While polyethylene has proven to be an extremely versatile and useful plastic, its properties are not ideal for all applications. For this reason, chemists have investigated the polymerization of other olefin monomers, particularly monomers that possess a substituent group other than hydrogen on one of the olefinic carbon atoms. The polymers that result from these reactions do, in fact, possess different physical properties from those of LPDE and HDPE and have found important applications. For example, the polymerization of propylene, which is identical to ethylene except that one hydrogen substituent has been replaced by a methyl (CH3) group, yields "polypropylene" (Scheme 6).
This material has a higher melting point
Other important polymers that are generated from substituted olefin monomers include polyvinylchloride (PVC) and polystyrene (Scheme 7).
The chlorine substituent groups on the
PVC polymer chain make it more fire resistant than polyethylene
or polypropylene. They also increase the force of attraction
between individual polymer chains, giving rise to a harder
plastic, which is used in pipes, house siding, toys, and
furniture. A copolymer of vinyl chloride and vinylidene chloride
Polystyrene is a glassy polymer with
sparkling clarity. It is hard but also rather brittle. Because
polystyrene melts around
Using Cochrane's Molecular Models, make a model of polypropylene. Compare it to a model that your neighbor has constructed. Are they identical?
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