Silarylene

The synthesis of block polymers of diacetylene-silarylene and diacetylene-carboranylenesiloxane polymers (99a-e) (Fig. 61) by the polycondensation reaction of 1,4-dilithiobutadiyne with l,4-bis(dimethylchlorosilyl) benzene and/or l,7-bis(tetramethylchlorodisiloxane)-m-carborane have been reported by Sundar and Keller.129 These polymers are a hybrid between the carboranylenesiloxane and silarylene-siloxane polymers and have high char yields (up to 85%) at 1000°C in N2 and in air, reflecting the thermal stabilizing effects of the carborane and aromatic units in the polymeric backbone. 

Figure 61 The hybrid silarylene-siloxane/carboranylenesiloxane polymers, 99a-e.

Guida-Pietrasanta, F. and Boutevin, B. Polysilalkylene or Silarylene Siloxanes Said Hybrid Silicones. Vol. 179, pp. 1-27. 

Silarylene polymers that contain more than one phenylene group in the repeat unit could be of considerable interest because of the various meta, para combinations that could presumably be synthesized. Cyclohexylene (C6H10) groups can switch between... 

Introduction of phenylene unit into the polyorganosiloxane chain causes a significant variation of the chain configuration and flexibility, which affects physical and chemical parameters of the po-lymer. Moreover, different combinations of linear =Si-0-Si= or silarylene fragments with cyclic on-es may change conformational flexibility of the chain... 

For the purpose of synthesizing dihydroxy-containing silarylene cyclosiloxane oligomers, HFC reac-tion of l,4-bis(chlorodimethylsilyl)benzene, synthesized by the known technique, with 1,5-dihyro-xyhexaphenylcyclotetrasiloxane and 1,7-... 

Initial divinylcyclosiloxanes, used in polyaddition reactions, represent a mixture of cis-and trans-isomers (at 46 54 ratio). Because these isomers could not be separated by rectification or fractional over-precipitation [115], synthesized silarylene... 

Table 17. Physical and chemical parameters of silarylene carboorganocyclosiloxanes...

In H NMR spectra of silarylene carboorganocyclosiloxanes in the area of 5.8 and 4.5 ppm, reflexes from protons belonged to =Si-CH=CH2 and =Si-H groups of initial monomers are absent. The reflex at 1.0 ppm, corresponded to protons of -CH2-CH2- group, formed in hydrosilylation reaction. Gene-rally, location of reflexes and the ratio of their intensities in 29Si and 1H NMR spectra prove the supposed structure of silarylene... 

For the purpose of carbosiloxane network synthesis, at the first stage in accordance with scheme (2.25), silarylene carboorganocyclosiloxanes with l,4-bis(dimethylsilyl) benzene excess and narrow MMD were obtained [116], Hence, synthesized oligomers of the structure XV are transparent, colorless and viscous products with MM = 800 - 2,500. At the second stage, polyaddition of reaction (2.23) product with tetramethyltetravinylcyclotetrasiloxane is performed in accordance with the scheme as follows ... 

Table 18. Deformation and strength parameters of films based on silarylene carboorganocyclosiloxanes of the structure XV [117]...

Table 19. Values of Mo, scattering asymmetry and the second virial coefficient, A2, for silarylene carboorganocyclosiloxanes fraction [117]...

The dependence of // and Mco values in lg[//] - lg Mo coordinates, shown in Figure 15, indicates that the following Mark-Kuhn-Hauvink equations are corresponded to silarylene carboorganosilo-xane copolymer ... 

For estimation of silarylene carboorganosiloxane macromolecules under natural conditions, when the coil is perturbed by interaction with the solvent, authors of the work [117] have used the fol-lowing prerequisites observed in the current case L a, i.e. the macromolecule is of the coil-shaped type (a=A/2) low concentrations of solutions, in which the Einstein equation is active the selected solvent is close to the 0-solvent. 

Table 21. Bond lengths and unit rotation angles in silarylene carboorganocyclosiloxane chain...

Table 21 shows assessment data on conformational parameters, persistent length (a), the Kuhn seg-ment (A) and structural parameter (ML) for silarylene carboorganocyclosiloxane fractions. Average values of a, A and ML, deduced from [q] and M of silarylene carboorganocyclosiloxane fracti-ons, equal 9.6 A, 19.2 A and 34.45x10s, respectively. Thus, the structural parameter, ML, calculated from M and [q] values, and the one given by chemical structure (ML=34.65xl08) of molecules are practically coincident. As a consequence, the above considered Afr really equals 19.2 A. Under natural conditions, the... 

Title High-Temperature Elastomers from Linear Poly(Silarylene-Siloxane-Acetylene)... 

Flexible and oxidatively stable thermosets were prepared by thermally curing linear poly(silarylene-siloxane-acetylene) elastomers at up to 450°C. Thermooxidative weight loss of 3.69% to 7.69% was observed for these crosslinked inorganic-organic hybrid polymers when isothermed at 350°C under air flow. 

Preparation of Hydroxyl Terminated Silarylene-Siloxane Prepolymer... 

TABLE 1. Physical and oxidative stability of poly(silarylene-siloxane-acetylene) elastomers after isothermal curing. 

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