Transformation of ethylene vinyl alcohol copolymer from a glassy state to a rubber state through post ester-exchange modification

Abstract

Polyolefins and their derivatives can be modified in both phase-state and function through post-modification techniques. This study presented a novel ethylene-vinyl alcohol-acetoacetate ester copolymer (EVOH-A), synthesized via a simple post ester-exchange method. The incorporation of acetoacetic ester not only alters the polymer's phase state but also enhances its potential for further functionalization. Two-dimensional infrared spectroscopy and molecular dynamics simulations showed that the ester-exchange modification weakens hydrogen bonds in EVOH, leading to a more amorphous structure. Thermal analysis reveals that the glass transition temperature (T_g) of modified EVOH decreases from 30 °C (EVOH) to −3 °C (EVOH-A4), indicating a transformation from a glassy to a rubbery state of polymers. The tensile strength and Young's modulus of the modified EVOH-A films decrease, while tensile elongation significantly increases. Additionally, this work demonstrates the application of modified polymers in the Hantzsch reaction, endowing the photoluminescence and hydrophobicity of polymers. This study introduces a new EVOH modification method with significant potential for developing multifunctional polyolefin materials.