Polydimethylsiloxane homopolymer

Dimethoxy (3-mercaptopropyl) methylsilane. See3-Mercaptopropylmethyldimethoxysilane Dimethoxymercaptopropyl-terminated polydimethylsiloxane homopolymer CAS 69430-38-2... 

Mercaptopropyl) methyl polydimethylsiloxane copolymer. See (Mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer Dimethoxymercaptopropyl-terminated polydimethylsiloxane homopolymer (Mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer CAS 102783-03-9... 

Acetal Alloxan monohydrate Aluminum orthophosphate Benzoyl peroxide Bismuth Bismuth subcarbonate Boron Chaparral (Larrea mexicana) extract 4-Chloro-o-phenylenediamine Chondroitin sulfate Cyclodextrin p-Cyclodextrin 2-Decyl tetradecanoic acid Dichlorophene Diethylaminoethanol Dill (Anethum graveolens) seed oil Dimethicone/mercaptopropyl methicone copolymer p-Dimethoxybenzene Dimethoxymercaptopropyl-terminated polydimethylsiloxane homopolymer 1,1-Dimethyl-1-(2-hydroxypropylamine) tetradecanimide... 

Decamethylcyclopentasiloxane Dimethicone/mercaptopropyl methicone copolymer Dimethoxymercaptopropyl-terminated polydimethylsiloxane homopolymer (Mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer PEG-8 isolauryl thioether hair creams/lotions Human placental protein hair dressing Corn (Zea mays) oil hair fixative, hair sprays VA/crotonates copolymer VA/crotonates/vinyl propionate copolymer hair fixative, setting lotions Sodium polystyrene sulfonate , VA/crotonates copolymer hair lacquer resin MDM hydantoin hair lotion Quassia hair perms Ammonium bisulfite... 

Although each of these cyclic siloxane monomers can be polymerized separately to synthesize the respective homopolymers, in practice they are primarily used to modify and further improve some specific properties of polydimethylsiloxanes. The properties that can be changed or modified by the variations in the siloxane backbone include the low temperature flexibility (glass transition temperature, crystallization and melting behavior), thermal, oxidation, and radiation stability, solubility characteristics and chemical reactivity. Table 9 summarizes the effect of various substituents on the physical properties of resulting siloxane homopolymers. The... 

Fig. 3. ESCA results on the surface segregation of the Polycarbonate homopolymer/Poly-carbonate-Polydimethylsiloxane segmented copolymer blends 1S0)...

Most dispersion polymerizations in C02, including the monomers methyl methacrylate, styrene, and vinyl acetate, have been summarized elsewhere (Canelas and DeSimone, 1997b Kendall et al., 1999) and will not be covered in this chapter. In a dispersion polymerization, the insoluble polymer is sterically stabilized as colloidal polymer particles by the surfactant that is adsorbed or chemically grafted to the particles. Effective surfactants in the dispersion polymerizations include C02-soluble homopolymers, block and random copolymers, and reactive macromonomers. Polymeric surfactants for C02 have been designed by combining C02-soluble (C02-philic) polymers, such as polydimethylsiloxane (PDMS) or PFOA, with C02-insoluble (C02-phobic) polymers, such as hydrophilic or lipophilic polymers (Betts et al., 1996, 1998 Guan and DeSimone, 1994). Several advances in C02-based dispersion polymerizations will be reviewed in the following section. 

For comparison with this material, a mixture of the homopolymers was examined. Portions of an anionically polymerized polymethyl methacrylate (Mn = 39,200) and a polydimethylsiloxane (Mn = 29,000) were combined to yield a mixture containing 42.2 wt % siloxane the mixture was spread to form a monolayer. Figure 7 shows the tt—A curve of this... 

Moisture and oxygen must be rigorously excluded from the system if the synthesis is to be successful. Inadvertant introduction of trace protic impurities of metal oxides during the synthesis leads to the formation of polydimethylsilioxane homopolymer. This material, present in even small amounts, is detrimental to the mechanical properties of the final block copolymer. This effect can be illustrated by deliberately including known amounts of polydimethylsiloxane in a block copolymer of demonstrated mechanical strength. These effects are summarized in Table I. 

Surface tension vs. temperature for PS and PTHF are shown in Figure 15. The data of Gains and Bender (17) on PS surface tensions (yGps) agree well with ours. However, our value for the surface tension of PTHF (yoPthf) is about 4.5 dynes/cm higher than Roe s value (18). The reason for this discrepancy is not clear. The y0i thf is always smaller than the yoPS by Ay = 3 dynes/cm, which is much smaller than the surface tension difference between the blocks of PS and polydimethylsiloxane. The time-dependent surface tensions of four blends (ST-PS, ST-PTHF, PS-PTHF, and PTHF-PS) were measured. To prepare the blends, the block or homopolymers were added in small amounts (0.3-1 wt %) to the homo-PS or PTHF. The mixture was completely dissolved in benzene, the solutions were quickly frozen by a dry ice-acetone mixture, and the samples were freeze dried. 

Polydimethylsiloxane-b-polystyrene polymers prepared by the new free radical synthesis display other characteristics typical of block polymers which distinguish them from physical blends of the two homopolymers. For example, solutions of the polymers show intense iridescence due to diffraction phenomena ascribed to the presence of two discrete uniformly dispersed microphases. These polymers are soluble in solvents such as nitropropane,... 

---