Condensation polymers silicones

Companson with the mineral silicates is instructive since there is a l l correspondence between the two sets of compounds, the methyl groups in the silicones being replaced by the formally iso-electronic 0 in the silicates (see p. 366). This reminds us of the essentially covalent nature of the Si 0-Si linkage, but the analogy should not be taken to imply identity of structures in detail, particularly for the more highly condensed polymers. Some aspects of the technology of silicones arc summarized in the concluding Panel. 

Condensation polymers commercial, 20 392-393t phenol-formaldehyde, 70 409 Condensation polymerization, of silicone fluids, 22 573... 

See under Siloxanes in article on Silanes in this Vol for the definition and a brief description of the basic molecular structure. The name silicone was created by F.S, Kipping as an analogy to ketones. However, his silicane-diols , (Aryl)2Si(OH)2 could not be dehydrated to silicones but always condensed to higher mw Si—0—Si compds. These structures were then (early 1900s) referred to as silicones. In time the name has come to represent any organo-silicon oxide polymer, such as polydimethy-siloxane (see below) ... 

Silicones are polymers that find widespread uses from high-temperature hydraulic fluids to medical prostheses. Draw a portion of the polymer formed by condensing out water from dimethylsilanediol, (CH3)2Si(OH)2. 

Synthesis of new functional silicon-based condensation polymers [Y. Imai, J. Macro-mol. Sci., Chem. 1991, A2S(11,12), 1115-1135],... 

The reaction of silicon tetrachloride with polyliydric alcohols produces a condensation polymer which may be called a silicon polyester. Some interesting condensation polymers related to these are produced by the reaction of ethyl silicate with glycols and phenols.40... 

The sodium condensation reaction of a,co-bis(chlorosilyl)-substituted compounds and the coupling reaction of dilithio derivatives of compounds bearing 7t-electron systems with dichlorosilanes offer a convenient route to various silicon containing polymers. However, the polymers prepared by these methods always contain a small proportion of siloxy units in the polymer backbone, which would interrapt the electron delocalisation. Therefore, new synthetic routes to organosilicon polymers have been developed in which no alkali metal halide condensations are involved [6, 7]. We report syntheses of organosilicon... 

The ADMET step condensation polymerization of carbosila- and carbosiloxa-dienes has generated a new class of unsaturated silicon-containing polymers when monomer structure/reactivity relationships, as described earher for the polar functionalities, are obeyed (equation 22). 

Quaternary ammonium compound Quaternary base Quaternary compound Quaternary compound Quaternary fatty acid derivative Quaternary fatty derivatives Quaternized condensation polymer Silica, colloidal Silica, colloidal Silica, colloidal Silica, modified Silica blend, reacted Silicate Silicic acid Silicone Silicone... 

Fig. 3. Various environments of silicon in the hydrolysis/condensation polymers (R = H, CH3, C Hs R" = CH3, C2H5).

Condensation polymers are classified as polyesters, polyamides, polyurethanes, and ether polymers, based on the internal functional group being ester (-COO-), amide (-CONH-), urethane (-OCONH-), or ether (-0-). Another group of condensation polymers derived by condensation reactions with formaldehyde is described under formaldehyde resins. Polymers with special properties have been classified into three groups heat-resistant polymers, silicones and other inorganic polymer, and functional polymers. Discussions in all cases are centered on important properties and main applications of polymers. 

We have synthesized some novel silarylene and silarylenesiloxane polymers via dicarbanions prepared from Lochmann s base. Lochmann s base, a powerful metalating reagent composed of equimolar amounts of n-butyl lithium and potassium r-butoxide in a hydrocarbon, has been used to dimetalate compounds such as m-xylene, 4,4 -dimethylbi-phenyl, and 2,3-dimethyl-1,3-butadiene in good yields. In this work the dicarbanion of m-xylene and 4,4 -dimethylbiphenyl have been used to prepare silicon containing monomers and polymers by two different routes. The first route involves a 1 1 condensation reaction between the dicarbanion and a dichlorodiorganosilane to produce a condensation polymer. The second route involves reaction of the dicarbanion with a chlorodiorganosilane which is then converted to a bis(silanol) and then polymerized. Spectroscopic as well as thermal characterization will be presented on the polymers which have been described. 

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 polymers nylon, teflon, polymethane, polycarbonate, amino resins, alkyl resins, and silicone resins... 

Keefer, K. D., Structure and Growth of Silica Condensation Polymers. In Silicon-Based Polymer Science. A Comprehensive Resource, Zeigler, J. M. Fearon,... 

The term silanol is used for any OH group attached to silicon and will be understood to include what has otherwise been referred to as siloxanol" and silicol groups. The term polymerization, strictly speaking, means a linking together of monomer units to form a polymer of the same composition, but, in the silica system the monomer. Si(OH)4, condenses to form polymer that ultimately has the composition (Si02)n- However, the term polymerization has been so widely used for the formation of condensation polymers that it will also be so used here. 

Silicones are polymers with backbones consisting of—[Si(R>2—O]— repeating units. They are prepared by reacting chlorosilanes with water to form silanols that condense to form siloxanes. Silicone oils made from dimethyldichlorosilane and methyltrichlorosilane are used as additives to reduce surface tension. Chemically modified silicone fluids, such as polysiloxane/polyether block copolymers, with broader ranges of compatibility have been described (175). 

The sodium condensation reaction of compounds involving two chlorosilyl groups attached to a thiophene ring offers a convenient route to silicon-containing polymers in which a regular alternating arrangement of disilanylene unit and n electron system is found in the polymer backbone. This synthetic route was first used by Weber [58] and was also studied by Ishikawa [60]. It is summarized in Scheme 14.17. 

This volume continues in the tradition of Volume I in presenting detailed laboratory instructions for the preparation of various types of polymers such as urea, melamine, benzoguanamine/aldehyde resins (amino resins-amino-plasts), phenol/aldehyde condensates, epoxy resins, silicone resins, alkyd resins, polyacetyls/polyvinyl acetals, polyvinyl ethers, polyvinyl pyrroli-dones, polyacrylic acids, and polyvinyl chloride. Polyvinyl acetate and related vinyl esters, allyl polymers, acetylene polymers, maleate and fumarate polymers, and several other addition-condensation polymer types will be covered at a later date in Volume III. 

The use of silicon-containing phenolic polymers with NDS compounds present as the photoactive polarity switch has been investigated. Formaldehyde condensation polymers with m-trimethyl-silylphenol (19) have been prepared. It is necessary to incorporate phenol as a comonomer in order to decrease the hydrophobicity of these resins so that they are soluble in aqueous base. The maximum silicon content obtainable is around 9% due to the acidolysis of the aromatic carbon-silicon bond during the acid-catalyzed polymerization process. Nevertheless, high resolution images with good oxygen etch resistance are obtained when these resins are formulated into resists with NDS derivatives present. 

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