Polysiloxanes resist materials

Polysiloxanes (silicones) are highly hydrophobic, inert polymers. As aresult, many silicone-based materials display good water repellency and weather resistance. Furthermore, the polysiloxane chain s flexibility gives rise to the macroscopic properties of smoothness and Inbricity. This makes silicones attractive candidates for the modification of snrfaces, snch as textiles, paper and leather. Polysiloxanes, however, have poor adhesive properties, dne to their limited interaction with other materials. Functional gronps have to be introdnced for this purpose. They are inserted at the end of the silicone polymer chain or into the side chains. 

Jt OLYSILOXANES WITH PENDANT SIDE CHAINS are interesting materials from both the theoretical and practical points of view. A number of polysiloxanes with various side chains, such as liquid crystals (i, 2), carbazole groups (3), electron-donor and electron-acceptor groups (4), polystyrene (5), and functional groups (hydroxyl or carboxyl) (6), have been synthesized. Polysiloxanes are known for their useful properties, which include flexibility, heat resistance, water repellence, and biological inertness. These properties, combined with the ease with which a tailored polymer structure can be prepared,... 

Polysiloxanes. The initial reports of the utility of polysiloxanes for lithographic applications spurred several research groups to further investigate this class of materials. The problem of low Tg was addressed by preparing chloromethylated poly(diphenylsiloxane) 16, 17). More recently, poly(sil-sesquioxanes) 18, 19) have been reported as sensitive, negative, e-beam, ion-beam, and UV resists. These soluble, ladder -type polymers prepared by the hydrolysis of substituted chloro- and alkoxysilanes are high-Tg materials (150 °C) with high silicon contents. 

The silicones (mainly polydimethyl siloxanes) are considerably more expensive than the polysulfides therefore, silicone use is restricted to more specialized applications where specific attributes of the materials are required. For example, virtually every U.S. missile or satellite contains some form of silicone sealant because of its long use life, low volatile content, and heat resistance. They are also used around aircraft windows and doors. High-temperature fuel tank sealants based on fluorocarbon-containing polysiloxanes have also been the subject of considerable government-sponsored research (21). 

The most important silicon-oxygen systems of course, are the linear polysiloxane polymers. These important materials are resistant to heat or oxidation, exhibit little change in properties with temperature, are water repellent and biologically inert. The history of the discovery and development of silicones has been summarized172. 

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