The simplest type of copolymer is one where two or more comonomers are simultaneously copolymerized. This technique is commonly used to modify and/or improve the mechanical and physical properties of many polymers. The relative rates of incorporation of each monomer in a given set of comonomers will be dependent on their reactivity ratios. These have been determined for the radical polymerization of numerous monomer pairs . Choosing comonomers that have reactivity ratios close to 1 produces statistical copolymers, where the radical chain ends react as often with their own monomer as they do with the others, assuming equal concentrations of both monomers. If both the reactivity ratios are significantly higher than 1, indicating that the radical would prefer to homopropagate rather than cross-propagate, the backbone copolymer exhibits a more blocky structure. If both are much lower than 1, indicating that both radicals would prefer to cross-propagate, the copolymer takes on an alternating structure. This is the most typical case for a radical polymerization. If the copolymerization obeys Bernoullian statistics, a random copolymer is formed. However, polymerization may follow other types of statistics (e.g., Markovian), resulting in a variety of statistical copolymers.
KeywordsRadical Polymerization Reactivity Ratio Statistical Copolymer Effect W111 CH2C1 C00CH251
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