with bismaleimide (BMI) via a Diels−Alder coupling reaction. The kinetics of the forward Diels–Alder reaction between the functionalized polymer and BMI was studied at different temperatures 50, 60, and 70°C by UV-Vis spectroscopy. The results indicated that the reaction rate constants increase when the temperature rises from 50 to 70 °C and showed that the reaction followed second-order kinetics. The activation energy of the cross-linking reaction for the furan functionalized HNP, PS, and PDMS with BMI were determined. The formed Diels−Alder cross-links polymer dissociates at elevated temperatures around 140–154 °C which was proven by DSC. Atomic force microscopy (AFM) were used to investigate the morphological characterization and the particle size of a polystyrene core, HNP, functionalized HNP with diene, and BMI cross-linked HNP. The results suggest that because of the shape and size of the furan functionalized HNPs, they are a good candidate for preparing thermoreversible polymer networks.