@article { ISI:000283759400011, title = {Polyethersulfone-expanded graphite nanocomposites: charge transport and impedance characteristics}, journal = {Composites Science and Technology}, volume = {70}, number = {14}, year = {2010}, month = {NOV0}, pages = {2111-2116}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Polyethersulfone (PES)-expanded graphite nanocomposites have been prepared by solution blending route after sonicating expanded graphite in dichloromethane. It has been observed that ultrasonication results in nanosheets formation leading to a low percolation threshold of 3 wt.\%. At 5 wt.\% filler loading the conductivity is of the order of 10(-2) S/cm. Hopping type of charge transport occurs at 3.2 wt.\% expanded graphite in PES below which capacitive effects couple. The effective dielectric constant at low frequency increases with filler concentration. Impedance measurement has been carried out to evaluate interfacial capacitance which, for 3.2 wt.\% expanded graphite addition in PES, increases to 110 pF from 32 pF for 1 wt.\% expanded graphite in the polymer. DSC analysis shows an increment of 12 C in the T(g) of PES with 3 wt.\% expanded graphite suggesting interaction between the polymer and filler. (C) 2010 Elsevier Ltd. All rights reserved.

}, keywords = {Differential scanning calorimetry (DSC), Electrical properties, Modeling, Polymers, Scanning/transmission electron microscopy (STEM)}, issn = {0266-3538}, doi = {10.1016/j.compscitech.2010.08.008}, author = {Ramanujam, B. T. S. and Mahale, Rajashree Y. and Radhakrishnan, S.} } @article { ISI:000301235200031, title = {Band edge modulated conjugated polymers for oxidation prevention}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, number = {13}, year = {2012}, month = {FEB}, pages = {4577-4583}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The impact of electron transfer (ET) from a series of band edge modulated polymers to atmospheric oxygen is examined in connection with substrate oxidation prevention. Polymers with the highest occupied molecular orbital (HOMO) energy level below and above the oxygen energy level were tested and the former showed better efficiency. Furthermore, the oxidation prevention efficiency of a polymer with lower HOMO increased by two orders of magnitude, when the pores on the film were filled with spherical molecules, [6,6]-phenyl-C61-butyric acid methyl ester. We found that the polymer surface hydrophobicity has little or no influence on oxidation prevention. It is interesting to note that a polymer with a hole mobility of 8 x 10(-10) cm(2) V-1 s(-1) showed a two-fold increase in oxidation prevention efficiency compared to a polymer with a hole mobility of 6 x 10(-5) cm(2) V-1 s(-1). Over all, from the concerted approach, we conclude that a polymer devoid of pores with the HOMO energy level below oxygen and low charge carrier mobility is a suitable candidate for prevention of substrate oxidation/corrosion.

