Silane polymers, types

In 1983 we began to study the chemistry and spectroscopy of substituted silane polymers and their potential applications to lithography (7-9). It was anticipated that materials of this type which contain only Si in the backbone would provide excellent etch barriers due to their relatively high silicon content. 

The polarity of Chromosorb P can be greatly decreased by silanizing the surface with hexamethyldisilazane, [(CH3)3Si]2NH. Ottenstein (Ref. 7) has reviewed the selection of solid supports, both diatomaceous earth and porous polymer types. 

Riedel et al. have appUed the hydroboration reaction for modifying polymethylvinylsilanes with several borane adducts. The polymethylvinyl-silane polymers were synthesized by a dechlorination reaction (Wurtz type reaction) of dichlorodimethylsilane and dichloromethylvinylsilane with sodium. The subsequent hydroboration of the vinyl groups has resulted in an enhanced crosslinking of the polymers. The viscosity of the polyorganosilanes can be tuned by varying the amount of borane as well as of vinyl groups in the starting polymer [61]. 

With isocyanatomethyl alkoxysilanes (a-NCO-silanes) as endcappers, polymers with enhanced properties are feasible. This concept involving a-NCO-silanes is not limited to distinct polymer types and therefore has a broad application base. Additionally, highly reactive ethoxy-functional crosslinking systems are now available. These polymers show low viscosity and consequently a higher formulation flexibility. 

Filler Polymers Type of silane Special effect Typical application... 

Table 25.1 Silane Coupling Agents Part 1. Match Organic Group to Polymer Type...

Several silanes may be recommended for one polymer type. Often the cure system, for example, for an epoxy resin, amine versus anhydride, high-temperature versus low-temperature cure, and... 

Turning now to other types of ceramic fibre, the most important material made by pyrolysis of organic polymer precursors is silicon carbide fibre. This is commonly made from a poly(diorgano)silane precursor, as described in detail by Riedel (1996) and more concisely by Chawla (1998). Silicon nitride fibres are also made by this sort of approach. Much of this work originates in Japan, where Yajima (1976) was a notable pioneer. 

The first type of polycarbosilane synthesized by using ADMET methodology was a poly[carbo(dimethyl)silane].14c Linear poly(carbosilanes) are an important class of silicon-containing polymers due to their thermal, electronic, and optical properties.41 They are also ceramic precursors to silicon carbide after pyrolysis. ADMET opens up a new route to synthesize poly(carbosilanes), one that avoids many of the limitations found in earlier synthetic methods.41... 

If such fillers are to be used, they should have a neutral or slightly alkaline pH, otherwise additives such as ethylene glycol and triethanolamine, which are preferentially adsorbed on the surface of the filler, should be used, preventing any undesirable interference reactions between the filler and the crosslinking peroxide. These additives must, however, always be added to the mix before the peroxide. With some mineral fillers, such as some types of clay, the polymer may be bound to the filler by means of silane treatment, and the surface of the filler becomes completely non-polar. Consequently, the interaction with the polymer matrix increases, while the adsorption of the crosslinking peroxide by the filler is severely suppressed. 

---