Polydimethylsiloxane chains

The most commonly used siloxane modifiers are those having phenyl, trifluoro-propyl and cyanopropyl substituents. Introduction of phenyl units into the polydimethylsiloxane backbone either in the form of methylphenylsiloxane or diphenyl-siloxane increases the thermal and oxidative stability, glass transition temperature and the organic solubility characteristics of the resulting copolymers. At low levels (5-10 percent by weight) of incorporation, bulky phenyl groups also break up the regularity of polydimethylsiloxane chains and inhibit the crystallization (Tc... 

Figure 3.1 Quadruple hydrogen-bonded 2-ureido-4-pyrimidinone units attached to the ends of a polydimethylsiloxane chain assemble to create materials with viscoelastic properties.

The present theoretical approach to rubberlike elasticity is novel in that it utilizes the wealth of information which RiS theory provides on the spatial configurations of chain molecules. Specifically, Monte Carlo calculations based on the RIS approximation are used to simulate spatial configurations, and thus distribution functions for end-to-end separation r of the chains. Results are presented for polyethylene and polydimethylsiloxane chains most of which are quite short, in order to elucidate non-Gaussian effects due to limited chain extensibility. 

In our studies of the polymerization of cyclic siloxane monomers we observed anomalies in the kinetics of the process and in the viscosity changes of the medium. The growing polydimethylsiloxane chain ends were found to associate... 

As EPR and EPDM elastomers, the vulcanization process is carried out using organic peroxides because the polymer chains do not contain unsaturated bonds. If the polydimethylsiloxane chains are modified by introducing a small quantity of vinyl groups, the vulcanization is carried out using cumyl peroxide. 

Protection of the linear polydimethylsiloxane chain with the bulky ladder polyphenyl-silsesquioxane (PPhSO) block copolymer molecule inhibits its cyclic depolymerization and retains the organic framework to a large extent. 

For a better understanding of the probe behavior in PDMS networks it was necessary to investigate the fluorescence behavior of a probe covalently bonded to a soluble polydimethylsiloxane chain. Therefore, a dialkoxysilane containing 4-piperidinobenzoic acid ester was allowed to react with a hydroxyl-terminated polydimethylsiloxane giving a soluble polymer with a covalently bonded probe at the main chain. This reaction occurs in the presence of Sn(II) octoate. The reaction scheme is drawn in Fig. 4. It was shown by GPC (UV detection) and NMR spectroscopy that the probe reacted with the hydroxyl groups of the polydimethylsiloxane chains. 

From the results presented in Table 3.27 and in accordance with the results of [157, 158], for oirr case at 333 K, the surface layer at maximum adsorption (surfactant mass fractions from 2.25 x 10 to 7.5 X 10 is an extremely compressed monolayer, whereas the majority of dimethylsiloxane units lie on the surface of the liquid. At higher temperatures (343—353 K) but in a narrower concentration range (from 5 x 10 to 7.5 x 10 ) the polydimethylsiloxane chain tears off the sirrface, forming spiral turns of 6—8 elements, as witnessed by a single element area of 0.09-0.11 nm, which may be referred to one spiral turn [157]. From the concentration and tempera-... 

The latter are limited to hydrocarbon, perfluorocar-bon and polydimethylsiloxane chains. While the formation of micelles is well known, surfactants also form a wide variety of liquid crystalline phases in water which are much less familiar. Almost all surfactants that form micelles also form liquid crystals, while many do not form micelles but do form liquid crystals. Thus, liquid crystal formation by surfactants is more widespread than micelle formation. Indeed, an understanding and knowledge of liquid crystals can provide a comprehensive guide to the application of surfactants. This is because the size and shape of the surfactant molecules determine the structure of the self-assembled aggregates, which in turn, controls the liquid crystal... 

Many silicone manufacturers and formulators supply current grades of amino-silicones either to textile finishers or to distributors. The drawbacks of this classical offer relate to yellowing, a consequence of thermal oxidation of the amines in the drying oven [1], and water repellency which results from the adsorption of polydimethylsiloxane chains onto the fabric. These are particularly detrimental to bath towels and similar goods, for which comfort, soft feel and good appearance are key success factors. 

Wright, P. V., Cyclization Equilibrium Constants and the Conformations of Polydimethylsiloxane Chains. J. Polym. Sci., Polym. Phys. Ed. 1973,11,51-64. 

Mark, J. E. Rahalkar, R. R. Sullivan, J. L., Model Networks of End-Linked Polydimethylsiloxane Chains. 111. Effect of the Functionality of the Cross-Links. J. Chem. Phys. 1979, 70,1794-1797. 

Mazan, J. Leclerc, B. Galandrin, N. Couarraze, G., Diffusion of Free Polydimethylsiloxane Chains in Polydimethylsiloxane Elastomer Networks. Eur. Polym. J. 1995, 31(8), 803-807. 

Llorente, M. A. Mark, J. E. (1979). Model Networks of end-Linked Polydimethylsiloxane chains. IV Elastomeric Properties of the Tetrafunctional Networks Prepared at Different Degrees of Dilution. Journal of Chemical Physics, Vol. 71, No. 2, pp. 682-689, ISSN 0021-9606... 

Mark JE, Andrady AL. Model networks of end-linked polydimethylsiloxane chains. X. Bimodal networks prepared in two-stage reactions designed to give high spatial heterogeneity. Rubber Chem Technol 1981 54 366-73. 

Llorente MA, Andrady AL, Mark JE. Model networks of end-linked polydimethylsiloxane chains. XIII. The effects of junction fimctional-ity on the elastic properties of the bimodal networks. Colloid Polym Sci 1981 259 1056-61. 

Zhang ZM, Mark JE. Model networks of end-linked polydimethylsiloxane chains. XIV. 

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