Abstract:
A free-radical polymerisation process, which has characteristics of a living polymerisation system, as it is capable of producing polymers of pre-determined molecular masses with a narrow molecular mass distribution, is discussed. It is also possible to make block-copolymers by adding different monomers. The basic objective was to describe, discuss and explain the results of the effects of alkyl iodides as chain transfer agents on the seeded emulsion homo- and co-polymerisation of styrene and butyl acrylate. lodoacetonitrile and 1-phenylethyliodide were used as alkyliodides, acting as degenerative chain transfer agents. First, the effects of these alkyl iodides as chain transfer agents on the molecular mass, molecular mass distribution, glass transition temperature, conversion and particle size for the seeded emulsion polymerisation of styrene were studied. Second, the effects of alkyl iodides as chain transfer agents on the kinetics of radical emulsion polymerisation, especially the average amount of radicals per latex particle, were investigated. Third, the possibility of producing block-copolymers by emulsion polymerisation, using alkyl iodides as chain transfer agents, was investigated. To the best of the author's knowledge, results of work carried out in this study offer the first proof that the "living"/controlled radical polymerisation of styrene, with alkyl iodides as chain transfer agents, can be successfully carried out in emulsion. Addition of different alkyl iodides as chain transfer agents, in different concentrations, led to marked changes in the molecular mass, molecular mass distribution, glass transition temperature, conversion and particle size for the seeded emulsion polymerisation of styrene. The molecular masses of the polystyrene that was produced ranged from 156 to 663 577 while the average molecular mass distribution was below 2. Addition of these alkyl iodides to a seeded styrene polymerisation under zero-one conditions led to an average number of free radicals per latex particle that was greater than 1. A styrene seed latex with functional iodine end-groups was created and was successfully co-polymerised with butyl acrylate to produce a perfect styrene-butyl acrylate block-copolymer. This work has industrial importance as it allows the molecular mass, molecular mass distribution and particle size of polymers to be controlled. These factors are directly related to their micro- and macrostructure of polymers.
