Siloxane block

Siloxane block copolymers, 451 Siloxanes, 450-456 Silyl ether displacement, poly(arylene ether sulfone) synthesis via, 340... 

Pioneering work in living anionic copolymerization of siloxanes was reported by Morton and co-workers 139 140, who synthesized isoprene-dimethylsiloxane block copolymers utilizing D4 as the siloxane monomer. The use of D3 in the synthesis of siloxane block copolymers with controlled structures was demonstrated by Bostick and others. Excellent reviews of these earlier studies and subsequent developments are available in the literature 22 137 13S). 

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. 

Poly(arylester)-polysiloxane multiblock copolymers have also been synthesized by the interfacial polymerization of aminopropyl terminated polysiloxane oligomers with bisphenol-A and a mixture of isophthaloyl and terephthaloyl chlorides117, 193-1951 as illustrated in Reaction Scheme XV. In these reactions the poly(arylester) blocks are formed in situ during the copolymerization, so the control of their block sizes is not very precise. It is also important to note that since aminopropyl terminated siloxane oligomers are employed, the linkages which connect the arylester and siloxane blocks are amide linkages. 

During the reactions backbone compositions of the siloxane oligomers employed have been varied between all dimethylsiloxane to 50/50 by weight dimethylsiloxane/ diphenylsiloxane and dimethylsiloxane/(trifluoropropyl,methyl)siloxane. Block molecular weights of the siloxane oligomers have been kept between 3,000-5,000 g/mole, whereas the overall level of siloxane incorporation into the copolymers have been varied between 0 and 60 weight percent. In most cases the ratio of terephthalate to... 

Sample No Siloxane Blocks Recovered Yield (wt%) w (dl/g) Copolymer Tg (°C)... 

Preparation and characteristics of ABA type polycaprolactone-b-polydimethyl-siloxane block copolymers have been recently reported 289). In this study, ring-opening polymerization of e-caprolactone was achieved in melt, using a hydroxybutyl terminated PSX as the initiator and a catalytic amount of stannous octoate. Reactions were completed in two steps as shown in Reaction Scheme XIX. 

Fig. 2. Stress-strain behavior of MDI-based siloxane-urea segmented copolymers as a function of siloxane block molecular weights (PSX-Mn g/mole), [1. PSX-1140, 2. PSX-1770, 3. PSX-2420, 4. PSX-3670] and their comparison with unfilled (curve 7) and silica filled (curves 5 and 6) conventional silicone rubbers51 158,358,359)...

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 initiation of the cyclic siloxane monomers with a living polymeric lithium species such as polystyryl lithium leads to block copolymers, as outlined in Scheme 2, were also of interest. These styrenic-siloxane block copolymers were prepared with siloxane contents from 10 to 50 weight percent. 

Table VI. ESCA Study of Styrenic-Siloxane Block and Graft Copolymers (Copolymer Composition 10 wt.% PSX)...

Styrenic-siloxane block and graft copolymers, Tg dependence on architecture and molecular weight, 95,95/ Styrenic-siloxane block copolymers, 86 Substrate catalyst ratio, chloromethylation, 18 Sulfonation, instability of sulfonated PPO, improvement, 6 Surface grafting... 

Figure 1. Stress-strain curves of polycarbonate-polydimethyl-siloxane block copolymers (Crosshead Speeds 5 cm/min). (Reproduced from Refs. 15 18. Copyright 1980, 1984 American Chemical Society.)...

The importance of thermally stable char was shown to be critical in a further study of siloxane block polymers by General Electric researchers. (18). The char enhancing action of magnesium soaps and a special silicate silane (19) and likewise the char stabilizing action of lead salts (20) were demonstrated in polyolefins by General Electric investigators. 

Lithographic Evaluation of Phenolic Resin—Dimethyl Siloxane Block Copolymers... 

SAMPLE NUMBER SILOXANE BLOCK 1 Tj CC)2 POLYMER wt % s t7cC)2 ... 

PHENOLIC COMPONENT SILOXANE BLOCK 1 tTcq2 POLYMER wt % Si3 tTcC)2 ... 

OXYGEN REACTIVE ION ETCHING (RIE) OF NOVOLAC-SILOXANE BLOCK COPOLYMERS... 

EFFECT OF POLY (DIMETHYL SILOXANE) BLOCK LENGTHS ON RESOLUTION CAPABILITIES... 

Thus, N-pyrimidine phthalimide reacted with hexylamine at room temperature to form an amide-amide. The initial amide-amide formation proceeded more rapidly in chloroform as compared to dimethylsulfoxide (DM SO). However, the ring closure reaction to the imide was favored by the more polar, aprotic DMSO solvent, yielding the imide in nearly quantitative yield after 3 hours at 75 °C. The authors were able to utilize this synthetic approach to prepare well-defined segmented poly(imide-siloxane) block copolymers. It appears that transimidi-zation reactions are a viable approach to preparing polyimides, given that the final polyimide has a Tg sufficiently low to allow extended excursions above the Tg to facilitate reaction without thermal decomposition. Additionally, soluble polyimides can be readily prepared by this approach. Ultimately, high Tg, insoluble polyimides are still only accessable via traditional soluble precursor routes. 

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... 

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