Styrene-dimethylsiloxane copolymer

Somewhat limited work has been reported over the last decade. There are several reports on the synthesis and physical and structural characterization of styrene-dimethylsiloxane 141 144) and methylmethacrylate-dimethylsiloxane145> diblock, triblock and multiblock copolymers. Several reports are also available on the thermal223), solution 224,2251 and surface196 2261 characterization of various styrene-dimethyl-siloxane block copolymers synthesized by anionic techniques. 

Fig. 51. Zimm plot156) for a styrene/dimethylsiloxane block copolymer in (a) cyclohexane and (b) toluene...

Cyclization studies have also been carried out on the chemical copolymers poly (ethylene, dimethylsiloxane), and poly(styrene, dimethylsiloxane).68,69 99 Numerous intramolecular interactions need to be taken into account in a chemical copolymer and,... 

S-DMS refers to styrene-dimethylsiloxane diblock copolymers S-l refers to sty-rene-isoprene diblock copolymers S-l-S and I-S-I refer to styrene-isoprene-styrene and to isoprene-styrene-isoprene triblock copolymers, respectively and S-EO and EO-S-EO refer to styrene-ethylene oxide diblock copolymers and to ethylene oxide-styrene-ethylene oxide triblock copolymers, respectively. 

Table II shows the values obtained for the glassy phase of the styrene-dimethylsiloxane block copolymers used in this work in the case of the block copolymers, neither DSC nor DTA gave a consistently higher value of Tg. The only peculiar sample in the table is sample R14, which exhibited two Tgs on both instruments at least occasionally during the first heating cycle. Although the presence of two Tgs implies some kind of phase separation, possibly in addition to microphase separation, the GPC of this sample shows no double peak, shoulder, or other peculiarity which might explain its peculiar phase behavior. This sample is an anomaly unless one wishes to dismiss all first heating data.

Many thanks to J. E. L. Roovers and to J. W. Dean for providing us with the styrene-dimethylsiloxane block copolymers thanks to the National Science Foundation, Contract No. DMR76-19488, for helping us with this work and thanks to the National Institutes of Health for providing one of us (S.K.) with a Research Career Award. 

Besides poly(dimethylsiloxane), other elastomeric polymers have been employed in the manufacturing of vaginal rings, such as poly(dimethylsiloxane/vinylmethylsi-loxane), styrene-butadiene-styrene block copolymer, and poly(ethylene-co-vinyl acetate) [123-125], In fact, poly(ethylene-co-vinyl acetate) (commonly referred as EVA) appeared in the mid 1990s as an alternative to poly(dimethylsiloxane), when the manufacturer of this last material stopped supplying it for human use, demonstrating it to be very suitable for the production of controlled-release systems. 

Galin, M. Rupprecht, M. C., "Gas Chromatographic Study of the Interactions in Styrene-Dimethylsiloxane Block Copolymers and Blends," Macromolecules, 12, 506 (1979). 

Samples of styrene-dimethylsiloxane and poly (2,6-diphenyl )phenylene ether-dimethylsiloxane block copolymers were also examined as spread films. The styrene-siloxane copolymers included AB, ABA, and repeating block copolymer types. In these cases, as with the polycarbonate, the organic homopolymers do not form monolayers when we try to spread volatile solvent solutions on water. The characteristics of the copolymer spread films, however, were similar to those of the BPAC—DMS copolymers. In all cases, sigmoidal 7r-A curves were obtained, and surface pressures above 10 dynes/cm were unstable. (All of the samples examined had organic blocks of 15 or more monomer units.) A typical curve, for a styrene-dimethylsiloxane repeating block copolymer (19), is shown in Figure 4. 

Donth, E., The size of cooperatively rearranging regions in polystyrene and styrene— dimethylsiloxane diblock copolymers at the glass transition temperature, Acta Polym., 35, 120-123 (1984). 

S. Kraus, M. Isleandar and M. Iqbal, "Properties of Low Molecular Weight Block Copolymers. 1. Differential Scanning Calorimetry of Styrene-Dimethylsiloxane Diblock Copolymers." Macromolecules 15 105 (1982). T.S. Ellis,... 

