Preparation of polymer whisker based on p-mercaptobenzoyl (S) and p-oxybenzoyl (0) blocks was examined by the polymerization of Sacetyl-4-mercaptobenzoic acid (AMBA) and the following addition of 4-acetoxybenzoic acid (ABA). Polymerization of AMBA was carried out in liquid paraffin at 300 degrees C for 3 h yielding poly(p-mercaptobenzoyl) (PMB) whisker, and then ABA was added stepwise at 3-hour intervals into the solution. Initial polymerization concentration was 1.98%. The length of the whisker increased with the addition and it became 26.7 mu m from 20.1 mu m after third ABA addition. The width increased very slightly. Both length and width increased with polymer yield but the length increased preferentially rather than the width. The number of whiskers was constant even after the addition of ABA and poly (p-oxybenzoyl) (POB) whisker was not newly formed by the addition. Microscopic FT-IR and selected area electron diffraction measurements revealed that polymer molecules were aligned along the long axis of the whiskers, and the center and tip parts were comprised of PMB crystal and POB crystal, respectively. The polymer whisker based on S and 0 blocks was successfully prepared as grafting POB crystal on PMB whisker with stepwise addition of ABA. Thermal property of the resulting whiskers was also discussed. (c) 2005 Elsevier Ltd. All rights reserved.