Dimethylsiloxane block copolymers

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). 

The structures of the dimethylsiloxane block copolymers and respective parent homopolymers prepared for use as positive, bilevel resist materials are shown in Figure 1. Most copolymers were synthesized with >10 wt % silicon. The selection of PDMSX block length and novolac chemical composition proved to be the two most critical variables in achieving adequate resolution. 

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

Table 12. Characteristic of imide-dimethylsiloxane block copolymers...

Mecham SJ, Sekharipuram VN, Rogers ME, Meyer GW, Kim Y, McGrath JE (1994) Gas permeability of polyimide/poly(dimethylsiloxane) block copolymers. Polym Prepr (Am Chem Soc Div Polym Chem) 35(2) 803... 

Volksen W, Hedrick JL, Russell TP, Swanson S (1997) Imide-dimethylsiloxane block copolymers design and synthesis of a permanent buried oxygen ion etch barrier. J Appl Polym Sci 66(1) 199... 

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. 

Impact Modification of Polysulfone with Polysulfone/Poly(dimethylsiloxane) Block Copolymers... 

The synthesis of polysulfone/poly(dimethylsiloxane) block copolymers was reported earlier (4, 5). Blends of the block copolymer with... 

Figure 6. TGA of polysulfone-poly(dimethylsiloxane) block copolymers ana homopolymers (in nitrogen at 10°C/min)...

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. 

Wang, B., and Krause, S., Properties of dimethylsiloxane micropases in phase-separated dimethylsiloxane block copolymers, Macromolecules, 20, 2201-2208 (1987). 

Domain Size Determination of Poly(phthalamide)/Poly(dimethylsiloxane) Block Copolymers by Solid-State Spin Diffusion NMR Spectroscopy... 

Summary H solid-state spin diffusion NMR spectroscopy was applied to calculate domain sizes of separated phases in poly(phthalamide)/poly(dimethylsiloxane) block copolymers. To initiate spin diffusion, the dipolar filter technique was used. The correlation between longer PDMS chains in the copolymer and bigger domains of the PDMS phase could be shown. 

Poly(dimethylsiloxane) (PDMS) is a well-known hydrophobic polymer with higher repellency for water than PS crosslinked siUcone elastomers (WCA = 112° for a smooth film) are commonly used for fabricating microfluidic devices. But forming solid fibers comprised solely of linear PDMS is not possible, due to its low glass transition temperature. Instead of using linear homopolymer PDMS, Ma et al. [21] electrospun fibers of poly(styrene-b-dimethylsiloxane) block copolymers blended with 23.4 wt% homopolymer polystyrene (PS-PDMS/PS) from a solution in a mixed solvent of THF and DMF. The resultant fiber mat, with fiber diameters in the range of 150-400 nm, exhibited a WCA of 163° and a hysteresis of 15°. An illustration of water droplets beaded up on such a mat is provided in Fig. 3. A PS mat of similar fiber diameter and porosity exhibited a WCA of only 138°. The difference was attributed to the lower surface tension of the PDMS component, combined with its spontaneous segregation to the fiber surface. X-ray photoelec-... 

Alkylate Arylate-Siloxane Copolymers.—Data published on the thermal stability of poly(phenolphthalein terephthalate/dimethylsiloxane) block copolymers, in... 

D. A. Schiraldi, Synthesis and properties of poly(butylene terephthalate)-poly(dimethylsiloxane) block copolymers, Polym. Prepr., 42 221-222,2001. 

Ma M, Hill RM, Lowery JL, Fridrikh SV, Rutledge GC. (2005) Electrospun poly(styrene-block-dimethylsiloxane) block copolymer fibers exhibiting superhydropho-bicity. Langmuir 21 5549-5554. 

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 ... 

Rutledge et al. showed that fiber mats composed solely of uniform fibers could be obtained by electrospinning a hydrophobic material (i.e., poly(styrene-block-dimethylsiloxane) block copolymer) blended with homopolymer polystyrene (PS) [24]. The roughness of the nonwoven mat, resulting from the small diameters of the fibers (150-400 nm), combined with the enrichment of the dimethylsiloxane... 

Fusion with alkali and sodium acetate also served to cleave bisphenol A polycarbonate - dimethylsiloxane block copolymer. Bisphenol A diacetate produced was identified by gas chromatography as a polycarbonate fragment and gas-solid chromatography was used to identify methane produced by cleavage of substituted siloxone. 

Juliano, P.C. and Mitchell, T.D., Synthesis, physical properties and crystallization studies on poly(2,6-diphenylphenylene oxide-dimethylsiloxane) block copolymers. Polym. Prepr., Am, Chem. Soc., Div. Polym. Chem., 1980. 21(2) p. 72-3. 

---