Block copolymers homopolymers

F. S. Bates, W. Maurer, T. Lodge, M. F. Schulz, M. W. Matsen, K. Almdal, K. Mortensen. Isotropic Lifshitz behavior in block copolymer-homopolymer blends. Phys Rev Lett 75 4429-4432, 1995. 

Instead of the familiar sequence of morphologies, a broad multiphase window centred at relatively high concentrations (ca. 50-70% block copolymer) truncates the ordered lamellar regime. At higher epoxy concentrations wormlike micelles and eventually vesicles at the lowest compositions are observed. Worm-like micelles are found over a broad composition range (Fig. 67). This morphology is rare in block copolymer/homopolymer blends [202] but is commonly encountered in the case of surfactant solutions [203] and mixtures of block copolymers with water and other low molecular weight diluents [204,205]. 

Microdomains of block copolymer/ homopolymer blends 25-A-diameter Pd clusters Metal-ion precursors, introduced into cast thin films of polymer microdomains, are reduced by high pressure hydrogen 60,61... 

This chapter is organized as follows. Section 6.2 is concerned with experiments on binary block copolymer/homopolymer blends, Section 6.3 deals with experiments on ternary blends containing a block copolymer and in Section 6.4 experiments on binary blends of block copolymers are reviewed. Theory for the corresponding type of blend is discussed successively in Sections 6.5 to 6.7. Finally, experiments on thin films are discussed in Section 6.8, separately from the work on bulk blends, in keeping with earlier chapters. 

Experiments on binary block copolymer/homopolymer blends... 

Table 6.1 Experimental studies of binary block copolymer/homopolymer blends. Adapted and extended from Roe and Rigby (1987)...

Macrophase separation after microphase separation has been observed in an AB block copolymer/homopolymer C blend (Hashimoto et al 1995). Blends of a PS-PB starblock copolymer (75wt% PS) and PVME homopolymer were prepared by solvent casting. Binary blends of PS and PVME exhibit a lower critical solution temperature (LCST), i.e. they demix at high temperatures. The initial structure of a 50% mixture of a PS-PB diblock and PVME shown in Fig. 6.20(a) consists of worm-like micelles. Heating led to macrophase separation as evident... 

It is important to control the time at which the second monomer is added to avoid formation of a tapered middle block between the two homoblocks [161]. If the second monomer is added too early, then tapered structures are formed. If the second monomer is added too late, then some chains may terminate and, in addition to block copolymer, homopolymer may be formed. 

Urbas, A., Fink, Y, and Thomas, E., One-dimensionaUy periodic dielectric reflectors from self-assembled block copolymer-homopolymer blends. Macromolecules, 32, 4748, 1999. 

Urbas, A., Sharp, R., Fink, Y. et al.. Tunable block copolymer/homopolymer photonic crystals, Adv. Mater., 12, 812, 2000. 

K. R. Shull (1993) Interfacial phase-transitions in block copolymer homopolymer blends. Macrom,olecules 26, pp. 2346-2360... 

Lee, J.H., Balsara, N.P., Chakraborty, A.K., Krishnamoorti, R. and Hammouda, B. (2002) Thermodynamics and phase behavior of block copolymer/homopolymer blends with attractive and repulsive interactions. Macromolecules, 35, 7748-7757. 

Bates, RS., Maurer, W., Lodge, T.P., Schulz, M.R, Matsen, M.W., Almdal, K. and Mortensen, K. (1995) Isotropic lifshitz behavior in block copolymer-homopolymer blends. Phys. Rev. Lett., 75, 4429-4432. 

Banaszak M, Whitmore MD. Mean field theory of the phase behavior of ternary block copolymer-homopolymer blends. Macromolecules 1992 25 249-260. 

Surface Activity of Block Copolymers. Modification of surface properties of a homopolymer by incorporating a small proportion of block copolymer has been studied for several block copolymer-homopolymer blends. LeGrand... 

Electron spectroscopy has been utilized by a number of investigators to study the surface behavior of block copolymers and block copolymer/homopolymer mixtures (17-19,24,25). 

Phase Separation in Block Copolymer-Homopolymer Blends... 

Floudas et al. (1997) studied theoretically and experimentally microphase segregation in block copolymer/homopolymer blends for an asymmetric diblock copolymer and homopolymer concentrations of less than 25 %. It was observed that the minority phase could solubilize only a small amount of added homopolymer. The addition of higher amounts resulted in the formation of nonequilibrium structures. Theoretical predictions in the strong segregation limit showed that (xN)c,... 

Images published from H. Park, J.U. Kim, S. Park, High-throughput preparation of complex multi-scale patterns from block copolymer/homopolymer blend films. Nanoscale 4 (2012) 1362-1367. 

Figure adapted from X. Li, L. Xue, Y. Han, Broadband antireflection of block copolymer/ homopolymer blend films with gradient refractive index structures. Journal of Materials Chemistry 21 (2011) 5817-5826. 

G. Floudas, N. Hadjichristidis, M. Stamm, A.E. Likhtman, A.N. Semenov, Microphase separation in block copolymer/homopolymer blends theory and experiment. Journal of Chemical Physics 106 (1997) 3318-3328. 

M.D. Whitmore, J. Noolandi, Theory of micelle formation in block copolymer-homopolymer blends, Macromolecules 18 (1985) 657-665. 

M.W. Matsen, Phase-behavior of block-copolymer homopolymer blends, Macromolecules 28 (1995) 5765-5773. 

If the noise term is turned off, the system is driven towards the nearest saddle point. Therefore, the same set of equations can be used to find and test mean-field solutions. The complex Langevin method was first applied to dense melts of copolymers [74], and later to mixtures of homopolymers and copolymers [80] and to diluted polymers confined in a slit under good solvent conditions [77]. Figure 2 shows examples of average density configurations (p ) for a ternary block copolymer/homopolymer system above and below the order/disorder transition. 

Albalak, R. J., and Thomas, E. L., Roll-casting of block copolymers and of block copolymer-homopolymer blends, J. Polym. Sci. B Polym. Phys., 32, 341-350 (1994). 

Urbas AM, Fink Y, Thomas EL (1999) Self assembled one dimensionally periodic dielectric reflectors from block copolymer/homopolymer blends. Macromolecules 32(14) 4748-4750... 

---