Determination of polybutadiene microstructures and styrene±butadiene copolymers composition by vibrational techniques combined with chemometric treatment Jean Guilment a , Liliane Bokobza b,* a Kodak European Research Laboratories, CRT 60.3, Chalon/Sao Ãne, France b Laboratoire de Physico-Chimie Structurale et Macromole Âculaire, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France Received 6 July 2000; received in revised form 28 March 2001; accepted 18 April 2001 Abstract Vibrational spectroscopy techniques have been used to study the polymer composition using only one technique at a time. In this paper, mid- and near-infrared NIR) as well as Raman spectroscopies are combined with partial least squares PLS) in order to determine the cis-, trans- and vinyl-con®gurations of polybutadienes as well as the composition of styrene±butadiene copolymers. A critical comparison of these techniques for the microstructure analysis will also be presented not only in terms ofquantitativeresultsbutalsointhewaythesamplescanbeanalyzedandthespectrainterpreted.Eachofthetechniquesgives comparableresultsintermsoftheprecisionofthemodelsdevelopedlimitedtotheprecisionofthereferencemethod),butwe can also see that the NIR spectroscopy is more reproducible in the short term due to the high signal to noise ratio obtained on the spectra. On the other hand, Raman excited in the NIR FT-Raman) is the only technique which is free of sample preparationandhandlingallowingtogetverygoodresultsinthelongterm. # 2001ElsevierScienceB.V.Allrightsreserved. Keywords: Polybutadiene; Microstructure; Infrared spectroscopy; Near-infrared spectroscopy; Raman spectroscopy; Partial least squares; Chemometrics; Quantitative prediction 1. Introduction The polymerization of 1,3-butadiene gives rise to polymers containing 1,4-cis, 1,4-trans, or 1,2-vinyl structural units or a mixture of these. The 1,2-units may be isotactic, syndiotactic or atactic. Vibrational spectroscopy can be used for the quantitative analysis of the different chemical sequences constituting poly- meric materials [1±5]. The microstructure of a polybutadiene PB), deter- mined by the content of the cis-, trans- and vinyl- con®gurations, is of peculiar importance since it in¯uences a wide range of physical properties. PBs and styrene±butadiene copolymers being completely hydrocarboned systems, are dif®cult to analyze by chemical methods. Spectroscopic techniques, such as infrared IR) [6±9], Raman [10±12] and NMR [13±15] spectro- scopies, were used to characterize the microstructure Vibrational Spectroscopy 26 2001) 133±149 * Corresponding author. Tel.: 33-140-79-45-15; fax: 33-140-79-46-86. E-mail address: liliane.bokobza@espci.fr L. Bokobza). 0924-2031/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0924-203101)00111-4