The stereoregularity and crystallinity of polyvinylchlorides of different origin

synopsis Convenient x-ray diffraction instrumentation for assessing PVC order is described. A reflectance diffractometer, copper radiation, a monochromator, and a proportional detector are used to make measurements on low molecular weight, highly crystalline PVC prepared using chain-transfer agents. Interpretation includes a correction for air scattering, employment of a trimodal noncrystalline pattern, and the calculation of crystallinity from the ratio of the crystalline to the total integrated intensity. The results are reasonably insensitive to the assumptions made. The noncrystalline pattern used is taken to indicate a single, partially ordered mesomorphous phase. A whole polymer prepared in the presence of butyraldehyde, a fraction therefrom prepared by precipitati_on, and a similar fraction terminated by butyl mercaptan have similar molecular weights (M,, ca. 1600) and crystallinities of 30, 44, and 44%, respectively. Fractionation apparently effects a separation with respect to syndiotactic content, and the resultant crystallinity appears to be the highest valid x-ray value reported to date for a PVC polymer, irrespective of polymerization variables, fractionation procedure, or molecular weight. The order in these polymers is due in part to their greater syndiotacticity (about 64% for the fractions by 1% NMR spectroscopy), although a more favorable tactic placement distribution may be involved in addition to a possible effect of molecular weight itself.

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The stereoregularity and crystallinity of polyvinylchlorides of different origin

Cited by 6 publications

References 25 publications

Fractionation of Polymers

Fractionation of Polymers

Polymerisation von Butadien und Vinylchlorid in einer Cyclophosphazen‐Einschlußverbindung

Degrees of order from X‐ray diffraction in highly crystalline poly(vinyl chloride)

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