Ribonucleic acids, often called a biological jack of all trades, contribute intimately to every aspect of gene expression, including the synthesis of other polypeptide biocatalysts. The fundamental importance of recurring structural motifs and the kinetics and energetics of the complex secondary and tertiary structure of RNA have been shown to be intimately linked with its functions in vivo. We have developed a novel enzymatic synthetic approach for covalent attachment of photoresponsive units into the RNA backbone. The synthetic conditions of this approach are extremely mild, involving the reverse micellar solubilization of nucleic acid along with lipase in apolar hydrocarbon solvents. Lipase catalyzed acylation of the 2' hydroxyl group in the ribose sugars of the RNA molecule has been used to incorporate photo-isomerizable azobenzene groups into the RNA strands. This micellar approach was envisaged for RNA functionalization while maintaining the conformational integrity of the macromolecular backbone in neutral buffer solution. The modification of RNA using covalently attached chromophores or fluorophores can be extended to other biomacromolecular matrices leading to the development of more versatile photoactive biopolymers. The photo-isomerizable groups incorporated in the RNA molecule can serve as optical ‘handles’ for the manipulation of the conformation of RNA and open new opportunities for biophotonic device applications.

Multilayer nanocomposite films have been prepared from exfoliated aluminosilicate/coumarin dye complex through layer-by-layer self-assembly using cationic polyelectrolytes. Coumarin dye molecules were intercalated into the layered aluminosilicate by an ion exchange reaction. Particles of the hectorite/dye complex were delaminated by extensive shaking and sonication of their water suspension into 2∼3 nm-thin silicate layers with molecules of the dye adsorbed on their surface. Atomic force microscopy and transmission electron microscopy data are in agreement with such a model. Ultrathin multilayered films were prepared using layer-by-layer self-assembly from the aluminosilicate platelets and a cationic polyelectrolyte polydiallyldimethylammonium chloride (PDAC). Linear build-up of the films up to 20 cycles was demonstrated and investigated using absorption spectroscopy and spectrofluorometer. The resulting transparent films have exhibited strong characteristic blue-green fluorescence due to coumarin dye molecules adhered to the exfoliated hectorite platelets.

Organic electroluminescent (EL) diodes based on fluorescent dyes and conducting polymers have attracted the interest of researchers, mainly because of their emission in the visible region and for application to large area portable flat panel display devices, driven at low voltages. Therefore, for the development of higher efficiency polymer EL diodes, the optimal combination of the merits of organic fluorescent dye molecules with that of conjugated polymer is an important approach. We report electroluminescence studies of polymer light emitting diodes (p-LEDs) fabricated with poly[2-(3-thienyl)ethanol n-butoxy carbonylmethyl urethane] (PURET) and its composite with 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H pyran (DCM) dye. These materials have been chosen in view of the fact that PURET exhibits a small overlap between emission and absorption spectra whereas DCM has a good efficiency of trapping both electrons as well as holes. Polyaniline has been utilized as hole injecting layer whereas tris-8-hydroxyquinoline-aluminum as electron injecting layer. Enhanced electroluminescence with bright yellow color has been observed in p-LEDs by the addition of dye.

Polyaniline (Pani) is one of the most interesting conducting polymers because of its promising electrical properties and unique redox tunability. Recently a new template assisted, enzymatic synthetic approach has been developed which yields a water-soluble and conducting complex of polyaniline and the template used. The mild reaction conditions in this approach allow for the utilization of delicate biological systems as template materials, such as DNA. Here we report the extension of this enzymatic approach to the synthesis of Pani on a DNA matrix. DNA serves as a suitable template for complexation and formation of conducting polyaniline. The redox behavior of Pani induces reversible conformational change in the secondary structure of DNA. Circular dichroism results suggest that the secondary structure of the DNA may be reversibly switched through manipulation of the redox state of the polyaniline.

