Kinetics free radical copolymerisation

FTIR spectroscopy was used to study the polymerisation of random copolymers of 4-vinylphenol with n-alkyl methacrylates which were prepared by free radical copolymerisation of 4-t-butyldimethyl-silyloxystyrene and the corresponding alkyl methacrylates in benzene at 60 °C using azobisiso-butyronitrile (AIBN) as an initiator (321). The thermal reaction of polyphenylene-1,2-dibromoethylene under argon flow was investigated using in situ kinetic IR spectroscopy (345). 

Attempts to polymerise isobutene by free radical catalysis have all failed [16,17] and copolymerisation experiments show that the t-butyl radical has no tendency to add to isobutene. The reasons for these facts are not at all obvious. Evidently, they cannot be thermodynamic and therefore they must be kinetic. One factor is probably that the steric resistance to the formation of polymer brings with it a high activation energy [17], and that the abstraction by a radical of a hydrogen atom from isobutene, to give the methallyl radical, has a much smaller activation energy. This reaction will also be accelerated statistically by the presence of six equivalent hydrogen atoms. 

This chapter focuses on key features to understand the emulsion copolymerisation kinetics and on the influence of operation on the copolymer composition of the final latex products. Focus is on batch and semi-batch or semi-continuous operation, see Figure 4.1. Only the free-radical emulsion copolymerisation of two monomers is considered but the concepts can be directly applied for formulations containing more than two monomers. The reacting monomers usually having different reactivities, polymerise simultaneously. The reactivities and the individual concentrations of the monomers at the locus of polymerisation, that is, the particle phase, govern the built-in ratio into the polymer chains at a certain time. 

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