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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.

Here, we have demonstrated a straight forward and easy synthetic route for preparation of three dimensional hierarchical and porous polyaniline (PANI)/manganese dioxide (MnO2)/reduced graphene oxide (rGO) ternary hybrid nanomaterials with surface decorated by ordered PANI whiskers. The nanostructured material shows different well defined morphology like tubular fiber, sphere which resembles natural tubular wiregrass sedge and spherical cactus. The simple removal of graphene surface modifier through selective dissolution from nanohybrids results further porous structure. The ternary hybrid materials show varying capacitance values depending on composition and nanostructured morphology with the best capacitance value of 762 F/g at current density 1.4 A/g with good electrochemical stability.

Here, we have demonstrated a well-defined strategy to prepare highly sulphonated reduced graphene oxide (S-rGO) sheets via non-covalent modification of rGO with water soluble rod-coil conjugated block copolymer poly(3-hexylthiophene)-block-poly (4-styrenesulfonic acid) (P3HT-b-PSSA) carrying a long PSSA block. S-rGO sheets are highly water soluble and its aqueous solution can be used to fabricate highly transparent conductive thin film coating on versatile smooth substrate surfaces like glass, indium tin oxide (ITO), quartz and flexible PET. The successful anchoring of sulfonic acid group on rGO surface via non-covalent modification by P3HT-b-PSSA was confirmed and analyzed by FTIR and XRD study. The bulk morphology of S-rGO reveals sheet like morphology where individual sheets are aligned with each other in a parallel arrangement through intercalation of PSSA chains driven by block copolymer selfassembly. AFM image of the thin film also supports nice parallel alignment of S-rGO sheets of average thickness ∼ 100 nm on substrate surface. S-rGO sample shows very high water uptake (∼ 91% in comparison to its initial weight) and proton conductivity 0.5 S/cm after water vapor exposure for 1 hour. Such high proton conductivity is due to the synergy of alignment of graphene sheets with a continuous network of proton conducting nanochannels created by block copolymer microphase separation on the rGO surface. Nyquist plot with two semicircles suggested the presence of grain boundaries in the sample. IÀ V measurement of transparent thin film device fabricated from S-rGO sheets shows linear behavior with systematic increase of current on increasing water vapor exposure time. The block copolymer device shows well correlated, systematic and reversible resistance change with relative humidity (RH) confirming its efficient sensing capability towards moisture. We believe that high proton conductivity and interesting, reversible moisture sensitive electrical property of this material will be useful in fabricating transparent and flexible moisture sensors, flexible electronics, moisture induced energy storage, fuel cell, biological applications and others.

In this report, the preparation of highly water‐soluble rod–coil conjugated block copolymer poly(3‐hexylthiophene)‐b‐polystyrenesulfonic acid (P3HT‐b‐PSSA) is demonstrated using a facile method with its moisture sensing properties. The block copolymer synthesis method comprises Kumada catalyst transfer polymerization and atom transfer radical polymerization from a bifunctional initiator followed by sulfonation of polystyrene using moderate reaction conditions. The polymerization results in the synthesis of well‐defined block copolymers with controllable block length. The successful synthesis of the block copolymer is studied by NMR and FTIR spectroscopy while optical and structural properties of the block copolymer are investigated using UV–vis, photoluminescence spectroscopy, XRD, and FESEM. In water, the block copolymer shows aggregated structure with crystalline core formed by rod‐like P3HT chain with absorption maxima at 558 nm, whereas in solid state the absorption maxima is blue shifted to 548 nm. The proton conductivity of the block copolymer P3HT‐b‐PSSA with ≈91% of PSSA (by weight) is measured from impedance study, and the values for bulk and grain conductivities are 5.25 × 10−4 and 4.66 × 10−6 S cm−1, respectively, at room temperature. The as‐synthesized block copolymer shows a very high water uptake with maximum ≈80% in comparison with its initial weight. The I–V measurement of the device made from block copolymer shows nonlinear, rectifying characteristic and the current increases with increase of relative humidity (RH%). The block copolymer device shows well‐correlated systemic and reversible resistance change with RH both in doped and undoped state. It is believed that the interesting and highly reversible moisture‐sensitive electronic properties of this block copolymer will be useful for the fabrication of moisture‐sensitive polymer‐based flexible electronic devices.

Here, we have described a simple and straightforward methodology for synthesis of rod–coil conjugated block copolymer poly­(3-hexylthiophene)-block-polystyrene (P3HT-b-PS) of varying molecular weight and low polydispersity by chain extension of either a rod or coil block starting from a single bifunctional initiator through combination of Kumada catalyst transfer polymerization (KCTP) and atom transfer radical polymerization (ATRP). Advantages of the present method include the facile synthesis of the Ni­(II) catalytic initiators from readily available laboratory reagents, avoiding high reactive intermediates for preparing Ni­(ii) catalytic initiator, and the in situ nature of all the steps making large scale preparation of the block copolymer viable. Studies on solvent-induced structure formation and their impact on optical and electronic properties of the block copolymer were systematically performed. The block copolymer device fabricated from toluene shows the best field effect mobility of (2.1 ± 0.75) × 10–3 cm2 V–1 s–1 compared to results for other solvents. Overall, this work describes a facile synthetic strategy for a rod–coil conjugated block copolymer and its solvent-induced structure formation as guidance for fabricating high-performance organic electronic and optoelectronic devices.

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