Asymmetric diblock copolymers

Zhao, J., Jiang, S., Ji, X., Lijia, L.An. and Jiang, B. (2005) Study of the time evolution of the surface morphology of thin asymmetric diblock copolymer films under solvent vapor. Polymer, 46, 6513-6521. 

Fig. 1. Scattering pattern of the lamellar phase for a moderately asymmetric diblock copolymer near its spinodal in the q, = 0 scattering plane. The plot shows and q in units of fco- The lamellae are oriented in the z -direction. Courtesy of An-Chang Shi.

Fig. 3. Computer simulation results using a time-dependent Ginzburg-Landau approach, showing the microstructural evolution after a temperature jump from the lamellar phase to the hexagonal cylinder phase for a moderately asymmetric diblock copolymer. The time units are arbitrary. (Reprinted with permission from Polymer 39, S. Y. Qi and Z.-G. Zheng, Weakly segregated block copolymers Anisotropic fluctuations and kinetics of order-order and order-disorder transitions, 4639-4648, copyright 1998, with permission of Excerpta Medica Inc.)...

Xu T, Zvelindovsky AV, Sevink GJA, Lyakhova KS, Jinnai H, Russell TP (2005) Electric field alignment of asymmetric diblock copolymer thin films. Macromolecules 38 10788-10798... 

Symmetric diblock copolymers (/a — /b) arrange into a lamellar morphology, with alternating layers of the constituent blocks. Asymmetric diblock copolymers (/a /b) self-assemble into morphologies where the minority component is... 

Han, E., Stuen, K.O., La, Y.-H., Nealey, P.F., Gopalan, P. Effect of cmnposition of substrate-modifying randmn copolymers on the orientation of symmetric and asymmetric diblock copolymer domains. Macromolecules 41, 9090 (2008)... 

The phase behavior of asymmetric diblock copolymers seems to be more complex than that of symmetric diblock copolymers and the phase behav-... 

Fig. 24 Self-assembled morphologies of an asymmetric diblock copolymer confined to cylindrical pores obtained by a simulated annealing method as a function of the ratio Dp/Lo> where Lq is the period of the BCP, for different wall-polymer interactions. The parameter Dp/f-o is given underneath each morphology. The outmost circles in the top views indicate the wall of the cylindrical pores. For some large diameters, the inner ring is shown separately, a The pore wall attracts the majority blocks b the pore wall attracts the minority blocks c neutral pore walls. Reproduced from [213]. (2006) American Physical Society...

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,... 

The last two columns in Table II present the results for an asymmetric diblock copolymer in which the soluble block is three times longer than the insoluble block. The influence of E gg on the cmc is even smaller for the asymmetric diblock copolymer than for the symmetric diblock copolymer. When compared with the previous work (5), where E g was varied, we find that the influence of E gg on the cmc is trivial compared with the influence of E as-... 

Del Valle-Carrandi, L. Alegria, A. Arbe, A. Colmenero, J., Unexpected PDMS Behavior in Segregated Cylindrical and Spherical Nanophases of PS-PDMS Asymmetric Diblock Copolymers. Macromolecules 2012,45, 491-502. 

Figure 27. Apparent spinodal phase diagram for N = 2000, / = f stiffness asymmetric diblock copolymer melt. Here = I, while F was varied. Numerical results (SFC) are shown for two choices of the bare attractive energy asymmetry variable A. The dashed curve shows the corresponding analytical thread predictions discussed in Section VII.C.

Wang, Q., Nealey, P.F. et al. (2003) Simulations of the morphology of cylinder-forming asymmetric diblock copolymer thin films on nanopatterned substrates. Macromolecules, 36(5), 1731-1740. 

Quiram DJ, Register RA, Marchand GR, Ryan AJ. Dynamics of structure formation and crystallization in asymmetric diblock copolymers. Macromolecules 1997 30 8338-8343. 

Figure 15.6 Self-assembled structures of asymmetric diblock copolymers confined in a thin film, (a) and (b) Parallel cylinder structures, (c) perpendicular cylinder structures, (d) and (e) lamellar structures, and (f) perforated lamellae structure.Huinink et al. [39]. Reproduced with permission of Elsevier.

Recently, researchers paid more attention to the guided self-assembly of block copolymer thin films on a patterned surface. The patterned surface means the surface of a constrained situation is chemically or physically modified to form a pattern with specific property and size. A series of exquisite structures are found in the microphase separation of block copolymer under the patterned surface. In the theoretic work of Wu and Dzenis [43], they designed two kinds of patterned surface to direct the block copolymer self-assembly (Fig. 15.7). The self-assembled structures are found strongly influenced by the commensurability of polymer bulk period and pattern period. With mismatched patterns on two surfaces, both MC simulation [44] and SCFT researching [45] predicted the titled lamellae and perforated lamellae structures for symmetric diblock copolymers. Petrus et al. carried out a detailed investigation on the microphase separation of symmetric and asymmetric diblock copolymers confined between two planar surfaces using DPD simulation [46,47]. It is found that various nonbulk nanostructures can be fabricated by the nanopatterns on the surfaces. 

Wang Q, Nealey PE, de Pablo JJ. Monte Carlo simulations of asymmetric diblock copolymer thin films confined between two homogeneous surfaces. Macromolecules 2001 34 3458. 

Yin Y, Sun P, Jiang R, Li B, Chen T, Jin Q, Ding D, Shi A-C. Simulated annealing study of asymmetric diblock copolymer thin films. J Chem Phys 2006 124 184708. 

Yokoyama, H., Kramer, E.J., Rafailovich, M.H., Sokolov, J., Schwarz, S.A. Stmcture and diffusion of asymmetric diblock copolymers in thin films a dynamic secondary ion mass spectrometry smdy. Macromolecules 31, 8826-8830 (1998)... 

In many applications, including colloid stabilization, polymers are end-grafted onto large particles which are intermediate between the planar brush and a star. Curved brushes, with either spherical or cyUndrical symmetry, can also be formed by asymmetric diblock copolymers in the strong segregation limit. When the grafting surface curves towards the polymers (concave curvature), the volume available to the polymer chains is lowered compared to a flat surface. In this case, the chains are stretched throughout the brush and the brush is qualitatively unaltered from the flat case. MC simulations on a tetrahedral lattice for chains inside a spherical cavity... 

Manipulation of the blends of BCs on surfaces and thin films constitutes an interesting alternative to finely tune the self-assembled structures formed in BCs. Studies of BC blends have been carried out from both an experimental and theoretical point of view. Bates and coworkers reported on the morphologies observed in blends composed of either symmetric or asymmetric diblock copolymers with variable molecular weight and compared the structures with the predicted using SCF calculations [181], The blend composition profiles in symmetric blends show non-uniformity in the distribution of the chains with the longer chains segregating to the domain centers and shorter chains being more... 

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