Structural and Dynamic Study of Ethylene−Vinyl Alcohol Copolymer Gels by ¹H Pulse NMR and Solid-State ¹³C NMR

Abstract

1 H pulse NMR and solid-state 13 C NMR spectra of ethylene-vinyl alcohol copolymer (EVOH) gels were measured as a function of ethylene content, and furthermore, the 13 C spin-lattice relaxation times (T1) and the 1 H spin-spin relaxation times (T2) have been measured, to elucidate the structure and dynamics of the mobile and immobile regions in the gels. From the 1 H pulse NMR experimental results, it is found that the 1 H T2 signal is mainly composed of two or three kinds of components with different molecular motions. The long T2 component is assigned to correspond to the mobile region, which comes from the un-cross-linked region, the short T2 component corresponds to the immobile region, which comes from the cross-linked region, and the intermediate T2 component corresponds to the intermediate region between the mobile and immobile regions, which comes from the vicinity of the cross-linked region in the EVOH gel. Furthermore, from the solid state 13 C NMR experimental results, it is found that the formation of hydrogen bonds between the hydroxyl groups in vinyl alcohol parts of EVOH copolymers with high vinyl alcohol fraction and the formation of hydrophobic interactions between the methylene groups in ethylene parts of EVOH copolymers with high ethylene fraction contributes to its gel formation.

Solid-State Nuclear Magnetic Resonance

“…Similarly the effects of pressure on dynamics of chains in atactic polypropylene as monitored by the effects on NMR spectra yielded an average correlation time described by a Vogel-Fulcher function (119). The dynamics of copolymers of PVA with ethylene were studied to determine different motional components (120). NMR relaxation in copolymers of methyl acrylate and sodium methacrylate is interpreted in terms of interchain interactions (121).…”

“…Curing and aging of elastomers (89) and vulcanized rubber (90) are also shown to be amenable to study by solid-state NMR spectroscopy, as is hydration of films of materials such as poly-(vinyl alcohol) (PVA) (91). Copolymers of ethylene with vinyl alcohol have also been analyzed with solid-state NMR techniques (92). The structure and dynamics of acrylate-polymer films on glass were examined with NMR (93).…”

Rheological behavior of aminosaccharide-based glycopolymers obtained from ethylene-vinyl alcohol copolymers

“…22 EVOH copolymers do not develop gels in aqueous solution because only a small amount is able to dissolve in water; however, EVOH copolymers form gels in mixtures of DMSO and H 2 O. 28 The formation of hydrogen bonds between the hydroxyl groups of the vinyl alcohols of EVOH copolymers and hydrophobic interactions between methylenic groups contributes to gel formation. The formation of gels is attributed to differences between the intermolecular interactions of DMSO-EVOH networks and H 2 O-EVOH networks.…”

“…The formation of gels is attributed to differences between the intermolecular interactions of DMSO-EVOH networks and H 2 O-EVOH networks. 28 The preparation of novel glycopolymers through the chemical modification of EVOH copolymers derived from three commercial monosaccharides (D-(+)-glucosamine, EVOHxF-Gl, D-(+)-galactosamine, EVOHxF-Ga and D-(+)-mannosamine, EVOHxF-Ma) has been described in a recent article. 29 The thermal behavior of the copolymers was analyzed, and results revealed that crystallite development was prevented when the hydroxyl groups were substituted with carbohydrates.…”