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The fibrillar poly(3-hexyl thiophene) single crystals were prepared from dilute solutions of toluene, xylene, and anisole (0.01 wt%), and were investigated from the perspective of structural properties. Next, the rectangular and hexagonal poly(ethylene glycol) single crystals were developed from the dilute solutions and molten thin polymer films. The developing methodology used for all growth systems was self-seeding. The dimensions of fibrillar and rectangular/hexagonal single crystals ranged from several nanometers to some microns. Random single-co-crystals were also grown from dilute solution (0.018 wt% in amyl acetate) of crystalline-amorphous diblock copolymers and homopolymers. The small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and atomic force microscopy analyses were employed to characterize prepared grained samples. The incident X-ray experiments demonstrated highly ordered and lamellar crystalline structures. [ABSTRACT FROM AUTHOR]

To precisely investigate the nano-convergence, single-co-crystals of poly(ethylene glycol) (PEG) homopolymers with molecular weights of 5000, 35,000, and 100,000 g/mol and poly(ethylene glycol)- b-polystyrene (PEG- b-PS) and poly(ethylene glycol)- b-poly(methyl methacrylate) (PEG- b-PMMA) diblock copolymers were grown from melt state. In PEG/PEG- b-PS, PEG/PEG- b-PMMA, PEG/PEG- b-PS, and PEG/PEG- b-PMMA single-co-crystals, a considerable convergence was detected by atomic force microscopy (AFM) and the interface distribution function of small angle X-ray scattering (SAXS) analyses. Whereas in previously grown PEG/PEG- b-PS and PEG/PEG- b-PMMA single-co-crystals, the characteristics of PEG- b-PS and PEG- b-PMMA phase regions were independent of the presence of homo-PEG chains. The convergence in melt-grown single-co-crystals was ascribed to the variance of molecular weight of PEG blocks in homopolymer and diblock copolymers. The higher molecular weight of homo-PEG chains were utilized for co-crystallization; the more significant convergence was observed between the substrates of bared and brush-covered phase regions. The lower increase in the thickness of PMMA-covered substrate in comparison with PS-covered substrate was attributed to higher osmotic pressure of PMMA chains on the surface of single crystals. Hence, to reach the equilibrium convergence in single-co-crystal structure, the decrease of PEG and PEG substrate thicknesses from respective homopolymer single crystals to PEG/PEG- b-PMMA single-co-crystals was higher than the decrease in thickness of PEG/PEG- b-PS ones. [ABSTRACT FROM AUTHOR]

Well-defined block copolymers of poly(ethylene glycol)- block-polystyrene (PEG- b-PS) were synthesized by atom transfer radical polymerization with predetermined molecular weights and narrow molecular weight distributions (1.06-1.08). The single crystals of PEG- b-PS copolymers were grown in chlorobenzene/octane mixed theta solvent using self-seeding technique. The effect of self-seeding temperature ( T) on single crystal lateral size was evaluated. The atomic force microscopy (AFM) height images were indicative of increasing the single crystal lateral sizes, which were of several microns, via elevating T. The non-ideal structures were increasing by moving away from the optimized T (41.5 °C). Here, we studied the transition point between non-interaction and interaction regimes in a mixed theta solvent for PS as well. The impact of the PS block hindrance and the influence of crystallization temperature on thickness, tethering density and reduced tethering density of PS brushes were also investigated. Although these factors did not have the same effect on thickness and tethering density, the trend of their influence on reduced tethering density was the same. The results were recognized by AFM, transmission electron microscopy and small angle X-ray scattering. [ABSTRACT FROM AUTHOR]

The effects of PS and PMMA brushes on the crystallization of PEG in poly(ethylene glycol)- block-polystyrene (PEG- b-PS) and poly(ethylene glycol)- block-poly(methyl methacrylate) (PEG- b-PMMA) single crystals that have the same crystalline block molecular weight but different amorphous block molecular weights were investigated. The quality of the solvent (amyl acetate) employed and the interaction of the single-crystal substrate with the brush were found to influence the conformations of the PS and PMMA brushes, leading to more extended and packed pancake conformations, respectively. For PS and PMMA brushes with similar features, the conformation of the PMMA brushes led to a higher osmotic pressure on the substrate, so the substrate thickness was found to be significantly less than that seen when PS brushes were used. Even when the molecular weight of PMMA ( M = 8,700 g/mol) is considerably lower than that of PS ( M = 14,800 g/mol), the substrate in the presence of PMMA is thinner than that in the presence of PS (3.65 vs. 4.14 nm). Moreover, because there is less entropic repulsion between PS brushes than between PMMA brushes, the thickening of the substrate chains beneath them was more conspicuous when the crystallization temperature was increased. [ABSTRACT FROM AUTHOR]

For designing the responsive polymer brushes, and tuning the local and chemical surface responses to the external stimuli, the epitaxial single crystals were patterned by combination of bared surfaces of poly(ethylene glycol) (PEG) substrate, polymer homo-brushes constructed from poly(ethylene glycol)- b-polystyrene (PEG- b-PS) as well as poly(ethylene glycol)- b-poly(methyl methacrylate) (PEG- b-PMMA), and PEG- b-PS/PEG- b-PMMA mixed-brush channels. To achieve this target, various single crystals and epitaxial structures grown from dilute solutions through self-seeding approach were utilized as seeds to fabricate the next channels. The characteristics and morphologies of different channels were detectable by atomic force microscopy (AFM). The influence of chemical (solvent quality and interaction of substrate with different brushes) and physical (presence of brushes from another type in their vicinity) environments on crystallization was studied. Due to the effect of chemical environment, the PS brushes hampered the growth of PEG crystals at M = 10,000 g/mol. However, the PMMA brushes allowed PEG crystals to grow completely at M =13,100 g/mol, and indicated their hindrance at higher molecular weights (here, M = 17,100 g/mol). It was feasible to neutralize the mentioned hindrance through fabricating the channels with brushes having the highest hindrance ( M = 14,800 g/mol and M = 17,100 g/mol), and altering the physical environment from homo- to mixed-brush morphology. The characteristics (thickness, tethering density, and domain size) of developed channels from a certain material, in all arrangements and in various channels were in good agreement with those of corresponding non-epitaxial single crystals grown under the same conditions. [ABSTRACT FROM AUTHOR]