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Conjugated block copolymers consisting of poly(3hexyl thiophene) (P3HT) and a thermoresponsive polymer poly(N-isopropyl acrylamide) (PNIPAM) with varying composition have been synthesized by facile click reaction between alkyne terminated P3HT and azide terminated PNIPAM. The composition-dependent solubility, thermoresponsive property in water, phase behavior, electrochemical, optical, and electronic properties of the block copolymers were systematically investigated. The block copolymers with higher volume fraction of PNIPAM form thermoresponsive spherical micelles with P3HT-rich crystalline cores and PNIPAM coronas. Both X-ray and atomic force microscopic studies indicated that the blocks copolymers showed well-defined microphase separated nanostructures and the structure depended on the composition of the blocks. The electrochemical study of the block copolymers clearly demonstrated that the extent of charge transport through the block copolymer thin film was similar to P3HT homopolymer without any significant change in the band gap. The block copolymers showed improved or similar charge carrier mobility compared with the pure P3HT depending on the composition of the block copolymer. These P3HT-b-PNIPAM copolymers were interesting for fabrication of optoelectronic devices capable of thermal and moisture sensing as well as for studying the thermoresponsive colloidal structures of semiconductor amphiphilic systems.

This Research Article demonstrates a very simple approach of a moisture-induced power-generating phenomenon using water-soluble rod-coil conjugated block copolymer (poly­(3-hexythiophene)-block-poly­(4-styrenesulfonic acid) (P3HT-b-PSSA)-modified reduced graphene oxide. The block copolymer-modified reduced graphene oxide (BCP-RGO) was prepared by noncovalent surface functionalization cum in situ reduction of graphene oxide. A simple device made from BCP-RGO can generate voltage upon exposure to water vapor or under different humidity conditions. The open-circuit voltage generated from the diode-like device varies with respect to the relative humidity, and the device can act as a self-powered humidity sensor. The as-prepared BCP-RGO is able to produce a maximum power density of 1.15 μW/cm2 (short-circuit current density J SC = 6.40 μA/cm2) at a relative humidity of 94%. Meanwhile, the BCP-RGO device produces a very high power density of 0.7 mW/cm2 (at a short-circuit current density of 1.06 mA/cm2) after 91% water absorption. We believe that the material presented here will be very useful for a self-biased humidity sensor and moisture-induced energy harvesting. The diode-like response of the BCP-RGO device with humidity or after water absorption will make the material applicable for self-biased humidity-controlled electronic switching.

Here, we have discussed the preparation of a highly solution processable graphene from a novel supramolecular assembly consisting of block copolymer polystyrene- b -poly(4-vinylpyridine) (PS- b -P4VP) and pyrenebutyric acid (PBA)-modified reduced graphene oxide (RGO). The PBA molecules anchored on the graphene surface form supramolecules with PS- b -P4VP through H-bonding between the carboxylic acid group of 1-pyrenebutyric acid and the pyridine ring of P4VP. The formation of a supramolecular assembly results in a highly stable solution of reduced graphene oxide in common organic solvents, such as 1,4-dioxane and chloroform. Highly transparent and mechanically stable thin films can be deposited from these supramolecular assemblies on a relatively smooth surface of different substrates such as silicon wafer, glass, indium tin oxide, and flexible polymer substrates like poly(ethylene terephthalate). The graphene surface modifier (PBA) can be selectively removed from the thin film of the hybrid material by simple dissolution, resulting in a porous structure. Hybrid thin films of around 50 nm thickness exhibit interesting electrochemical properties with an areal capacitance value of 17.73 μF/cm 2 at a current density of 2.66 μA/cm 2 and good electrochemical stability. The pendent P4VP chains present in the composite thin film were further exploited for electrochemical detection of metal ions. The electrical measurement of the thin film sandwich structure of the composite shows a bipolar resistive switching memory with hysteresis-like current–voltage characteristics and electrical bistability. The OFF state shows ohmic conduction at a lower voltage and trap-free space-charge-limited current (SCLC) conduction at high voltage, whereas the ON state conduction is controlled by ohmic at low bias voltage, trap-free SCLC at moderate voltage, and tarp-assisted SCLC at high voltage.