There are two general ways to introduce functionalities into a polymeric structure: functionalization of the monomeric units before polymerization and postfunctionalization of the preformed polymer. Building libraries of polymers with different functionalities can be completed with significantly less effort by the second method, as each postfunctionalization of a single batch of polymeric backbone can involve as little as one synthetic step. One method of building a polymeric backbone for postfunctionalization involves the synthesis of hyperbranched conjugated polymers (HCPs) from AB2 monomeric units. A polymer formed from n AB2 monomeric units should contain n reactive B groups, which act as sites of functionalization. Utilizing this principle, two different hyperbranched poly(phenylene vinylene-phenylene ethynylene) scaffolds were synthesized and studied in both their inherent properties and functionalization. The first HCP synthesized was compared against a monomeric cruciform model and a linear polymer with a similar structure. The hyperbranched polymer has red-shifted absorption and emission in comparison to the cruciform model and linear polymer. The HCP quenches paraquat more efficiently than the linear polymer by a factor of about two, suggesting a greater rate of energy transfer. The functionalization of HCPs was studied; iodine groups decorating the HCPs were replaced with terminal alkynes by Pd-catalyzed coupling, providing a library of 24 differently functionalized HCPs. Elemental analyses of the postfunctionalized polymers show nearly complete substitution of the iodine groups. The postfunctionalized polymers show increased fluorescence compared to the original iodine decorated polymers, due to the loss of the heavy atom effect inducing iodine groups. The emissions of the postfunctionalized polymers in solution show a strong dependence on the groups attached to the conjugated structures, with emission maxima ranging from 505 nm to 602 nm; quantum yields range from 0.7% to 25%. Solid-state emission studies show stronger and more red-shifted spectra compared to emissions observed in solution.

Volatile organic compounds (VOCs) in air and heavy metal ions, anions, microorganism in water are environmental contaminants that require detection at certain low concentrations to avoid detrimental effects. Analytical instruments can accurately determine the concentration and composition of the contaminants at trace levels. However, these methods require skilled personnel to operate. Hence sensors should have fast response, low maintenance and easy to handle. In the present work, environmental monitoring sensor for volatile organic compounds, anion and E. coli was developed. The sensor is resistive sensor architecture with organic nanocomposite as sensing layer. The conjugated organic molecule with receptor moieties that can interact and exhibit affinity to each of the analyte was designed and synthesized. A new conducting polymer for sensing toluene, aldehyde is designed and fabricated. The sensor shows highest sensitivity and selectivity for targeted analyte. The sensor response is explained by molecular dynamics simulation. The solubility parameter of the new polymers is calculated by molecular dynamics and is used for elucidation of rationale of the mechanism for selectivity. The interaction energy of the sensing layer calculated by simulation is higher for targeted analyte than that for other analytes. The adsorption of vapors on the sensing layer results in volumetric change of the sensing layer. The effect can be experimentally determined by monitoring the thickness of the film and the change in the parameters such as mass change, capacitance, resistance change, refractive index change that occurs due to absorption of vapors in the polymers. Here, laser Doppler vibrometry, a non contact method is used to measure the displacement occurring due to interaction of a new polymer film with analyte vapors. A sensor for real time monitoring of nitrate ion concentration in water is fabricated. A new conjugated polymer is designed for selection of nitrate is used as a sensing molecule. The sensor is tested for various concentrations of nitrate ions and possible interferents effect. An organic nanocomposite based resistive sensor is designed and fabricated to detect E. coli in water. The organic molecule with receptor groups was selected such that receptor group would interact and exhibit affinity to the functional groups present on outer membrane of the cell wall of the E. coli. The resistance change is caused due to interaction and is because of E. coli acting as p-dopant to sensor molecule. The electrostatic interaction between positively charged amine groups on sensor molecule and negatively charged E. coli is believed to be the interaction mechanism. This work demonstrates that the conjugated molecules with suitable moieties can bind with analyte like VOCs, heavy metal ions, anions, microorganism, that can be used as sensing element in resistive sensor architecture.

