Synthesis Of New Monomer And Exploration Of Resin And Fiber For Hydroxy Modified Benzazole Polymers

Polybenzazoles(PBZ)are a class of heterocyclic polymers,it divides into two categories which including bisazole and azole.Among the bisazole,it includes polybenzobisthiazole,polybenzobisimidazole and poly(p-phenylene benzobisoxazoles)which is the most famous of bisazole.The fiber which made by these polymers have the advantages of high strength,high modulus,high temperature resistance and flame retardancy,meanwhile,they has shown great application prospects.However,research on the monomer of modified PBZ has gradually become the research hotspot,especially on AB-type monomer of PBZ.The modified PBZ fiber which prepared by these AB-type monomer,it focuses on the improvement of the fiber which has some defects of inert surface,resistant to compression performance and UV stability problems,at the same time,it avoids the problems caused by the original process.In this paper,by studying the simplest structure polymers of azole(PBZo),and choosing hydroxy modification as the target.Through the design of novel AB-type monomer of modified PBZ,which including poly 6-hydroxy-2,5-benzoxazole(HPBOo)and poly 6-hydroxy-2,5-benzimidazole(HPBIo),to explore the effect of its application in homopolymerization or copolycondensation with the monomer of PBO which synthesis of hydroxy and imidazole comprehensive modified PBO resin and fiber.So that the axial compressive strength and composite performance of PBO fiber could be improved.The research contents mainly include the following four aspects:Firstly,two synthesis technology of the key intermediate4-amino-2-hydroxy-5-nitrobenzoic acid(AHNA)for AB-type monomer of hydroxy-modified PBIo were systematically study: AHNA was synthesized by acylation,nitration and hydrolysis three-step reactions using 4-aminosalicylic acid(ASA)as raw material.Meanwhile,the nitration and hydrolysis reaction were optimized,the total yield was 56.3%,the purity of 99.21%.At the same time,using methyl 4-amino-2-hydroxybenzoate(MAHB)as the starting material,AHNA was alsosynthesized though nitration and hydrolysis two-step reactions,the total yield was66.6%,the purity of 98.22%.On the basis of these,the AB-type monomer 4,5-diamino-2-hydroxybenzoic acid(DAHBA)of hydroxy-modified PBIo was synthesized by reduction one-step reaction using AHNA as the raw material,and the reduction process was optimized,the total yield was 55.3%,the purity of 98.84%.Then,the DAHBA was synthesized by the diazo-coupling and reduction reaction which using ASA as the starting material,and the process was optimized,the total yield was 39.4%,the purity of 99.04%.Meanwhile,the successful synthesis of DAHBA was used as a reference,new synthesis route of 5-amino-2,4-dihydroxybenzoic acid(DHABA)of hydroxy-modified PBOo was explored and it synthesized by diazo-coupling and reduction reaction which using 2,4-dihydroxybenzoic acid as raw material,the total yield was 34.5%,the purity of 95.12%.Finally,the modified PBO of hydroxy and imidazole which named poly6-hydroxy-2,5-benzimidazole/p-phenylene-benzobisoxazoles(HI-PBO)was explored by using the DAHBA and AB-type PBO monomer ammonium 4-(5-amino-6-hydroxy benzoxazol-2-yl)benzoate(ABAA)as the material,its thermal decomposition temperature reached 552 ?,the results show that the high thermal decomposition temperature along with the increased molecular weight of HI-PBO.In this paper,the molecular structures of several intermediates and new monomers were confirmed by IR,NMR,MS and other qualitative analysis.This novel study has good prospects for development of industrialization,moreover,it's provide technical support and promote the development of modified PBO fiber.