Morphological diversity and nanofiber networks of poly(p-oxybenzoyl) generated by phase separation during copolymerization

Poly(p-oxybenzoyl) (POB) precipitates prepared by reaction-induced phase separation during copolymerization exhibit wide variety of morphologies such as fibril, needle, slab, spindle, and sphere. The morphology is significantly influenced by the copolymerization conditions of structure of trifunctional comonomers, copolymerization ratio, solvent, concentration, and temperature of the polymerization. Among them, POB nanofiber networks like a texture of nonwoven fabrics are obtained only by the polymerization of 4-acetoxybenzoic acid with 3,5-diacetoxybenzoic acid (DABA) in aromatic solvent at a concentration of 1.0-2.0% at the content of DABA in feed of 10-20 mol % at 320°C. The network is comprised of fibrillar crystals connected each other at spherical nodal points. The diameters of the fibers are 90-129 nm. This network is highly crystalline and the molecules are aligned along the long direction of the fibers. Various parameters characterized the networks can be controlled by the polymerization concentration.