The study of conjugated polymers, in particular PPV derivatives, continues to fascinate researchers both from the standpoint of developing new routes to control their structure and photophysical properties; this is also driven by the immense potential since this class of polymers has demonstrated in the context of various devices, such as LEDs, photovoltaics, FETs, etc. Also, there has been great interest in utilizing conjugated polymers in developing sensory devices. This thesis has examined a few interesting aspects that could be used to control the structure and consequently the photophysical properties of PPV derivatives. The first chapter of this thesis provides a brief introduction to conjugated polymers, with an emphasis on PPV based polymers, different synthetic methodologies for their preparation, previous attempts to obtain PPV with controlled conjugation length, and also a brief discussion of conjugated polymer nanoparticles (CPNs) and their preparation by various methods. The second chapter deals with the preparation of conjugated polymer (MEHPPV) nanoparticles by reprecipitation method and utilization of these nanoparticles in detection of nitro explosives in aqueous medium. Nanoparticles of MEHPPV with different sizes were prepared by a simple precipitation method from a THF solution into water. Although these nanoparticles were prepared from very hydrophobic MEHPPV, these nanoparticles were reasonably stable in aqueous medium, especially when their sizes were relatively small; their UV-visible and fluorescence spectra could be readily recorded using simple solution methods. The sizes could be controlled by varying the concentration of the polymer solution used. The CPNs are spherical particles as confirmed by atomic force microscopy (AFM). The emission maximum of the nanoparticles is red shifted compared to a solution of the polymer. The fluorescence spectrum of this aqueous nanoparticle dispersion exhibited very high sensitivity to electron-deficient aromatic compounds, in particular the explosive TNT; the CPNs were able to sense nanomolar concentrations of the explosives. Stern-Volmer constant (KSV) is higher for 2,4,6-trinitro toluene (TNT) than any other analytes studied. Among the different sized nanoparticles studied the bigger one showed highest quenching efficiency. Electron-deficient aromatic molecules were shown to quench the fluorescence of the nanoparticles, possibly by excited state electron transfer mechanism; this hypothesis was supported by quenching experiments carried out using a variety of nitro-aromatic molecules with varying reduction potentials, in addition to a few electron-rich aromatic molecules. A fairly good correlation between the quenching efficiency of the analyte and its reduction potential was noticed; however, in a few instances this correlation failed. This suggested that a second factor, namely the solubility of the analyte in water (its hydrophobicity) also is a key factor as this governs the tendency of the analyte to adsorb on the nanoparticle surface, which clearly is the first step in the quenching process. In the third chapter synthesis and characterization of MEHPPV with reduced conjugation length by utilizing the concept of conjugation breaking using non-coplanar entities are presented. MEHPPV with reduced conjugation length was prepared by incorporating non-coplanar entities, such as biphenyl and binaphthyl units, along the polymer backbone. Both Gilch and Witting-Horner methods were successfully utilized to prepare copolymers; the former approach permitted the variation of the level of the twisted comonomer incorporation, whereas the latter approach only provided an alternating copolymer. Although biphenyl based monomers could not be homopolymerized by Gilch method, it was possible to prepare copolymers using xylylene type comonomers. The polymers prepared by the Gilch method are random copolymers; the solubility decreases with increase in the amount of biphenyl incorporation, which was ascribed to the presence of a substantial fraction of longer conjugated segments in such random copolymers. The non-coplanar entities cause truncation of conjugation length in MEHPPV, as evident from their absorption spectra. The copolymers prepared via the Gilch method exhibited a blue shift of about 57 and 20 nm in the absorption and emission, respectively; while the alternating copolymers prepared by Wittig-Horner-Emmons method exhibited a larger blue-shift of about 84 and 54 nm clearly implying a significantly larger reduction in the conjugation length. The copolymers prepared by Wittig-Horner-Emmons method are alternating in nature and therefore leads to a greater reduction in conjugation length; this was evident from the substantially higher blue-shift in the absorption and fluorescence spectra. An interesting feature in the alternating copolymers is the distinct difference in the relative changes in the absorption and emission spectra of the biphenyl and binaphthyl containing copolymers, which appear to suggest in the latter case there is a greater extent of planarization of the excited state. Both these systems provided some useful insights into the various factors that govern the photophysical properties of this class of truncated conjugated polymers. Further examination of this aspect could reveal some other unique features of these copolymers. In the fourth chapter, an approach to prepare copolymer precursors to unsubstituted PPV that holds the potential to control conjugation length is described. The precursor copolymers were prepared by changing the monomer feed ratio of the two monomers, viz. dithiocarbamate (DTC) and xanthate, using the Gilch copolymerization to generate the precursors having varying extents of DTC and xanthate groups. The percentage composition of the precursor copolymers was calculated using 1H NMR and compared with the values calculated from thermogram; the copolymer composition varies linearly with monomers feed suggesting that any desired composition can be readily accessed. Thermogravimetric analysis (TGA) of the precursors, as a preliminary study to examine the possibility of selective elimination of one of these groups to generate conjugated polymers with varying conjugation lengths, demonstrates that a certain level of selectivity in thermal elimination can be achieved because of the distinctly different thermal labilities of the xanthate and DTC groups. These studies clearly suggest that fine-tuning of the thermally eliminatable groups, specifically using xanthate and DTC, could serve as a useful approach to vary the conjugation length of unsubstituted PPVs, which could have important implication in device fabrication. Clearly further work is needed to characterize the selectively eliminated polymers using other spectroscopic methods, such as UV-visible and fluorescence, before device work could be taken up.

