Influence of the Metal Cross-Linking on the Dielectric, Mechanical, and Thermal Properties of a Liquid Crystalline Polyazomethine

Abstract

Cross-linked polymeric materials have been synthesized by copper(II) complexation of a semiflexible main-chain liquid crystalline polyazomethine. The influence of the copper(II) cross-linking density on the thermal properties has been studied by DSC. The relaxation behavior of both the parent polymer and the complexed polymers has been investigated by dielectric spectroscopy and dynamic mechanical measurements. The parent compound exhibits three relaxations (denoted by α, β, and γ), together with a conductive process at low frequency. The relaxations have been associated with the glass transition (α), rotational motions located in the rigid mesogenic core (β), and local motions of the decamethylene flexible spacer (γ). Semiempirical calculations have been carried out in order to evaluate the rotational energy barriers which can account for the β process. The influence of the degree of cross-linking on the activation energies and on the strength and shape parameters has also been studied in the copper(II)-complexed polymers.

DC electrical conductivity of some oligoazomethines

“…These structures are illustrated in Fig 9. The energies were calculated using MOPAC‐MM2 taking the minimum energy structure as the initial geometry 22, 23…”

An overview of LC polyazomethines with aliphatic–aromatic moieties: Thermal, optical, electrical and photovoltaic properties

“…PAZ showed a glass transition at 57 1C and a melting transition into mesomorphic ones at approximately 190 1C. Polymer exhibited the N phase, but after annealing, the N phase of the sample at the mesophase temperature (several hours) changed to SmC, as confirmed by POM and X-ray diffraction [63]. PAZ complexes with Cu caused a change of the thermal behaviour and formed anisotropic glasses.…”

“…Using dielectric spectroscopy and dynamic mechanical measurement (DMA), the authors observed two secondary sub-glass relaxations and a relaxation process associated with Tg for PAZ. Increases in the relaxation temperatures and decreases in the strength of the relaxation were found for PAZs with Cu (II), along with an increase in the content of copper [63].…”

“…Puertolas et al [63] investigated the relaxation behaviour of PAZs ( Fig. 1 structure XIV) and their complexes with Cu by using dielectric relaxation spectroscopy and dynamic mechanical measurement.…”

Complexation of Silver Ions with Poly(butyl methacrylate) and Propylene Toward Facilitated Propylene Transport

“…For polymer systems containing ionic species, the dielectric loss factor (e99) is composed of two parts according to Equation (2) e99 = e99 ion + e99 dipole (2) where and are the contributions of dipolar groups and ionic species, respectively. [19,20] is not significant at low temperature due to the low mobility of ion species but becomes more significant with increasing temperature. Thus, it is suggested that the c-peak is related to the motion of the pendant ester groups under these experimental conditions.…”