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This work reports a comparative study of the response of poly(2,3-dimethoxybenzyl methacrylate), poly(2,5-dimethoxybenzyl methacrylate), and poly(3,4-dimethoxybenzyl methacrylate) to electrical perturbation fields over wide frequency and temperature windows with the aim of investigating the influence of the location of the dimethoxy substituents in the phenyl moieties on the relaxation behavior of the polymers. The dielectric loss isotherms above T g exhibit a blurred relaxation resulting from the overlapping of secondary relaxations with the glass−rubber or α relaxation. At high temperatures and low frequencies, the α relaxation is hidden by the ionic conductive contribution to the dielectric loss. As usual, the real component of the complex dielectric permittivity in the frequency domain increases with decreasing frequency until a plateau is reached corresponding to the glass−rubber (α) relaxation. However, at high temperatures, the real permittivity starts to increase again with decreasing frequency until a second plateau is reached, a process that presumably reflects a distributed Maxwell−Wagner−Sillars relaxation or α′ absorption. The α and α′ processes appear respectively as asymmetric and symmetric relaxations in the loss electrical modulus isotherms in the frequency domain. To facilitate the deconvolution of the overlapping absorptions, the time retardation spectra of the polymers were computed from the complex dielectric permittivity in the frequency domain using linear programming regularization parameter techniques. The spectra exhibit three secondary absorptions named, in increasing order of time γ′, γ, and β followed by the α relaxation. At long times and well separated from the α absorption the α′ relaxation appears. The replacement of the hydrogen of the phenyl group in position 2 by the oxymethyl moiety enhances the dielectric activity of the poly(dimethoxybenzyl methacrylate)s. The temperature dependence of the relaxation times associated with the different relaxations is studied, and the molecular origin of the secondary relaxations is qualitatively discussed.

Copolymers containing vinylpyrrolidone and mono and dialkyl itaconate units with different length in the side chains were synthesized and characterized. Copolymers of vinylpyrrolidone with three different compositions of monomethyl, monoethyl, monopropyl, monoamyl, dimethyl, diethyl, dipropyl, and diamyl itaconate were obtained by radical polymerization. The reactivity ratios was estimated by using the classical Fineman−Ross and Kelen Tüdos procedures. These parameters were also estimated using a computer program based on nonlinear minimization algorithm, starting from the values of r 1 and r 2 obtained by the linear procedures. The copolymers can be considered as random. Fractionation of the copolymers were achieved by fractional precipitation. Fractions were characterized by viscometry and light scattering measurements. The unperturbed dimensions were determined using the Stockmayer−Fixman method. Higher rigidity indexes and characteristic ratios are observed in copolymers containing diitaconate units than that with monoitaconate moieties. The dependence of the glass transition temperature T g with copolymer composition and its correlation with the chain stiffness is also analyzed.

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.

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