Poly[2,2‐dimethyl‐4‐(methoxylcarbonyl) butylene]: Synthesis with an ethylaluminum sesquichloride–peroxide initiator and NMR characterization

The alternating copolymer of isobutylene and methyl acrylate (the polymer of the title) has been obtained by using ethylaluminum sesquichloride (AlEt1.5Cl1.5) and 2‐methylpentanoyl peroxide as the initiating system in benzene solution. The alternating copolymer is obtained at an acrylate/Al molar ratio of 17. Higher ratios increase the level of acrylate residues in the copolymer isolated; in the absence of AlEt1.5Cl1.5, an equal molar feed gives a copolymer with 75 mole % acrylate units. 1H‐ and 13C‐NMR spectra have been used to study the details of polymer structure and support the equal molar, alternating nature of the macromolecule. The details of the methoxy and gem‐dimethyl peaks in the PMR spectra are consistent with a Bernoullian process determining the polymer configurational sequences, with Pm = 0.55–0.60.