Solid-state 13C NMR of microscopic order in transcrystalline films of isotactic poly(propylene).
The microscopic orientational order in a variety of transcryst. films of isotactic poly(propylene) was investigated by means of two-dimensional solid-state NMR. From the exptl. results the orientation distribution function of the microcrystallites relative to the macroscopic growth direction was detd. The NMR measurements were performed at room temp. on samples that had been crystd. at conditions at which the morphol. of spherulitic crystn. changes as a function of temp. or compn. For transcryst. samples of isotactic poly(propylene) crystd. in the a-modification a drastic breakdown of mol. order was obsd. at a crystn. temp. of 137 Deg, with the abs. degree of order depending on the mol. mass of the polymer. For samples crystd. in the b-modification a small stepwise decrease of mol. order was obsd. at a crystn. temp. of 128 Deg. A continuous decrease of the orientational order of the isotactic part was obsd. by blending iso-tactic poly(propylene) with atactic poly(propylene).
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