Effect of Aromatic Rings in AESO-VDM Biopolymers on the Local Free Volume and Diffusion Properties of Polymer Matrix

In this work, the influence of aromatic rings on the local free volume of cured mixtures of acrylate epoxidized soybean oil (AESO) and vanillin dimethacrylate (VDM) was investigated. Cross-linking took place under the influence of UV light in the presence or absence of a photoinitiator. The local free volume and its homogeneity were characterized using the Positron Annihilation Lifetime Spectroscopy (PALS) technique. It was found that increasing the content of VDM, which contains aromatic rings, caused a decrease in the local free volume of the cured polymer network, with consequences for the diffusion properties of the polymer, which were tested for the case of water. Another consequence of increasing the content of VDM was a decrease in the conversion of double bonds in the finally cured samples, characterized by near-infrared spectroscopy (NIR). This finding illustrates a case where the decrease in free volume is not necessarily related to an increase in the crosslinking density of the polymer, but is a consequence of the presence of an increase in the occupied volume of aromatic rings in the volume of the polymer.