One-pot, multi-molecular macrocyclization allows the highly selective preparation of strained macrocyclic aromatic hexamers structurally stabilized by an inward-pointing continuous hydrogen-bonding network.

SynopsisIn this article, the polycondensation of terephthaloyl chloride and p-phenylenediamine was systematically studied, including the liquid-crystalline state of the solution and the spinning of poly(l,4-phenyleneterephthalamide) (PPTA). High-molecular-weight PPTA with )7,& = 5-7 was prepared and the main factors influencing the solution polycondensation of 1,4-phenylenediamine with terephthaloyl chloride were studied in detail. Experimental results showed that the water content of the reaction system, reactant concentration, and volume ratio of mix solvents have a great influence on the inherent viscosity of the poly(l,4-phenyleneterephthalamide) obtained. The highest )7rnh was obtained at 0.3Mlliter reactant concentration in a mixed solvent ratio HMPA/DMAC of 4/1 (by volume), a t 0.35Mlliter reactant concentration in a mixed solvent of HMPA/NMP = 7/3, and a t 0.5Mlliter of reactant concentration in a mixed solvent of HMPA/THF = 9/1. The water content must be controlled to less than 100 ppm in the polymerization system. In the early stage of the polycondensation process, the q,nh of the polymer obtained increased rapidly with time. The system gelled within 2 or 3 min, while the monomer conversion reached about 100%. However, the reaction of polycondensation continued after gelation and the ?))nh of the polymer increased appreciably. We have studied the viscosity behavior at 20-155OC for the anisotropic solution of PPTA in 100% sulfuric acid ()7f,,h of PPTA 2.5-4.9). Experimental results showed that, a t low concentrations the viscosity of isotropic solution increases with the increase of polymer concentration to reach a maxium near the critical polymer concentration, beyond which the solution changes to an anisotropic liquid-crystalline solution. The appropriate spinning region was obtained as shown in the phase diagram determined by viscosity, degree of depolarization anisotropy, and region of thermal depolymerization. Fibers of PPTA with high modulus and high tenacity were obtained by dry-jet wet spinning. The fibers obtained have a tenacity of -22 g/denier, a modulus of -600 g/denier, and elongation at break -3.5%.

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SynopsisTwo new routes to polyamides were established, based on the polycondensation of two new typical active diesters: the active diester of N-hydroxy-5-norbornene-2,3-dicarboximide, such as N,N'-(isophthaloyldioxy)bis(5-norbornene-2,3-dicarboximide) and N,N'-(terephthaloyldioxy)bis(5norbornene-2,3-dicarboximide), and the active diester of 3-hydroxy-4-0~0-3,4-dihydr0-1,2,3-benzotriazine, such as 3,3'-(isophthaloyldioxy)bis(4-oxo-3,4-dihydro-1,2,3-benzotriazine) with diamines. The polycondensation occurred a t room temperature in solution without added catalyst. Dipolar aprotic solvents which included dimethyl sulfoxide and N-methyl-2-pyrrolidone were used as solvents for polymerization. Before polymer synthesis the aminolysis of two active monoesters was carried out as a model compound study.