Linear Viscoelastic and Dielectric Properties of Strongly Hydrogen-Bonded Polymers near the Sol–Gel Transition

Abstract

Linear viscoelastic and dielectric measurements were conducted for a model associating polymer system, n-butyl acrylate (PnBA)-based copolymers containing 2-ureido-4[1H]-pyrimidinone (UPy) groups as stickers. The number of stickers per chain was varied from less than one to more than two, which covered a sol-to-gel transition region. Fitting the linear viscoelasticity (LVE) to an analytical model developed in our previous study, we found necessity of distinguishing the intra- and interchain association in the model, with only the latter contributing to the gel formation. For the PnBA-Upy sample slightly above the gel point, the relaxation processes due to the Rouse motion and the sticker dissociation were commonly detected in the same range of T covering from 20 to 60 °C. This feature enabled us to make the time–temperature superposition separately for respective relaxation processes, and two sets of shift factors, reflecting the temperature dependence of the Rouse time τ0 and dissociation time τs, were o...