Effect of Acid Comonomer on the Morphology, Thermal, Mechanical and Solvent Stability Properties of Electrospun Membranes of Poly(Acrylonitrile-Co-Methacrylic Acid)

This study assessed the morphology and thermal, mechanical, and chemical properties of electrospun membranes made of acrylonitrile-methacrylic acid copolymers (PANCMAA). Copolymers were synthesized using the aqueous suspension method with varying comonomer contents (homopolymer,PAN, lower acid, PANCMAA1, and higher acid, PANCMAA2) and characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). Electrospun fibers were produced by adjusting the polymer concentration in the DMF solution, and the optimal conditions yielded nanofibrous membranes. PAN and PANCMAA membrane properties were evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Dynamic Mechanical Thermal Analysis (DMTA), stress-strain tests, and swelling behavior in a phosphate buffer solution. The comonomer content influenced the crystallinity of the electrospun nanofibers, reducing the 16.8° XRD peak intensity from PAN to PANCMAA2. DSC indicated an increased T_g (from 113°C in PAN to 127°C in PANCMAA2) and a decreased exothermic cyclization enthalpy (311 J.mg^-1 in PAN to 271 J.mg^-1 in PANCMAA2). PANCMAA1 exhibited higher stiffness than PANCMAA2 and PAN, with a storage modulus of 0.16 GPa, a Young’s modulus of 135.7 MPa, and a lower elongation at break (3.98%). The presence of the acid comonomer significantly enhanced the swelling behavior of the electrospun membranes in phosphate buffer solution.

Keywords:
Poly(acrylonitrile-methacrylic acid); copolymerization; thermo-mechanical properties; aqueous solvent resistance