Multiporous materials from thermoreversible poly(vinyledene fluoride) gels

Abstract

Poly(vinylidene fluoride)(PVF₂) produces thermoreversible gels with alkyl diesters of general formula (CH₂)_n (COOEt)₂ as well as with camphor, a naturally occurring ketone. These gels containing polymer-solvent intercalates yield multiporous materials when subjected to controlled solvent removal techniques. The micro and meso pores are attributed to polymer-solvent complexation while the macro pores are formed as a result of removal of the solvent trapped in the fibrillar network. PVF₂ -diethyl azelate (DEAZ, n = 6) and PVF₂ -camphor gels produce porous polymer network when dried by cyclohexane leaching. FESEM images exhibit porous network structures with fibrillar morphology. Mercury intrusion porosimetry (MIP) shows presence of pores having diameter in the range 4 nm-400µm for both the systems. The BJH pore size distribution curves for both systems confirm the presence of mesoporosity. The HK pore size distribution plots indicate that micropores are also created and it also puts evidence of single molecule solvent intercalation between the PVF₂ strands. The hysteresis between the extrusion and the intrusion curves indicates the presence of channel type/ink-bottle type structure in these systems.