Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star-shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (A m B n and ABC miktoarm) star copolymers and starshaped [(A-b-B) n ] copolymers with nonlinear architecture.

wileyonlinelibrary.comspeed, and simplicity of the process. [1][2][3][4][5] Although vertical orientation of lamellar and cylindrical nanodomains of block copolymers on a substrate is desirable, parallel orientation is usually obtained in a thin fi lm because of different affi nity between two block segments in a block copolymer toward the substrate and/or air. To induce vertical orientation, diverse preor post-treatments to neutralize the preferential affi nity have been introduced in the literature, for instance, solvent vapor annealing, [6][7][8][9] surface neutralization by random copolymer brush treatment, [10][11][12] blend system, [ 13 ] graphoepitaxy, [ 14,15 ] temperature gradient, [ 16,17 ] electric fi eld [ 18,19 ] or top coating. [20][21][22] Among them, solvent vapor annealing is one of the most powerful post-treatment methods for developing vertical orientation of block copolymer nanodomains. However, this method is diffi cult to apply for industrial applications owing to the use of solvents and the dewetting problem. To avoid using solvent, thermal annealing of block copolymer thin fi lms would be the most promising platform for commercialization of DSA due to easy and large scale process. However, to induce vertically oriented nanodomains, neutralization of a substrate by various surface modifi cations, for instance, functionalization with random copolymers, introducing rough substrates, employing graphene fi lms or nanoparticle monolayers, [ 11,13,[23][24][25] is still needed to tune interfacial interactions between a substrate and each block of the block copolymer. Therefore, a simple and cost-effective DSA process that does not require above-mentioned neutralization methods and solvent vapor annealing is demanded for the fabrication of vertically oriented nanodomains to compete with conventional top-down lithography.Kramer and co-workers [ 26 ] investigated the effect of block copolymer chain architecture on the orientation of nanodomains in relatively thick fi lms (600-800 nm) using poly(cyclohexylethylene)-block -poly(ethylene) (PCHE-b -PE) block copolymers. They found that PCHE-b -PE-b -PCHE triblock copolymer showed perpendicularly oriented nanodomains by introducing lower surface energy block as the midblock, whereas PCHE-b -PE diblock copolymer exhibited parallel Vertical Orientation of Nanodomains on Versatile Substrates through Self-Neutralization Induced by Star-Shaped Block CopolymersSangshin Jang , Kyuseong Lee , Hong Chul Moon , Jongheon Kwak , Jicheol Park , Gumhye Jeon , Won Bo Lee , and

The phase behavior of 18-arm star-shaped polystyrene-block-poly(methyl methacrylate) copolymers ((PS-b-PMMA)18) with various volume fractions of PMMA block (f PMMA) was investigated by transmission electron microscopy and small-angle X-ray scattering. (PS-b-PMMA)18 was synthesized by atom transfer radical polymerization from α-cyclodextrin (α-CD) having 18 functional groups for the initiation. We also prepared the corresponding linear PS-b-PMMAs by cutting the ester groups connecting α-CD and PS chains in (PS-b-PMMA)18 through the hydrolysis. The microdomains of (PS-b-PMMA)18 changed from body-centered-cubic spheres (BCC), hexagonally packed cylinders (HEX), perforated lamellae (PL), and lamellae (LAM), with increasing f PMMA from 0.3 to 0.8. Interestingly, (PS-b-PMMA)18 with f PMMA of 0.77 showed highly asymmetric lamellar microdomains, while the corresponding linear PS-b-PMMA with the same volume fraction should not have lamellar microdomains. Thus, the microdomains are highly affected by the molecular architecture of block copolymer. The experimental results are discussed with the prediction based on the self-consistent mean-field theory.

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We report a novel approach for the fabrication of a photo-responsive surface with fast and reversibly switchable wettability between hydrophobicity and hydrophilicity induced by a photothermal effect.