Mahesh P. Bhatt

Grignard metathesis (GRIM) polymerization for the synthesis of conjugated block copolymers containing regioregular poly(3-hexylthiophene)

The synthesis of various conjugated block copolymers of regioregular poly(3-hexylthiophene) by Grignard metathesis (GRIM) polymerization is described.

Electronic Properties-Morphology Correlation of a Rod–Rod Semiconducting Liquid Crystalline Block Copolymer Containing Poly(3-hexylthiophene)

The influence of the solvent and annealing temperature on the field-effect mobilities and morphologies of poly(3-hexylthiophene)-b-poly(γ-benzyl-L-glutamate) (P3HT-b-PBLG) rod-rod diblock copolymer has been investigated. Thin film X-ray diffraction studies show peaks originating from both P3HT and PBLG indicating that the crystalline nature of both the blocks is conserved after the formation of the block copolymer. It has been observed that the field-effect mobilities of the diblock copolymer are independent of the annealing temperatures for thin films deposited from both 1,2,4-trichlorobenzene and chloroform solvents. The correlation between the field-effect mobility and morphology indicates that the P3HT block self-assembles at the surface SiO(2) dielectric.

A semiconducting liquid crystalline block copolymer containing regioregular poly(3-hexylthiophene) and nematic poly(n-hexyl isocyanate) and its application in bulk heterojunction solar cells

A liquid crystalline diblock copolymer containing regioregular poly(3-hexylthiophene) (P3HT) and poly(n-hexyl isocyanate) (PHIC) was synthesized by the combination of Grignard metathesis polymerization (GRIM) and titanium mediated coordination polymerization methods. The poly(3-hexylthiophene)-b-poly(n-hexyl isocyanate) (P3HT-b-PHIC) diblock copolymer used in this study contained ∼10 mol% of P3HT and ∼90 mol% of PHIC. The diblock copolymer displayed solvatochromism in THF–water and THF–methanol mixtures. The field-effect mobilities of the synthesized block copolymer were measured in bottom gate-bottom contact organic field-effect transistors (OFETs). The surface morphology of the polymer thin film was investigated in the channel region of the OFET devices by tapping mode atomic force microscopy (TMAFM). The diblock copolymer displayed nanostructured morphology in thin film and had good mobility despite the low content of the semiconducting P3HT block. The diblock copolymer was also used as an additive to improve the performance of P3HT/PCBM bulk heterojunction (BHJ) solar cells. Liquid crystalline characteristics of the diblock copolymer were examined by cross-polarizing microscopy and X-ray diffraction.

Benzodithiophene homopolymers synthesized by Grignard metathesis (GRIM) and Stille coupling polymerizations

Poly{4,8-bis(95-dodecylthiophene-2-yl)benzo[1,2-b:4,5-b′]dithiophene} has been synthesized by both Grignard metathesis (P1) and Stille coupling polymerizations (P2). Polymers P1 and P2 were characterized and their optoelectronic properties, charge carrier mobilities, and photovoltaic properties were compared. The field-effect mobilities of the polymers were measured on both untreated and heptadecafluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane (FS) treated organic field effect transistor (OFET) devices. The polymers were also evaluated in bulk heterojunction (BHJ) solar cells with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor.

Synthesis and characterization of a polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) triblock copolymer

A polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) triblock copolymer was synthesized by anionic coupling of living polyisoprene-b-polystyryl lithium with allyl-terminated poly(3-hexylthiophene). The triblock copolymer retained the opto-electronic properties and morphology found in the poly(3-hexylthiophene) homopolymer despite the insulating polyisoprene and polystyrene blocks, making it potentially useful as an elastomeric semiconducting material.

Nitrogen containing graphene-like structures from pyrolysis of pyrimidine polymers for polymer/graphene hybrid field effect transistors

Nitrogen containing graphene like structures were obtained by the pyrolysis of two pyrimidine polymers at 600 °C. Pyrimidine polymers were prepared by the base catalyzed aldol condensation reactions between 2-decyloxy-4,6-dimethylpyrimidine and two aromatic dialdehydes. Pyrolyzed products were shown to have a graphitic structure by Raman spectroscopy, scanning electron microscopy, and powder X-ray diffraction studies. The presence of nitrogen in the graphitic structures was proved by elemental analysis and energy dispersive X-ray analysis experiments. Fluorescence quenching experiments with poly(3-hexylthiophene) (P3HT) showed that the resultant graphitic material can act as an acceptor. These materials were tested in P3HT/graphene hybrid field effect transistors which exhibited higher mobilities and comparable on/off ratios compared to P3HT only devices.