Abstract: The process of preparing high-purity new AB-PBO monomer：4-(5-amino-6- hydroxybenzoxazole-2-yl) benzoic acid（ABA）was studied，and the effect of pH on ABA molecular morphology and IR absorption were investigated. The results showed that ABA was conveniently synthesized from methyl 4-(5-amino-6-hydroxybenzoxazole-2-yl)benzoate (MAB) with purity of 99.5% and yield of 85% via alkali hydrolysis of K2CO3 at 60—100℃ and crystallization at pH 6.0 in aqueous solution of weak acid salt with reducing properties，such as Na2S2O4 or NaHSO3，which had the advantages of simple procedure and easy industrialization. The prepared ABA had the characteristics of high-quality，polymer retarder DMF-free，excellent thermo- and antioxydation -stability，and safe operation in polymerization. New progress was achieved in preparing polymer grade AB-PBO monomer.

摘要： 系统地研究了AB型新单体：4-(5-氨基-6-羟基-2-苯并口恶唑基)苯甲酸（ABA）的合成方法以及产品析出时pH值条件对其分子形态及红外吸收的影响。以4-(5-氨基-6-羟基-2-苯并口恶 唑基)苯甲酸甲酯（MAB）为原料，60～100 ℃于碳酸钾水溶液中水解反应至溶液澄清，用还原性弱酸性盐的水液在pH值6.0析出结晶、制得纯度99.5%以上高质量的新单体、经FT-IR归属剖析确认为游离的酸式单体ABA，收率达85%；具有过程工艺简便，单体稳定性优异、且无残留DMF阻聚杂质以及聚合操作安全等特点，在制备聚合级AB型PBO单体中取得新进展。