Silanol polymers

Another approach to preparing a stable reversed phase with fewer residual silanols is the use of polyfunctional silanes of the type R2SiX2. These react to form a polymeric stationary phase that shields the siloxane bonds and restricts access to residual silanols. Polymer phases have higher carbon loads and are typically more retentive than monomeric phases. However, they are more difficult to synthesize reproducibly and may exhibit batch-to-batch variability in their properties. They also exhibit poorer mass transfer kinetics and so provide poorer efficiency than monomeric phases. 

SYNTHESIS OF NOVEL SILANOL POLYMERS AND COPOLYMERS BY A SELECTIVE OXIDATION OF SI—H BOND FROM CORRESPONDING PRECURSOR POLYMERS... 

A series of novel styrene- and siloxane-based silanol polymers and copolymers were synthesized by a selective oxidation of the Si—H bond with a dimethyldioxirane solution in acetone from corresponding precursor polymers. The conversion of the Si—H to Si—OH in the polymer modification proceeded rapidly and selectively. The silanol polymers obtained in situ showed no tendency for self-condensation to form siloxane crosslinks in solution. Moreover, stable silanol polymers in the solid states were obtained by placing bulky substitute groups bonded directly to the silicon atom. It was found that the properties of these novel silanol polymers and copolymers depended largely on substituents bonded directly to the silicon atom and silanol composition in the copolymers as well. 

Polymer modification is of particular interest when the desired polymer is not readily available from its corresponding monomer by conventional polymerization methods. The primary challenge of polymer modification is to achieve a high conversion and selective modification of the appropriate functional group. In this paper, we describe a new convenient polymer modification to prepare novel silanol polymers by a rapid and selective oxidation of the Si—H bond with a dimethyldioxirane solution in acetone from their corresponding precursor polymers. 

To a methyl ethyl ketone solution of =Si—H containing polymers or copolymers, a cold solution (ca. -10 °C) of dimethyldioxirane in acetone was quickly added and reacted for 30 min at 0 °C. The mole ratio of dioxirane to polymer was ca. 1.2 1.3. The resulting silanol polymers or copolymers were obtained either in solution or precipitated into hexanes followed by vacuum dry at 40 °C for 24 h. 

The conventional methods for the synthesis of organosilanols can be accomplished by the hydrolysis of the appropriate substituted silane in the presence of catalysts such as an acid or a base.1 This synthetic route, however, had some difficulty when applied to the synthesis of silanol polymers which demanded not only high conversion of the functional groups for polymer modification but also resistance to the transformation of silanols to siloxane by self- or catalytic condensation during the preparation. 

Dioxiranes constitute a new class of organic peroxides that possess great potential as oxidants with a variety of applications in synthetic organic chemistry.5 7 A new convenient route for the synthesis of silanol polymers has been developed by the selective oxidation of =Si—H bonds with dimethyldioxirane. A series of styrene-based silanol polymers and copolymers were synthesized (Scheme l).8 9 The precursor polymers and styrene copolymers containing =Si—H bond were first synthesized by free radical polymerization of the corresponding monomers or copolymerization of the... 

The properties of these siloxane-based silanol polymers depended largely on the silanol composition. Polymer materials obtained by the condensation of the silanols led... 

A new convenient polymer modification for the conversion of the Si—H to Si—OH by the selective oxidation of the Si—H bond by dimethyldioxirane has been described. The oxyfunctionalization of the silane precursor polymers proceeded rapidly and quantitatively and can be applied to the synthesis of a wide variety of novel silanol polymers with specific properties from the corresponding precursor polymers containing Si—H functional groups. Control over the properties of these silanol polymers, such as reactivity and self-association of silanols, was realized through the placement of different substitute groups bonded directly to the silicon atom and by the variation of silanol composition in a copolymer. These novel silanol polymers with a... 

Unfortunately, because self-condensation of silanols on the same siHcone can occur almost spontaneously, the reaction of disilanol or trisilanol compounds with telecheHc silanol polymers to form a three-dimensional network is not feasible. Instead, the telecheHc polymers react with cross-linkers containing reactive groups such as alkoxysilanes, acyloxysilanes, siHcon hydrides, or methjiethjioximesilanes, as in the reactions in equations 18—21 (155). 

With F2 excimer laser lithography at 157 nm, even polymers based on aerylates and norbonenes are too opaque to be of any useful value in resist appheations. Therefore, fluorocarbons and silanol polymers are the two main classes of polymers that have reasonable transparency at this wavelength. Again, like their 193-nm and 248-nm counterparts, the 157-nm resists employ chemical amplification in their imaging mechanism, for quite similar reasons. 

A new convenient method for the synthesis of silanol polymers was developed by the selective oxidation of corresponding precursor polymers containing Si—moiety with a dimethyldioxirane solution in acetone. A series of styrene-... 

Another novel series of inorganic siloxane-based silanol polymer or copolymers were also prepared by reacting poly(methylhydrosiloxane) (PMHS) or methylhydrosiloxane dimethylsiloxane copolymers with a dimethyldioxirane solution in acetone (Scheme... 

Silanol Polymer (n greater than 4000) for solvent-based products... 

To raise the solids content or to render the system totally solventless, the molecular weight (and viscosity) of the silanol polymer must be drastically reduced, but the working life of such a solventless system becomes only a few minutes at room temperature. This becomes impractical, and since there is no known means of inhibiting the tin soap catalyst (necessaiy for completion of the thermal crosslinking reaction), other chemical systems are needed for truly solventless coatings. 

Because of the instability of silanols, polymers possessing free silanols can hardly be present. In Section 3.18.2.1, Si-O-C linkages in silyl ethers are demonstrated to be stable under the conditions of anionic polymerization and to be quantitatively cleaved by mild acidic hydrolysis. This suggests that alkoxysilane-protected styrene monomers can also be anioni-cally polymerized in a living manner and the resulting polymers are equivalent to free silanol-functionalized polymers. These polymers are useful and versatile functional... 

Silanol Polymer (4000 mpa.s) Calciiun Carbonate Methyl Vinyl Di (N-Methyl Acetamido) Silane Aminoxy Siloxane Copolymer... 

Two-part type. As for one-part-type silicones, both the catalyst and the cross-linking agent are incorporated in the base compound just before use. They are generally silanol polymers, cross-linked with alkoxy silane or oligomers and organic tin compound catalyst. Two-part-component-type silicones are typically used for applications in coatings, adhesives, and encapsulants. 

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