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

Abstract

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-re-propyl itaconate) (PDPI), poly(di-re-butyl itaconate) (PDBI), poly(diisopropyl itaconate) (PDIPI), and poly(diisobutyl itaconate) (PDIBI). Three dielectric relaxation processes, labeled as , ß, and y 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 re-alkyl side group increases. This behavior is similar to that reported for poly(re-alkyl methacrylates), ß relaxation is only detected at some frequencies, and it is more easily detected in terms of£" or e" than in terms of tan d. This relaxation is less pronounced than in the case of poly(re-alkyl methacrylates). An important difference between these polymers and polyire-alkyl methacrylates) is the existence of a new relaxation process labeled as y 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.

Investigation of local chain dynamics in poly(di-n-alkylitaconate)s

“…1, have a rather sterically hindered backbone with one of the two main-chain carbons in the repeat unit bearing two side chains whose length is defined by the number of carbons, n, in each of the alkyl groups. As shown by their mechanical and dielectrical properties and by their thermal transitions in bulk [1][2][3][4][5], PDAI's exhibit a complex relaxational behavior which strongly depends on the alkyl side-chain length. Their different sub-glass and glass relaxation processes have been recently revisited by dielectric spectroscopy [6], which clearly confirms the existence of an additional low-temperature glass-transition, a L , in derivatives with six carbon atoms at least in the alkyl part.…”

Laminin chains in rat and human peripheral nerve: Distribution and regulation during development and after axonal injury

“…In previous research, we reported the dielectric and mechanical relaxations in poly(monoitaconates) and poly(diitaconates) 2, 3, 8–14. Poly(diitaconates) are a family of vinyl polymers obtained from the diesters of itaconic acid.…”

“…These polymers show important changes in their properties, both in solution and the solid state 15–17. The thermal stability and dielectric and viscoelastic properties of several series of poly(itaconates) and copolymers containing itaconate units have been assessed by several researchers 8–14, 16, 18–23. In the case of poly(di‐ n ‐alkyl itaconates), there is an important increase of the steric hindrance because of the presence of two side groups per repeating unit.…”

Dielectric relaxation studies of aromatic polyamides

“…Values of the activation energy for this peak in polymers 2 and 3 are 45 { 5 and 50 carbonates (PTCs). 25 Due to the fact that all the polymers exhibit { 5 Kcal/mol. As we can see, the uncertainty is higher than for g peak.…”