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The morphology of superstructures formed by bottlebrush block copolymers in the melt can be tuned by changing the side chain length or/and their grafting density at constant volume fractions of the blocks. This feature enables fabrication of microphase separated bulk structures and mesoporous materials thereof with spherical or cylindrical domains (precursors of the mesopores), with high porosity unattainable for materials produced from conventional linear block copolymers. These paradigms are proven by DPD simulations that allow constructing morphological phase diagrams of the melt of block copolymers comprising one linear and one bottlebrush block and comparing the simulation results to the predictions of the mean field analytical theory. While the binodal lines separating the stability regions of spherical and cylindrical domains predicted by the theory perfectly match the simulation results, the simulation indicates appearance of a gyroid phase around the theoretical binodal separating the stability ranges of cylinders and lamellae. The results of our work provide guidelines for macromolecular design of novel composite and mesoporous materials with a wide spectrum of potential applications. [ABSTRACT FROM AUTHOR]

Brushes formed by arm-tethered starlike polyelectrolytes may exhibit internal segregation into weakly and strongly extended populations (stratified two-layer structure) when strong ionic intermolecular repulsions induce stretching of the tethers up to the limit of their extensibility. We propose an approximate Poisson-Boltzmann theory for analysis of the structure of the stratified brush and compare it with results of numerical self-consistent field modeling. Both analytical and numerical models point to the formation of a narrow cloud of counterions (internal double electrical layer) localized inside a stratified brush at the boundary between the layers. [ABSTRACT FROM AUTHOR]

We present a mean-field theory for the solution properties of polyelectrolyte molecular brushes, comprising multiple ionically charged side chains tethered to the main chain (backbone). The power-law dependences for local and large-scale conformational properties, i.e., the brush thickness, extension of spacers between the grafts, and end-to-end distance for the main chain macromolecule, are derived as a function of architectural parameters (the lengths of the main chain and of the grafts, grafting density). We demonstrate that at high grafting density or/and a large fraction of charged monomer units in the grafts, the localization of counterions in the intra-molecular volume occurs and we specify the onset of this transition. We prove that such localization of the counterions is accompanied by full extension of the main chain of the polyelectrolyte molecular brush in salt-free solution. This stretching of the main chain is relaxed upon an increase in the salt concentration. The dependence of the macromolecular dimensions of the polyelectrolyte molecular brush on the salt concentration is derived, and multiple power-law exponents valid in different salt concentration ranges are predicted. [ABSTRACT FROM AUTHOR]

The self-consistent field theory of brushes of neutral water-soluble polymers described by two-state models is formulated in terms of the effective Flory interaction parameter χ[sub eff](T,[lowercase_phi_synonym]) that depends on both temperature, T, and the monomer volume fraction, [lowercase_phi_synonym]. The concentration profiles, distribution of free ends and compression force profiles are obtained in the presence and in the absence of a vertical phase separation. A vertical phase separation within the layer leads to a distinctive compression force profile and a minimum in the plot of the moments of the concentration profile versus the grafting density. The analysis is applied explicitly to the Karalstrom model. The relevance to brushes of Poly(N-isopropylacrylamide)(PNIPAM) is discussed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the interaction between surfaces coated with triblock copolymers. Creation of polymer-coated colloidal systems with additional minima in the interaction; Use of the systems for optical switches; Formation of stable crystal structures; Impact of morphological changes on surface interactions.

Polyelectrolyte brushes are formed by charged macromolecules tethered by the end segment to a solid-liquid interface. At low ionic strength of the solution, the intermolecular electrostatic interactions lead to strong stretching of the macromolecules that may, as a result, approach the limit of their extensibility (the contour length). Here, we present an analytical theory of polyelectrolyte brushes developed within the Poisson-Boltzmann approximation which explicitly accounts for finite extensibility of the brush-forming chains. In contrast to earlier theories based on the approximation of Gaussian elasticity of the brush-forming chains, the current approach enables avoiding artificial result of stretching of the chains beyond the contour length at high degrees of ionization or/and large grafting densities.