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Organometallic and Inorganic–Organic Polymers 401

Synthetic zeolites are also used today for this purpose. Today, most ion-exchange resins are based
on styrene and divinylbenzene (vinylstyrene) resins that are then sulfonated. When the resin is ready
for use, sodium ions generated from rock salt (simple sodium chloride) is passed through the resin
bed replacing the hydrogen ion (protons). The sulfonate functional groups have a greater affi nity
for multiple-charged cations than for the single-charged sodium ion and the multivalent metal ions
replace the sodium ions, resulting in the water having a lower concentration of the ions responsible
for the water being hard. Eventually, the sulfonate sites on the resin become filled and the resin bed

must be recharged by adding large amounts of dissolved sodium ions (derived from sodium chlo-
ride) which displace the more tightly bound but overwhelmingly outnumber “hard ions.” After the
system is flushed free of these “hard ions,” the resin bed is again ready to give “soft water” for our

use. This sequence is described in Figure 11.2.

11.7 SUMMARY

1. There is a wide variety of inorganic and metal-containing polymers. The potential uses are
many and include the broad areas of biomedical, electrical, optical, analytical, catalytic,
building, and photochemical applications.
2. The bond strength from any combination is higher than for many traditional polymers with
many having superior thermal stabilities.
3. Metal and inorganic polymers can be formed through a variety of reaction types, including
condensation, coordination, and addition reactions.
4. The majority of the condensation polymerizations can be considered extensions of typical
Lewis acid–base reactions.
5. Polysiloxanes (silicons) offer a good combination of properties not found in organic polymers.
Silicons are employed in a number of applications, including antifoaming agents, lubricants,
caulks, sealants, gaskets, and as biomaterials.
6. Polyphosphazenes offer unique thermal properties and have shown a number of uses in the

field of electronics and medicine.
7. The number and variety of organometallic polymers and potential applications for organome-
tallic polymers is great. Because of the high cost of production of many of these materials,
uses will often be limited to applications employing minute quantities of the polymers. This is
not true for many polymers containing silicon, tin, and main-group materials since these are
available in large quantities at reasonable cost.

GLOSSARY
Borazoles: Molecules composed of boron and nitrogen atoms.
Capping: Protecting end groups.
Carboranes: Molecules composed of carbon and boron atoms.
Coordination polymers: Polymers based on coordination complexes.
Metallocenes: Sandwich or distorted sandwich-like molecules generally containing two
cyclopentadienes and a metal atom bonded to them.
Polyphosphonitrile: Polymer with a repeat unit of –P=N–
RTV: Room temperature vulcanization.
Siloxanes and Silicones: Polymers containing –Si–O– backbones.

EXERCISES

1. What is meant by “lost loops” in the production of silicones?
2. How could you produce a silicone with a low DP?

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