CO-ISOTACTIC SHIFT CONTRIBUTIONS IN C-13 NMR-SPECTRA OF PROPYLENE-BUTENE-1 COPOLYMERS

Experimental data are presented which were used to formulate a suggestion about the effect of molecular structure of isotactic porpylene-butene capolymers on coisotactic shift contribution. These shift contributions for peak assignment are caused by sterically crowded isotactic side-chain allyl groups. Previously disputed analyses of methine triads and PB tetrads of backbone methylene carbons ( alpha , alpha prime -CH//2) have been verified using first-order Markovian distribution theory. Coisotactic shift contributions also account for the reverse order of the propylene-centered triads from that predicted by the Grant-Paul equation.