RECYCLABLE THERMOPLASTIC ELASTOMERS FROM DYNAMICALLY CROSSLINKED HAIRY NANOPARTICLES (HNPs)

Abstract

Chain-end furan-functionalized hairy nanoparticles (HNPs) with robust polystyrene (PS) cores and flexible polydimethylsiloxane (PDMS) shells were successfully synthesized through a one-pot high vacuum anionic living polymerization process. The synthesis involved the preparation of the living core by copolymerizing styrene and divinylbenzene, followed by the addition of hexamethylcyclotrisiloxane (D3) as the second monomer to the living polystyrene core. The resulting living polymer was terminated with dimethylchlorosilane, yielding HNPs terminated with Si-H functional end groups (HNP-SiH). Furan-functionalized HNPs were then obtained by hydrosilylation of HNP-SiH with 2-vinylfuran to (HNP-F). In parallel, furan end-functionalized poly(dimethylsiloxane) and poly(styrene) were synthesized using anionic living polymerization. The successful synthesis of these structures was confirmed through 1H NMR and FT-IR spectra. Differential scanning calorimetry revealed two thermal transitions of HNP, indicating the presence of a poly(dimethylsiloxane) soft phase and a poly(styrene) hard phase, classifying the HNP as thermoplastic elastomers. A Diels−Alder chemistry approach was employed as a proof of principle for creating thermoreversible cross-linked networks in the polymer. Furan-functionalized HNP demonstrated the formation of thermoreversible elastomeric networks upon cross-linking with bismaleimide (BMI) via Diels−Alder coupling reactions. Kinetic studies of the forward Diels–Alder reaction between the functionalized polymer and BMI revealed a temperature-dependent increase in reaction rate constants, following second-order kinetics. The activation energy of the cross-linking reactions for furan functionalized HNP, PS, and PDMS with BMI were determined. The resulting retro-Diels−Alder cross-links in the polymer dissociated at elevated temperatures (around 140–154 °C), as confirmed by (DSC). Scanning electron microscopy (SEM) was used to study the morphological changes of furan-functionalized hairy nanoparticles, polystyrene, and PDMS at the un-crosslinked, crosslinked, and decrosslinked stages in reaction with bismaleimide. The analysis provided detailed insight into structure development in such types of materials at each cross-linking stage. The results suggest that furan functionalized HNPs are promising building blocks for preparing thermo-reversible elastomeric networks.