Silanol-containing polymers

Pearce, E. Kwei, T. K. Lu, S. Hydrogen Bond Interactions and Self-Condensation of Silanol-Containing Polymers in Polymer Blends and Organic-Inorganic Polymeric Hybrids. In Silicones and Silicone-Modified Materials-, Clarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Eds. ACS Symposium Series 729 American Chemical Society Washington, DC, 2000 pp 419-432. 

Hydrogen Bond Interactions and Self-Condensation of Silanol-Containing Polymers in Polymer Blends and Organic-Inorganic Polymeric Hybrids... 

A new convenient polymer modification has been developed to synthesize a series of novel silanol-containing polymers by a selective oxidation of Si—containing precursor polymers with a dimethyldioxirane solution in acetone. The silanol hydrogen bonding interactions in polymer blends as well as the silanol self-condensation to form siloxane semi-interpenetrating polymer networks in miscible polymer blends and organic-inorganic polymeric hybrids are discussed. 

Synthesis and Characterization of Silanol-Containing Polymers and Copolymers. 

A new convenient polymer modification for synthesis of silanol-containing polymer was developed by the selective oxidation of the Si—H bond with a dimethyldioxirane solution in acetone. The oxyfunctionalization of the silane precursor polymers can be utilized to synthesize a wide variety of silanol-containing polymers. Control over the properties of these silanol polymers, such as stability and self-association of silanols, was realized through the placement of different substitute groups bonded directly to the silicon atom. The miscibility in either polymer blends or polymeric hybrids was achieved by the formation of strong inter-polymer hydrogen bonds between the... 

Chojnowski, J. The Behaviour of the Silanol Function in Polycondensation Systems. In Silicon-Containing Polymers Jones, R. G., Ed. Special Publication 166 - Royal Society of Chemistry Cambridge, 1995 pp 59-72. 

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. 

Synthesis of mono-silanol-tenninated polymers is possible by the use of the title compound isocyanatometiiyl-dimethylmonomethoxy silane. The isocyanato group readily reacts with polymers having terminal groups containing active hydrogen. 

The poly(siloxane) polymers are usually prepared by the acid or base hydrolysis of appropriately substituted dichlorosilanes or dialkoxysilanes, or by the catalytic polymerization of small ring cyclic siloxanes [71-75]. The silanol-terminated polymers are suitable for use after fractionation or are thermally treated to increase molecular weight and in some cases endcapped by trimethylsilyl, alkoxy or acetyl groups [76,77]. Poly(siloxanes) synthesized in this way are limited to polymers that contain substituent groups that are able to survive the relatively harsh hydrolysis conditions, such as alkyl, phenyl, 3,3,3-trifluoropropyl groups. Hydrosilylation provides an alternative route to the synthesis of poly(siloxanes) with labile or complicated substituents (e.g. cyclodextrin, oligoethylene oxide, liquid crystal, amino acid ester, and alcohol) [78-81]. In this case... 

Polymer Preparation. In order to prepare silicon containing polymers which include the m-xylyl and dimethylenebiphenyl moieties, two distinct polymerization routes were chosen. The first route consists of condensation of a dichlorodialkyl(or aryl)silane with a dicarbanion, namely 12 or 12. The material which is formed consists of an all silicon-carbon and carbon-carbon backbone. The second polymerization utilizes the bis(silanol) monomers discussed in the previous section. These materials are heated and undergo a self condensation reaction to form polymers which contain silicon-carbon, silicon-oxygen, and carbon-carbon bonds in the backbone. 

Condensation to form siloxane bonds occurs by either an alcohol-producing reaction [Eq. 5.26)] or a water-producing reaction [Eq. (5.27)]. The most basic silanol species, namely silanols contained in monomers or weakly branched oligomers (very short chain polymers), are most likely to be protonated so that condensation reactions are likely to occur between neutral species and protonated silanols situated on monomers and the end groups of chains. 

The functionalized oligomers offer potential in the modification of inorganic surfaces, and subsequently aid in the adhesion promotion of organic coatings. Preliminary adhesion studies have shown that the precursors react quantitatively with silanol-containing surfaces. Extraction of the fimctionalized surfaces with THF did not remove the covalently bound polymers. Improved adhesion of a polystyrene homopolymer was evident when the molecular... 

Amorphous sihca exists also ia a variety of forms that are composed of small particles, possibly aggregated. Commonly encountered products iaclude sihca sols, sihca gels, precipitated sihca, and pyrogenic sihca (9,73). These products differ ia their modes of manufacture and the way ia which the primary particles aggregate (Fig. 8). Amorphous sihcas are characterhed by small ultimate particle si2e and high specific surface area. Their surfaces may be substantially anhydrous or may contain silanol, —SiOH, groups. These sihcas are frequentiy viewed as condensation polymers of sihcic acid, Si(OH)4. 

Unfortunately, because self-condensation of silanols on the same silicone can occur almost spontaneously, the reaction of disdanol or trisilanol compounds with telechelic sdanol polymers to form a three-dimensional network is not feasible. Instead, the telechelic polymers react with cross-linkers containing reactive groups such as alkoxysdanes, acyloxysdanes, silicon hydrides, or methylethyloximesilanes, as in the reactions in equations 18—21 (155). 

---