Influence of the Coil Block on the Properties of Rod−Coil Diblock Copolymers with Oligofluorene as the Rigid Segment

Rational Construction of Protein-Mimetic Nano-Switch Systems Based on Secondary Structure Transitions of Synthetic Polypeptides

The manipulation of the flexibility/rigidity of polymeric chains to control their function is commonly observed in natural macromolecules but largely unexplored in synthetic systems. Herein, we construct a series of protein-mimetic nano-switches consisting of a gold nanoparticle (GNP) core, a synthetic polypeptide linker, and an optically functional molecule (OFM), whose biological function can be dynamically regulated by the flexibility of the polypeptide linker. At the dormant state, the polypeptide adopts a flexible, random-coiled conformation, bringing GNP and OFM in close proximity that leads to the "turn-off" of the OFM. Once treated with alkaline phosphatase (ALP), the nano-switches are activated due to the increased separation distance between GNP and OFM driven by the coil-to-helix and flexible-to-rigid transition of the polypeptide linker. The nano-switches therefore enable selective fluorescence imaging or photodynamic therapy in response to ALP overproduced by tumor cells. The control over polymer flexibility represents an effective strategy to manipulate the optical activity of nano-switches, which mimics the delicate structure-property relationship of natural proteins.

Synthesis, optical properties and photovoltaic applications of hybrid rod–coil diblock copolymers with coordinatively attached CdSe nanocrystals

Hybrid rod–coil diblock copolymers containing coordinatively binded CdSe nanocrystals in the coil block give better solar cell performance over their corresponding diblock copolymers without CdSe attachment.

Fluorene-based macromolecular nanostructures and nanomaterials for organic (opto)electronics

Nanotechnology not only opens up the realm of nanoelectronics and nanophotonics, but also upgrades organic thin-film electronics and optoelectronics. In this review, we introduce polymer semiconductors and plastic electronics briefly, followed by various top-down and bottom-up nano approaches to organic electronics. Subsequently, we highlight the progress in polyfluorene-based nanoparticles and nanowires (nanofibres), their tunable optoelectronic properties as well as their applications in polymer light-emitting devices, solar cells, field-effect transistors, photodetectors, lasers, optical waveguides and others. Finally, an outlook is given with regard to four-element complex devices via organic nanotechnology and molecular manufacturing that will spread to areas such as organic mechatronics in the framework of robotic-directed science and technology.

Brownian molecular dynamics simulation on self-assembly behavior of diblock copolymers: influence of chain conformation

Brownian molecular dynamic simulations are applied on the self-assembly behavior of AB-type diblock copolymers. The influence of chain conformation of core-forming A-block changing from rigid to flexible on the aggregation structure formed by AB copolymers is investigated. It is found that at a high rigid fraction f(R) of A-block, a disk structure can be formed at a high aggregation interaction epsilon(AA) of A-bead pairs because of the tendency of orientational packing of rigid portion within the aggregate core. Transitions of aggregation structure from disk to string, further to small aggregates, and to unimers are observed with decreasing epsilon(AA). The packing of A-blocks becomes more random at relatively lower values of f(R), resulting in the formation of spherical structure. The region of string becomes narrower while the regions of the small aggregates and sphere become wider as decreasing f(R). Meanwhile, the onsets of string, disk, and sphere formation move to higher epsilon(AA). The phase diagrams for the influences of rigid potion location within the A-block and the chain rigidity of the A-block are mapped. The comparison of simulation results with existing experimental observations is also presented. Our simulation results tend to bridge a gap of different micellization behaviors between rod-coil block copolymers and coil-coil block copolymers and extend to investigate chain conformation influence on phase diagram.

Isotropic-nematic phase transition in athermal solutions of rod-coil diblock copolymers

We present a hybrid method to investigate the isotropic-nematic (I-N) transition in athermal solutions of rod-coil copolymers. This method incorporates the scaled-particle theory for semiflexible chains with two-chain Monte Carlo simulation for the osmotic second virial coefficient and for the angle-dependent excluded volume. We compare the theoretical prediction with Monte Carlo simulations for fused rod-coil copolymers and find good agreement for both the equation of state and the orientational order parameter. The theory is also used to examine the effects of the bond length, the chain length, and the chain composition on orientational ordering in athermal solutions of rod-coil block copolymers. It predicts I-N transition in rod-coil copolymers with fixed rod length but a variable flexible tail in good agreement with experiments.

Thermally Stable Blue Emitting Terfluorene Block Copolymers

Spectroscopic and morphological studies on a series of rod-coil block copolymers containing terfluorene segments as the rigid blocks and polystyrene as the flexible parts demonstrate an increase in the photoluminescence intensity and the exciton lifetime as well as formation of isolated spheres as thin films upon thermal annealing in air (200 degrees C for 30 min). Moreover, no appearance of the low energy emission band centered at 520 nm was found after the same thermal treatment which permits these copolymers to emit pure blue light.

Morphological study of the organization behavior of rod-coil copolymers and their blends in thin solid films

A detailed study of the self-assembly ability of triblock coil-rod-coil copolymers containing a rigid di(styryl)-anthracene segment covalently linked to oxadiazole-based blocks and their binary blends with oxadiazole-based homopolymers is presented here. The self-organized microdomains seem to pack into a fascinating ordered hexagonal structure obtained at a critical concentration without any significant influence of the sample preparation method, based on evidence obtained by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence microscopy studies. The compatibilization efficiency of these coil-rod-coil copolymers in polymer blends composed of an electron-accepting polyoxadiazole and a luminescent polyanthracene-based pair was studied by atomic force microscopy (AFM). The common feature of all observed morphologies is the compatibilizing function of the rod-coil molecule, which intercalates between the incompatible domains to prevent the formation of well-defined phase separated nanostructured surfaces.