Effects of quenching and physical aging on the relaxation behavior of nanophase-separated side chain polymers

Abstract

The influence of quenching and physical aging on the relaxation behavior of poly(nalkyl methacrylates) with long alkyl groups in the side chain is studied by dielectric spectroscopy. Typical for these side chain polymers is a nanophase separation of incompatible main and side chain parts and the existence of alkyl nanodomains with a typical dimension of 0.5-1.5nm. In larger alkyl nanodomains a polyethylene-like glass transition αPE occurs at temperatures below the conventional a relaxation. For quenched samples additional peaks on the high frequency wing of this aPE process have been detected in a similar frequency-temperature range where the Arrhenius-like βPE process is observed for slowly cooled side chain polymers with short alkyl groups and small alkyl nanodomains. This is interpreted as an amplification of the localized dynamics in the alkyl nanodomains and related to the production of additional free volume in quenched samples which disappears during physical aging slightly below Tg(α). Similarities to the aging behavior of conventional glasses and the importance of non-equilibrium effects for the properties of nano-structured materials in the glassy state are discussed.