Block copolymer blends

Couman W.J., Heikens D., and Sjoerdsma S.D., Dilatometric investigation of deformation mechanism in polystyrene-polyethylene block copolymer blend Correlation between Poisson ratio and adhesion. 

Fig.66 Phase diagrams of a symmetric (peo = 0.51, Mn = 2700, Mw/Mn = 1.10) and b asymmetric (0peo = 0.32, Mn = 2100, Mw/Mn = 1.14) PEO-fc-PEP block copolymers blended with epoxy resin. Phase transitions which originate from swelling of PEO chains with epoxy and/or curing agent are drawn as single lines, without implication that there are no coexistence regions. From [197]. Copyright 2001 Wiley...

Gergen, W. P. and Davison, S., Thermoplastic block copolymer blends, US Patent 4101605, 1978. 

Asari T, Aral S, Takano A, Matsushita Y. Archimedean tiling structures from ABA/CD block copolymer blends having intermolecular association with hydrogen bonding. Macro-molecules 2006 39 2232-2237. 

Jiang S, Gopfert A, Abetz V. Novel morphologies of block copolymer blends via hydrogen bonding. Macromolecules 2003 31 6171-6177. 

Homopolymer/Block Copolymer Blends with Controllable Hydrogen Bonding. 165... 

Table 6. Comparative tensile properties of block copolymer blended molecular composite fibers...

Cohen, R.E., Tschoegl,N.W, Dynamic mechanical properties of block copolymer blends—a study of the effects of terminal chains in elastomeric materials. I. Torsion pendulum measurements. Intern. J, Polymeric Mater. 2, 49-69 (1972) II. Forced oscillation measurements. Ibid 2, 205-223 (1973) III. A mechanical model for entanglement slippage. Ibid (in press). 

The improved notched impact strength obtained in a 5%, 5000/5000, PSF/PSX block copolymer blend is achieved with minimal sacrifice in polysulfone properties. The data in Table VII indicate that heat distortion temperature is reduced by only 5°C. Tensile strength and modulus are reduced by ca. 10%, and elongation and tensile impact strength (unnotched) are essentially unchanged. 

Block Copolymer Blends with Hydrogen Bonding. 125... 

Zhou, N., Lodge, T.P. and Bates, RS. (2006) Influence of conformational asymmetry on the phase behavior of ternary homopolymer/block copolymer blends around the bicontinuous microemulsion channel. /. Phys. Chem. B, 110, 3979-3989. 

Vilgis TA, Noolandi J. Theory of homopolymer—block copolymer blends the search for a universal compatibilizer. Macromolecules 1990 23 2941-2947. 

In a first step we prepared block copolymer blend samples. Blending with a large amount of the homopolymer will inevitably led to a spherical morphology, but we need to investigate whether the photophysical behavior of the minority segment is maintained or changed. 

In addition to, or instead of, polystyrene and oils, polymers such as polypropylene, polyethylene, or ethylene-vinyl acetate copolymer can be blended with these block copolymers. Blends with S-B-S or (S-B) -X block polymers usually show greatly improved ozone resistance (S-EB-S already has excellent ozone resistance). In addition, these blends have some solvent resistance. In certain cases, some oils that are stable to UV radiation reduce the stability of the blends however, the effects can be minimized by the use of UV stabilizers and absorptive or reflective pigments (e.g., carbon black or titanium dioxide). 

Grafted block copolymer blends Divers The soluble polymer usually was the matrix with the other resins forming isolated domains. Physical properties and morphology IMerret, 1957 Beecher et aL, 1969 Inoue et al., 1960 Pedemonte et aL, 1975 Kraus and RoUman, 1976 Kawai et al., 1971]... 

Generally PSAs are well known for their very viscoelastic behavior, which is necessary for them to function properly. It was therefore important to characterize first the effect of the presence of diblocks on the linear viscoelastic behavior. Since a comprehensive study on the effect of the triblock/diblock ratio on the linear viscoelastic properties of block copolymer blends has recently been reported [46], we characterized the linear viscoelastic properties of our PSA only at room temperature and down to frequencies of about 0.01 Hz. Within this frequency range all adhesives have a very similar behavior in terms of elasticity, as can be seen in Fig. 22.10. The differences appear at low frequency, a regime where the free iso-prene end of the diblock chain is able to relax. This relaxation process is analogous to the relaxation of an arm of a star-like polymer [47], and causes G to drop to a lower plateau modulus, the level of which is only controlled by the density of triblock chains actually bridging two styrene domains [46]. 

Much effort has been dedicated to the development of better molecularly based models, which have been discussed in an excellent recent review [50]. Since our block copolymer blends are not strictly speaking rubbers (PS spheres occupy some volume and have a high functionahty relative to chemical crosslink points), any quantitative comparison between our data and a molecularly based model should be taken with a bit of caution. We feel however that the insight provided by the molecularly based model is essential for the understanding of the mechanical properties of our systems. 

Lee, S.-G., Lee, J. H., Choi, K.-Y., and Rhee, J. M., Glass transition behavior of polypropylene/polystyrene/styrene-ethylene-propylene block copolymer blends, Polym. Bull, 40, 765-771 (1998). 

M. P. Stoykovich, M. Mueller, S. O. Kim, H. H. Solak, E. W. Edwards, J. J. de Pablo, P. F. Nealey, Directed assembly of block copolymer blends into nonregular device-oriented structures. Science, 2005,308,1442. 

Tang, C., Hur, S., Stahl, B.C., Sivanandan, K., Dimitriou, M., Pressly, E., Fredrickson, G.H., Kramer, E.J., Hawker, C.J. Thin film morphology of block copolymer blends with tunable supramolecular interactions for lithographic applications. Macromolecules 43, 2880 (2010)... 

Phase Separation in Block Copolymers and Block Copolymer Blends... 

At the same time, based on the microphase separation occurring in block copolymers blends, including the latter may result in phase separated films exhibiting nano-domains. The formation of nanostructured domains at the interface induced by surface segregation of block copolymers is an interesting strategy to fabricate surfaces with controlled functionality and patterned in one single step. 

The gyroid phase was first identified in diblock copolymers by two groups in 1994 [82, 83]. Following these first investigations the g5u-oid phase has been observed in AB [50, 84, 85] and ABA [86-88] block-copolymers, blends of two AB diblocks [58], and AB diblocks blended with homopolymers [52, 67] or small plasticizing molecules [89]. A comprehensive review can be found in Ref. [81]. 

Commercial membranes for CO2 removal are polymer based, and the materials of choice are cellulose acetate, polyimides, polyamides, polysulfone, polycarbonates, and polyeth-erimide [12]. The most tested and used material is cellulose acetate, although polyimide has also some potential in certain CO2 removal applications. The properties of polyimides and other polymers can be modified to enhance the performance of the membrane. For instance, polyimide membranes were initially used for hydrogen recovery, but they were then modified for CO2 removal [13]. Cellulose acetate membranes were initially developed for reverse osmosis [14], and now they are the most popular CO2 removal membrane. To overcome state-of-the-art membranes for CO2 separation, new polymers, copolymers, block copolymers, blends and nanocomposites (mixed matrix membranes) have been developed [15-22]. However, many of them have failed during application because of different reasons (expensive materials, weak mechanical and chemical stability, etc.). 

Hillmeyer, M.A., Maurer, W.W., Lodge, T.R, Bates, F.S., and Almdal, K., Model bicon-tinuous microemulsions in ternary homopolymer/block copolymer blends, 7. Phys. Chem. B, 103, 4814, 1999. 

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-... 

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