Proton magnetic resonance investigation of structure of ω-alkyl-α-olefin/SO2 copolymers

The 100 MHz proton magnetic resonance (PMR) spectra of free radical alternating ω-alkyl-α-olefin/SO₂ copolymers has been investigated. The data obtained from the quantitative evaluation of the spectra are consistent with a copolymer structure containing unrearranged olefinic monomer units. The 4-methyl-1-pentene/SO₂ copolymer shows a quadruplet resonance in the CH₃ proton region. This multiplicity, observed also in the analogous 1,2-dichloro-4-methylpentane and 1,2-dibromo-4-methylpentane, arises from the presence of magnetically nonequivalent CH₃ protons located in the vicinity of the asymmetric carbon atoms of the main chain. There is no detectable nonequivalency of CH₃ protons in the 5-methyl-1-hexene/SO₂ copolymer, probably because the center of asymmetry is further removed from the isopropyl group. In poly-4-methyl-1-pentene, prepared with Ziegler-Natta catalyst, the polymer structure around the main chain tertiary carbons is fairly symmetrical; and, as expected, the CH₃ protons of the isopropyl group are magnetically equivalent.