Multilayer films were fabricated employing a new layer-by-layer complexation technique by alternatively dipping substrates in solutions of macromolecular ligands and Eu3+ ions. A luminescent poly[2-(3-thienyl)ethanol hydroxycarbonyl-methyl urethane] (H-PURET) was prepared by hydrolysis of thiophene polymer, poly[2-(3-thienyl)ethanol butoxycarbonyl-methyl urethane] (PURET), which was developed in our laboratory. H-PURET was used as macromolecular ligands. The multilayer deposition was monitored using UV-visible spectroscopy. As the number of bilayers increases, the absorption due to the polymer increases. The multilayer films were characterized by infrared and fluorescence spectroscopic techniques. Electroluminescence brightness easily obtained from the multilayer film of conjugated polymer-Eu3+ complex was measured to be about 40nW.

A series of azobenzene functionalized polymers has been synthesized by post polymerization azo coupling reaction. Photo-fabrication of surface relief gratings were studied on the polymer films. Epoxy based azo polymers were prepared by post azo coupling reaction to form polymers containing donor-acceptor type azo chromophores. The azo chromophores were designed to contain ionizable groups to impart self-assembling and photoprocessing capabilities to the polymers. The polymers containing 4-(4-(carboxylic acid)phenylazo)aniline chromophores can be directly photofabricated to form surface relief gratings with large surface modulations. Charge interactions had a strong influence on the details of the writing process. A new soluble polydiacetylene, post-functionalized with azobenzene groups was also prepared. Large amplitude surface gratings could be fabricated on this polydiacetylene film as well.

We have developed a technique to immobilize a multilayer enzyme assembly on an optical fiber surface. The technique utilizes a bifunctional amino coupling agent to link between different layers of enzymes. The method offers the flexibility of controlling the number of enzymes on a fiber surface. Multilayers of enzyme — Alkaline Phosphatase have been characterized using ellipsometry and surface plasma resonance. Chemiluminecence experiments have been conducted as a function of number of enzyme layers. The results indicated that at least 3 layers of enzyme can be assembled on a fiber surface. Utilising the new immobilization technique, a novel fiber optic biosensor system for the detection of organophosphorous-based pesticide has been developed. The detection mechanism is the pesticide inhibition of alkaline phosphatase catalyzed chemiluminescence. As a model analyte, paraoxon with ppb level concentration has been detected.

The electrochemical properties of o-dianisidine have been studied in both aqueous and organic solvents. This aryl diamine has been electrochemically polymerized on ITO coated glass electrodes and it was determined that the optical properties of these films are influenced by the polymerization conditions. The use of this polymer film as substrate for chemical coupling of biomaterials has been demonstrated with the light harvesting protein, phycoerythrin. Fabrication and bioanalytical application of enzyme electrodes by electrochemical copolymerization of odianisidine with the enzymes glucose oxidase and horseradish peroxidase, modified with odianisidineis described.

Conjugated polymers in general, and polythiophenes in particular have been attracting attention in the field of molecular electronics. Polythiophenes functionalized at the β- position with various groups have resulted in processable, conjugated polymeric systems with applications such as organic electrodes, photorefractive materials, electro-luminescent devices, among others. We report the synthesis of a thiophene copolymer with alkyl and chiral amino acid substituents at the β- position. We have synthesized a solution processable poly[3-octylthiophene-co-(N-1-carboxyl, 2- (4-hydroxy-3-nitrophenyl)ethyl)-3-thiophene acetamide] with 3-nitro-L-Tyrosine as the chiral amino acid side chain. The UV-Visible and optical rotatory dispersion spectra of the new copolymer are discussed.

Two types of second-order nonlinear optical epoxy-based polymers functionalized with tricyanovinyl chromophores were synthesized. One was prepared by azo coupling between an epoxy prepolymer and 4-tricyanovinylaniline while the other was synthesized by reacting the epoxy prepolymer with tetracyanoethylene. The d33 for the polymers were determined to be 243 and 178 pm/V at 1.064 μm respectively. Retentions of deff value of 83% and 65% were observed after the polymers had been heated at 80°C for 1000 hours.