}, issn = {1463-9076}, doi = {10.1039/c2cp23544g}, author = {Mahale, Rajashree Y. and Arulkashmir, Arulraj and Dutta, Kingshuk and Krishnamoorthy, Kothandam} } @article {43314, title = {Reversible assembly and disassembly of micelles by a polymer that switches betweenhydrophilic and hydrophobic wettings}, journal = {Langmuir}, volume = {28}, year = {2012}, month = {JUN}, pages = {10097-10104}, abstract = {Supramolecular complexes involving nanoscopic amphiphilic assemblies (AAs) and polyelectrolytes have been used to prepare a variety of materials, wherein the dynamic AAs retain the structural features, but the polyelectrolytes undergo conformational changes. Here we show that a charge bearing rigid conjugated polymer can alter the structural features and disassemble AAs. We also demonstrate reversible assembly and disassembly of AAs by controlling the number of charges on the rigid polymer. During the disassembly, the guest molecules sequestered in the AAs are released. The rate of release has been modulated by changing the morphology of the charge bearing polymer. Concomitant to the AAs disassembly, the polymer surface becomes hydrophobic due to the binding of the amphiphiles on the charges of the polymer backbone. By controlling the charges on the polymer, the surface wettability was varied gradually from hydrophilic to hydrophobic.}, doi = {10.1021/la301760a}, author = {Dutta, Kingshuk and Mahale, Rajashree Y. and Arulkashmir, Arulraj and Krishnamoorthy, Kothandam} } @article {43315, title = {Supramolecular interaction facilitated small molecule films for organic field effect transistors}, journal = {Polymer Chemistry}, volume = {3}, year = {2012}, month = {APR}, pages = {1641-1646}, abstract = {Metalloporphyrins and metal free porphyrins have been explored as active materials in field effect transistors. Amorphous forms of these porphyrins are preferred over their crystalline analogue due to the ease of solution processability. To achieve solution processability, a metalloporphyrin was anchored on a vinyl polymer by taking advantage of the supramolecular interaction between the metal and the pyridine moiety of the polymer. Non covalent bonding was preferred because it provides an opportunity to better manipulate the polymer{\textquoteright}s properties compared to its covalent bonding analogue. The binding between the porphyrin and the polymer was optimised in solution and the supramolecular complex was spun on various substrates to form thin films. The porphyrin was found to be uniformly distributed throughout the polymer films contrary to the existing approaches, wherein small molecule phase segregates in the polymer film. Field effect transistors were fabricated using the porphyrin-polymer complex and the device parameters were measured at atmospheric condition. The devices annealed at 80 degrees C showed hole carrier mobility of 2.0 x 10(-4) cm(2) V-1 s(-1) with charge trapping at the dielectric semiconductor interface. Furthermore, the high carrier mobility observed at low temperature annealing makes this supramolecular complex an attractive candidate to explore in flexible substrates.}, doi = {10.1039/c2py20146a}, author = {Arulkashmir, Arulraj and Mahale, Rajashree Y. and Dharmapurikar, Satej S. and Jangid, Manoj K. and Krishnamoorthy, Kothandam} } @article {43593, title = {Effect of heterocycles on field-effect transistor performances of donor-acceptor-donor type small molecules}, journal = {Chemical Physics Letters}, volume = {661}, year = {2016}, month = {SEP}, pages = {107-113}, abstract = {Two D-A-D small molecules comprising triphenylamine and diketopyrrolopyrrole were synthesized having either furan or thiophene connected to the fused lactam ring. In this design, furan/thiophene diketopyrrolopyrrole acts as an acceptor and triphenylamine acts as a donor. Propeller shaped triphenylamine has its effect on packing, processability and plays a vital role in determining the pi-pi molecular orbital stacking in such compounds and thus the mobility of charge carriers. With TDPPT and FDPPT, maximum hole carrier mobility obtained is 2.88 x 10(-3) cm(2) V-1 s(-1) and 1.60 x 10(-3) cm(2) V-1 s(-1), respectively using bottom gate bottom contact field-effect transistor. (C) 2016 Elsevier B.V. All rights reserved.}, doi = {10.1016/j.cplett.2016.08.073}, author = {Chini, Mrinmoy Kumar and Mahale, Rajashree Y. and Chatterjee, Shyambo} } @article {43651, title = {Influence of thermocleavable functionality on organic field-effect transistor performance of small molecules}, journal = {Chemical Physics Letters}, volume = {678}, year = {2017}, month = {JUN}, pages = {139-145}, abstract = {Diketopyrrolopyrrole based donor-acceptor-donor conjugated small molecules using ethylene dioxythiophene as a donor was synthesized. Electron deficient diketopyrrolopyrrole unit was substituted with thermocleavable (tert-butyl acetate) side chains. The thermal treatment of the molecules at 160 degrees C eliminated the tert-butyl ester group results in the formation of corresponding acid. Optical and theoretical studies revealed that the molecules adopted a change in molecular arrangement after thermolysis. The conjugated small molecules possessed p-channel charge transport characteristics in organic field effect transistors. The charge carrier mobility was increased after thermolysis of tert-butyl ester group to 5.07 x 10(-5) cm(2)/Vs. (C) 2017 Elsevier B.V. All rights reserved.}, doi = {10.1016/j.cplett.2017.04.041}, author = {Mahale, Rajashree Y. and Dharmapurikar, Satej S. and Chini, Mrinmoy Kumar and Venugopalan, Vijay} } @article {43788, title = {Synthesis of amphiphilic isoindigo co-polymers for organic field effect transistors: A comparative study}, journal = {Journal of the apllied polymer science}, volume = {134}, year = {2017}, month = {NOV}, chapter = {45461}, abstract = {

