Methyl acrylate/1-octene copolymers: Lewis acid-mediated polymerization

Copolymerization of methyl acrylate (MA) with 1-octene (1-Oct) was conducted in the presence of free radical initiator, 2,2'-azobis(2-methylpropionitrile) (AIBN) using heterogeneous Lewis acid, acidic alumina. The polymers obtained were transparent and highly viscous liquids. The copolymer composition calculated from ¹H NMR showed alkene incorporation in the range of 10-61%. The monomodal nature of chromatographic curves corresponding to the molecular weight distribution in gel permeation chromatography (GPC) further confirmed that the polymers obtained are true copolymers. The number-average molecular weights (Mn) of the copolymers were in the range of 1.1 x 10⁴-1.6 x 10⁴ with polydispersity index of 1.75-2.29. The effects of varying the acidic alumina amount, time of polymerization, and monomer infeed on the incorporation of 1-Oct in the polymer chain were studied. Increased 1-Oct infeed led to its higher inclusion in the copolymer chain as elucidated by NMR. DEPT-135 NMR spectral analysis was used to explicate the nature of arrangement of monomer sequences in the copolymer chain.