Vibrational spectra of chlorinated poly(vinyl chloride).

In order to refine the force field for secondary chlorides which is applicable to chlorinated poly (vinyl chloride), CPVC, 2,3,4-trichloro-pentanes and 2,2,3-trichloro-butane were synthesized. To avoid trouble upon separation of a meso and racemic isomer mixture of 2,3,4-trichloro-pentanes, we used a new method to obtain each isomer exclusively. Each isomer was identified by NMR. However, to confirm the identification, one of the tosylates, which is a precursor to be converted to the meso form, was structurally determined by X-ray crystallography. The ir and Raman spectra were observed for both isomers of 2,3,4-trichloro-pentanes and 2,2,3-trichloro-butane at room temperature and in the crystalline states. The force constant refinement procedure was divided into two steps. In the first step, force constants related to adjacently chlorinated units such as -CHCl-CHCl-CHCl- were refined by using meso and racemic isomers of 2,3,4-trichloro-pentanes, meso and racemic isomers of 2,4-dichloro-pentanes, and two trans isomers (MRSM, MRRM) of 2,3-dichloro-butanes. In the next step, the force constants related to CCl$\sb2$ were refined by using trans and gauche isomers of 2,2-dichloro-butane, 2,2-dichloro-propane, and trans, gauche and gauche ($-$) forms of 2,2,3-trichloro-butane. The final refined force constants are tabulated. To validate the transferability of the refined force constants, the normal frequencies were calculated for 2-chloro-butane, 3-chloro-pentane, and syndiotactic, isotactic, and heterotactic isomers of 2,4,6-trichloro-heptanes, as well as syndiotactic PVC. The calculated bands well matched the observed bands. In particular, C-Cl stretches, which are sensitive to the conformation, were predicted within 5 cm$\sp{-1}$. The ir and Raman spectra of PVC and CPVC for the five different chlorine contents, 57.70%, 61.48%, 63.34%, 67.92%, and 70.92% were observed. To elucidate these spectra, normal mode analyses (NMA) were conducted for tetrad PVC fragments (010101010), and for CPVC fragments such as (010111010), (011111010), (0102010), (0121010), (0121110), (010202010), and (010202110). (Numerical designation was used for the three carbons in CPVC: CH$\sb2$ = 0, CHCl = 1, CCl$\sb2$ = 2). According to the NMA, CH$\sb2$ groups of the center r unit of r-r-m, and m-r-m heterotactic PVC tetrads were chlorinated in the early stages of the reaction.PhDMolecular physicsPhysical chemistryPolymer chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128251/2/8907013.pd