Study on conformational transition of EVA random copolymer in selective solvent mixtures

The dilute solution property of ethylene-vinyl acetate (EVA) random copolymer in 1,2-dichloroethane/cyclohexane (DCE/CYH) selective solvent mixture has been studied by viscometry, light scattering, differential refractomertry and UV spectrophotometry. It was found that both ethylene- and viny1 acetate sequence associations of EVA random copolymer displayed in both DCE and CYH solvents respectively, especially in DCE. Disassociation appeared when the volume fraction of CYH in the DCE/CYH solvent mixture φc was from 0.6 to 0.8. However, in this region, the extreme values of the intrinsic viscosity [η], Huggins constant k′, unperturbed dimension Kθ, refractive index increment dn/dc occurred, and a discontinuity behavior of the preferential adsorption coefficient λ′ and UV spectra demonstrated. These phenomena were attributed to conformational transition of the EVA molecule in solution, which was caused by DCE and CYH selective solvents, respectively.