The creation of smart materials is a current goal of many laboratories including our own. We are involved in studying a number of thin film and monolayer systems which share the common features of involving highly conjugated conducting organic polymers and the evolved properties of specific biological macromolecules. In this report we describe a generic ‘cassette’ methodology for immobilizing biotinylated biological macromolecules to hydrophobic surfaces using a novel class of conducting copolymers of polythiophene. These copolymers are derivatized with long alkyl chains and biotin moieties to bind, respectively, to the hydrophobic surface and the biotinylated species, through the biotin - streptavidin interaction. We utilize the monolayer ‘cassette’ approach to attach a signal transducing biomolecule alkaline phosphatase to the surface of a glass capillary. This produces a flexible system in which chemiluminescence provides the basis for a useful measurement strategy. A novel technique involving the generation of chemiluminescence signal from alkaline phosphatase catalyzed dephosphorylation of a macrocyclic phosphate compound is described. Detection of paraoxon and methyl parathion, both enzyme inhibitors, has been achieved at ppb levels. The technique is rapid, sensitive, and is applicable to the detection of all organophosphorus based insecticides. The technique will be used in developing a fiber;optic biosensor for remote detection of insecticides.

A new class of IPN system has been prepared and investigated. This IPN system combines the polybismaleinimide network and the NLO-active phenoxysilicon network. The second-order NLO coefficients, d33, values of the samples range from 2.5 to 6.7 pm/V depending on the composition and the processing conditions. The temporal stability of the second-order nonlinearities for these samples at 110 °C varies from 47 to 88 % retention after 274 h.

The coupling of a photodynamic protein to an electroactive polymer may be employed in opto-electronic signal transduction for optical displays, color mimicking and biosensor applications. We have synthesized a novel biomaterial, biotin-LC-hydrazide substituted poly(3-undecylthiophene-co-3-thienylcarboxaldehyde) [B-PUAT], which is capable of incorporating any biotinylated molecule through a bridging streptavidin protein. A long spacer group between the conjugated polymer backbone and the biotin side group improves monolayer formation at the airwater interface and enhances the material's ability to bind protein. The LB technique has been employed to couple this biomaterial and streptavidin through the well known biotin-streptavidin complexation. Biotinylated phycoerythrin [B-PE] is incorporated into the above monolayer by binding the unoccupied biotin binding sites on the bound streptavidin.

The polycation conducting polymer, oxidized polypyrrole (PPy), possesses the ability to form complexes with DNA. Our previously proposed diffusion limited binding model for double helical DNA was also found to be applicable to single stranded DNA in this study. Single stranded DNA was found to bind PPy at a nearly identical level to that of double helical DNA. An investigation of electropolymerized PPy film morphology using SEM revealed two distinctly differing surface morphologies for the Platinum (Pt) electrode face (smooth) and polymeric growth face (rough). The DNA uptake levels were found to be consistently different on either surface, being higher on the rough surface. DNA penetrated into the disk interior with increasing time periods of exposure while a similar phenomenon but to a lesser extent was observed for single stranded DNA.

A novel hierarchical biomaterial capable of incorporating any biotinylated biomolecule has been created. Our strategy is to biotinylate one-dimensional electroactive polymers and use a bridging streptavidin protein on Langmuir-Blodgett (LB) organized films. The following copolymeric system which enables functionalization of other molecules and formation of good monolayers was employed. Biotinylated poly(3-methanolthiophene-co-3-undecylthiophene) (B-PMUT) demonstrated a significantly better isotherm implying superior molecular packing compared to poly(3-methanolthiophene-co-3-undecylthiophene) (PMUT) on the LB airwater surface. The isotherm showed significant area expansion when streptavidin was injected below the B-PMUT monolayer in 0.1mM NaH2PO4/0.1 M NaCl buffer (pH 6.8) subphase. We then incorporated biotinylated phycoerythrin (B-PE) into this novel biomaterial by binding the unoccupied biotin binding sites on the bound streptavidin (4 sites total). The pressure-area isotherm of the protein injected monolayer showed area expansion. A characteristic fluorescent emission peak at 576nm was detected from the monolayer transferred onto a solid substrate. These observations demonstrated the function of B-PMUT in hierarchical monolayer assembly of molecules incorporating the biotin / streptavidin interaction.

