New heat-resistant and soluble aramids synthesized by palladium-catalyzed carbonylation-polycondensation : Environmental benign manufacturing and material processing toward dematerialization

Abstract

As a candidate for the alternate of conventional, insoluble thermosetting resins that are matrix components of fiber reinforced plastics (FRP), soluble and heat-resistant aramids (wholly aromatic polyamides) were synthesized. To obtain rigid biphenyl-containing aramid, one-step procedure from dihalobiphenyl and aromatic diamine by palladium-catalyzed carbonylation-polycondensation was successfully applied. Reaction parameters, such as base, solvent, palladium-phosphine catalyst and CO pressure in the reaction of 2,7-dibromo-9,10-dihydrophenanthrene (1) and 4,4'-diaminodipheyl ether (2a), were very important for successful synthesis. They affected the molecular weight of resulting aramid significantly. Under optimum conditions, poly[amino-1,4-phenyleneoxy-1,4-phenyleneaminocarbonyl(9,10-dihydro-2,7-phenanthrenediyl)carbonyl] (3a) Was obtained in 99% yield with high molecular weight (polystyrene equivalent M W = 128100). The procedure was applied to some other diamines. The aramid 3a was heat-resistant and soluble in polar organic solvent. On the basis of thermal analysis, 10% weight loss temperature (T 10 ) of the aramid was 461°C. The tensile strength and tensile modulus were 48 MPa and 1.6 GPa, respectively; these properties are roughly in the same level as those of conventional unsaturated polyester resin. Judging from the data, aramid 3a is applicable for matrix of FRP. Some other aramids exhibited similar properties.