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There is a clearly demonstrated relationship between the microstructure, processing and resulting optoelectronic properties of conjugated polymers. Here, we exploited this relationship by exposing polyfluorene thin films to various solvent vapors via confined-solvent vapor annealing to optimize their microstructure, with the final goal being to enhance their emission properties. Our results have demonstrated enlargements in photoluminescence intensity of up to 270%, 258% and 240% when thin films of polyfluorenes of average molecular weights of 105,491 g/mol, 63,114 g/mol and 14,000 g/mol, respectively, experienced increases in their β-phase fractions upon processing. [ABSTRACT FROM AUTHOR]

Biopolymers exhibit a large variety of attractive properties including biocompatibility, flexibility, gelation ability, and low cost. Therefore, especially in more recent years, they have become highly suitable for a wider and wider range of applications stretching across several key sectors such as those related to food packaging, pharmaceutic, and medical industries, just to name a few. Moreover, biopolymers' properties are known to be strongly dependent on the molecular arrangements adopted by such chains at the nanoscale and microscale. Fortunately, these arrangements can be altered and eventually optimized through a plethora of more or less efficient polymer processing methods. Here, we used a space-confined solvent vapor annealing (C-SVA) method to subject various biopolymers to rich swelling in solvent vapors in order to favor their further crystallization or self-assembly, with the final aim of obtaining thin biopolymer films exhibiting more ordered chain conformations. The results obtained by atomic force microscopy revealed that while the gelatin biopolymer nucleated and then crystallized into granular compact structures, other biopolymers preferred to self-assemble into (curved) lamellar rows composed of spherical nanoparticles (glycogen and chitosan) or into more complex helix-resembling morphologies (phytagel). The capability of the C-SVA processing method to favor crystallization and to induce self-assembly in various biopolymeric species or even monomeric units further emphasizes its great potential in the future structuring of a variety of biological (macro)molecules. [ABSTRACT FROM AUTHOR]

L-poly(lactic acid), poly(3-hydroxybutyrate), and poly-hydroxybutyrate-co-hydroxyvalerate are biodegradable polymers that can be obtained from renewable biomass sources. The aim of this study was to develop three types of environmentally friendly film biocomposites of altered microstructure by combining each of the above-mentioned polymers with cellulose nanocrystal fillers and further processing the resulting materials via space-confined solvent vapor annealing. Cellulose was previously obtained from renewable biomass and further converted to cellulose nanocrystals by hydrolysis with the lactic acid. The solutions of biodegradable polymers were spin-coated onto solid substrates before and after the addition of cellulose nanocrystals. The obtained thin film composites were further processed via space-confined solvent vapor annealing to eventually favor their crystallization and, thus, to alter the final microstructure. Indeed, atomic force microscopy studies have revealed that the presence of cellulose nanocrystals within a biodegradable polymer matrix promoted the formation of large crystalline structures exhibiting fractal-, spherulitic- or needle-like morphologies. [ABSTRACT FROM AUTHOR]

In this study, we employed a polymer processing method based on solvent vapor annealing in a confined environment to swell-rich thin films of polybutadiene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) triblock copolymers and to promote their crystallization. As revealed by optical and atomic force microscopy, thin films of triblock copolymers containing a rather short crystalline poly(ethylene oxide) block that was massively obstructed by the other two blocks were unable to crystallize following the spin-casting process, and their further swelling in solvent vapors was necessary in order to produce polymeric crystals displaying a dendritic morphology. In comparison, thin films of triblock copolymers containing a much longer poly(ethylene oxide) block that was less obstructed by the other two blocks were shown to crystallize into dendritic structures right after the spin-casting procedure, as well as upon rich swelling in solvent vapors. [ABSTRACT FROM AUTHOR]

In this study we have employed a polymer processing method based on solvent vapor annealing in order to condense relatively large amounts of solvent vapors onto thin films of block copolymers and thus to promote their self-assembly into ordered nanostructures. As revealed by the atomic force microscopy, a periodic lamellar morphology of poly(2-vinylpyridine)-b-polybutadiene and an ordered morphology comprised of hexagonally-packed structures made of poly(2-vinylpyridine)-b-poly(cyclohexyl methacrylate) were both successfully generated on solid substrates for the first time. [ABSTRACT FROM AUTHOR]

