SYNTHESIS OF UCST-TYPE THERMORESPONSIVE POLY(ACRYLAMIDE-CO-ACRYLONITRILE) DOPED PVDF NANOFIBRE MEMBRANE

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Ensuring access to clean and safe water requires the development of advanced membrane materials with tunable and adaptive surface properties. However, conventional polymeric membranes typically exhibit static physicochemical characteristics, limiting their ability to respond to changing operating conditions. In this study, a stimuli-responsive poly(vinylidene fluoride) (PVDF) nanofibre membrane was developed through the incorporation of a thermoresponsive copolymer, poly(acrylamide-co-acrylonitrile) (PAAm-co-AN), which exhibits upper critical solution temperature (UCST) behaviour. The PAAm-co-AN copolymer was synthesized in-house via free-radical copolymerization of acrylamide (AAm) and acrylonitrile (AN) at a 70:30 molar ratio and blended with PVDF at 0, 3, and 10 wt%. Electrospun membranes displayed uniform nanofibrous architectures with interconnected pore networks. Scanning electron microscopy (SEM) revealed systematic morphological evolution with increasing PAAm-co-AN content, transitioning from uniform smooth fibres in neat PVDF to slightly thicker fibres and a more interconnected nanofibrous network at higher copolymer loadings. Surface wettability measurements showed a significant reduction in water contact angle from approximately 90° for pure PVDF to 49° and 34° for membranes containing 3 and 10 wt% PAAm-co-AN, respectively, indicating enhanced hydrophilicity. Temperature-dependent behaviour was further examined using dynamic light scattering (DLS), which demonstrated a greater than 60% increase in hydrodynamic diameter at 60 °C compared to room temperature, attributed to strengthened hydrogen bonding and interpolymer complexation between PAAm amide groups and the PVDF backbone. Overall, the results confirm that incorporating PAAm-co-AN into PVDF nanofibre membranes enables temperature-responsive modulation of structural and surface properties, providing a promising material platform for the future development of smart membrane systems.

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