Andrew P. Chafin

Synthesis of polyazapolycyclic caged polynitramines

Abstract Syntheses of new polyazapolycyclic caged polynitramines are described. Sequentially reacting 4,10-dibenzyl-2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (5a) with NOBF4 and NO2BF4 in sulfolane solvent produces 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo-[5.5.0.05,9.03,11]dodecane, 6). Syntheses of two new polyazapolycyclic caged trinitramines, 3,5,12-trinitro-3,5,12-triazawurtzitane (7a) and 2,4,10-trinitro-2,4,10-triazaadamantane (12a), as well as their labile parent secondary amines, are discussed. A new caged polynitrosamine, 3,5,12-trinitroso-3,5,12-triazawurtzitane (7d), has been obtained by ring-cleavage nitrosation of the new hexamine-wurtzitane compound 3,5,7,9-tetraazahexacyclo-[9.3.1.13,7.02,9.04,13.05,10]-hexadecane (10).

Synthesis of an Isophorone‐Based Nonlinear Optical Chromophore

Abstract The synthesis of a “CLD‐type” nonlinear optical chromophore incorporating the isophorone unit to rigidize the polyene segment is described. The synthesis required seven steps with an overall yield of 17%.

Poly(thiophenylanilino) and poly(furanylanilino) polymers

Novel hybrid polymers with thiophenylanilino and furanylanilino backbones and substituted phenyl side groups are reported. The new monomers bis-(4-heterocyclic-2-yl-phenyl)-aryl-amine (heterocyclic = thiophen with aryl = 4-benzoyl (2a), 4-nitro-phenyl (2b) and furan with aryl = 4-benzoyl-phenyl (3a), 4-nitro-phenyl (3b)) were prepared by monosubstituting triphenylamine under electrophilic aromatic conditions affording 4-nitrotriphenylamine and 4-benzoyltriphenylamine. Di(bromination) of the latter compounds followed by Stille cross-coupling reactions with 2-tributylstannylthiophene or 2-tributylstannylfuran produces the new monomers 2a–b and 3a–b in high yield. The monomers are electrochemically polymerized at relatively low potentials (<0.8 V versus Ag+/AgCl) in acetonitrile electrolytes resulting in electroactive films. All the new polymers can be repeatedly oxidized and reduced with little loss of electrochemical activity. Vibrational spectroscopy reveals that the monomer units are connected predominately via coupling of the thiophenyl or furanyl rings yielding the novel polymers. Single-crystal molecular structure determinations of 4-nitrotriphenylamine and monomer 3b indicate the importance of the electron-withdrawing groups on the pendent phenyl groups in determining the extent of delocalization of the extended multi-ring systems. Molecular orbital calculations suggest that the HOMO of 2b is delocalized about both anilino and thiophenyl portions of the molecule.

High-performance electro-optic polymers for high-frequency modulators

New thermally stable, spin-castable, electro-optic (EO) polymers designed for high frequency optical modulators are reported (the third generation accordion polymers). The softening temperature (the glass transition temperature) is about 240 degrees Celsius, and the upper limit on short term thermal baking stability is about 320 degrees Celsius. The refractive index at 1.3 microns is about 1.73 and fairly birefringent. The second-order nonlinear optic coefficient, d33, of a second generation accordion polymer containing essentially the same chromophore, measured by second- harmonic generation at 1.06 microns, is 120 pm/V (resonance enhanced by the 495 nm absorption). Measurement of the electro-optic coefficient, r33, is in progress. The added thermal stability in these polymers is due to the all- aryl amine electron donor. The molecular topology of the polymer backbone makes it possible for over 85 weight percent of the bulk material to be comprised of EO-active chromophore. The chromophores are configured in a head-to- head mainchain topology. The films are completely amorphous (no microcrystalline scattering sites).

Second harmonic generation from new dyes in polymer films

One might say this paper is about something old, something new, something borrowed, something blue -- finding chromophoric brides to be wed to polymeric husbands. Several dyes have been synthesized that are red, magenta, or blue in color and have large ground-state dipole moments. Dyes synthesized in our laboratory were characterized by differential scanning calorimetry and UV-VIS spectroscopy. First molecular hyperpolarizabilities ((beta) o) of the dyes were calculated using MOPAC (V6). Some of the dyes were dissolved in poly(methyl methacrylate), corona poled above the glass transition temperature, and cooled to room temperature to freeze in the polar order. Second-order nonlinear optical properties of these guest-host films were compared by optical frequency doubling measurements.

