Polydimethylsiloxane block copolymers

The use of small amounts (0.5-3%) of polyethylene-polydimethylsiloxane or polystyrene-polydimethylsiloxane block copolymers in blends with a host... 

Perfectly Alternating Polycarbonate-Polydimethylsiloxane Block Copolymers. 

Fig. 10 Plots of Le/f-cw vs. dimensionless graft density a (1) PS brushes prepared by adsorption of PS-polydimethylsiloxane block copolymers (Mw,ps = 60000) and 0 (Mw,ps = 169000) [21,22]. (2) PEO brushes prepared by adsorption of PEO-PS block copolymers A (Mw.peo = 30800) and V (Mw.peo = 19600) [201]. (3) PMMA brushes prepared by surface-initiated ATRP (M = 31 300 267400). Data reprocessed from [116,117]...

Mecham SJ (1994) Gas permeability of polyimide-polydimethylsiloxane block copolymers MS dissertation, Virginia Polytechnic Institute and State University, Blacksburg... 

Schauer J, Sysel P, Marousek V, Pientka Z, Pokorny J, Bleha M (1996) Pervaporation and gas separation membranes made from polyimide/polydimethylsiloxane block copolymers. J Appl Polym Sci 61(8) 1333... 

FIG. 17. NMR spectrum of a bisphenol A polycarbonate-polydimethylsiloxane block copolymer with average silicone block length Hpoms = 10. (85)... 

Table II. Effect of Polystyrene Block Size on Mechanical Properties of Compression Molded Polystyrene-Polydimethylsiloxane Block Copolymers Containing 30% Polystyrene...

Melt viscosity increases as the molecular weight of the polystyrene blocks is increased, but the effect tends to diminish as the rate of shear is increased. The influence of block size is expressed as a family of converging viscosity—shear rate curves for three copolymers of differing block size, (Figure 3). These curves also illustrate the non-Newtonian character of the polystyrene-polydimethylsiloxane block copolymers. The effect of changing block size cannot be expressed as a single master curve as in the case of overall molecular weight. Such master curves must be based on polymers of constant block size. 

S. Ndonl, M. E. Vigild, and R. H. Berg, "Nanoporous Materials with Spherical and Gyroid Cavities Created by Quantitative Etching of Polydlmethylsiloxane in Polystyrene-Polydimethylsiloxane Block Copolymers,"/Am. Chem.Soc. 125,13366-13367 [2006]. 

Dumelow (123) used SEC-LALLS with dual concentration detectors to study the variation in compositional heterogeneity with molecular weight in polystyrene-polydimethylsiloxane block copolymers. The results showed that some of the copolymers were in fact blends. The largest errors in the analysis... 

Poly sty rene-polydimethylsiloxane block copolymer PS-PDMS (polysimethylsiloxane) blend Four 30 cm 10 pm packings (Polymer Laboratories 10, 105, 1Q4 103 C,H,C1, (tetrachloroethylene) quoted pore size concentration 5 x 10"3 g/cm 3 or less RI, FALLS (dual detector) Compositional heterogeneity correlation with MWD 54... 

Nodera, A. Kanai, T., Flame Retardancy of Polycarhonate-Polydimethylsiloxane Block Copolymer/Silica Nanocomposites. J. Appl. Polym. Sci. 2006,101, 3862-3868. 

The preparation of polymeric materials from renewable resources is of great economic and ecological significance. Oils and fats are one of the most important renewable materials since they offer a large number of possibilities for application that can be rarely met by petrochemistry. Although the hydrosilylation of olefins has been widely studied, a few reports have appeared on the fatty acid esters (4). Carbohydrate-modified polysiloxanes are another very important group of hybrid materials. Some examples of such modified, comb-structured polysiloxanes and also a few examples of carbohydrate-segmented polydimethylsiloxane block copolymers have been described. Hydrosilylation has also been used for the synthesis of silylated polycarbonates or polycarbonate-disiloxane-polycarbonate triblock copolymers. 

Karal-Yilmaz and co-workers [7] characterised blends of polymonoalkyl/itaconate and polyvinylchloride (PVC) and monoitaconate-polydimethylsiloxane block copolymers using DETA, differential scanning calorimetry and stress-strain measurements. It was revealed that addition of as little as 1% of the polymonoitaconate to PVC or 1-3% of block copolymers containing polydimethylsiloxane had a plasticising effect. 

Nodera A, Kanai T. Flame retardancy of polycarbonate-polydimethylsiloxane block copolymer/silica nanocomposites. J Appl Polym Sci 2006 101 3862-3868. 

Preparation and thermal crosslinking reactions of oc, -vinylbenzyl terminated polysulfone-b-polydimethylsiloxane, ABA type block copolymers have been discussed 282,313) However, relatively little characterization was reported. Molecular weights of polysulfone and PDMS segments in the copolymers were varied between 800-8,000 and 500-11,000 g/mole, respectively. After thermal curing, the networks obtained showed two phase morphologies as indicated by the detection of two glass transition temperatures (—123 °C and +200 °C) corresponding to PDMS and polysulfone phases, respectively. No mechanical characterization data were provided. 

