Silanol-terminated poly

Mark and his co-workers reported the reinforcement of poly(dimethylsiloxane) networks by silica gel particles [1-6]. For example, bis(silanol)-terminated poly-(dimethylsiloxane) was reacted with tetraethoxysilane in the presence of acid-catalyst to produce the reinforced siloxane networks. The reaction proceeded homogeneously. The content of the silica filler can be controlled by the feed ratio of polysiloxane and tetraethoxysilane. 

Torsional braid analysis indicates that the —Si—O—Si— flexible chain is present and persists, although its flexibility is somewhat impaired, even when the material is fully cured. This indicates that there is a substantial proportion of the R—Si—O— units which are neither crosslinked nor involved in ring formation. However, a spiral structure with the hydroxyl groups enclosed along the core meets the requirements. Such a structure has been suggested by Birchall et al. [12] for silanol-terminated poly(oxymethylenes). 

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... 

The crosslinking reaction indicated above is important for another reason. It is also the root cause of thermal degradation of poly(siloxanes) resulting in column bleed at high temperatures. The main degradation products from the heating of silanol-terminated poly(siloxanes) have been identified as hydrocarbons and small ring cyclic... 

Poly (p-toluenesulfonamide-co-formaldehyde). See Tosylamide/formaldehyde resin Polytrap 6603, Polytrap Q5-6603. See Acrylates copolymer Polytrifluorochloroethylene Poly (trifluoroethylene chloride) Poly (trifluoromonochloroethylene). See Chlorotrifluoroethylene polymer Poly (trifluoropropyl (methyl) siloxane Poly (3,3,3-trifluoropropylmethylsiloxane). See Polymethyl-3,3,3-trifluoropropylsiloxane Polytrifluoropropylmethylsiloxane, silanol-terminated. See Polymethyl-3,3,3-trifluoropropylsiloxane, silanol-terminated Poly(trifluorovinyl chloride). See Chlorotrifluoroethylene polymer Polytrimethylene terephthalate Synonyms PIT... 

Yoshinaga, I. Yamada, N. Katayama, S., Inorganic-Organic Hybrids Synthesized from Metal Alkoxides and Silanol-Terminated Poly(dimethylsiloxane). 

TPEEs based on poly(dimethylsiloxane)s were synthesized by catalyzed two-step transesterification in the melt, from dimethyl terephthalate, 1,4-butanediol and poly(dimethylsiloxane)s with either disilanol (PDMS-OH) or dicarboxypropyl (PDMS-CP) terminal groups. Incorporation of silanol-terminated poly(dimethylsiloxane)s... 

Poly(dimethylsiloxane) (PDMS) is one of the most popular inorganic elastomers and can be modified with many nanofillers. Pan et al. used silanol-terminated PDMS and modified this matrix with mono-POSS and tetra-POSS cages which were physically blended into the matrix. The authors prepared another type of PDMS which had vinyl terminal groups that are also able to react with the central siloxane core by hydrosilylation. The idea was to obtain larger POSS-based fillers than silica particles typically used to reinforce elastomers (Fig. 8). 

The fundamental component of most silicone sealants is the polymeric siloxane referred to earlier, most often a silanol-terminated poly (dimethylsiloxane) ... 

Poly(dimethyl siloxane), hydroxy terminated Silanol-terminated di-Me siloxanes 70131-67-8 Siloxanes and silic[Pg.2285]

Poly(oxyethylene)-Si02 ormosils have been prepared as an approach to the preparation of biologically active polymer-apatite composites. For this purpose, Yamamoto et al. [72] obtained these Class II hybrids from triethoxysilyl-terminated poly(oxyethylene) (PEG) and TEOS by using the in situ sol-gel process. After being subjected to the biomimetic process to form the bone-like apatite layer, it was found that a dense apatite layer could be prepared on the hybrid materials, indicating that the silanol groups provide effective sites for CHA nucleation and growth. 

The mechanism has been verified by studying the yield of hexamethylcyclotrisiloxane from poly(dimethylsiloxane) with various terminal groups, such as OH, OCH3, OCu(AcAc) (where AcAc is an acetylacetonate fragment), OFe(AcAc), and OZr(AcAc) [16], The yield of hexamethylcyclotrisiloxane is significantly higher for the case of free silanol end groups. 

---