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In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical, cation, or anion. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers.
Branching may occur randomly or reactions may be designed so that specific architectures are targeted. [1] It is an important microstructural feature. A polymer's architecture affects many of its physical properties including solution viscosity, melt viscosity, solubility in various solvents, glass transition temperature and the size of ...
Step-growth polymerization can be divided into polycondensation, in which low-molar-mass by-product is formed in every reaction step, and polyaddition. Example of chain polymerization: Radical polymerization of styrene, R. is initiating radical, P. is another polymer chain radical terminating the formed chain by radical recombination.
Chain-growth polymerization or chain-growth polymerisation is a polymerization technique where monomer molecules add onto the active site on a growing polymer chain one at a time. [1] There are a limited number of these active sites at any moment during the polymerization which gives this method its key characteristics.
The original polymer chain is terminated and a new one is initiated. [6] The kinetic chain is not terminated if the new radical can add monomer. [1] However the degree of polymerization is reduced without affecting the rate of polymerization (which depends on kinetic chain length), since two (or more) macromolecules are formed instead of one. [7]
In polymer chemistry, chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule: [1] [2] + + where • is the active center, P is the initial polymer chain, X is the end group, and R is the substituent to which the active center is transferred.
Living polymerization: A chain polymerization from which chain transfer and chain termination are absent. Note : In many cases, the rate of chain initiation is fast compared with the rate of chain propagation, so that the number of kinetic-chain carriers is essentially constant throughout the polymerization.
where P x and P y denote chains of degrees of polymerization x and y, respectively, and L a low-molar-mass by-product. The earlier term 'polycondensation' was synonymous with 'condensation polymerization'. The current definitions of polycondensation and condensative chain polymerization were both embraced by the earlier term 'polycondensation'. [1]