This thesis consists of two parts and nine chapters. The first part (Part I) presents theoretical studies on non-radiative mode of excitation energy transfer (EET) in donor-acceptor (D-A) systems involving metal nanoparticles. Part I contains four chapters and describes EET in following different D-A systems: (i) dye and a spherical metal nanoparticle of different sizes, (ii) two spherical metal nanoparticles, and (iii) two prolate shaped metal nanoparticles at different relative orientations. Part II provides a detailed study on the origin of photochemical funneling of excitation energy in conjugated polymers like poly-[phenylenevinylene] (PPV) and consists of three chapters. The ninth chapter provides a concluding note. The thesis begins with a basic introduction on Forster resonance energy transfer(FRET), presented in chapter 1. This chapter provides a detail derivation of Forster’s rate expression for a non-radiative process of EET from a donor to an acceptor molecule and discusses the limitations of Forster theory. The chapter highlights the huge success of FRET technique in understanding biological processes assisted by changes in conformations of biopolymers under conditions where Frster theory is valid. The chapter also discusses practical limitations of FRET technique such as use of pre-averaged value of orientation factor and photobleaching of dye molecules. Part I starts with chapter 2 which explains the advantages of using metal nanoparticles over dye molecules in D-A systems. The chapter discusses recent experimental re-ports of excitation energy transfer to nanoparticles, now commonly referred to as nanoparticle surface energy transfer (NSET). Theories describing the process of EET from a dye molecule (dye molecule is assumed to be a point dipole) to a planar metallic surface are discussed. In the case of energy transfer from a donor dye molecule to a planar metallic surface, the distance dependence of the rate of EET is found to vary as 1/d4 where dis a distance from the center of a dye molecule to the metallic surface. This is unlike conven-tional FRET where rate of EET follows 1/R6 distance dependence with R as a distance between the centers of D and A. Also, a recent experimental study by Yun et al [J. Am. Chem. Soc. 127, 3115 (2005)] on energy transfer from a dye molecule to a spherical gold nanoparticle reports that the rate of EET follows 1/d4 distance dependence. The remaining chapters of this part focus on understanding this deviation from the Forster theory in different D-A systems. Chapter 3 describes quantized electro-hydrodynamic approach used to model the plasmonic excitations in metal nanoparticles. The optical absorption frequencies of nanoparticles computed here are subsequently used in chapters 4 and 5 for the calculation of the rate of EET. The chapter discusses the merits and de-merits of electro-hydrodynamic approach in comparison to other available techniques. The electro-hydrodynamic method of calculating the absorption frequencies provide a physically appealing, mathematically simple and numerically tractable approach to the problem and is also at the same time, semi-quantitatively reliable. The optical frequencies obtained as a function of size and aspect ratio of metal nanoparticles are found to be in good agreement with physical predictions. Chapter 4 studies the distance dependence of rate of EET for a D-A system similar to one studied by Yun et al [J. Am. Chem. Soc. 127, 3115 (2005)]. The chapter contains the relevant derivations of the quantities required for computing the interaction matrix elements. The dependence of the rate of EET on R is found surprisingly to be in agreement with Forster theory even at intermediate distances compared to the size of spherical nanoparticles (a). However, the dependence of rate of EET on d is found to vary as 1/dσwith σ=3 - 4 at intermediate distances which is in good agreement with the experimental results of Yun et al. At large values of d, the distance dependence of rate is found to vary as 1/d6 . The chapter discusses the physical basis behind these results. The theory predicts a non-trivial dependence of rate on the size of a nanoparticle which ultimately attains the asymptotic a3 size dependence. The rate of EET is also studied for different orientations of dye molecule. Chapter 5 studies surface