Page 425 - Carrahers_Polymer_Chemistry,_Eighth_Edition

388 Carraher’s Polymer Chemistry

The first Silly Putty (TM), also called Nutty Putty, was made more than 50 years ago from
mixing together silicone oil with boric acid. The original formula has changed only a little, though
colorants have been added giving the material brighter colors and some the ability to “glow-in-the-
dark”. Today, the formula contains about 70% dimethylsiloxane and boric acid, 17% quartz, 9%

Thixatrol ST (a commercial rheology modifier that is a derivative of caster oil), and several other
minor constituents. Silly Putty is a dilatant material (Chapter 13), meaning it has an inverse thix-
otropy (a thioxotropic liquid is one whose viscosity decreases with time). In essence, the resistance

of flow increases faster than the increases in the rate of low. Thus, under short interaction times
(Chapter 13), it behaves as a solid where the various molecular components resist ready movement,
acting as a solid and under sharp impact like hitting it with a hammer or rapidly “snapping” it, it
will act as a brittle material. Under a relatively long-interaction time the molecular chains are able
to yield and the material acts as a liquid. Under moderate interaction times there is segmental move-
ment and the material acts as a rubber.
Silly Putty is one of several materials whose discovery occurred at about the same time by dif-
ferent individuals. In this case, the two individuals are Earl Warrick, working for Dow Corning, and
James Wright, a researcher for General Electric. The discoveries occurred in 1943 while searching
for synthetic rubber during World War II. Initially no practical use was found. By 1949, it was found
in a local toy store as a novelty item. Despite its good sales, the store dropped it after 1 year. The
next year Peter Hodson began packaging it in the now familiar plastic egg. Today, it sells for about
the same price it did in 1950. Silly Putty sells at a rate of about 6 million eggs, or 90 tons, yearly.

11.3.2 ORGANOTIN AND RELATED CONDENSATION POLYMERS
Carraher and coworkers have produced a wide variety of organometallic condensation polymers
based on the Lewis acid–base concept. Polymers have been produced from Lewis bases containing
amine, alcohol, acid, thiol, and related units, including a number of drugs, such as ciprofl oxacin and
acyclovir. Lewis acids containing such metals and metalloids as Ti, Zr, Hf, V, Nb, Si, Ge, Sn, Pb, As,
Sb, Bi, Mn, Ru, P, Co, Fe, and S have been employed. These compounds have potential uses in the
biomedical arena as antifungal, antibacterial, anticancer, Parkinson’s treatment, and antiviral drugs.
These polymers show promise in a wide variety of other areas, including electrical, catalytic, and
solar energy conversion. Polymers referred to as polydyes, because of the presence of dye moieties

in the polymer backbones, have impregnated paper products, plastics, rubber, fibers, coatings, and
caulks, giving the impregnated material color, (often) added biological resistance, and special photo
properties. Some of the polymers, including the metallocene-containing products, show the ability
to control laser radiation. Depending on the range of radiation, laser energy can be focused allowing
the material to be cut readily or it can be dispersed imparting to the material containing the polymer
added stability toward the radiation.
A number of these polymers exhibit a phenomenon called “anomalous fiber formation,” reminis-

cent of “metallic whiskers.”
There are more organometallic compounds containing tin than for any other metal. Further, the
volume of organotin compounds employed commercially is greater than for any other organometal.
Worldwide, the production of organotin compounds, about 120 million pounds yearly, accounts for
about 7% of the entire tin usage. Tin has been included into polymers for a variety of reasons. The
two major reasons are its biological activities known for about 100 years, and the second reason
involves its ability to help stabilize PVC. This second behavior accounts for about 70% by weight
of the organotin compounds used commercially. These materials are employed to improve the heat
stability of PVC as it is formed into piping. Today, because polymers leach much slower than small
molecules, organotin polymers initially synthesized by Carraher and coworkers are being used as
heat stabilizers in PVC piping.
The emphasis on organotin-containing polymers is the results of several factors. The fi rst one
involves the early discovery of their biological activity and more recently that these organotin

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