Effect of Cross-Linking on the Molecular Motions and Nanodomains Segregation in Polymethacrylates Containing Aliphatic Alcohol Ether Residues

Abstract

The dielectric relaxation spectra of poly(2-ethoxyethyl methacrylate) in the frequency domain exhibits above Tg and at high frequencies a well-developed secondary  relaxation. This process is followed in decreasing order of frequency for a relatively weak  relaxation and an ostensible glass-rubber relaxation which at high temperatures and low frequencies is dominated by electrode-polymer interfacial processes. By slightly crosslinking the polymer using 1% (mol) of 2-ethoxyethyldimethacrylate as crosslinking agent, the  relaxation disappears, leaving the  relaxation. The activation energy of the  relaxation for the crosslinked and uncrosslinked polymers is ca. 30 kJmol-1, about 10 kJmol-1 below that of the  relaxation. Crosslinking shifts the location of the glass-rubber relaxation nearly 10º C to higher temperatures, without widening the distribution of relaxation times. The X-rays pattern of the crosslinked polymer presents two peaks at q =5.6 nm-1 and 12.76 nm-1 resembling the X-ray patterns of poly(n-alkyl methacrylate)s. The peaks in poly(n-alkyl methacrylate)s were attributed to the formation of nanodomains integrated by side chains flanked by the backbone. However, whereas this heterogeneity produces an PE peak in poly(n-alkyl methacrylate)s with n  2, this microheterogeneity gives rise to a Maxwell-Wagner-Sillars (MWS) relaxation in the crosslinked polymer located at lower frequencies than the glass rubber relaxation. Finally the interfacial-electrode conductive processes of the crosslinked and uncrosslinked polymeric systems are studied in the light of current theories.