Trisiloxane polymers

It is a common misunderstanding that silicones and silicone surfactants are incompatible with hydrocarbon oils this is only partly correct. Small silicone surfactants, such as the trisiloxanes, are very compatible with organic oils. For example, aqueous solutions of the trisiloxane surfactants give very low interfacial tension against alkane oils. The incompatibility between polymeric silicones and some hydrocarbon oils is due more to the polymeric nature of the silicone block rather than to strong phobicity such as that between fluorocarbon and hydrocarbon groups. The compatibility between two species, such as a polymer and a... 

The latest class of silicone surfactants to be prepared are the fluorosilicone copolymers (73,74). These compounds combine disiloxane or branched trisiloxane structures modified with fiuoroalkyl radicals as the hydrophobic moiety and polyethylene oxide units as the hydrophilic group. Two copolymers containing different fiuoroalkyl groups have been reported for use in shampoo systems. The materials containing 3,3,3, trifluoropropyl units were characterized by surface tensions approximately equivalent to dimethicone fluids ( 20.1 mN/m), while polymers containing 3,3,4,4,5,5,6,6,6, nonafluorohexyl groups displayed surface tensions as low as 17.6 mN/m (75). 

A very similar chemical approach with a trisiloxane co-monomer and a tetracyclic crosslinker was used to realize main chain LCEs with pentaphenyl mesogens incorporated side-on into the polymer main chain [35]. Such elastomers have an Sa phase behavior due to the segregation of the aromatic and the siloxane moieties. 

Boileau, Kaempf, Schue and coworkers have studied the cryptate mediated anionic addition polymerization of several systems including ethylene oxide [38], propylene sulfide [39-40], isobutylene sulfide [40], isoprene [38], methyl methacrylate [38], hexamethyl trisiloxane [40], e-caprolactone [41], styrene [38, 40, 41], ct-methylstyrene [41], 1,1-diphenylethylene [41] and /3-propiolactone [42]. The polymerization of the latter compound induced by dibenzo-18-crown-6 complexed sodium acetate has also been reported [43]. In general, it was found that the polymer-... 

In Table 3.2, the cychc trisiloxanes appear as two isomers, as and trans. The microstructure of the polymers bearing trifluoropropyl and phenyl substituents has been reviewed [118]. The rate of polymerization depends to a large extent on the nature of the substituent with, in general, the electron-withdrawing substituents increasing the reactivity, although the situation may be more complex [13]. 

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