Effect of Head-to-Head Association/Dissociation on Relaxation of Entangled Chains

For entangled high-cis polyisoprene (PI-COOH) undergoing mono-functional, head-to-head association/dissociation through hydrogen bonding of COOH groups attached at the chain head, viscoelastic and dielectric relaxation behavior was examined in bulk state. The relaxation was found to deviate significantly from that of a simple mixture (blend) of non-associative unimer PI and dimer (PI)₂ having the same composition as the associative PI-COOH (determined from FTIR spectroscopy for the COOH group). This deviation is attributed to an association/dissociation-induced motional coupling between the PI-COOH unimer and its dimer. Analysis based on the reptation eigenfunction expansion lends support to this conclusion.