Molecular weight dependence of the thermal degradation of poly(epsilon-caprolactone): a thermogravimetric differential thermal Fourier transform infrared spectroscopy study.
The effect of molecular weight on the thermal degradation of poly(epsilon-caprolactone) (PCL) was investigated by thermogravimetric analysis in combination with differential thermal analysis and Fourier transform infrared spectroscopy (TGA/DTA/FT-IR). The measurements were made in the temperature range 40-720 degrees C and it was found that PCL undergoes completely different degradation processes in nitrogen and oxygen atmosphere. Thus, in nitrogen atmosphere low molecular weight (M(n) = 10,000 g/mol) PCL (PCL(10k)) decomposed in a three-step mechanism. The evolved gases detected by FT-IR spectroscopy were identified as epsilon-caprolactone, 5-hexenoic acid, CO(2), and methyl pentanoate and traces of H(2)O. In the case of high molecular weight (M(n) = 80,000 g/mol) PCL (PCL(80k)) only a two-step degradation was observed. By FT-IR spectroscopy 5-hexenoic acid, CO(2), H(2)O, and methyl pentanoate were detected as decomposition products. In an oxygen environment, similar degradation products were detected for the different molecular-weight PCLs. The recorded FT-IR spectra of the evolved gases were identified as CO(2), CO, H(2)O, and short-chain carboxylic acids.
Unger
Miriam
M
Department of Physical Chemistry, University of Duisburg-Essen, Campus Essen, Schuetzenbahn 70, D-45117 Essen, Germany. miriam.unger@stud.uni-due.de
Vogel
Christian
C
Siesler
Heinz W
HW
D008970:Molecular Weight; D010100:Oxygen / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013696:Temperature; D013818:Thermogravimetry / Q000379:methods
D011091:Polyesters; C016240:polycaprolactone; D010100:Oxygen