The basic principles of non-equilibrium polycondensation

Polyesters

“…Reaction order 1 in each reactant and in tertiary amine has been often reported or assumed, 207,295 but the kinetics of the reaction appears to be much more complex and is still not well understood. The nature and polarity of the solvent, the basicity of tertiary amine, and the reaction temperature seem to play a major role in reaction kinetics: Increasing solvent polarity results in a dramatic increase in reaction rate, 297 but it has also been reported that reaction rate decreases in solvents which are able to form H bonds with phenols.…”

“…296 The rate constants for the first and second COCl of the acid chloride monomer may be quite different, depending on the acid chloride structure and the nature of bisphenol monomer. 207 This feature has been applied to the synthesis of polyesters with predominant head-to-head or tail-to-head microstructures. 297 Polymer precipitation during the course of reaction is often observed, preventing the formation of high-molar-mass compounds unless the solvent exhibits a high swelling power with respect to the polymer.…”

“…On the other hand, reactions involving acid chlorides or activated carboxylic acids are generally regarded as "nonequilibrium" polyesterifications, due to the high value of their equilibrium constant (K = 4700 for acid chloride-phenol polyarylate synthesis). 207 Polyesterifications can, therefore, be divided into two main categories: (i) high-temperature bulk polyesterifications, mainly hydroxy-carboxy reactions and hydroxy-ester and carboxy-ester interchange reactions, and (ii) nonequilibrium polyesterifications, generally low-temperature solution reactions involving highly reactive monomers such as acid chlorides or activated carboxylic acids. A third class of polyester syntheses consists of reactions that are generally not regarded as polyesterifications: epoxy-carboxy reaction, ring-opening polymerization of cyclic esters, and some miscellaneous, sometimes exotic, reactions.…”

“…207 These reactions generally involve highly reactive monomers such as acid chlorides or activated carboxylic acids and are conducted either in solution or in heterogeneous medium. They present some marked advantages over equilibrium polyesterifications since they can yield high-molar-mass polymers in mild conditions in a short time without ester interchange or degradative side reactions.…”