Microwave‐Assisted Alcoholysis of Ethylene–Vinyl Acetate: Phenomenological and Thermal Evolution of <scp>EVAOH</scp> Terpolymers

ABSTRACT The alcoholysis of ethylene–vinyl acetate (EVA) was examined as a coupled chemical–structural transformation in which reaction kinetics, solvent thermodynamics, hydrogen bonding, and crystallization are closely associated. Controlled alkaline alcoholysis enabled correlating the degree of alcoholysis (DA) with melting behavior, hydrogen bonding, and microstructural evolution. Differential scanning calorimetry showed a sigmoidal increase in melting temperature from ~74°C for EVA‐rich materials to above 110°C at high DA, reflecting a transition from ethylene‐rich crystallites to hydrogen‐bonded vinyl‐alcohol‐rich (VOH‐rich) crystalline domains. A two‐population logistic model described this trend, while stabilization of the VOH‐rich phase for DA ≥ 40% followed the Flory copolymer melting relation. Fourier‐transform infrared spectroscopy, interpreted using the Coleman–Painter association model, revealed a progressive increase in hydrogen bonding with increasing VOH content. In parallel, the solubility parameter of the reaction medium influenced the homogeneity of alcoholysis by affecting polymer coil swelling and alkoxide transport, thereby influencing conversion kinetics and the distribution of hydroxyl groups along the polymer chain. The results provide a phenomenological approach linking the DA, hydrogen‐bond formation, crystalline phase evolution, and solvent quality to the thermal and structural properties of partially hydrolyzed EVA.