Effect of slight crosslinking on the mechanical relaxation behavior of poly(2-ethoxyethyl methacrylate) chains

Abstract

Elsevier Carsí Rosique, M.; Sanchis Sánchez, MJ.; Díaz Calleja, R.; Riande, E.; Nugent, MJD. (2013). Effect of slight crosslinking on the mechanical relaxation behavior of poly(2-ethoxyethyl methacrylate) chains. Abstract The synthesis, thermal and mechanical characterizations of uncrosslinked and lightly crosslinked poly(2-ethoxyethyl methacrylate) are reported. The uncrosslinked poly(2-ethoxyethyl methacrylate) exhibits in the glassy state two relaxations called in increasing order of temperature, the gamma and beta processes respectively. These are followed by a prominent glass-rubber or alpha relaxation. By decreasing the chains mobility by a small amount of crosslinking, the beta relaxation disappears and the peak maximum associated with the alpha relaxation is shifted from 268 K to 278 K, at 1 Hz. An investigation of the storage relaxation modulus of the crosslinked polymer indicates two inflexion points that presumably are related to segmental motions of dangling chains of the crosslinked networks and to cooperative motions of the chains between crosslinking points. Nanodomains formed by side-groups flanked by the backbone give rise to a Maxwell-Wagner-Sillars relaxation in the dielectric spectra that have no incidence in the mechanical relaxation spectra. 2

The effect of cross-linking on the molecular dynamics of the segmental and β Johari–Goldstein processes in polyvinylpyrrolidone-based copolymers

“…The homopolymer from found that the cross-linking may produce different effects in the sub-glass transitions, which may be related to their molecular origin. [17][18][19][20][21][22][23] Thus, the secondary relaxations can have (i) an intramolecular origin, which involves the independent motion of an isolated group or (ii) an intermolecular origin, which involves the motion of essentially the entire molecule (repeat unit in the case of a polymer). The latter are known as Johari-Goldstein (JG) relaxations.…”

A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis

“…This behavior has been observed in some systems where the formation of nanodomains, integrated by the side chains flanked by the backbone, is produced (Carsí, et al, 2012;Carsí, et al, 2013). This effect can be understood due to a decrease in the free volume.…”

“…The dynamic mechanical and dielectric properties are intrinsically correlated and they are associated with a structural polymer feature (McCrum, et al, 1991;Sanchis, et al, 1999;Carsí, et al, 2012;Carsí, et al, 2013;Deutsch, et al, 1954). The dynamic relaxation properties of cross-linked polymer networks are highly sensitive to network composition and polymer chain architecture.…”

“…The effect of cross-linking in the segmental transition, also called α relaxation, usually broadens the dispersion and makes its relaxation time more sensitive to temperature, that is, the material becomes more fragile. On the other hand, it is found that the cross-linking may produce different effects in the sub-glass transitions, which may be related to their molecular origin (Casalini, et al, 2010;Carsí, et al, 2012;Carsí, et al, 2013;Kalakkunnath, et al, 2007;Sabater i Serra, et al, 2009) In the previous chapter, the effect of copolymer composition in a family of VP and BA copolymers with a different proportions of monomers and a fixed cross-linker molar ratio of 1% was studied using different characterization techniques. The dielectric spectra showed three relaxations, γ, β and α, followed by conductive processes.…”

“…Their electrical response is mainly associated with relaxation phenomena occurring under the influence of the alternated current (ac). The ac electrical response of disordered systems to electric perturbations results in the superposition of different contributions (Kremer, et al, 2003;Carsí, et al, 2013). These contributions are related to: (i) the hopping process of localized charge carriers, (ii) the response produced by the molecular structure deformation, following on the diffusion of charges through percolation paths, and (iii) the dispersive response of the bound charges (dipolar response).…”