Ionic Liquids in Charge Storage Devices: Effect of Purification on Performance

Ionic liquids have been the subject of study over the past several years and there are quite a few advantages to their use in charge storage devices such as extremely low volatility, high voltage window, and inherently high concentration of cations and anions for charge transport processes1-8. Several ionic liquids are also commercially available. Purity of ionic liquids has been the subject of several publications9-11. The impurities (chloride or water for example) discussed in these publications have a profound effect on the physical properties of the ionic liquids. There is a continuing discussion about the effect of ionic liquid purification on the electrochemical performance of electroactive charge storage devices. In this chapter we examine the effect of column chromatography purification of ethyl methyl imidazolium bis(trifluoromethanesulfonylimide), (EMIBTI) (synthesized by our laboratory on the 100 gram scale) on the performance of a Type I electroactive polymer supercapacitor based upon poly(propylene dioxythiophene) (PProDOT). The EMIBTI was purified on a 100-gram scale preparatory column using 20% acetonitrile and 80% chloroform as the eluting solvent. A detailed analysis was performed on the ionic liquid and impurities such as water, lithium chloride, imidazolium, and other elements and compounds. Best efforts were made to quantify the amounts of these impurities. An attempt was made to correlate the presence or absence of an impurity with electrochemical growth and performance of the Type I electroactive supercapacitor.

Synthesis and characterization of chiral conjugated polymers for optical waveguides

In the pursuit of new photonic devices, the unique waveguide properties of chiral films made from single-handed helical molecules are under investigation. The synthesis of polymers with a hierarchical structure is the first step. In this paper we present results on the synthesis and characterization of poly(p-phenylenes) (PPPs) and polythiophenes possessing amine and amide chiral side-chains. A regioirregular PPP possessing one chiral side group per repeat unit was prepared. Regioregular PPPs possessing two chiral side groups per repeat unit were also synthesized; however, lower molecular weights were achieved due to steric constraints. The PPPs exhibited total optical rotation that was a function of the concentration of the chiral side group, with 35- per chiral group or 70- per repeat unit. A regioirregular polythiophene was prepared using oxidative polymerization. A molecular structure that leads to helical polymer chains that undergo supramolecular packing in spin-cast films is the goal.

Alternating polyanion/polycation second-order nonlinear optical films by aqueous solution deposition

Alternating polyelectrolyte deposition (APD) in aqueous solutions may be used to process nonlinear optical polymers (NLOPs) into noncentrosymmetric ordered films at ambient temperature. Second-order NLOP films were prepared by alternately dipping a substrate into aqueous solutions of a polycation and a polyanion. Polyepichlorohydrin substituted with stilbazolium side-chain chromophore was used as the cationic NLOP. The inactive polyanion was polystyrene sulfonate. Uniform layer to layer deposition is observed as evidenced by a linear increase of UV-Visible absorbance and quadratic increase of second harmonic generated light intensity as a function of film thickness. Films have been uniformly deposited up to 24 bilayers. Films have been further characterized by contact angle measurements, interferometry, and polarized light microscopy. Work is in progress to deposit thicker films of the same quality and to quantify NLO figures of merit.

Accordion polymers for nonlinear optical applications

Abstract The design and synthesis of mainchain chromophore polymers in a syndioregic (head-to-head) configuration is described. Polymers were designed for both electric-field poling and Langmuir-Blodgett-Kuhn (LBK) deposition. LBK deposition gives intrinsically polar films (no E-field poling) as evidenced by nonlinear optical (χ (2) ) properties.

Synthesis and Characterization of bis(Tetrahydrofurfuryl) Ether

Abstract Despite the availability of a large number of alkyl tetrahydrofurfuryl ethers that have a wide range of applications, pure bis(tetrahydrofurfuryl) ether (BTHFE) has not been previously synthesized. Here, we report the synthesis of BTHFE (consisting of the RR, SS, and meso stereoisomers) at greater than 99 % purity from tetrahydrofurfuryl alcohol, using (tetrahydrofuran‐2‐yl)methyl methanesulfonate as an intermediate. Additionally, we demonstrate that BTHFE can be used as a non‐volatile solvent in poly(3,4‐propylenedioxythiophene)‐based supercapacitors. Supercapacitor devices employing solutions of the ionic liquid 1‐ethyl‐3‐methyl‐imidizolium bis(trifluoromethylsulfonyl)imide in BTHFE display similar performances to those prepared by using the neat ionic liquid as an electrolyte, although solution‐based devices exhibit a somewhat higher resistance.