Fabrication of Thermally Crosslinked Hydrolyzed Polymers of Intrinsic Microporosity (HPIM)/Polybenzoxazine Electrospun Nanofibrous Membranes

Abstract

In this study, thermally crosslinked hydrolyzed polymers of intrinsic microporosity (HPIM)/polybenzoxazine electrospun nanofibrous membranes (NFMs) are successfully produced. The nanofibers having 800 +/- 260 to 670 +/- 150 nm average fiber diameters from HPIM and blends of HPIM/ benzoxazine (BA-a) ranging from HPIM:(BA-a) weight ratio of 9:1 to 2:1 w/w are produced by electrospinning. Self-standing HPIM/(BA-a) NFMs are thermally step-wise cured resulting in crosslinked HPIM/Poly(BA-a) NFMs. Structural characterization of as-electrospun HPIM/(BA-a) and crosslinked HPIM/Poly(BA-a) NFM is conducted by FT-IR spectroscopy to trace the ring opening and crosslinking reactions. Elemental analysis and XPS studies show an increase in carbon content and reduction in nitrogen content due to the crosslinking reaction. Decomposition temperature (T-d) of HPIM NFM increases from 218 to 270 degrees C with the crosslinking based on the DSC. DMA analysis shows that the mechanical strength of the NFMs has increased significantly with crosslinking. Young's moduli of HPIM NFM is increased from 16 +/- 7 to 67 +/- 1 MPa for crosslinked HPIM/Poly(BA-a)%33 NFM. Similarly, higher storage modulus is observed for HPIM/Poly(BA-a) NFMs compared to HPIM NFM. The crosslinked HPIM/Poly(BA-a) NFMs keep their fibrous morphology after solvent treatment in dimethylformamide revealing their structural stability compared to pristine HPIM NFM.