SMFP. See,Sodium fluorophosphate (Na2P0sF) Smilax aristolochiaefolia Smilax aristolochiaefolia extract. See Sarsaparilla (Smilax aristolochiaefolia) extract SMO. See Sorbitan oleate SMS. See Styrene/a-methyl styrene resin Sorbitan stearate SMS-022, SMS-042, SMS-992. See (Mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer SMTC. See Sodium dimethyidithiocarbamate Snac-Kote XTR. See Hydrogenated vegetable oil... 

Xytrex 300. See Polyethersulfone resin Xytrex 450. See Polyetheretherketone Xytrex 646. See Polyphenylene sulfide resin XZ 26001.00, XZ 26005.00. See Styrene/acrylates copolymer Yacca. See Red gum YAD-122. See (N-Pyrrolidonepropyl) methylsiloxane-dimethylsiloxane copolymer Yara yara. See P-Naphthyl methyl ether Yarmor Yarmor pine oil. See Pine (Pinus palustris) oil... 

Covalent Coupling of Two Polymeric Precursors. This method requires selective, fast and complete coupling reaction to give satisfactory results. Due to their incompatibility, polymer chains of different nature tend to minimize their contacts and therefore the collisions between their antagonist reactive sites hardly occur. An example of this method is given by the synthesis of styrene-dimethylsiloxane block copolymers ... 

In addition to providing fully alkyl/aryl-substituted polyphosphasenes, the versatility of the process in Figure 2 has allowed the preparation of various functionalized polymers and copolymers. Thus the monomer (10) can be derivatized via deprotonation—substitution, when a P-methyl (or P—CH2—) group is present, to provide new phosphoranimines some of which, in turn, serve as precursors to new polymers (64). In the same vein, polymers containing a P—CH group, for example, poly(methylphenylphosphazene), can also be derivatized by deprotonation—substitution reactions without chain scission. This has produced a number of functionalized polymers (64,71—73), including water-soluble carboxylate salts (11), as well as graft copolymers with styrene (74) and with dimethylsiloxane (12) (75). 

Drug Release from PHEMA-l-PIB Networks. Amphiphilic networks due to their distinct microphase separated hydrophobic-hydrophilic domain structure posses potential for biomedical applications. Similar microphase separated materials such as poly(HEMA- -styrene-6-HEMA), poly(HEMA-6-dimethylsiloxane- -HEMA), and poly(HEMA-6-butadiene- -HEMA) triblock copolymers have demonstrated better antithromogenic properties to any of the respective homopolymers (5-S). Amphiphilic networks are speculated to demonstrate better biocompatibility than either PIB or PHEMA because of their hydrophilic-hydrophobic microdomain structure. These unique structures may also be useful as swellable drug delivery matrices for both hydrophilic and lipophilic drugs due to their amphiphilic nature. Preliminary experiments with theophylline as a model for a water soluble drug were conducted to determine the release characteristics of the system. Experiments with lipophilic drugs are the subject of ongoing research. 

A. Mayer et al. examined poly(dimethylsiloxane)-bIock-poly(ethylene oxide) (PDMS-b-PEO), poly(styrene)-f)Iock-poly(ethylene oxide) (PS-b-PEO), polystyrene-block-poly(methacryhc acid) (PS-b-PMAA) as amphiphihc block copolymers with regard to their properties in stabilizing colloidal metal nanoparticles [37, 49]. All three polymers are successfully used to stabihze various transition metal coUoids... 

Dawkins and Taylor109 dispersed poly(methyl methacrylate) (PMMA) or polystyrene (PS) particles in n-alkanes stabilized by AB block copolymers of styrene and dimethyl-siloxane. In these cases, styrene blocks act as anchors and dimethylsiloxane blocks give a surface layer. The thickness 6 of the dimethylsiloxane layer was determined by viscosity measurements as a function of the molecular weight of dimethylsiloxane blocks. 

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