Eudragit E, a copolymer of N,N-dimethylaminoethyl methacrylate and neutral methacrylic acid esters, has been found to form sixmembered cyclic anhydrides via intramolecular ester condensation by a heating process only, without adding any catalyst or initiator. A novel reflectance Fourier transform infrared microspectroscopy system equipped with differential scanning calorimetry (FTIR/DSC) was used to determine the thermal-dependent anhydride formation of Eudragit E film. The anhydride-related IR peaks at 1801, 1763 and 1007 cm -¹ appeared from 180°C and increased with the heating temperature, while the peaks at 2820 and 2770 cm -¹ for the dimethylamino group reduced gradually with the increase of temperature, strongly suggesting that the anhydride formation by ester condensation started above 180°C. The appearance of peaks at 1801 and 1763 cm -¹ not only illustrates the asymmetric and symmetric stretching vibration mode of the carbonyl group existing in the anhydride structure, but also exhibits the formation of six-membered cyclic anhydrides during the heating process. Moreover, the higher peak intensity ratio of 1763 cm -¹/1801 cm -¹ also reveals the predominant role of intramolecular ester condensation in anhydride formation in Eudragit E film.
Посилання на статтю:
Polymer Communication Formation of six-membered cyclic anhydrides by thermally induced intramolecular ester condensation in Eudragit E film / Shan-Yang Lin, Hui-Ling Yu, Mei-Jane Li // Polymer. – 1999. – N 40. – P. 3589–3593.