Polydimethylsiloxane , surface energies

Luo et al. [6] used a polydimethylsiloxane macro-initiator to initiate polymerization of methacrylate monomers with fluorinated side groups to prepare fluorosilicone polymers. To obtain diblock copolymers with a low surface energy, they designed poly(dimethylsiloxane)-block-poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) (PDMS-1 -PHFBMA) diblock copolymers by atom transfer radical polymerization (ATRP) technique. To initiate 2,2,3,3,4,4, 4-heptafluorobutyl methacrylate polymerization, bromine end-capped polydimethylsiloxane (PDMS-Br) was used as the macro-initiator. Scheme 6.5 shows a schematic representation of the PDMS-fc-PHFBMA diblock copolymers. The system was strictly deoxygenated... 

The surface applications of silicone products, particularly those based on polydimethylsiloxane (PDMS), are many and varied (7). Familiar examples include release liners for pressure-sensitive adhesives (PSAs), antifoaming agents, and water-repellent treatments for a wide variety of substrates. This broad diversity of application is a direct consequence of the low surface energy of PDMS which is lower than most other polymers except for those based on aliphatic fluorocarbon moieties. Despite the commercial importance of this aspect of the properties of polydimethylsiloxane, there is no fully satisfactory contact angle characterization of PDMS yet available. There is no lack of potential candidates part of the difficulty in identifying a definitive study lies in the breadth of these diverse wetting... 

The classical pure silicones are made from hydrolysis of RSiXj, R SiX and RgSiX, where R, in most cases, is methyl, phenyl or a mixture of both. If only methyl substituted D units are used, with few M units as chain stoppers, extremely nonpolar polydimethylsiloxanes, commonly known as silicone oils (Figure 2.70), are obtained. Their viscosity is governed by the D M ratio. They are chemically inert, non-film forming products. Nevertheless, due to their low surface energy, they are extensively used as wetting additives, flow modifiers and defoamers. 

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