Task: Chain Growth Polymerization Outline Chain growth polymerization is a polymerization process or technique Chain growth polymerization has the chemical equation. (-M-)N (polymer) +M (monomer) ->. (-M-) n+1
It leads to the generation of different material composites and polymers
Polystyrene is a polymer of styrene consists of adjoined identical molecules.
Polythene is composed of–CH2– units
Chain growth polymerization corresponds to a polymerization process or technique in which unsaturated monomer molecules add to the active site of a growing polymer chain. These occurs one monomer at a time. This process has distinct characteristics because of the limited number of active sites on the polymer. Chain growth polymerization can be symbolized using this chemical equation. (-M-)N (polymer) +M (monomer) ->. (-M-) n+1 (Peacock and Allison 86). In this case, n refers to the degree or extent of polymerization and M occurs as an unsaturated compound. Chain growth polymerization occurs in distinctive steps. The first step involves chain initiation in which an initiator commences the chemical process. The next step involves chain elongation followed by chain transfer. Chain transfer concludes the chain after which the active site is moved to the new chain. Polymers, solvents and monomers can facilitate this. This processes leads to an increase in the branching of the ensuing polymer. Chain termination occurs as the last step through disproportion or combination. Termination in fundamental polymerization occurs when free radicals combine.
The active center for a chain growth polymerization can assume the state of a free radical in the corresponding polymerization. Radical polymerization in this case involves the successive addition of radical building blocks. This can occur through several mechanisms, which involve different initiator molecules (Wünsch 131). After the generation process, the initiating radical adds monomer units, which leads to the growth of the polymer.
Chain growth polymerization such as radical polymerization reactions leads to the generation of different material composites and polymers. Radical polymerization involves different initiators such as thermal decomposition in which the bond is homolytically cleaved leading to the production of two radicals. Photolysis involves the use of radiation in cleaving bonds homolytically. The initiation step is followed by the propagation in which the polymer increases its chain length. The termination process follows unless the reaction has contaminants, which can contribute to the addition of monomers (Richardson, and Erik 92). Chain transfer occurs as the last step, which leads to the destruction of a radical and construction of another radical. However, the new radical usually does not have propagation capabilities.
Chain growth polymerization leads to the formation of an elevated molecular weight polymer at low conversion. In this case, the mass depends on the rate of chain termination upon comparison to the rate of propagation. This incorporates both chain termination, as well as chain transfer steps. Temperatures above the ceiling temperatures disrupt the polymerization process (Wünsch 77).
Practical Uses of Polystyrene and Polythene
Polystyrene is a polymer of styrene consists of adjoined identical molecules. It appears as a neutral and oily substance. It has a structure that resembles inflexible and transparent thermoplastic or stiff white foam (Wünsch 101). It is a common plastic found in home and industrial applications. Polystyrene is used by the package industry in making packaging bags that keep delicate materials safely enclosed. It is also used in DVD cases and plastic forks, models of cars, housing computers and most plastic materials. Polythene is relatively soft, and facilitates the construction of plastic films. The common categories of polythene are known based on their density.
Peacock, Andrew J, and Allison Calhoun. Polymer Chemistry: Properties and Applications. Munich [u.a.: Hanser, 2006. Print.
Richardson, Terry L, and Erik Lokensgard. Industrial Plastics: Theory and Application. Albany, NY: Thomson Delmar Learning, 2003. Print.
Wünsch, J R. Polystyrene: Synthesis, Production and Applications. Shawbury, Shrewsbury: Rapra Technology Ltd, 2000. Print.