羟基改性聚对亚苯基苯并二唑单体3,3′-二氨基-4,4′-二羟基联苯盐酸盐的合成

为改进聚对亚苯基苯并二唑（PBO）纤维复合黏结性能差等缺点，在苯环上引入极性基团羟基进行化学分子结构改性，3,3′-二氨基-4,4′-二羟基联苯盐酸盐（DADHBP·2HCl）是羟基改性PBO的关键单体。以4,4′-二羟基联苯（DHBP）为原料经硝化、还原反应合成得到中间体3,3′-二硝基-4,4′-二羟基联苯（DNDHBP）和羟基改性PBO的单体DADHBP·2HCl，并对其反应条件进行了优化。结果表明：对于硝化反应，以甲苯、冰乙酸的混合液为反应溶剂，n(DHBP)∶n(HNO₃)=1∶2，反应温度5℃，反应时间2.5h，收率81.39％，高效液相色谱（HPLC）纯度(质量分数)92.43％；还原反应，n(DNDHBP)∶n(FeSO₄·7H₂O)=1∶9，乙醇为溶剂，七水合硫酸亚铁为助剂，n(DNDHBP)∶n(N₂H₄·H₂O)=1∶5.5，反应温度78℃，反应时间9h，热过滤，滤饼盐酸精制后得到DADHBP·2HCl，收率67.16%，HPLC纯度（质量分数）98.20%。中间体和产物结构经红外光谱、核磁氢谱和电喷雾质谱表征确认。

Synthesis of hydroxyl-modified PBO monomer 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride

In order to improve the poor performance of PBO composite bonding, a polar group hydroxyl group is introduced into the benzene ring for structural modification, and 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride（DADHBP·2HCl） is a key monomer for modification. The intermediate 3,3′-dinitro-4,4′-dihydroxybiphenyl (DNDHBP) and the hydroxyl-modified PBO monomer DADHBP·2HCl were synthesized by the nitration and reduction reaction of 4,4′-dihydroxybiphenyl, and the reaction conditions were optimized. The results showed that for the nitration reaction, the yield of 65% of DNDHBP with a HPLC purity 98.65% could be achieved under the conditions of reaction temperature 5℃, reaction time 2.5h and n(DHBP)∶n(HNO₃)=1∶2 in the mixed solvent of toluene and glacial acetic acid. The catalytic reduction reaction was conducted in ethanol as solvent under the conditions of n(DNDHBP): n(N₂H₄·H₂O)=1∶5.5, reaction temperature 78℃ and reaction time 9h using ferrous sulfateheptahydrate as auxiliary n(DNDHBP):n(FeSO₄·7H₂O)=1∶9]. After the hot filtration of the reaction mixture, DADHBP·2HCl could be obtained with a yield of 67.16% and a HPLC purity of 98.20% through refined by hydrochloric acid. The intermediate and product structures were confirmed by FT-IR, ¹H-NMR and EI-MS.