Physical characterization of poly(omega-pentadecalactone) synthesized by lipase-catalyzed ring-opening polymerization

The Candida antarctica lipase B (Novozyme-435)-catalyzed ring-opening polym erization of omega -pentadecalactone in toluene was performed. Poly(w-penta decalactone) [poly(PDL)] was obtained in a 93% isolated yield in 4 h with a number-average molecular weight of 64.5 x 10(3) g/mol. and a polydispersit y index of 2.0. The solid-state properties of poly(PDL) were investigated b y thermogravimetric analysis (TGA) coupled with mass spectrometry, differen tial scanning calorimetry (DSC), stress-strain measurements, wide-angle X-r ay diffraction, and dynamic mechanical and dielectric spectroscopies. Poly( PDL) is a crystalline polymer that melts around 100 degreesC. The polyester shows good thermal stability, with a main TGA weight loss centered at 425 degreesC. Because of the high degree of poly(PDL) crystallinity, the glass transition (-27 degreesC) is revealed by relaxation techniques such as dyna mic mechanical and dielectric spectroscopies, rather than by DSC. In additi on to the glass transition, the viscoelastic spectrum of poly(PDL) also sho ws two low-temperature secondary relaxations centered at -130 (gamma) and - 90 degreesC (beta). They are attributed to local motions of the long methyl ene sequence (gamma) and complex units involving water associated with the ester groups (beta). The mechanical properties of poly(PDL) are typical of a hard, tough material, with an elastic modulus and yield parameters compar able to those of low-density polyethylene. (C) 2001 John Wiley & Sons, Inc.