plasmon mediated EET between two metal nanoparticles. The rate of EET between two prolate and spherical shaped silver nanoparticles is studied as a function of Rand d. d, in present chapter denotes surface-to-surface separation distance between two nanoparticles. In case of EET between two non-spherical nanoparticles, even at separations larger than the size of the nanoparticle, a significant deviation from 1/R6 dependence is obtained. However, 1/R6 distance dependence of EET rate is found to be robust for spherical nanoparticles over an entire range of separations. The deviation of rate from 1/R6 distance dependence becomes more pronounced with in-crease in the aspect ratio of the nanoparticle. The relative orientation of the nanoparticles is found to markedly influence the R-dependence of EET rate. Interestingly, the relative orientation of nanoparticles effect the d-distance dependence of the rate to a lesser extend in comparison to the R-dependence of the rate. Therefore, we predict that for non-spherical nanoparticles studying EET rate as a function of will provide more conclusive results. The chapter also discusses the size dependence of rate of EET for this particular D-A system. In Part II, excitation energy transfer (EET) in a conjugated polymer is studied. To start with, chapter 6 provides a brief introduction to photophysics of conjugated polymers. The chapter discusses the nature of photoexcitations in these systems and stresses on the influence of polymer’s morphology on the optical properties of conjugated polymers. Chapter 7 describes the theory used for modeling conjugated polymer chain. A polymer chain consists of number of spectroscopic units (chromophores) of varying lengths. The average length of chromophores in conjugated polymer depends on defect concentration. In the present study we treat an excitation generated on each chromophore within “particle-in-a-box” formalism but one that takes into account the electron-hole interactions. The transition dipole moments and the radiative rates are computed for different lengths of chromophores with parameters appropriate for PPV chain. These quantities are used in chapter 8 for calculating the absorption and emission spectra of conjugated polymer chains at different defect concentrations. The main aim of Chapter 8 is to understand the origin of photochemical funneling of excitation energy in conjugated polymers. PPV chain is modeled as a polymer with the length distribution of chromophores given either by a Gaussian or by a Poissonian distribution. We observe that the Poissonian distribution of length segments explains the optical spectra of PPV rather well than the Gaussian distribution. The Pauli’s master equation is employed to describe the excitation energy transfer among different chromophores. The rate of energy transfer is assumed to be given here, as a first approximation, by the well-known Forster expression. The observed excitation population dynamics confirm the photochemical funneling of excitation energy from shorter to longer chromophores of the polymer chain. The calculations show that even in steady state more than one type of chromophore contribute towards the emission spectrum. The observed difference between the calculated emission spectra at equilibrium and in steady state indicates the existence of local domains in a polymer chain within which the non-radiative excitation energy transfer from shorter to longer chromophores take place. These results are found to be in agreement with recent experimental reports. The concluding chapter 9 gives a brief summary of the outcome of the thesis and ends up with suggestion of a few future problems which in current scenario are of great interest.

This research serves as a meticulous examination into cross-conjugated materials and how alterations of the frontier molecular orbitals can be utilized for applications in "chemical tongue" organic sensing devices. With conjugated materials being used in the development of new sensory devices for detection of metals, bacteria, and chemical warfare agents, the field of organic sensing is growing faster than ever. The purpose of this dissertation is to provide a precedence for the synthesis of new cross-conjugated compounds and outline potential applications of these materials as chemical sensors and molecular probes.

