A Simple Pathway toward Quantitative Modification of Polybutadiene: A New Approach to Thermoreversible Crosslinking Rubber Comprising Supramolecular Hydrogen Bonding Networks

Abstract

A commercial polybutadiene (PB) was modified by a simple three-step polymer analogous reaction (epoxidation, oxirane ring-opening, and sulfonyl isocyanate addition), and the degree of modification is quantitatively controlled by epoxidation reaction. Because of the introduction of sulfonyl urethane groups (-O-CO-NH-SO2-) which is prone to self-complementary thermoreversible supramolecular hydrogen-bonding (HB) networks, the PB was modified from a rubbery material to a thermoplastic elastomer. The modified rubbers were characterized by using 1H NMR, FTIR, DSC, and dynamic mechanical analyses. FTIR spectra showed a shift of S=O stretching to lower frequency with increasing degree of modification as a result of the formation of HB complexes. DSC analysis showed that the crystalline melting was suppressed, and the glass transition was elevated to higher temperatures. From the dynamic mechanical analysis it revealed much clearer the crystallization suppression and the glass transition shifts. The changes in thermal and mechanical properties were attributed to the formation of HB supramolecular networks in the modified polybutadienes.