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The double gyroid network morphology has been the focus of extensive research efforts as one of the most appealing block copolymer structures for practical applications. We performed an extensive study of the phase behavior of the supramolecular complex PS-b-P4VP(PDP)(x) to develop a systematic route to its double gyroid morphology. The morphological characterization of complexes was accomplished by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Several compositions with the cubic Ia(3)over bard symmetry were found in a narrow region between the lamellar and the cylindrical phase. Experimental TEM images were compared to computer simulations of projections through multiple gyroid planes. Typical gyroid patterns "double wave" and "wagon wheel" were regularly found. The size of the gyroid unit cell was calculated from the SAXS data. The lattice parameter could be varied (from ca. 70 to 125 nm) by altering the molar mass of the block copolymer precursors. A number of complexes were found to exhibit characteristic biphasic morphologies coexisting lamellar and gyroid phase or gyroid and cylindrical phase. Finally, gyroid complexes with different relative PDP ratios were obtained which provides the opportunity to generate nanoporous structures with tunable porosities by dissolving the amphiphiles.

This article proposes data treatment for estimating the individual (and unimodal) molar mass distributions (MMDs) of each polymer component in a blend from multimodal concentration chromatograms obtained by size exclusion chromatography (SEC/GPC). The Differential Refractometer (DR) chromatograms are deconvoluted into linear combinations of exponentially-modified Gaussian distributions. The deconvolutions are possible if the individual peaks are not fully overlapped and if the mass fractions of the minor components are not too low. To help determine the number and approximate location of the individual peaks, the second derivative of the chromatogram is employed. For blends of chemically identical homopolymers, the deconvolution stage directly provides the mass fractions of the individual peaks. For blends of two chemically different homopolymers, the chemical composition and detector responses of the individual components must be determined, for example with the help of dual detection (UV/DR). The procedure was validated with blends of a priori known components Fil: Clementi, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Tecnologica Nacional; Argentina Fil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Berek, Dusan. Universidad Tecnológica Nacional. Facultad Regional Santa Fe; Argentina Fil: Ronco, Ludmila Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Vega, Jorge Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Tecnologica Nacional; Argentina

The influence of elongational flow on the association behavior of binary mixtures of functionalized polymers capable of forming single reversible orientationally dependent bonds, such as hydrogen bonds, is studied analytically. Applying a mean-field approach with an external potential representing the effect of the elongational flow, the orientation distribution functions for the dumbbell model and the freely jointed model of a polymer chain were obtained. Two opposite factors determine the association of “linear” diblock copolymerlike chains: the unfavorable extra stretching under flow of associated polymer chains and the favorable orientation of the chains (segments) along the flow direction. The former dominates and the fraction of associated “linear” chains decreases with increasing flow rate. For mixtures of polymers which are capable of forming associated T-chains, the association also decreases, however, more slowly, and this time due to unfavorable orientational effects. If the formation of associated linear and T-polymers as well as complex linear/T-polymers is possible, a strong preference for the formation of associated T-chains is found. At high flow rates any type of association becomes unfavorable.

Block copolymer (BCP) self-assembly is an effective and versatile approach for the production of complex nanopatterned interfaces. Monolayers of BCP films can be harnessed to produce a variety of different patterns, including lines, with specific spacings and order. In this work, bilayers of cylinder-forming polystyrene-block-polydimethylsiloxane block copolymer (PS-b-PDMS) were transformed into arrays of silica lines with half the pitch normally attained for conventional monolayers, with the PDMS acting as the source for the SiO x. The primary hurdle was ensuring the bilayer silica lines were distinctly separate; to attain the control necessary to prevent overlap, a number of variables related to the materials and self-assembly process were investigated in detail. Developing a detailed understanding of BCP film swelling during solvent annealing, blending of the PS-b-PDMS with PS homopolymer, utilization of a surface brush layer, and adjustment of the plasma exposure conditions, distinct and separate silica lines were prepared. On the microscale, the sample coverage of PS-b-PDMS bilayers was investigated and maximized to attain >95% bilayers under defined conditions. The bilayer BCP structures were also amenable to graphoepitaxy, and thus, dense and highly ordered arrays of silica line patterns with tightly controlled width and pitch were fabricated and distributed uniformly across a Si surface. © 2013 American Chemical Society.

Symmetric diblock copolymer blends A(f)B(1-f)/A(1-f)B(f) (0 less than or equal to f less than or equal to 0.5) are theoretically discussed in terms of a multiorder parameter approach and numerically investigated by Monte Carlo simulations. Theoretically, our main result is that below f congruent to 0.3, but still in the microphase separation region given by 0.21 less than or equal to f less than or equal to 0.5, the concentration profiles of the long and short A-blocks as well as the long and short B-blocks are out of phase. Monte Carlo simulations were used to investigate the nature of the phase transition, micro versus macro, as a function off. Using the canonical ensemble, the microphase separation temperature (MIST) was determined. The macrophase separation temperature (MAST) was studied with the semi-grand-canonical ensemble combined with the histogram extrapolation technique. The phase diagram differs considerably from the theoretical predictions due to the stretching/polarization of the molecules already far above the transition temperature, thus stabilizing the macroscopically homogeneous state. The out-of-phase behavior between the long and short blocks near the critical value f congruent to 0.21, separating the micro- and macrophase separation regimes, was confirmed by the simulations.

We report the observation of a cubic phase consistent with the double gyroid structure in strongly Segregated diblock copolymers of PS-b-PDMS over a volume fraction (phi(PDMS)) range of similar to 0.39 to 0.45. The samples have respective molecular weights of 127 kg/mol and 73 kg/mol and degree of segregation N chi equal to 187 and 106, respectively, at annealing temperature of 130 degrees C. It is important to highlight that two out of the total four samples investigated, exhibited hexagonally close packed cylindrical domains of PDMS and alternating lamellae at phi(PDMS) = 0.39 and 0.45, respectively, indicating the possible narrow range of the DG morphology for the specific diblock copolymers. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2419-2427, 2009 Journal of Polymer Science Part B-Polymer Physics

International audience; The morphology of micelles formed from blends of linear and cyclic poly(styrene-b-isoprene) (PS-b-PI) block copolymers has been investigated in solution using dynamic light scattering (DLS) and in thin solid deposits by atomic force microscopy (AFM) and transmission electron microscopy under cryogenic conditions (cryo-TEM). Micelles of the pure cyclic PS290-b-PI110 copolymers are wormlike cylindrical objects built by unidirectional aggregation of 33 nm wide sunflower micelles, while the linear block copolymer having the same volume fraction and molar mass forms spherical micelles 40 nm in diameter. The DLS, AFM, and cryo-TEM results consistently show that the addition of the linear copolymer (even for amounts as low as 5% w/w) to the cyclic copolymer rather favors the formation of spherical micelles at the expense of the cylindrical aggregates. Those results clearly show that the linear block copolymer chains can be used to stabilize the thermodynamically unstable elementary sunflower micelle. The thermal stability of the micelles (from the pure copolymers and from the blends) has been examined in solid deposits with in situ AFM measurements. Coalescence starts at about 70 degrees C, and the surface roughness shows a two-step decrease toward a fully homogeneous and flat structure.