Summary: Copolyesters containing aliphatic units in the main chain were obtained by reacting high molar mass poly(ethylene terephthalate) (PET) with ε‐caprolactone or δ‐valerolactone at high temperature in the bulk. γ‐Butyrolactone did not react in these conditions. Thermal properties were studied by DSC and TGA, and structural characterizations were carried out by 1H NMR spectroscopy and SEC/MALDI‐TOF mass spectrometry off‐line coupling. These techniques demonstrate the insertion of lactone units in PET chains. Linear species with hydroxy, carboxy and vinyl ester end‐groups were clearly identified in the mass spectra, together with cyclic copolymer species. Narrow‐distribution copolyester SEC fractions were characterized by MALDI‐TOF mass spectrometry and used to establish a SEC calibration curve against absolute molar masses. The results indicate that the conventional polystyrene SEC calibration strongly overestimates copolyester molar masses. The degree of randomness of these copolyesters, determined by 1H NMR, shows that chain microstructure presents some block‐copolymer character. The thermal properties of the copolyesters are also discussed.Reaction between PET and γ‐butyrolactone (x = 3), δ‐valerolactone (x = 4), or ε‐caprolactone (x = 5).magnified imageReaction between PET and γ‐butyrolactone (x = 3), δ‐valerolactone (x = 4), or ε‐caprolactone (x = 5).

Kinetic studies of the reactions between a model carboxylic acid and bisoxazoline coupling agents, namely 2,2′‐(1,3‐phenylene)bis(2‐oxazoline) (mbox), 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (pbox), and 2,2′‐(2,6‐pyridylene)bis(2‐oxazoline) (pybox), were carried out in bulk at 140–220 °C. A second‐order two‐step reaction mechanism was proposed and was verified by the experimental results. The results also indicate that the reactivity of the oxazoline groups is unchanged after the reaction of the other oxazoline group of the same coupling agent moiety, that is, oxazoline groups are equireactive. Rate constants and activation enthalpies and entropies were determined, allowing the comparison of bisoxazoline reactivity. The following reactivity order was found: pybox > mbox > pbox. The formation of a stabilized protonated complex is postulated to explain the much higher reaction rate observed with the new coupling agent pybox.Variation of the experimental concentrations of reactants and reaction products versus time.magnified imageVariation of the experimental concentrations of reactants and reaction products versus time.

A TEMPO-based free radical initiator (4a) containing a dibenzo-24-crown-8 (DB24C8, 2a) moiety was synthesized. A similar initiator (4b) based on bis(m-phenylene)-32-crown-10 (BMP32C10, 1b) was also synthesized. The crown-based initiators were used to prepare crown ether terminated polystyrenes of narrow molecular weight distribution (PDI). The DB24C8-terminated polymer 5 was demonstrated to form a pseudorotaxane complex (18) with dibenzylammonium hexafluorophosphate (17), but because of its small cavity, 5 cannot complex bulky N,N‘-dialkyl-4,4‘-bipyridinium (paraquat or viologen) salts. On the other hand, the BMP32C10-terminated polymer 11 complexed N,N‘-bis(p-tert-butylbenzyl)-4,4‘-pyridinium bis(hexafluorophosphate (paraquat salt, 23) strongly, but did not interact with dibenzylammonium hexafluorophosphate (17) to a detectable extent. Therefore, these new polymeric hosts are capable macromolecular building blocks for supramacromolecular chemistry using pseudorotaxane complexation, and furthermore, both show selectivity; the DB24C8 polymer is selective for secondary ammonium ion complexation, and the BMP32C20 polymer is highly selective for paraquat recognition. Future work will involve application of these new functional polymers to preparation of star, graft, and block structures by self-assembly.

The synthesis of poly(glycolic acid) (PGA) by polyesterification of glycolic acid was studied using ionic liquids, mainly 1,3-dialkylimidazolium salts, as reaction media. The 1 H NMR spectra of PGA oligomers were assigned and end-group signals were used to follow the reaction. Low PGA yields were obtained by the direct polyesterification of glycolic acid at 200-240 8C, because of monomer evaporation during the reaction. On the other hand, PGAs of DP n up to 45 were obtained by the postpolycondensation of a preformed oligomer in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIm þ Tf 2 N À ). The precipitation of PGA in reaction medium at long reaction times limited the achievable molar mass. Rate constants were determined for catalyzed and noncatalyzed reactions, assuming a second-order reaction mechanism. The efficiency of esterification catalysts such as Zn(OAc) 2 was low in these media, as only about twofold increases in reaction rate were observed. This was assigned to the preferential interaction of Zn 2þ with ionic liquid anion instead of the polymer carboxylic acid end-groups. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: [3025][3026][3027][3028][3029][3030][3031][3032][3033][3034][3035] 2006