Microwave syntheses of poly(?-caprolactam-co-?-caprolactone)

Microwave irradiation was applied to synthesize poly(ε-caprolactam-co-ε-caprolactone) directly from the anionic catalyzed ring opening of two cyclic monomers, ε-caprolactam and ε-caprolactone using a variable frequency microwave furnace, programmed to a set temperature and controlled by a pulsed power on–off system. Dielectric properties of ε-caprolactam, ε-caprolactone, and their mixture were measured in the microwave range from 0.4 to 3 GHz, showing that both ε-caprolactam and ε-caprolactone exhibited effective absorption of microwave energy to induce a fast chemical reaction. The microwave induced anionic copolymerization of ε-caprolactam and ε-caprolactone generated copoly(amide-ester)s in yields as high as 70%. Conventional thermal and microwave copolymerization studies were also conducted for comparison with the microwave results. These studies demonstrated that an effective and efficient microwave method to copolymerize ε-caprolactam with ε-caprolactone in higher yield, higher amide content, and higher Tg 's, relative to the thermal process, has been developed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1379–1390, 2000