The exciton diffusion length, which is the distance an exciton can diffuse in its lifetime, is an important parameter that has a critical impact on the operation of many organic optoelectronic devices, including organic solar cells, light emitting diodes and lasers. Knowledge of the exciton diffusion length can be a powerful aid for the design and optimisation of these devices. This thesis details the development of techniques based on time-resolved fluorescence for measuring the exciton diffusion in organic semiconductors. Two main methods were used to investigate exciton diffusion in the conjugated polymers P3HT, MEH-PPV and F8BT: the surface quenching technique and exciton-exciton annihilation. In particular, the surface quenching technique was adapted to avoid some of the potential pitfalls that have plagued earlier measurements. Using a titania quencher, measurements were performed using the surface quenching technique and fitted with an exciton diffusion model, allowing the calculation of the exciton diffusion length. Results from measurements of the exciton-exciton annihilation rate, which is a diffusion controlled process, where in good agreement with those from surface quenching, confirming the robustness of this twofold approach. A novel method for the control of the β-phase conformation in PFO films was used to produce films containing varying concentrations of β-phase. Exciton-exciton annihilation was used to investigate exciton diffusion in these films, revealing a gradual rise with increasing β-phase fraction due to improved interconnectivity. This work demonstrates how simple processing techniques can be used to control both film morphology and the exciton diffusion. The thickness dependence of the photoluminescence lifetime in conjugated polymers is a phenomenon that has so far received little attention and, thus, remained unexplained. This study demonstrates that it is not due to exciton quenching by external factors, but can be explained by a change in the morphology with decreasing film thickness.

FLUORINATED ARENE, IMIDE AND LACTAM-FUNCTIONALIZED DONOR ACCEPTOR CONJUGATED POLYMERS: SYNTHESIS, STRUCTURE-PROPERTY AND DEVICE STUDIES After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the molecular self-assembly and (opto)-electronic properties. The body of this thesis mainly focuses on the substituent effects: how different substituent’s affect the (opto)-electronic properties of the donor-acceptor (D-A) conjugated polymers. The main priority goes to understand, how different alkyl substituent effect to the polymer solubility, crystallinity, thermal properties (eg: glass transition temperature) and morphological order. Three classes of D-A systems were extensively studied in this work. The second chapter mainly focuses on the synthesis and structure-property study of fluorinated arene (TFB) base polymers. Here we used commercially available 1,4-dibromo-2,3,5,6-tetrafluorobenzene (TFB) as the acceptor material and prepare several polymers using 3,3’-dialkyl(3,3’-R2T2) or 3,3’-dialkoxy bithiophene (3,3’-RO2T2) units as electron donors. A detail study was done using 3,3’-bithiophene donor units incorporating branched alkoxy-functionalities by systematic variation of branching position and chain length. The study allowed disentangling the branching effects on (i) aggregation tendency, intermolecular arrangement, (iii) solid state optical energy gaps, and (iv) electronic properties in an overall consistent picture, which might guide future polymer synthesis towards optimized materials for opto-electronic applications. The third chapter mainly focused on the structure-property study of imide functionalized D-A polymers. Here we used thiophene-imide (TPD) as the acceptor moiety and prepare several D-A polymers by varying the donor units. When selecting the donor units, more priority goes to the fused ring systems. One main reason to use imide functionality is due to the, open position of the imide nitrogen, which provides an attaching position to alkyl substituent. Through this we can easily manipulate solubility and solid state packing arrangement. Also these imide acceptors have low-lying LUMOs due to their electron deficient nature and this will allow tuning the optical energy gap by careful choice of donor materials with different electron donating ability. The fourth chapter mainly contribute to the synthesis and structure property study of a completely novel electron acceptor moiety consist of a unsaturated pyrrolidinone unit known as Pechmann dye (PD) core. Pechmann dyes are closely related to the Indigo family. This can refer as 3-butenolide dimer connected via an alkene bridge, containing a benzene ring at the 5 and 5’ positions of the lactone rings. We have prepared several D-A polymers using this PD system with benzodithiophene (BDT) as the donor unit. Different to common D-A polymers the HOMO and LUMO of the PD acceptor moiety are energetically located within the gap of the BDT, so that the electronic and optical properties (HOMO-LUMO transition) are dictated by the PD properties. The promising electronic properties, band gaps, high absorption coefficients and broad absorption suggest this new D-A polymers as an interesting donor material for organic solar cell (OSC) applications.

