Kinetics of an interfacial polycondensation reaction. Part 2.—Reaction of terephthaloyl chloride with piperazine

Abstract

The kinetics of the polymerization of terephthaloyl chloride dissolved in n-heptane with piperazine in aqueous buffer in a stirred, two-phase system have been studied by measuring the rate of consumption of terephthaloyl chloride. The fast reaction has been slowed down in two ways so that it can be followed by normal procedures : (i) the concentration of monomers was only 10^–2-10^–5M, (ii) the concentration of the uncharged (reactive) form of piperazine was kept very small by using aqueous phases of pH 5–6. The hydrolysis of terephthaloyl chloride is much slower than the polyamidation reaction and can be allowed for quantitatively. The rate process for the consumption of terephthaloyl chloride is first order with respect to the acid chloride, but for piperazine decreases from 0.89 to 0.50 as its concentration increases. The rate of the reaction increases with increasing pH and increasing temperature and has an energy of activation of about 4 kcal mole^–1.

The production of polymer of high molecular weight (10000–40000) at low concentration and slow rate of reaction is due to a more rapid rate of condensation of acid chloride functional groups with amine-ended oligomers, than with piperazine itself.