Suzuki-Miyaura coupling reaction of brominated butyl rubber (BIIR) with 4-vinylphenylboronic acid were carried out in THF using cyclopalladated complex as catalyst. The degree of 4-vinylphenyl group introduction was estimated from the ratio of RI and UV peak area in the size exclusion chromatogram (SEC) of modified butyl rubber (St-IIR). Considerable amount of 4-vinylphenyl group could be introduced to butyl rubber in the presence of small amount (Pd/Br≈1/1000) of Pd catalyst.
Quantitative analysis for the degree of 4-vinylphenyl group introduction was made by 1H-NMR. The exo methylene signals in BIIR decreased by the reaction whereas signals attributable to the viny protons of 4-vinylphenyl group increased with reaction time. When reaction was carried out in THF at reflux temperature for 12 h in the presence of 0.01 eq. of Pd catalyst, 4-vinylphenyl group was introduced quantitatively. The peroxide curing behavior of St-IIR was also examined.
