Ananda M. Sarker
University of Massachusetts Amherst
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Featured researches published by Ananda M. Sarker.
Polymer | 1994
Paul M. Lahti; Ananda M. Sarker; Raul O. Garay; Robert W. Lenz; Frank E. Karasz
Abstract The base-induced polymerization of 1,4-bis(tetrahydrothiopheniomethyl)-2-cyano-5-methoxybenzene dibromide in aqueous acetonitrile yields a soluble polyelectrolyte which may be thermally eliminated to give the electronically ‘push-pull’ substituted poly(2-cyano-5-methoxy-1,4-phenylene vinylene). Ultraviolet-visible and infra-red spectral studies showed production of the conjugated polymer, with a band gap of ca. 2.6–3.0eV (410–480 nm) that varied somewhat as a function of elimination conditions. Elemental analysis indicates some retention of tetrahydrothiophenium side groups in the polyelectrolyte polymer, despite the use of a variety of elimination conditions. The retention of side chains in this synthesis is possibly due to a significant degree of irregularity in the positions of the cyano and methoxy substitutents in the eliminated polymer, resulting from non-regioselectivity in this polymerization. This reaction demonstrates the potential in the Wessling process for polymerization of p-xylylenes that have electronically very asymmetric (‘push-pull’) substitution patterns.
Synthetic Metals | 2003
Ananda M. Sarker; E.Elif Gürel; Liming Ding; Eric Styche; Paul M. Lahti; Frank E. Karasz
Abstract Poly(para-phenylenevinylene-alt-3-tert-butyl-meta-phenylenevinylene) was synthesized by Wittig condensation with varying ratio of cis and trans olefin bonds. The luminescent properties of the unisomerized and trans-isomerized polymers (1 and 2, respectively) were compared. Nearly identical emission spectra were observed for both polymers in dilute solutions, but the emission intensity of 1 is lower. This is attributed to the cis vinylic moieties in 1, which favor nonradiative excited state decay processes by limiting formation of a planar excited state. Double layer LEDs with the configuration ITO/PPV/(1 or 2)/Ca–Al were fabricated. Substantially better efficiencies and luminances were observed for devices made with polymer 2 as the emissive layer, by comparison to 1. The results show that the elimination of cis olefin defects in these polymers is important for the optimization of LEDs.
ChemPhysChem | 2003
Bernd Strehmel; Ananda M. Sarker; Heiner Detert
Journal of the American Chemical Society | 1999
Bernd Strehmel; Ananda M. Sarker; John H. Malpert; Veronika Strehmel; Holger Seifert; Douglas C. Neckers
Macromolecules | 1997
Ronald M. Gurge; Ananda M. Sarker; Paul M. Lahti; Bin Hu; Frank E. Karasz
Macromolecules | 2000
Min Zheng; Ananda M. Sarker; E. Elif Gürel; Paul M. Lahti; Frank E. Karasz
Macromolecules | 1996
Ronald M. Gurge; Ananda M. Sarker; Paul M. Lahti; and Bin Hu; Frank E. Karasz
Macromolecules | 1999
Ananda M. Sarker; Bernd Strehmel; Douglas C. Neckers
Journal of Polymer Science Part A | 1992
Frank R. Denton; Ananda M. Sarker; Paul M. Lahti; Raul O. Garay; Frank E. Karasz
Macromolecules | 1999
Ananda M. Sarker; Ken Sawabe; Bernd Strehmel; and Yuji Kaneko; Douglas C. Neckers