We demonstrate a methodology to estimate the percent crystallinity of polymers directly with Raman spectroscopy and multivariate curve resolution (MCR) by alternating least-squares (ALS). In this methodology, the Raman spectrum of semicrystalline polymer is separated into two constituent components (crystalline and molten) and their corresponding concentrations. The percent crystallinity can be estimated as the change in area intensity of the molten spectral-component when polymer cools from a temperature above melting point to room temperature. The number of carbons in the crystalline lattice has also been estimated from the position of longitudinal acoustic (LA) Raman bands with the correlation established by Mizushima and Simanouti [ Mizushima, S.; Simanouti, T. J. Am. Chem. Soc. 1949, 71, 1320 ]. The new method allows direct Raman estimation of absolute percent crystallinity of polymers. Until now, Raman spectroscopic estimation of percent crystallinity was possible only in conjunction with other techniques or by using internal standards.
ASJC Scopus subject areas
- Analytical Chemistry