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Hyperbranched Siloxanes – Powerful Polymers for Many Applications

IP.com Disclosure Number: IPCOM000029069D
Publication Date: 2004-Jun-15
Document File: 2 page(s) / 17K

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Abstract

Having physical properties so different from their linear counterparts siloxanes with hyperbranched structures became more and more popular among formulators. Fortunately, many methods for their manufacture have been established over the years, so a whole range of hyperbranched siloxanes is available by now.

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Hyperbranched Siloxanes – Powerful Polymers for Many Applications

Having physical properties so different from their linear counterparts siloxanes with hyperbranched structures became more and more popular among formulators. Fortunately, many methods for their manufacture have been established over the years, so a whole range of hyperbranched siloxanes is available by now.

A more or less classic approach for making these polymers is the equilibration of linear or cyclic polysiloxanes with siloxane compounds which contain tri- or tetrafunctional so-called T- or Q-units. Also well known are condensation methods which require regular PDMS-diols in combination with trimethoxy silanes. At proper stoichiometric ratios this thermally driven reaction

yields hyperbranched siloxanes with the former silanes as branching points.

Much younger are methods based on the hydrosilylation reaction, e.g. the addition of the SiH-function across C-C-multiple bonds. Hyperbranched unsaturated siloxane polymers are available by action of an excess of organic dienes or trienes on multi-SiH-functional siloxanes under catalytic conditions. The number of functions per molecule as well as the stoichiometry employed need to be tuned in order to get hyperbranching. Also, vinyl siloxanes with at least two vinyl groups can be used instead of the multifunctional organic olefins. The remaining unsaturation (excess of olefinic double bonds) in these hyperbranched siloxanes is a useful candidate for reaction with H-silanes for further modification of the polymer.

Hydrosilylation can yield SiH-functional hyperbranched siloxanes as well. Reaction of a monovinyl siloxane with a least two additional SiH-groups in the same molecule with various hydrosiloxanes results in build-up of energy during the course of this reaction, expertise and proper handling of the compounds is strictly required. Less dramatic, of course, is the polyaddition of an excess of telechelic dihydro siloxane polymers and polyfunctional alpha-olefinic compounds: depending on the density of functional groups in the mix the exotherm can be almost negligible. The active hydrogen of these hyperbranched products can easily be hydrolyzed to yield SiOH-functionality or exchanged with chlorine or other heteroatom containing groups.

Hyperbranched siloxanes can be made with small as well as very large segment lengths. The least ones tend to exhibit high viscosities up into millions of centistokes. For handling reasons such products are usually made in solvents, as blends with lower molecular compounds or even in emulsion.

This new type of polymers, the mentioned blends and emulsions thereof give a major contribution to the overall conditioning in hair and skin care applications.

In shampoos, conditioning shampoos, conditioners, after dye treatment and hair relaxer treatments and hair styling applications tests showed for example reduction of dry and wet combing forces, color protection. This conditioning agent can give ha...