We report on the enhancement of photoluminescence in thin films of poly[2-methoxy-5-((2′-ethylhexyl)oxy)-1,4-phenylenvinylene], neat or embedded in polystyrene, upon illumination with light as a function of annealing temperature, with our data emphasizing the picture of a light-induced conformation change that leads to the altered photophysical response of this polymer. [ABSTRACT FROM AUTHOR]

It is increasingly obvious that the molecular conformations and the long-range arrangement that conjugated polymers can adopt under various experimental conditions in bulk, solutions or thin films, significantly impact their resulting optoelectronic properties. As a consequence, the functionalities and efficiencies of resulting organic devices, such as field-effect transistors, light-emitting diodes, or photovoltaic cells, also dramatically change due to the close structure/property relationship. A range of structure/optoelectronic properties relationships have been investigated over the last few years using various experimental and theoretical methods, and, further, interesting correlations are continuously revealed by the scientific community. In this review, we discuss the latest findings related to the structure/optoelectronic properties interrelationships that exist in organic devices fabricated with conjugated polymers in terms of charge mobility, absorption, photoluminescence, as well as photovoltaic properties. [ABSTRACT FROM AUTHOR]

We have investigated the formation of poly(γ-benzyl l-glutamate) (PBLG) crystals from semidilute thin film solutions.Crystallization was initiated by adding methanol, a nonsolvent. Afterdrying, each PBLG crystal possessed an internal domain structure exhibitinga zigzag pattern consisting of parallel stripes of alternating orientationsbetween domains. X-ray scattering and electron diffraction revealedwithin these crystals a pseudohexagonal packing of the PBLG α-heliceswith their axis oriented parallel to the plane of the substrate. Onthe basis of optical anisotropy studies, it could be shown that theorientation of the helix axis was parallel to the stripes. While formingin solution, the objects are assumed to consist of a hexagonal columnarliquid crystalline phase. Upon drying, lateral packing density ofthe helices increased and resulted in a net dilative strain perpendicularto the columns, which is supposed to cause the formation of zigzagpatterns. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (RGO) is considered to be a promising candidate in tissue engineering and our research has been focused towards the behavior of colon-26 tumor carcinoma cells on thin films of RGO. We have obtained homogeneous thin films of RGO by drop casting and spin coating water suspensions of RGO synthesized using microwave assisted route. We concluded that RGO is homogeneously and yet randomly distributed on the substrates as observed with inverted optical and atomic force microscopes. Therefore, these RGO films seemed to be a good platform to sustain tumor carcinoma cells with the aim to realize a comprehensive analysis of their behavior in such environment. [ABSTRACT FROM AUTHOR]

We apply here an optimized polymer processing approach, based on solvent vapor annealing in a space-confined environment, to generate previously unrevealed self-assembled microstructures comprised of periodic lamellar or hexagonal nanostructures of molecular dimensions, depending on the type of block copolymer that is used. [Display omitted] • An improved polymer processing method, based on solvent vapor annealing in a space-confined environment, is proposed. • Thin polymers films are swollen-rich to become quasi-2D "solutions" and favor the mobile polymer chains to self-assemble. • Self-assembled lamellar and hexagonal microstructures of two block copolymers are revealed after processing. [ABSTRACT FROM AUTHOR]

• Deposition of thin films by convective self-assembly allowed control over microstructure. • Introduction of fullerenes led to optimized microstructure with rich absorption properties. • Under specific film casting conditions, the microstructure changed with fullerene size. It is nowadays accepted that the optoelectronic properties of the donor-acceptor active layers are microstructure dependent and can be manipulated by employing various film deposition techniques. In this work, we show that fully intercalated co-crystalline polymer:fullerene microstructure can be obtained when depositing thin films using convective self-assembly technique. Moreover, this microstructure appears to be dependent, under specific film casting conditions, on the fullerene size. Use of slightly bigger fullerenes is leading to a multi-phase microstructure comprised of neat polymer domains, fullerene aggregates and co-crystalline polymer:fullerene structures. [ABSTRACT FROM AUTHOR]