The modified poly(p-phenylene benzoxazole)(PBO) containing ionic groups in polymer chains(sulfonated poly p-phenylene benzoxazole,SPBO) was obtained by copolymerization from 1,3-diamino-4,6-dihydroxybenzenedihydrochloride(DAR) and terephthalic acid(TPA),with addition of certain amounts of 5-sulfoisophthalic acid monosodium salt in replace of TPA,in polyphosphoric acid.The SPBO fiber was obtained for the first time through a dry-jet wet-spinning technique.After incorporation of ionic groups into PBO macromol...