Influence of Polymer Matrix Selection on the Properties of PVC- and PLA-Based Polymer Inclusion Membranes Containing D2EHPA

Abstract

Polymer inclusion membranes (PIMs) are promising materials for separation processes due to their tunable structure–property relationships and compositional versatility. In this work, PIMs were prepared by solvent casting using di(2-ethylhexyl) phosphoric acid (D2EHPA) as a carrier and either poly(vinyl chloride) (PVC) or poly(lactic acid) (PLA) as supporting matrices. The membranes were comparatively characterized to assess the influence of polymer selection on their physicochemical properties. FTIR analysis confirmed the successful incorporation of D2EHPA into both polymer matrices while preserving their chemical structures, while SEM–EDS revealed continuous membranes with distinct surface morphologies and average thicknesses of approximately 157 μm (PVC) and 141 μm (PLA), without evidence of macroscopic phase separation. Thermal analysis revealed matrix-dependent thermal stability and degradation behavior, with T5% values of approximately 220 °C for PVC-based membranes and 210 °C for PLA-based membranes and glass transition temperatures of approximately 60 and 58 °C, respectively. Water contact angle measurements revealed moderately wettable surfaces, with contact angles of 59.2° for PVC-based membranes and 64.3° for PLA-based membranes. Mechanical testing revealed a marked contrast: PVC-based membranes exhibited greater ductility (160.1% elongation at break) and lower stiffness (31.8 MPa), whereas PLA-based membranes showed substantially higher stiffness (369.1 MPa) and lower elongation at break (41.87%). Overall, these findings demonstrate that polymer matrix selection governs the physicochemical properties of D2EHPA-based polymer inclusion membranes, with PLA representing a promising biodegradable alternative for applications requiring enhanced stiffness and dimensional stability.