Copolymerization effect of m-acetoxybenzoic acid on morphology of poly(oxy-1,4-benzenediylcarbonyl) whiskers

Copolymerizations of p-acetoxybenzoic acid (p-ABA) and m-acetoxybenzoic acid (m-ABA) were carried out in liquid paraffin at 330°C without stirring. Needlelike crystals are obtained when the content of m-ABA in the feed (χ_f) is in the range of 0-30 mol %. These needlelike crystals are inclined to show the fibrillation in both ends and the radial growth nature from the central part as χ_f increased. At higher χ_f than 40 mol %, crystals are not precipitated during polymerization. The content of m-oxybenzoyl units in the obtained whiskers (χ_w) are much lower than χ_f. The details of the polymerization and crystallization processes reveal that cooligomers containing more m-oxybenzoyl units cannot participate in the formation of needlelike crystals due to the higher solubility and the segregation effect of crystallization. The whiskers are predominantly formed by co-oligomers consisting almost entirely of p-oxybenzoyl units.