title: Study of epsilon-caprolactone polymerization by NIR spectroscopy.
abstract: Near-infrared (NIR) spectroscopy is proposed for the in-line quantitative and kinetic study of the polymerization of epsilon-caprolactone and eventually to facilitate real-time control of the manufacturing process. Spectra were acquired with a fibre-optic probe operating in transflectance mode immersed in the reactor. The NIR data acquired were processed using a multivariate curve resolution alternating least squares (MCR-ALS) algorithm. The proposed method allows calculation of the concentration and spectral profiles of the species involved in the reaction. The key point of this method is the lack of reference concentrations needed to perform the MCR-ALS method. The use of an extended spectral matrix using both process and pure analyte spectra solves the rank deficiency. The concentration profiles obtained were used to calculate a kinetic fitting of the reaction, but the method was improved by applying kinetic constraints (hard modelling). The rate constants of batches at different temperatures and the energy of activation for this reaction were calculated. Whenever possible, the hard modelling combined with the MCR-ALS method improves the fit of the experimental data: the results show good correlation between the NIR and reference data and allow the collection of high-quality kinetic information on the reaction (rate constants and energy of activation).
authors.affiliation: Grup de Quimiometria Aplicada, Departament de Química (Unitat Analítica), Facultat de Ciències, Universitat Autònoma de Barcelona, 01893 Bellaterra, Barcelona, Spain.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Blanco
authors.forename: M Jesús
authors.initials: MJ
authors.lastname: Sánchez
authors.forename: Manel
authors.initials: M
authors.lastname: Alcalà
mesh_terms: D002208:Caproates / Q000737:chemistry*; D007783:Lactones / Q000737:chemistry*; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D002208:Caproates; D007783:Lactones; D011108:Polymers; C121056:caprolactone