Synthesis Of Modified PPTA New Monomers With Hydroxy Methyl And Modified PBI Monomer Exploration

Poly(p-phenylene-terephthalamide)(PPTA)and poly(p-phenylene-benzobisimidazole)(PBI)as the wide used high-performance organic fibers,with excellent tensile strength,high temperature resistance and wide application,has become a research hotspot.Presently,PPTA and PBI have shortages like poor compressive strength and composite bonding properties.New polymers such as poly(hydroxy-p-phenylene-terephthalamide)(H-PPTA),poly(hydroxy-p-phenylene-benzobisimidazole)(H-PBI)were designed for the monomer synthesis research and conditions exploration of mono-hydroxy modified high-performance fibersFirstly,a new AA-type monomer,2-hydroxyterephthalic acid(HTA),was successfully synthesized by carboxylation of 3-hydroxybenzoic acid(3-HBA).Dimethyl 2-hydroxyterephthalate(DMHT),HTA derivatives,were obtained by di-esterification of HTA with methanol in the presence of thionyl chloride.3-hydroxy-4-(methoxycarbonyl)benzoic acid(2-MHT)and 3-hydroxy-4-(methoxycarbonyl)benzoyl chloride(3,4-HMBC)were high selectively synthesised through mono-hydrolysis of DMHT at low-temperature.On the basis that introducing a hydroxy or/and methyl and hydroxy group to molecular structure of PPTA can lead to a higher performance of the polyamides(PA),five new AB-type monomers for modifying PPTA were synthesized successfully.Three class monomers including 4-((4-amino-3-methylphenyl)carbamoyl)-2-hydroxybenzoic acid(AMHBA)and its methyl ester(MAMHB)?4-((4-amino-3-methyl phenyl)carbamoyl)benzoic acid(AMBA)and its methyl ester(MAMB)?4-((4-aminophenyl)carbamoyl)-2-hydroxybenzoic acid(APHBA)had been synthesized by the condensation reaction of 2-methyl-p-phenylenediamine(MPPD)and p-nitroaniline(PNA)with 2-MHT(3,4-HMBC)or 4-(methoxycarbonyl)benzoyl chloride(MBC).The yield and purity of products is 62.62%?69.56%?82.91%?91.30%?76.91%and more than 99%respectively.Secondly,it preliminarily explored the synthesis of 4-(5,6-diamino-benzoimidazolyl)-2-hydroxybenzoic acid(ABIHBA),a new AB-type monomer of mono-hydroxy modified PBI fiber.Synthetic method of its intermediate 1,2,4-triamine-5-nitrobenzene(TANB)are researched as follows:(1)4,6-dinitro-1,3-phenylenediamine(DADNB)was prepared by the ammonolysis reaction of 1,5-dichrolo-2,4-dinitrobenzene(DCDNB)with high yield and purity,the optimum conditions were 1,4-dioxane as solvent,the molar ratio(ammonia to DCDNB)of 8,the pressure of 1.1 MPa,the temperature of 150?,the total reaction time of 5 hours.(2)after reduction reaction of DADNB with sodium polysulfide for 2.5 hours,TANB with the purity of 99.23%and the yield of 37.32%,was obtained.The credibility of the synthetic stability were more than 99%.In this paper,the series of new monomers and intermediates molecular structure were confirmed by IR,1H-NMR,13C-NMR,MS qualitative analysis.