Initiation of stannous octoate-catalyzed copolymerization of e-caprolactone with glycerol was used to prepare a series of trifunctional hydroxy-end blocked oligomers, which were then treated with hexane-1,6-diisocyanate to form elastomeric polyesterurethanes with different crosslink densities (49). Initiation of e-caprolactone polymerization with a hydroxypropyl-terminated polydimethylsiloxane in the presence of dibutyl tin dilaurate has been used to prepare a polyester-siloxane block copolymer (Fig. 4) (50). 

The drawbacks can be overcome by employing a block copolymer composed of poly(ethylene-a/f-propylene), PEP, and polydimethylsiloxane... 

Epoxy-functional polydimethylsiloxane oligomers are another group that can be cured by UV radiation. Epoxysilicone block copolymers exhibit a good photoinitiator miscibility, high cure rate, and compatibility with epoxy and vinyl ether monomers. These block copolymers form flexible films with excellent release properties and are therefore used as release coatings. ... 

Chemically unlike polymers are incompatible, and it sometimes happens that the reaction medium is heterogeneous at the beginning. However, once some block copolymer is formed it acts as a "compatibilizer" and the reaction medium gradually becomes homogeneous. Many examples of such reactions could be quoted. A recent one is the hydrosilylation reaction carried out between a polystyrene fitted at a chain end with vinylsilane groups, and an a,u-dihydrogenopolydimethylsiloxane. This process is carried out at high concentration and it yields polystyrene-polydimethylsiloxane-polystyrene block copolymers. 2... 

Copolymers. Copolymers from mixtures of different bisphenols or from mixtures of dichlorosulfone and dichlorobenzophenone have been reported in the patent literature. Bifunctional hydroxyl-terminated polyethersulfone oligomers are prepared readily by the polyetherification reaction simply by providing a suitable excess of the bisphenol. Block copolymers are obtained by reaction of the oligomers with other polymers having end groups capable of reacting with the phenol. Multiblock copolymers of BPA-polysulfone with polysiloxane have been made in this way by reaction with dimethyl amino-terminated polydimethylsiloxane the products are effective impact modifiers for the polyethersulfone (79). Block copolymers with nylon-6 are obtained when chlorine-terminated oligomers, which are prepared by polyetherification with excess dihalosulfone, are used as initiators for polymerization of caprolactam (80). 

Chen, Gardella and Kumler106 have studied a series of polydimethylsiloxane-polystyrene block copolymers and examined the surface composition by ATR-FTIR and XPS. For AB-type PS-PDMS diblock copolymers (26) with siloxane block molecular weights of between 38,000 and 99,000, the surface was found to be exclusively polydimethylsiloxane down to a depth of 10 nm by XPS. ATR-FTIR, which samples... 

Koberstein and coworkers121 have examined the effects of a polydimethylsiloxane-polystyrene (PDMS-PS) block copolymer on the interfacial tensions of blends of PDMS and polystyrene. As little as 0.002 wt% of the copolymer, added to the siloxane phase, was sufficient to lower the interfacial tension by 82% in the case of a blend of polystyrene (Afn = 4,000) and PDMS (Mn = 4,500). No further reduction in interfacial tension was observed at higher copolymer levels due to micelle formation. Riess122 has polymerized styrene in the presence of a silicon oil and a polydimethylsiloxane-polystyrene block copolymer to obtain a polystyrene in which 0.1-1 pm droplets of silicone oil are dispersed. This material displayed a lowered coefficient of kinetic friction on steel compared to pure polystyrene. 

The interfacial tension is a key property for describing the formation of emulsions and microemulsions (Aveyard et al., 1990), including those in supercritical fluids (da Rocha et al., 1999), as shown in Figure 8.3, where the v-axis represents a variety of formulation variables. A minimum in y is observed at the phase inversion point where the system is balanced with respect to the partitioning of the surfactant between the phases. Here, a middle-phase emulsion is present in equilibrium with excess C02-rich (top) and aqueous-rich (bottom) phases. Upon changing any of the formulation variables away from this point—for example, the hydrophilie/C02-philic balance (HCB) in the surfactant structure—the surfactant will migrate toward one of the phases. This phase usually becomes the external phase, according to the Bancroft rule. For example, a surfactant with a low HCB, such as PFPE COO NH4+ (2500 g/mol), favors the upper C02 phase and forms w/c microemulsions with an excess water phase. Likewise, a shift in formulation variable to the left would drive the surfactant toward water to form a c/w emulsion. Studies of y versus HCB for block copolymers of propylene oxide, and ethylene oxide, and polydimethylsiloxane (PDMS) and ethylene oxide, have been used to understand microemulsion and emulsion formation, curvature, and stability (da Rocha et al., 1999). 

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