Siloxane polymers surface activity

The surface activity of organosilicon polymers with backbones other than siloxane is not very well known. Interest in varying the backbone in organosilicon polymers does not normally stem from a desire to modify surface properties. Usually, the purpose of backbone variation is to increase thermal stability, as for example, with poly(silphenylenesiloxane) and poly-(carboranesiloxane) copolymers. Because thermal stability is often achieved by increasing TgS by using rigid backbones, most backbone variations will have a detrimental effect on polymer surface activity. 

The unique surface characteristics of polysiloxanes mean that they are extensively used as surfactants. Silicone surfactants have been thoroughly studied and described in numerous articles. For an extensive, in-depth discussion of this subject, a recent chapter by Hill,476 and his introductory chapter in the monograph he later edited,477 are excellent references. In the latter monograph, many aspects of silicone surfactants are described in 12 chapters. In the introduction, Hill discusses the chemistry of silicone surfactants, surface activity, aggregation behavior of silicone surfactants in various media, and their key applications in polyurethane foam manufacture, in textile and fiber industry, in personal care, and in paint and coating industries. All this information (with 200 cited references) provides a broad background for the discussion of more specific issues covered in other chapters. Thus, surfactants based on silicone polyether co-polymers are surveyed.478 Novel siloxane surfactant structures,479 surface activity and aggregation phenomena,480 silicone surfactants application in the formation of polyurethane foam,481 foam control and... 

In a recent review by Drake et al. 1 the surface activity of linear polymers and co-polymers is discussed, based on many recent references. They refer to the research correlating surface characteristics of siloxanes to the nature of end groups575 and to their concentration576 in linear polymers. A few examples of the recent work on siloxane migration to the interfaces, with the emphasis on the behavior of block577 and graft co-polymers,578 and their blends with... 

The observed enhancement in oxygen index could be attributed to phase segregation in these block copolymers, which leads to domination of siloxane on the polymer surface. Siloxanes have solid-phase activity rather than vapor-phase activity and reduce flammability through increased formation of pyrolytic char. 

Owen, M. J. Siloxane Surface Activity , in Silicon-based Polymer Science A Comprehensive Resource (Eds. J. M. Zeigler, F. W. G. Fearon), American Chemical Society (ACS Adv. Chem. Ser. 224), Washington, DC, 1990, Chap. 40, p. 705. 

I have focused on methyl derivatives of nonsiloxane organosilicon backbones to achieve a useful comparison of polymer backbones. There are studies on materials with pendant groups other than methyl and backbones other than siloxane. The most useful of these studies is the direct liquid-surface-tension measurement by Feher and co-workers (96) of silane oligomers from trisilane to heptasilane, including some branched species (Table XV) (96-99). The data are useful because they answer the question of the surface activity contribution of the Si-H group. The situation with SiH-containing siloxanes... 

M.J. Owen, Siloxane surface activity, in Silicon-Based Polymer Science, J.M. Zeigler and F.W.G. Fearon, eds.. Advances in Chemistry Series 224, American Chemical Society,... 

Molecular Structure.—A review has appeared that compares the relationship between polymer structure and surface-active properties of the poly(dimethyl siloxane)s (PDMS) with that of hydrocarbon and fluorocarbon polymer systems." A mathematical study of the spreading of (PDMS) oil drops has been presented and experimental data shown to be in good agreement with predictions. Quantitative comparison of previously published n.m.r. spin-relaxation data for poly(diethyl iloxane)s with theoretical predictions for a variety of motional processes, have allowed both the nature and time scale of molecular motions to be identified."... 

Surface activity of these PAMAMOS dendrimers was determined by the Wilhelmy plate method for the water soluble dendrimers and by the Langmuir trough technique for the insoluble ones. Some preliminary data on water soluble PAMAMOS have already been published (5,42), It was shown that the best of these materials lower the surface tension of water to just below 30 mN/m at 5 wt. %, with no break to a constant surface tension that would indicate micelle formation. Thus, these PAMAMOS behave more like considerably surface active water soluble polymers than surfactants. However, it is probable that their homologues with longer siloxane dendrons than the trimethylsilyl- groups studied so far will have considerably more surfactant-like behavior. 

Owen MJ (1990) Siloxane surface activity. In Zeigler JM, Fearon FWG (eds) Sihcon-based polymer science a comprehensive resource. American Chemical Society, Washington, D.C., pp 705-739... 

With many synthetic elastomeric polymers, the strength properties obtained from a non-reinforced crosslinked polymer are very low and generally unsuitable for industrial applications. Silicones are no exception and although carbon black can be used for reinforcement, fine particle size fume silica is the usual choice for property enhancement. The incorporation of these highly surface-active silicas into silicone gums is a difficult process due to the rapid interaction between polymer and filler resulting in a pseudo-vulcanised mass. For this reason a variety of siloxane based filler treatments are generally used to control viscosity and other properties. 

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