|
|
 Polystyrene:
Polytyrene is one of the most prevalent materials in our daily lives. It
is found in everything from the molding of your printer case to the styrofoam
in a cooler to the impact absorbing material found in a bicycle helmet.
While each of these materials vary in their mechanical and thermal properties
each is basically derived from the same monomer - styrene.
Polystyrene, a vinyl polymer, is formed via free radical vinyl polymerization
of styrene.
Typical polystyrene is referred to as atactic. In these molecules the phenol
group alternates sides of the long chain randomly without a pattern. With
a more complicated process, syndiotatic polystyrene can be created. In
this molecule, the phenol group alternates sides every monomer unit. Since
this polystyrene molecule exhibits a regular pattern, syndiotactic polystyrene
is crystalline resulting not only in different mechanical properties, but
also a much higher melting temperature.Styrene based copolymers can be created
by polymerizing styrene in the presence of another hydrocarbon chain. An
illustration of styrene polymerized with polybutadiene resulting in resilient,
high-impact polystyrene (HIPS) can be found on the University of Southern
Mississippi's Department of Polymer Science's website. Styrene is not just
for styrofoam and plastics. Scientists at the National Research Council
of Canada have developed a method to produce a straight single molecule
nanowire on silicon using styrene ( TRN article ). The researchers coated
a silicon sheet with hydrogen atoms then removed a single hydrogen with
a scanning tunneling microscope. They then exposed the region to styrene
molecules. The reactive spot on the silicon  where
the hydrogen was removed attracts a styrene molecule which itself becomes
unstable. This results in the styrene grabbing the adjacent hydrogen molecule
perpetuating the cycle.
Thomas Gaborski
Pittsford-Mendon Class of 1998
Cornell University Class of 2002 - B.S. Biological and Environmental Engineering
Currently a graduate student (PhD) at the University of Rochester - Biomedical
Engineering
|
|
