Tales of the unexpected. The non-random statistical copolymerisation of myrcene and styrene in the presence of a polar modifier

Abstract

In recent years bio-based terpene monomers such as myrcene and farnesene have come to prominence in both academia and industry, as potential replacements for oil-based dienes, especially in the manufacture of rubbers such as solution styrene–butadiene rubber (sSBR). It is well-known that the comonomer sequence in commercial sSBR is randomised by the addition of a polar modifier, typically an amine or ether. We report here (unexpected) results for the statistical anionic copolymerisation of myrcene and styrene in the presence of a commercial modifier (TMEDA). Specifically, when 2 equivalents of TMEDA (with respect to BuLi) is added to the copolymerisation of styrene and myrcene, the resulting copolymer was far from random as initially expected. Instead the outcome was a tapered-block copolymer with a styrene-rich block formed in the first instance. Reactivity ratios for the copolymerisation in the presence of TMEDA were estimated as r_Mry = 0.15 and r_Sty = 17.52 and are indicative of the formation of a block-like sequence.