Relaxations in Poly(di-n-alkyl and diisoalkyl itaconates)

A systematic study about the viscoelastic and dielectric relaxations was performed for a family of poli(di-re-alkyl and diisoalkyl itaconates): poly(dimethyl itaconate) (PDMI), poly(diethyl itaconate) (PDEI), poly(di-n-propyl itaconate) (PDPI), poly(di-n-butyl itaconate) (PDBI), poly(diisopropyl itaconate) (PDIPI), and poly(diisobutyl itaconate) (PDIBI). Three dielectric relaxation processes, labeled as α, β, and γ were observed in all cases. Nevertheless, in some polymers a poor resolution of the peaks is observed and only small indications of the phenomena can be seen. In the case of PDPI and PDBI measurements at very low temperatures were performed and dielectric absorption processes are found at those temperatures. Behavior similar to that observed for dielectric relaxations is found for the mechanical one. The temperature at which the a relaxation, associated with the glass transition temperature, is present diminishes as the length of the n-alkyl side group increases. This behavior is similar to that reported for poly(re-alkyl methacrylates), β relaxation is only detected at some frequencies, and it is more easily detected in terms of E″ or ∈″ than in terms of tan d. This relaxation is less pronounced than in the case of poly(n-alkyl methacrylates). An important difference between these polymers and poly-(n-alkyl methacrylates) is the existence of a new relaxation process labeled as γ relaxation between –40 and –120 °C. This relaxation is very sensitive to the dryness of the sample or to the presence of molecules of low molecular weight in the matrix.