Donor-acceptor copolymers have received a great deal of attention for application as organic semiconductors, in particular as the active layers in low-cost consumer electronics. The functional groups grafted to the polymer backbones generally dictate the molecular orbital energies of the final materials as well as aid in self-assembly. Additionally, the side chains attached to these functional groups not only dictate the solubility of the final materials, but also their morphological characteristics. The bulk of the research presented in this dissertation focuses on the synthesis and structure-property relationships of polymers containing novel acceptor motifs. Chapter 2 focuses on the synthesis of 1,2-disubstituted cyanoarene monomers as the acceptor motif for copolymerization with known donors. It was found that cyanation of both benzene and thiophene aromatic cores resulted in a decrease of the molecular orbital energy levels. Additionally, the small size of this functional group allowed favorable self-assembly and close π-stacking to occur relative to related acceptor cores carrying alkyl side chains as evidenced by UV-Vis and WAXD data. Chapter 3 describes the systematic variation of side chain branching length and position within a series of phthalimide-based polymers. Branching of the side chains on bithiophene donor units resulted in the expected increase in solubility for these materials. Furthermore, a correlation was found between the branching position, size, and the HOMO energy levels for the polymers. Additionally, it was demonstrated that branching the alkyl side chains in close proximity to polymer backbones does not disrupt conjugation in these systems. A novel acceptor motif based on the 1,3-indanedione unit is presented in Chapter 4. Despite the stronger electron withdrawing capability of this functional group relativeto phthalimide, it was found that polymers based on this unit have the same HOMO molecular orbital energy levels as those presented in Chapter 3. It was found, however, the presence of orthogonal side chains greatly enhanced the solubility of the final polymers. Additionally, UV-Vis and WAXD measurements revealed that thermal annealing had a profound effect on the ordering of these polymers. Despite the presence of orthogonal side chains, long range order and close π-stacking distances were still achieved with these materials. Finally, alkynyl “spacers” were used in Chapter 5 to separate the solubilizing alkyl side chains from the polymer backbones on bithiophene donor monomers. The alkynyl groups allowed for conjugated polymer backbones to be achieved as well as low HOMO energy levels. A correlation between the side chain size, π-stacking distances and HOMO-LUMO energy levels was measured in this polymer series.

L'élaboration de réseaux poreux pi-conjugués par l'auto-organisation de molécules organiques, les cyclotriphosphazènes spirocycliques, a été explorée. L'étude de la stabilité des réseaux obtenus à partir du tris(o-phénylènedioxy)cyclotriphosphazène (TPP) conjointement à l'étude de la réactivité du N3P3Cl6 face à l'attaque nucléophile de différents dérivés du catéchol ont permis de définir de nouvelles cibles. Dans ce cadre, un nouveau composé, le tris(2,3-triphénylènedioxy)cyclotriphosphazène (TTPP) dans lequel le motif central est substitué par trois systèmes pi-conjugués étendus de type triphénylène a été synthétisé. Les tectons TTPP, de symétrie C3, présentent une orientation atypique des motifs aromatiques. Leur forme, analogue à celle d'une roue à aubes, leur permet d'engendrer à l'état cristallin des lacunes sous forme de deux types de nano-canaux de respectivement 6,1 Å et 8,4 Å de large et 10,7 Å et 12,4 Å de large, pouvant inclure des molécules de 1,2,4-trichlorobenzène. Ce matériau contient la plus grande porosité obtenu à partir de cyclotriphosphazènes spirocycliques à ce jour. La formation de réseaux poreux chiraux a également été réalisée à partir de tectons portant chacun trois motifs (S)-binol. Le (S,S,S)-tribinolcyclotriphosphazène ((S,S,S)-TBP) a ainsi pu être co-cristallisé avec des molécules d'o-xylène. Ainsi, des informations permettant de mieux comprendre la structure moléculaire de cyclotriphosphazènes portant des spirocycles à sept chaînons ont été obtenues. Enfin, les propriétés optoélectroniques des tectons ont été étudiées en solution. L'influence de l'agent directeur cyclotriphosphazène sur les propriétés optiques des chromophores a, en particulier, été abordée. / Elaboration of pi-conjugated networks through self-organization of spirocyclic cyclotriphosphazene molecules has been explored. The stability of the networks built from described tris(o-phenylenedioxy)cyclotriphosphazene (TPP) jointly with the study of the reactivity of N3P3Cl6 undergoing nucleophilic attack by catechol derivatives allowed to design new tectons. In this context, a new tris(2,3-triphenylenedioxy)cyclotriphosphazene (TTPP) compound embedding a central hub substituted by pi-conjugated triphenylene unit has been synthesized. TTPP tectons exhibits a particular shape with specific orientation of aromatic units. Their paddle-wheel like shape allows the elaboration of a porous network having two types of nano-tunnels of respectively 6.1 Å and 8.4 Å large and 10.7 Å and 12.4 Å large. This material has the biggest channel size described for network build from spirocyclic cyclotriphosphazenes and inclusion compounds with 1,2,4-trich lorobenzene molecules were made. Elaboration of chiral porous network from tectons constituted by three (S)-binol units has also been realized. Tribinolcyclotriphosphazene has been co-cristallized with o-xylene molecules. Thus, useful informations on seven-membered spirocyclic cyclotriphosphazene molecular structure have been obtained. Finally, tectons opto-electronic properties have been studied in solution. Influence of the cyclotriphosphazene directing agent on optical chromophore properties has been a particular matter of attention.

