Browsing by Author "Rainbolt, Elizabeth A."
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Item Benzodithiophene Homopolymers Synthesized by Grignard Metathesis (GRIM) and Stille Coupling Polymerizations(Royal Soc Chemistry, 2014-04-16) Magurudeniya, Harsha D.; Kularatne, Ruvini S.; Rainbolt, Elizabeth A.; Bhatt, Mahesh P.; Murphy, John W.; Sheina, Elena E.; Gnade, Bruce E.; Biewer, Michael C.; Stefan, Mihaela C.; 0000 0003 8371 1336 (Gnade, BE); 00049719 (Gnade, BE); 55039821 (Stefan, MC); Gnade, Bruce E.; Biewer, Michael C.; Stefan, Mihaela C.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-C-71-butyric acid methyl ester (PC71BM) as the acceptor.Item Fine-tuning Thermoresponsive Functional Poly(ε-caprolactone)s to Enhance Micelle Stability and Drug Loading(Royal Society of Chemistry, 2015-01-16) Rainbolt, Elizabeth A.; Miller, J. B.; Washington, Katherine E.; Senevirathne, Suchithra A.; Biewer, Michael C.; Siegwart, D. J.; Stefan, Mihaela C.; 55039821 (Stefan, MC); Biewer, Michael C.; Stefan, Mihaela C.Block copolymers synthesized by the ring-opening polymerization of γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone (ME₃CL), γ-2-methoxyethoxy-ε-caprolactone (ME₁CL), and ε-caprolactone (CL) are reported. Previously, diblock copolymers of PME₃CL-b-PME₁CL displayed excellent thermoresponsive tunability (31-43 ⁰C) and self-assembled into micelles with moderate thermodynamic stability. In this report, two strategies are employed to enhance thermodynamic stability of PME₃CL/PME₁CL-type block copolymer micelles while maintaining their attractive thermoresponsive qualities: modification of the end group position and alteration of hydrophobic block composition by using both ME₁CL and CL. These new thermoresponsive amphiphilic block copolymers showed lower critical micelle concentration (CMC) values by one order of magnitude and formed thermodynamically stable micelles. Furthermore they demonstrated good biocompatibility and up to 4.97 wt% doxorubicin loading, more than double the amount loaded into the PME₃CL-type polymeric micelles previously reported.Item Nitrogen Containing Graphene-Like Structures from Pyrolysis of Pyrimidine Polymers for Polymer/graphene Hybrid Field Effect Transistors(Royal Soc Chemistry, 2014-09-02) Gunathilake, Samodha S.; Huang, Peishen; Bhatt, Mahesh P.; Rainbolt, Elizabeth A.; Stefan, Mihaela C.; Biewer, Michael C.; 55039821 (Stefan, MC); Stefan, Mihaela C.; Biewer, Michael C.Nitrogen containing graphene like structures were obtained by the pyrolysis of two pyrimidine polymers at 600 degrees 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.Item 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(Royal Soc Chemistry, 2014-08-06) Bhatt, Mahesh P.; Du, Jia; Rainbolt, Elizabeth A.; Pathiranage, Taniya M. S. K.; Huang, Peishen; Reuther, James F.; Novak, Bruce M.; Biewer, Michael C.; Stefan, Mihaela C.; 0000 0000 8413 1147 (Novak, BM); 98037603 (Novak, BM); 55039821 (Stefan, MC); Novak, Bruce M.; Biewer, Michael C.; Stefan, Mihaela C.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.Item Synthesis and Characterization of a Polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) Triblock Copolymer(2012-12-06) Nguyen, Hien Q.; Bhatt, Mahesh P.; Rainbolt, Elizabeth A.; Stefan, Mihaela C.; Stefan, Mihaela C.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.Item Synthesis and characterization of novel semiconducting polymers containing pyrimidine(Royal Soc Chemistry, 2013-02-27) Gunathilake, Samodha S.; Magurudeniya, Harsha D.; Huang, Peishen; Nguyen, Hien; Rainbolt, Elizabeth A.; Stefan, Mihaela C.; Biewer, Michael C.; 55039821 (Stefan, MC); Stefan, Mihaela C.; Biewer, Michael C.The acidic methyl protons of 4,6-dimethylpyrimidines can be easily deprotonated with a base to generate a resonance stabilized carbanion which can be used as a substrate for aldol condensation reactions. A series of novel conjugated polymers were synthesized by the aldol condensation reaction of 2-decyloxy-4,6-dimethylpyrimidine with various aromatic dialdehydes.