Chain extension of carboxy-terminated aliphatic polyamides and polyesters by arylene and pyridylene bisoxazolines

The bulk reactions between carboxy-terminated polyamide-12 (PA12) or carboxy-terminated poly(butane-1,4-diyl adipate) (PBDA) and 2,2'-(1,3-phenylene)bis(2-oxazoline) (mbox), 2,2'-(1,4-phenylene)bis(2-oxazoline) (pbox), 2,2'-(2,6-pyridyline)bis(2-oxazoline) (pybox) as chain-coupling agents were studied by size exclusion chromatography, carboxy end- group titration, and NMR spectroscopy. The chain-coupling reaction yielded high-molar mass polymers within 20 to 80 min, depending on reaction temperature, starting oligomer molar mass, bisoxazoline/oligomer molar ratio, and the nature of bisoxazoline. No side-reactions were observed. Bisoxazoline pybox, used for the first time in the bulk chain extension of carboxy-terminated polymers, exhibited the highest reaction rates. The thermal properties of the resulting polymers, studied by differential scanning calorimetry and thermogravimetric analysis, are also discussed.