Studies on the copolymerisation of <i>n</i>-alkyl itaconates with styrene

Abstract

The synthesis and characterization of <i>n</i>-hexyl itaconate (HI) and <i>n</i>-octyl itaconate (OI) monomers and their homopolymerisation and copolymerisation with styrene in bulk using azobisisobutyronitrile (AIBN) as an initiator have been reported. Copolymer composition has been determined from ¹H-NMR by taking the ratio of intensities of signals due to -OCH₂ protons of itaconates (δ =3.9 ppm) and aromatic protons of styrene (δ =6.8-7.2 ppm). The intensity of signal due to -OCH₂ proton increases with increasing mole fraction of itaconate monomers in the feed. The reactivity ratios are found to be r_l = 1.2 (styrene), r₂ = 0.75

(HI) and r_l ₌ 1.38 (styrene), r₂ = 0.62 (OI). All the samples have high moleculer weight, i.e., Mn in the range of 40 × 10³ to 62 × 10³ and <i>M_w </i>in the range of 43 × 10³ to 113 × 10³ with polydispersity index in the range of 1.64-1.85. Intrinsic viscosity [η] of the

copolymers decreases with increasing amount of itaconate in the copolymers. Inspite of having very high molecular weight (77,000-78,000) the homopolymers (PHI, POI) have a very low value of [η] (4±0.5 ml/g). These low values of [η] may be due to the presence of long branches in itaconates showing comb type structure. Thermal studies of the copolymers show all the samples to be stable up to 300°C.