Telechelic siloxanes

J. H. K. K. Hirschbeig, F. H. Beijer, H. A. van Aert, P. C. M. M. Magusin, R. P. Sijbesma, E. W. Meijer, Supramolecular polymers from linear telechelic siloxanes with quadruple hydrogen bonded units , Macromolecules 1999, 32, 2696-2705. 

The synthesis and phase behavior of the model polydiethylsiloxane networks have also been studied. The networks were made by hydrosilylation of well-defined vinyl and allyl telechelic siloxanes obtained by kinetically controlled polymerization of cyclic trisiloxane.314 The effects of molecular weight between the cross-linkings on segment orientation in polydiethylsiloxane elastomers were studied.315... 

Hirschberg JHKK, Beijer FH, van Aert HA, Magusin PCMM, Sijbesma RP, Meijer EW. Suptamolecular polymers from linear telechelic siloxanes with quadniple-hydrogen-bonded units. Macromolecules 1999 32 2696-2705. 

Chakraborty, R. Soucek, M. D., Synthesis of Amine and Epoxide Telechelic Siloxanes. Macromol. Chem. Phys. 2008, 209, 604-614. 

FTIR analysis of the unprotected telechelic siloxanes shows typical siloxane vibrations (i.e. vSi-CHa 1263 cm"l and vSi-CH2 1420 cm l) concomitant with carboxylic acid vibrations (vCOOH 3350 cm l and vc=0 1210 cm l). The decrease in intensity of the C-H vibrations at 2960 to 2850 cm"l corresponds to the loss of the tert-butyoxycarbonyl group of (24). The vibrations at 3060 cm"l are characteristic of the aromatic C-H stretching vibrations of the phenyl group in phenylalanine. 

Figure 1 SEM photograph of the fracture surface of 10 phr telechelic siloxane 12 in PT-30 after curing. Left image is at 500x. (inset bar is 200pm), right image at 1,500 X (inset bar 120 pm).

An important advantage in the preparation of a,eo-functionally terminated siloxane oligomers, over the other telechelic systems, is the flexible polymerization chemistry of cyclic organosiloxane monomers and intermediates. This is mainly due to the partial... 

Table 4. Important a,oj-organofunctionally terminated di-siloxanes precursors for reactive, Telechelic polyorgano-siloxanes...

The polycondensation reaction between telechelic hydride and telechelic methoxy siloxane in the presence of very low levels of B(CgFj)3 has been described. The compromise between large polymer content and reasonable molar masses is found by tailoring the addition rate and excess content of L H reagent. Rubinsztajn et al. showed that with silphenylene-co-PDMS copolymers, the reaction was completed... 

The hydrosilylation of acetyl-protected allylglucoside with a Si-H-ended telechelic polysiloxane, followed by deprotection has also been described by Nagase et al. for the preparation of glyco-oligodimethylsiloxanes as transdermal penetration enhancers (Fig. 10) [16-18]. The status of the siloxane chain after deprotection has been checked by size exclusion chromatography (SEC). When they used MeOH/K COj for deprotection, they observed by SEC the formation of two peaks... 

Microwave irradiation Grafting onto method Various catalysts are used [4,4 -Azobis (4-cyanovaleric acid)] Telechelic polymers, polyethylene glycol, poly-dimethyl siloxane... 

Alternatively, the chemical transformation of functional gronps attached to the siloxane prepolymers by reacting with appropriate reagents provides desired functionalization. For example, electroactive pyrrole functional polysiloxanes were prepared from the corresponding amino telechelics... 

In addition, ADMET has been utilized to polymerize a telechelic oligomer formed from the hydrosilation of 1,4-pentadiene with 1,1,3,3-tetramethyl-disiloxane [107]. ADMET has also been used to produce copolymers with backbone siloxanes and methoxy-substituted silanes [109]. These methoxy-substituted silanes gradually cross-link upon exposure to air, a potentially useful phenomenon (Figure 13.15). Carbosiloxane and oligo(oxyethylene) polymers... 

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