Consumer awareness of the link between dietary fats and health outcomes has led to increased demand for food products enriched with bioactive fatty acids (FA). Ruminant-derived fats, such as dairy fats, contribute significantly to the American diet and contain many unique beneficial FA, such as short- and medium-chain FA, n-3 FA, conjugated linoleic acids (CLA), vaccenic acid (VA), as well as odd-and branched-chain FA (OBCFA). Increasing these FA in dairy products by altering farm management practices, such as breed, lactation stage, and nutrition, may improve human health without a change to the diet. The overarching goal of this dissertation was to evaluate on-farm strategies to increase the content of bioactive FA in bovine milk. The first objective was to enrich milk fat with bioactive FA via supplementation with echium oil, a terrestrial oil rich in n-3 FA. Treatments were 1.5% and 3.0% dry matter as lipid encapsulated echium oil (EEO) which were compared to a control (no EEO). Milk fat contents of n-3 FA increased with EEO supplementation but the transfer of n-3 FA from EEO into milk fat was rather low (< 5%). In a subsequent trial, ruminal protection of EEO and post-ruminal release of EEO-derived FA was examined. EEO-derived FA were preferentially incorporated into plasma lipid fractions unavailable to the mammary gland. Moreover, fecal excretion of EEO-derived FA ranged from 7-14% of intake, and VA and CLA, the biohydrogenation and metabolism products of n-3 FA, increased in milk and feces with EEO supplementation. Therefore, lipid-encapsulation provided inadequate digestibility and low transfer efficiency of n-3 FA into milk. The second objective was to compare the bacterial community structure and unique bioactive FA in bacterial membranes and milk fat between Holstein (HO), Jersey (JE), and HO x JE crossbreeds (CB) across a lactation. Lactation stage had a prominent effect on rumen bacterial taxa, with Firmicutes being most abundant during early lactation. The FA composition of bacterial cells was affected by both lactation stage and genetics, and OBCFA in bacterial cells were positively correlated with several bacteria of the Firmicutes phylum. HO and CB exhibited greater contents of various bioactive FA in milk than JE. The highest content of all bioactive FA occurred at early lactation, while OBCFA were highest at late lactation. The third objective was to determine the effects of grazing a monoculture vs. a diverse pasture on rumen bacterial and protozoal taxa, their membrane FA composition, and milk FA. Microbial communities shifted in response to grazing regime accompanied with changes in their membrane FA profiles. Rumen microbiota from cows grazing a diverse pasture had higher contents of n-3 FA and VA, but lower contents of OBCFA. Microbial membrane FA correlated with microbial taxa, the contents of ALA and n-3 FA were positively correlated with the bacterial genus Butyrivibrio and the protozoal genus Eudioplodinium. Milk contents of CLA and n-3 FA increased when cows grazed a diverse pasture, while grazing a monoculture led to greater milk contents of OBCFA. In conclusion, grazing cows on a diverse pasture, when compared to genetic effects and lipid supplementation, was the most efficacious strategy to increase the content of bioactive FA in milk.