TABLE OF CONTENTS Polysiloxanes are inorganic polymers that contain alternate silicon and oxygen atoms in their backbone [ [1] [2] [3] [4] [5] [6]]. While the silicon atom has two sidegroups the oxygen atom carries none. In this regard they are similar to polyphosphazenes that we have seen in Chap. 3. The most widely studied polymer of this family is poly(dimethylsiloxane) (PDMS) which contains methyl groups as the substituents on silicon. PDMS is isoelectronic with poly(isobutylene) as well as poly(dimethylphosphazene) although its properties are dramatically different (Fig. 6.1).
PDMS has several unusual properties [ [1], [5]]. These are listed as follows.
Extremely low T g ( ?123 C)
Very high hydrophobicity
High thermal stability
Low surface tension
Low variation of viscosity with temperature
High gas permeability
Non-toxicity
These properties have made PDMS and related polymers the most important inorganic polymers from a commercial point of view. In fact, they are the only inorganic polymers that have achieved a remarkably high level of utility and consequently are produced in large quantities throughout the world. Thus, it is estimated that nearly 800,000 metric tons of this family of polymers is manufactured every year with a commercial value of over 4 billion U.S. dollars [ [7]]. The applications of these polymers are in extremely diverse areas. These include areas such as high-temperature insulators, antifoam applications, biotransplants, contact lenses, drug-delivery systems, flexible elastomers, personal care products and many more [ [1]