In this work, the amphiphilic isoindigo (am-iInd) based conjugated polymers namely poly(am-iInd-DT) and poly(am-iInd-TT) and their regular counterpart poly(reg-iInd-DT) and poly(reg-iInd-TT) were synthesized to compare their opto-electronic and charge transport properties. They were used to fabricate organic field effect transistors. Charge transport properties in conjugated polymers depend upon intermolecular interaction which is strongly affected by the nature of side chains. The amphiphilic nature of the conjugated polymers has little impact on the charge transport properties. The charge carrier mobility of amphiphilic conjugated polymers was comparable with the regular polymers except poly(reg-iInd-DT) which can be correlated by X-ray diffraction and thin film morphology. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45461.

}, keywords = {Alkyl, Applications; Conducting polymers; Copolymers; Optical and Photovoltaic applications, conjugated polymers, High-performance, mobility, Packaging, Semicondoctors, Side-chains, Solar-cells, Thin-film Transformer}, issn = {0021-8995}, doi = {10.1002/app.45461}, author = {Dharmapurikar, Satej S. and Arulkashmir, Arulraj and Mahale, Rajashree Y. and Chini, Mrinmoy Kumar} } @article {44429, title = {Chemical oxidative and solid state synthesis of low molecular weight polymers for organic field effect transistors}, journal = {Chemical Physics Letters}, volume = {696}, year = {2018}, month = {MAR}, pages = {48-54}, abstract = {Solution processability of the precursor molecules is a major issue owing to their limited solubility for the synthesis of conjugated polymers. Therefore, we favour the solvent free solid state chemical oxidative polymerization route for the synthesis of diketopyrrolopyrrole (DPP) based donor-acceptor (D-A) type conjugated polymers. D-A type polymer Poly(S-OD-EDOT) which contains DPP coupled with EDOT donor units is synthesized via solid state polymerization method. The polymer is employed as an active layer for organic field-effect transistors to measure charge transport properties. The Polymer shows good hole mobility 3.1 x 10(-2) cm(2) V-1 s(-1), with a on/off ratio of 1.1 x 10(3). (C) 2018 Elsevier B.V. All rights reserved.}, doi = {10.1016/j.cplett.2018.02.021}, author = {Mahale, Rajashree Y. and Dharmapurikar, Satej S. and Chini, Mrinmoy Kumar} } @article {48087, title = {Instabilities as the origin of large-area self-assembled and aligned organic semiconductor nanocrystals}, journal = {ACS Applied Electronic Materials}, volume = {4}, year = {2022}, month = {APR}, pages = {1815-1822}, type = {Article}, abstract = {

Aligned nanocrystals of organic semiconductors (OSCs) are highly desirable for electronic devices and biomedical and photonic applications. Solution-based wet processing routes have the potential to produce aligned nanocrystals over large areas in small time frames. Herein, we demonstrate that by optimizing the hydrodynamic evaporative processes, controlled long-range crystalline assemblies of OSCs can be achieved (longest nanocrystal similar to 3 mm) purely through physical processes: namely, from fingering instabilities. Self-assembly is achieved here without strong noncovalent interactions such as hydrogen-bonding interactions. Experimentally our approach involves just placing a drop of a solution on an inclined substrate. Nanocrystals with widths of 300-800 nm and lengths of millimeters (length/width aspect ratios \>10(5)) are formed in less than 2-8 s. A hydrazine chemiresistive sensor based on the aligned crystalline patterns show unprecedented responsivity (similar to 10(-6)), 2 orders greater than those of stick-slip patterns. Finally, experimental parameters that need optimization to achieve nanocrystal patterns are investigated in detail and pointers to fabricate such OSC nanocrystals are provided.

}, keywords = {aligned fibers, diketopyrrolopyrrole, fingering instability, nanocrystal arrays, naphthalenediimide, organic semiconductors}, doi = {10.1021/acsaelm.2c00061}, author = {Venugopalan, Vijay and Jain, Bhanprakash and Mahale, Rajashree Y. and Subramani, Kumar and Krishnamoorthy, Kothandam} }