Abstract: | Coisotactic shift contributions caused by sterically crowded isotactic side-chain alkyl groups are proposed for peak assignments of isotactic propylene/butene-1 copolymers. Previously disputed analyses of methine triads and PB tetrads of backbone methylene carbons (α,α′-CH2) 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. |