Phase of block copolymer

The minor phase of block copolymer microdomains are selectively removed by either chemical or physical degradation, thereby generating a defined porosity in crosslinked polymer bulk matrices or thin films... 

Horvat A et al (2008) Specific features of defect structure and dynamics in cylinder phase of block copolymers. ACS Nano 2(6) 1143-1152... 

The structures formed by polystyrene-poly(propylene imine) dendrimers have also been analyzed. Block copolymers with 8, 16, and 32 end-standing amines are soluble in water. They have a critical micelle concentration of the order of 10"7 mol/1. At 3x10 4 mol/l they form different types of micelles. The den-drimer with eight amine groups (80% PS) form bilayers. The dendrimer with 16 amine groups (65% PS) forms cylinders and the dendrimer with 32 amine groups (50% PS) forms spherical micelles [38,130,131]. These are the classical lamellar, cylindrical, and spherical phases of block copolymers. However, the boundary between the phases occurs at very different volume fractions, due to the very different packing requirements of the linear polymer and spherical dendrimer at the interphase. 

Fig. 13. Plot of the amplitude (envelope) function B(Z) vs Z, for a planar interface between coexisting disordered (Z— >o) and lamellar (Z—>-< >) phases of block copolymer melts in the bulk. The midpoint of the profile (Z,B)=(0,1/2) is denoted by an open circle, while the inflection point (solid circle) is at [—(1/2) ln(3/2), 1/V3]. From Fredrickson and Binder [234]...

Since there is no symmetry between the ordered and disordered phases of block copolymers, this profile is not antisymmetric around its midpoint. Now for >0 (%<%t) Eq. (79) shows that the amplitude of the profile B0 at which saturation would occur is somewhat reduced, and also the finite distance of the midpoint of the profile from the wall (Fig. 12) implies that the left part of the envelope B( ) is cut off . 

Fig.17A-C. SUicates with A spherical pores of cubic order B hexagonally ordered cylindrical pores C lamellar pores, prepared from lyotropic phases of block copolymers [5,60]...

Bohbot-Raviv Y, Wang ZG (2000) Discovering new ordered phases of block copolymers. Phys... 

Guo ZJ, Zhang GJ, Qin F, Zhang HD, Yang YL, Shi AC (2008) Discovering ordered phases of block copolymers new results from a gtmeric Fourier-space approach. Phys Rev Lett 101 028301... 

Pinna, M Zvelindovsky, A.V., Todd, S and Goldbeck-Wood, G. (2006) Cubic phases of block copolymers under shear and electric fields by cell dynamics simulation. /. Chem. Pkys., 125 (15), 154905. 

Reproduced with permission from K.G. Yager, E. Lai, C.T. Black, Self-assembled phases of block copolymer blend thin films, ACS Nano 8 (2014) 10582-10588. 

The order parameter IJ/ is analogous to the orientational order parameter in liquid crystals, and the order-disorder transition in the two systems is quite similar (although with increasing molecular weight the transition in block copolymers becomes closer to continuous, while the transition in liquid crystals is strongly first order). In fact, certain microphase-separated phases of block copolymers can be identified as liquid crystalline, as described next. 

Hajduk et al., 1995, High-pressure effects on the disordered phase of block-copolymer melts, Macromolecules, Vol. 28, No. 21, PP. 7148-7258 1996, High-pressure effects on the order-disorder transition in block copolymer melts, Macromolecules, Vol. 29, No. 5, PP. 1473-1481... 

A characteristic property of polymer mixtures in the homogeneous phase is the increase of the concentration fluctuations accociated with an approaching of the point of unmixing. A similar behavior is found for the homogeneous phase of block copolymers, and a first example is given in Fig. 3.42. The figure shows scattering functions measured for a polystyrene-6/ocfc-polyisoprene under variation of the temperature. The temperature of the transition to the... 

Lin C-Y, Schick M. Self-consistent field study of the alignment by an electric field of a cylindrical phase of block copolymer. J Chem Phys 2006 125. 

The addition of homopolymers further enhances the tolerance of mismatching and allows chemical epitaxy of stractures more complex than the typical bulk phases of block copolymers. Stoykovich et al. introduced a ternary blend to further extend their surface-directed method. Such a blend system enables the block copolymer lamellae to conform to substrate stripe arrays with sharp bends. In the imblended block copolymer S3 tem, a high strain builds up in the polymer film at sharp comers of the chemical pattern because the comer-to-comer distance is much larger than the natural periodicity of the block copolymer. Successful replication of arrays of tilt boundaries with 45° and 90° angles was observed as a result of the redistribution of the homopolymer. (The polymer blend includes 20% PMMA homopolymer, 20% PS homopolymer, and 60% symmetric PS-b-PMMA.) Homopolymers are depleted above commensurate regions and concentrated above the distorted regions of the pattern to reduce the strain from incommensurability. 

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