Tunable Thermal Switch via Order-Order Transition in Liquid Crystalline Block Copolymer.

Organic material-based thermal switch is drawing much attention as one of the key thermal management devices in organic electronic devices. This study aims at tuning the switching temperature (TS) of thermal conductivity by using liquid crystalline block copolymers (BCs) with different order-order transition temperature (Ttr) related to the types of mesogens in the side chain. The BC films with low Ttr of 363 K and high Ttr of 395 K exhibit reversible thermal conductivity switching behaviors at TS of ∼360 K and ∼390 K, respectively. The BC films also exhibit thermal conductivity variation originating from the anisotropy of the internal structures: poly(ethylene oxide) domains and liquid crystals. These results demonstrate that the switching behavior is attributed to an order-order transition between BC films with vertically arranged cylinder domains and the ones with ordered sphere domains. This highlights that BCs become a promising thermal conductivity switching material with tailored TS.

Slowing the translocation of single-stranded DNA by using nano-cylindrical passage self-assembled by amphiphilic block copolymers.

We report a novel approach to slow the translocation of single-stranded DNA (ssDNA) by employing polyethylene oxide (PEO) filled nano-cylindrical domains as transportation channels. DNA strands were demonstrated to electrophoretically translocate through PEO filled cylindrical domains with diameters of 2 and 9 nm, which were self-assembled by amphiphilic liquid crystalline block copolymers. The average translocation rate of ssDNA strands was effectively reduced to an order of 10 µs per nucleotide, which was 1-2 orders slower than that attained by utilizing conventional solid-state nanopore devices.

Engineered Asymmetric Composite Membranes with Rectifying Properties.

Asymmetric composite membranes with rectifying properties are developed by grafting pH-stimulus-responsive materials onto the top layer of the composite structure, which is prepared by two novel block copolymers using a phase-separation technique. This engineered asymmetric composite membrane shows potential applications in sensors, filtration, and nanofluidic devices.

Linear assembly of a porphyrin-C60 complex confined in vertical nanocylinders of amphiphilic block copolymer films.

Linear assemblies of a 1 : 1 porphyrin-fullerene C60 complex were formed in vertical cylindrical polyether nanodomains of amphiphilic block copolymer films by a simple spin coating-annealing method. The nanocylinder structures were retained even with high contents of the complex in the polymer films.

Solvent induced formation of an ordered nanorod array of gold/polymer composite by block copolymer film templating.

We report a novel method to fabricate ordered arrays of gold-polymer composite nanorods with the orientation in the vertical direction using block copolymer (BCP) film. The salt precursor is selectively infiltrated within vertically aligned cylindrical domains of the BCP film by immersing the template in a simple aqueous solution of HAuCl(4). Scanning electron microscopy suggests that the salt might be uniformly positioned along the polymeric cylinders. A subsequent vacuum ultraviolet light irradiation simultaneously reduces the HAuCl(4) into spherical gold nanoparticles with mean diameter around 2 nm and removes the matrix of the BCP template to produce metal-polymer composite nanorods. While the solvent is methanol, the salt might be concentrated at the bottom of the BCP film. As a result, a periodic pattern of gold nanoparticles with average diameter around 11 nm is formed where the BCP film is completely etched away. The solvent can effectively tune the spatial distribution of the salt precursor along the polymeric cylinders, which is responsible for the different morphologies of the photochemically fabricated nanostructures.