In this study, poly(3-hexylthiophene)-block-poly(δ-decanolactone)s (P3HT-b-PDLs) with the molecular architecture of AB, BAB, B2AB2, and B3AB3 (A: P3HT, B: PDL) were synthesized for stretchable organic field-effect transistors (OFETs) through the Cu-catalyzed azido–alkyne click reaction (CuAAC) with a high yield. The effects of triblock and branched architectures on the thermal, mechanical, and electrical properties of the prepared block copolymers were studied. Block copolymer thin films prepared from the selective solvent of cyclohexane exhibited a distinct phase separating the domain of P3HT with a nanofibrillar structure. Grazing-incidence X-ray scattering results indicated that all of the block copolymer thin films possessed the P3HT crystalline domains with the same domain spacing regardless of the branched architecture. However, the branched soft segments led to a more random phase separation of the block copolymer and lower crystallinity of the P3HT block. Consequently, thin films made by the triblock copolymers with branched PDL segments (B2AB2 and B3AB3) exhibited favorable electrical properties with significantly improved stretchability and smaller elastic modulus. The carrier mobility of the block copolymer-based OFETs showed a comparable performance to that of the pristine P3HT homopolymer. Also, the B3AB3-based OFET could maintain 72–75% on the charge mobility under 100% strain and 71–75% after 500 stretch–release cycles at 50% strain. The study revealed that the stretchability of the conjugated/elastic block copolymers can be significantly enhanced by our architecture design without losing their semiconducting property.
This study reports the first well-defined and stable nanomicelles (20 − 30 nm in diameter) self-assembled from amphiphilic brush (comb-like) cyclic and tadpole-shaped copolymers composed of hydrophobic n-decyl and hydrophilic 2-(2-methoxyethoxy)ethoxy) ethyl bristle blocks based on a poly(glycidyl ether) backbone. The micelle formation behaviour and structural details were investigated by synchrotron X-ray scattering analysis in a rigorous and complementary manner. The amphiphilic brush cyclic topology facilitates more compact and stable aggregation behaviour in the micelle core and a more densely packed corona, which prevents intermicellar aggregation. The presence of a hydrophobic component with brush cyclic topology inside the core is identified as the primary micelle stabilizing factor, enabling stable core aggregation and sharper core-corona interface formation. The presence of a hydrophilic brush cyclic component in the corona is determined as the secondary micelle stabilizing factor, helping nullify the corona penetration by polymer chains from other micelles and ultimately prevent the intermicellar aggregation-mediated collapse of the micellar structure. Overall, the brush cyclic topology was confirmed to be beneficial for forming highly stable nanomicelles with an extremely narrow (pseudo-monodisperse) size distribution compared with conventional linear topology and tadpole topologies. All the results of this study provide a unique opportunity for designing advanced functional high-performance amphiphilic materials for nanomicelles that are unattainable by other conventional methods and broadening their applications in various fields, including drug delivery, biomedical imaging, foods, cosmetics, smart coatings, photonics and molecular electronics.
A series of miktoarm star polymers, [poly(nhexyl isocyanate)(12K)]−[poly(ε-caprolactone) 1−3 (5K)] (PHIC−PCL 1−3 ) (composed of a rigid self-assembling PHIC arm and one to three flexible crystallizable PCL arms), were investigated to examine the polymers' thermal properties and nanoscale thin film morphologies. The miktoarm polymers were stable up to 180 °C. The PHIC and PCL arm components underwent phase separation during the solution casting, drying, and post toluene-annealing processes, forming interesting but very complex thin film morphologies. The resulting thin film morphologies were examined in detail for the first time using synchrotron grazing incidence X-ray scattering (GIXS) measurements and quantitative data analysis. All of the miktoarm star polymer films formed vertically well-oriented lamellar structures, regardless of the number and length of PCL arms. These structures were quite different from the cylindrical structures commonly observed in conventional flexible diblock copolymer films having comparable volume fractions. The individual PHIC and PCL lamellar domains self-assembled to form their own respective morphological structures. The PHIC lamellae consisted of a mixture of horizontal and vertical multibilayer structure domains, as observed in the PHIC homopolymer film. The PCL lamellae formed fringed micelle-like crystals and/or highly imperfect folded crystals that differed significantly from the structures found in a PCL homopolymer film composed of typical folded lamellar crystals. These PCL crystals were formed with a mixture of vertical and horizontal orthorhombic lattices. Overall, the GIXS analysis revealed that the parameters that characterized the hierarchical structures in the thin films depended significantly on the number and length of the PCL arm and its crystallization characteristics as well as the chain rigidity and multibilayer structure formation characteristics of the PHIC arm.
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