Epoxy based material incorporating 4-(4'-nitrophenylazo) phenylamine has been synthesized and subsequently functionalized with cinnamoyl groups. These materials can be easily solution-processed into thin films by spin-coating. The uncrosslinked polymer has excellent thermal and linear optical properties. Glass transition temperature of 115°C and degradation temperature (air) of 278°C were recorded.

This material exhibits large second order nonlinear optical (NLO) effects subsequent to poling. In a poled film sample, second harmonic generation coefficient, d33, of 34 pm/V was observed at 1.06 μm. Crosslinking is brought about by exposure to UV radiation at 254 nm wavelength. In a poled and crosslinked film sample, a d33 of 22 pm/V was observed. This d33 value is less than the d33 value of the poled and uncrosslinked film sample due to photo-induced cis-trans isomerization and partial degradation of the NLO chromophores. Nevertheless, the poled and crosslinked film shows a much more stable second order response at ambient conditions compared to the poled film which has not been crosslinked.

Enzymatic polymerization of a number of monomers in an ordered lattice on a Langmuir trough (L-T) was investigated. The assembly and polymerization of two mixed monomeric systems consisting of 4-tetradecyloxyphenol (C14PP) with phenol, and 4-hexadecylaniline (C16PA) with aniline, in various ratios were carried out. Polymerization was obtained with C14PP and phenol (in the ratio 1:10), and C16PA and aniline (in the ratio 1:2) on buffered MilliQ water (pH 7.5) using the enzyme horseradish peroxidase (HRP) at 20°C. Polymerized monolayers were then transferred to appropriate substrates for UV-Vis, third order non linear optical (NLO) properties, and thickness measurements. Thermogravimetric analysis (TGA) was performed on the final polymers. Results suggest that the lattice controlled polymerization results in highly ordered conjugated polymers with improved functional, electronic, NLO and processability properties, which form a basis for intelligent materials design and applications.

The polycation conducting polymers, oxidized polypyrrole and polyalkylthiophene, possess the ability to form complexes with polyanionic DNA molecules through largely electrostatic interactions. This study demonstrated the solution uptake and binding of 32p radiolabeled DNA by conducting polymer thick films (50–100μm). Polypyrrole (PPy) was synthesized by electrochemical methods and poly(3-hexylthiophene) (PHT) and poly(3-undecylthiophene) (PUT) were synthesized by chemical methods. The DNA binding rates on PPy films were affected by DNA concentration and the oxidation state (measured as conductivity). The DNA kinetics support a diffusion limited model for binding. We measured DNA binding levels onto all three polymer films; PUT, PHT, and PPy. The binding levels increased in the same order as the conductivities of the polymer films. DNA binding onto oxidized PPy film was diminished upon electrochemical reduction. These observations showed, therefore, the binding may be linked with the positive charge sites responsible for conduction in the polymer films.

The optimum processing condition for a photocrosslinking Nonlinear Optical(NLO) polymeric system was established. Parameters such as change in heat capacity at glass transition temperature, rate of decrease of absorbance of residual uncrosslinked chromophores, and measurement of mass loss upon heating were used to set up the optimum condition. Poly(vinyl cinnamate) was used as the photocrosslinkable polymer and 3- cinnamoyloxy-4-[4-(N, N-diethylamino)-2-cinnamoyloxy phenyl azo] nitrobenzene was used as the NLO molecule. Poling at 70°C for 5 minutes followed by photocrosslinking with a dose of 2.5 mW/cm 2 for 10 minutes results in a stable second order nonlinear optical material.

The temporal and thermal stability of second order nonlinear optical properties of polymers is an important issue in the development of poly meric electro-optic devices. This has been addressed by introducing interchain crosslinking. A number of crosslinked systems developed by photochemical reactions have been presented.