The statistical anionic copolymerization of 1,3-dienes (butadiene or isoprene) with styrene initiated by butyllithium (BuLi) in hydrocarbon solvents leads to tapered, block-like polymers in one step. This is due to the highly disparate reactivity ratios leading to preferential incorporation of the diene at first, followed by the formation of a pure polystyrene block. By using in situ NMR and FT-NIR spectroscopies as well as kinetic Monte Carlo simulations we determined the rate constants of homo- and cross-propagation as well as their activation energies. These data provide understanding how the temperature and solvents control the gradient of the resulting tapered copolymer. Both parameters can be deliberately used to control the monomer incorporation and microstructure. This knowledge can be exploited to generate complex polymer architectures in few steps. Besides isoprene, the bio-based monomers myrcene and farnesene were combined with styrene and 4-methylstyrene (4MS) in the way of a statistical copolymerization to generate tapered diblock- and multiblock copolymers with up to 10 blocks. The statistical copolymerisation of Myr/S and Myr/4MS afforded block-like, tapered copolymers due to highly diverging reactivity ratios (rMyr = 36; rS = 0.028 and rMyr = 140; r4MS = 0.0074). Farnesene combined with styrene behaved in a similar way, showing highly disparate reactivity ratios upon copolymerization with styrene, enabling the facile synthesis of block copolymers with long alkyl side chains in the flexible blocks.

Combining the bio-based terpene monomers myrcene and farnesene with styrene: Block and multiblock copolymers via statistical anionic copolymerization

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.