Controlled alternating copolymerisation of maleic anhydride and electron donating monomers
Maleic anhydride (MA) is a strong electron acceptor and so homopolymerises with difficulty. Copolymerisations with electron donor monomers are however facile. Free-radical and controlled radical polymerisation (CRP) techniques have been used to probe the structure and mechanism of MA alternating copolymers. Conventional free-radical polymerisation was used to synthesise poly (octadecene -alt- MA) (PODMA). Molar masses ranging from 4,000 g morl to 61,000 g morl were successfully prepared by variation of polymerisation conditions. Molar mass characterisation was by size exclusion chromatography (SEC) and dilute solution viscometry. Calculation of monomer reactivity ratios revealed PODMA to have a strictly alternating structure. NMR analysis indicated that PODMA had 100% trans stereochemistry and the initiation and termination mechanisms were elucidated. The optimised copolymerisation was scaled up from gram to kilo scale, providing an important precursor for high performance crankcase oil dispersants. MA has proved to be a challenging monomer for CRP. Reverse addition fragmentation transfer (RAFf) copolymerisation was used to copolymerise MA with styrene (St) monomers. Kinetic studies indicated controlled copolymerisation and living characteristics were observed such as predetermined molar mass, narrow molar mass distribution and chain extension to form novel block copolymers. The RAFT mechanism and its effectiveness in producing controlled copolymers incorporating MA are discussed.