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Self-assembling Process (self-assembling + process)
Selected AbstractsSimulated Annealing Study of Self-Assembly of Symmetric ABA Triblock Copolymers Confined in Cylindrical NanoporesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2-3 2008Zheng Wang Abstract We report a simulated annealing study of the self-assembly of symmetric lamella-forming ABA triblock copolymers confined in cylindrical nanopores. We systematically examine the dependence of the self-assembled morphologies and structural parameters on the degree of confinement and the strength of the surface preference. We find that the confined morphologies for the symmetric ABA triblocks with fA,=,1/2 are similar to those for the symmetric or nearly symmetric AB diblock copolymers under the same confinement. We also find that different structural parameters can reflect different information. The predicted bridging fraction value for the bulk phase is in good agreement with previously established values, whereas the predicted values for the confined morphologies change with both the degree of confinement and the strength of the surface preference. We further explore the self-assembling process by examining the morphology and various ensemble-averaged thermodynamic quantities and structure parameters as a function of the reduced temperature. [source] Self-assembled structures in blends of disordered and lamellar block copolymers: SAXS, SANS and TEM studyPOLYMER INTERNATIONAL, Issue 1 2009Jaroslav Holoubek Abstract BACKGROUND: The phase behaviour of copolymers and their blends is of great interest due to the phase transitions, self-assembly and formation of ordered structures. Phenomena associated with the microdomain morphology of parent copolymers and phase behaviour in blends of deuterated block copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA), i.e. (dPS- block - dPMMA)1/(dPS- block -PMMA)2, were investigated using small-angle X-ray scattering, small-angle neutron scattering and transmission electron microscopy as a function of molecular weight, concentration of added copolymers and temperature. RESULTS: Binary blends of the diblock copolymers having different molecular weights and different original micromorphology (one copolymer was in a disordered state and the others were of lamellar phase) were prepared by a solution-cast process. The blends were found to be completely miscible on the molecular level at all compositions, if their molecular weight ratio was smaller than about 5. The domain spacing D of the blends can be scaled with Mn by D , Mn2/3 as predicted by a previously published postulate (originally suggested and proved for blends of lamellar polystyrene- block -polyisoprene copolymers). CONCLUSIONS: The criterion for forming a single-domain morphology (molecularly mixed blend) taking into account the different solubilization of copolymer blocks has been applied to explain the changes in microdomain morphology during the self-assembling process in two copolymer blends. Evidently the criterion, suggested originally for blends of lamellar polystyrene- block -polyisoprene copolymers, can be employed to a much broader range of block copolymer blends. Copyright © 2008 Society of Chemical Industry [source] Self-assembled honeycomb polycarbonate films deposited on polymer piezoelectric substrates and their applicationsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2005Edward Bormashenko Abstract Self-assembled honeycomb polycarbonate films were deposited on polymer piezoelectric (poled polyvinylidene fluoride) substrates under a fast dip-coating process. Ordered structures with micro-scaled pores dispersed in the polycarbonate matrix were obtained, demonstrating two-dimensional (2D) hexagonal packing. A theoretical model explaining the self-assembling process is proposed. Fabricated structures have a potential as 2D tunable photonic crystals. Photonic bandgap location was estimated. Visible-IR transmittance spectrum of the self-assembled films was studied with a FT-IR spectrometer. Diffraction properties of the honeycomb patterns were investigated. High transparency of the components makes possible IR optics applications of obtained structures. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of hydrophobicity and anions on self-assembly of the peptide EMK16-IIBIOPOLYMERS, Issue 4 2010Dawei Zou Abstract Effects of hydrophobic and electrostatic interactions on the self-assembling process of the ionic-complementary peptide EMK16-II are investigated by atomic force microscopy imaging, circular dichroism spectra, light scattering, and chromatography. It is found that the hydrophobicity of the peptide promotes the aggregation in pure water even at a very low concentration, resulting in a much lower critical aggregation concentration than that of another peptide, EAK16-II. The effect of anions in solution with different valences on electrostatic interactions is also important. Monovalent anions (Cl, and Ac,) with a proper concentration can facilitate the formation of peptide fibrils, with Cl, of smaller size being more effective than Ac, of larger size. However, only small amounts of fibrils, but plenty of large amorphous aggregates, are found when the peptide solution is incubated with multivalent anions, such as SO, C6H5O, and HPO. More importantly, by gel filtration chromatography, the citrate anion, which induces a similar effect on the self-assembling process of EMK16-II as that of SO and HPO, can interact with two or more positively charged residues of the peptide and reside in the amorphous aggregates. This implies a "salt bridge" effect of multivalent anions on the peptide self-assembling process, which can interpret a previous puzzle why divalent cations inhibit the formation of ordered nanofibrils of the ionic-complementary peptides. Thus, our results clarify the important effects of hydrophobic and electrostatic interactions on the self-assembling process of the ionic-complementary peptides. These are greatly helpful for us to understand the mechanism of peptides' self-assembling process and protein folding and aggregation. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 318,329, 2010. This article was originally published online as an acceptedpreprint. The "Published Online" date corresponds to the preprintversion. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Self-assembling peptides: Sequence, secondary structure in solution and film formationBIOPOLYMERS, Issue 11 2008Roberta Gambaretto Abstract Peptides of alternating charge and hydrophobic amino acids have a tendency to adopt unusually stable ,-sheet structures that can form insoluble macroscopic aggregates under physiological conditions. In this study, analogues of a well-known self-assembling peptide, characterized by the same polar/nonpolar periodicity but with different residues, were designed to study the relationship between sequence, conformation in solution and film-forming capacity in saline solution. Peptide conformation, evaluated by circular dichroism, correlated with film forming capacity observed by inverted optical microscopy after addition of saline solution and subsequent drying. We found that polar/nonpolar periodicity of several analogues is not criterion enough to induce ,-sheet and thus film formation and that conformations different from ,-sheet also allow self-assemblage. Furthermore, addition of the short adhesive sequence RGD to a known self-assembling sequence was shown to not prevent the self-assembling process. This finding might prove useful for the design of biomimetic scaffolds. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 906,915, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | ||||||||||