A Possible Means to Assist the Processing of PET, PTT and PBT Matteo Alessi, Lucia Conzatti, Philip Hodge,* Santolo Taglialatela Scafati, Paola Stagnaro* Introduction Ring-chain equilibria, i.e. the equilibria that can exist, in the presence of a suitable catalyst, between a condensation polymer and the corresponding family of homologous macrocyclic oligomers (MCOs), have been of theoretical interest for many years. [1–4] Recently, however, they have begun to find practical applications. [5,6] The latter are generally based on the fact that the position of the equilibrium is very sensitive to the concentration. Thus, under neat conditions, or at very high concentrations, the equilibria lie heavily in favor of the condensation polymer. For example, a neat equilibrated mixture typically contains >98 wt.-% polymer and <2 wt.-% MCOs. This provides the basis of a method of polymerization, since treating a macrocycle, or an homologous family of MCOs, under conditions under which equilibration occurs results in efficient polymer synthesis. [5,6] Since most if not all of the MCOs are strainless, such polymerizations are driven by entropy. These are, therefore, entropically driven ring-opening polymerizations (ED-ROPs). On the other hand, at low concentrations, typically <3% w/v, the equilibrium mixture consists very largely of MCOs. The conversion of polymers to MCOs at low concentrations is called cyclo-depolymerization (CDP) and is a convenient route to certain MCOs. Recently, we reported that the addition of small amounts of MCOs 1 (Scheme 1) to Radel TM , 2, results in a significant drop in the melt viscosity of the latter. [7] For example, addition of 10 wt.-% of MCOs 1 results in a drop, at 1.0 rad  s 1 and 320 8C, from 11.3  10 3 to 2.2  10 3 Pa  s. [7] Under similar conditions the MCOs 1 themselves had a viscosity of 7.25 Pa  s. Consequently Radel is potentially Full Paper M. Alessi, L. Conzatti, P. Stagnaro Istituto per lo Studio delle Macromolecole ISMAC-CNR, Via De Marini 6, 16149 Genova, Italy Fax: þ39 010 6475 880; E-mail: stagnaro@ge.ismac.cnr.it S. Taglialatela Scafati Istituto per lo Studio delle Macromolecole ISMAC-CNR, Via E. Bassini 15, 20133 Milano, Italy P. Hodge Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK E-mail: Philip.Hodge@manchester.ac.uk Blends of PET, PTT and PBT with the corresponding MCOs have lower melt viscosities than the pure polymers. This effect of MCOs on viscosity has the potential for exploitation in polymer fabrication and especially in the processing of composite materials. Thus, the blends can be more easily melt-processed than the pure polymers, and the MCOs can then subsequently be converted in situ into high-molar-mass polymers by ED-ROPs. No catalyst is needed for the ED-ROPs. It was shown that suitable poly- mer/MCO blends can be obtained directly by carrying out cyclo-depolymerizations at appro- priate concentrations. Suitable polymer/MCO blends can also, almost certainly, be obtained by carrying out the original polyester syntheses at lower concentrations than normally used. n (CH 2 ) O 2 C CO 2 x n (CH 2 ) O 2 C CO 2 x n (CH 2 ) O 2 C CO 2 x + Blend prepared directlyby cyclo-depolymerization. Blend has lower melt viscosity than pure polymer. Entropically-driven ring-opening polymerization 300 o C High molecular weight polymer Blend prepared directly by cyclo-depolymerization. Blend has lower melt viscosity than pure polymer. 374 Macromol. Mater. Eng. 2010, 295, 374–380 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mame.200900307