The utilization of plasmonic energy in the form of heat, resonance energy, and/or hot carriers offers unique possibilities for various applications, like in catalytic and medical applications, due to their simple recyclability or administration. A common strategy to make this plasmonic energy available to the direct environment is to introduce conductive polymer coatings to transfer the energy and to increase the excitons lifetime. However, their practical use is limited due to the limited spectral match of gold with commonly used polymeric materials and semiconductors, the oxidation vulnerability of silver, and the short range of the required strong plasmonic interactions. To overcome these challenges, we developed the synthesis of conjugated polymer–gold–silver hybrid colloids that simultaneously enable silver as the central plasmonic material and prolong the internal relaxation by a heterojunction with a conductive polymer shell. The introduced thin gold layer focuses the plasmonic energy to the metal surface, enhancing and enabling the photocatalyzed polymerization of polypyrrole (PPy) while maintaining the plasmonic properties of silver. Hence, the introduced hybrid particles allow the foreseeable use of plasmonic energy in real-world applications via the strong plasmonics of silver and compatible conductive polymer shells as mediators.

No presente trabalho foram estudadas as propriedades mecâncias (resistência à tração e porcentagem de alongamento na ruptura e resistência à perfuração), propriedades ópticas, permeabilidade ao gás oxigênio e ao vapor d\'água, migração total em simulante aquoso (ácido acético 3%) e gorduroso (n- heptano), e a formação de produtos voláteis da radiólise, com vistas à avaliar o efeito da radiação ionizante (raios gama e feixe de elétrons) em filmes flexíveis mono e multicamadas comerciais, fabricados no Brasil para a indústria de produtos cárneos. Os filmes estudados foram: um monocamada de polietileno de baixa densidade (LDPE) e um multicamadas coextrusado composto de polietileno de baixa densidade (LDPE), copolímero de etileno e álcool vinílico (EVOH) e poliamida (PA), ou seja, a estrutura: LDPE/EVOH/PA. As irradiações foram realizadas em uma fonte de 60Co do tipo Gammacell e em um acelerador de elétrons do tipo eletrostático (l,5MeV), com doses de até 30 kGy, na temperatura ambiente e presença de ar. As alterações nas propriedades foram avaliadas de acordo com a dose de radiação aplicada, oito dias após a irradiação e novamente, dois a três meses após a irradiação. Os resultados mostraram que as reações de cisão predominaram sobre as reações de reticulação para ambos os filmes estudados, irradiados com raios gama ou com feixe de elétrons. As variações observadas em função da irradiação, nas propriedades avaliadas não limitam a aplicação final desses filmes, uma vez que não ultrapassaram o limite de segurança especificado pelo fabricante em nenhuma dose e período em que foram estudadas. Concluiu-se que os filmes estudados podem ser utilizados, sob o ponto de vista das propriedades avaliadas, como embalagens para produtos pasteurizáveis por radiação e radioesterilizáveis usando irradiadores gama ou aceleradores de elétrons, nas doses de radiação estudadas. / In this study the mechanical properties (tensile strength and percentage elongation at break and penetration resistance), optical properties, gas oxygen and water vapor permeability, the overall migration tests into aqueous food simulant (3% aqueous acetic acid) and fatty food simulant (n-heptane), as well as the formation of volatile radiation product tests were used to evaluate the effects of ionizing radiation (gamma irradiation or electron-beam irradiation) on commercial monolayer and multilayer flexible plastics packaging materials. These films are two typical materials produced in Brazil for industrial meat packaging, one of them is a monolayer low-density polyethylene (LDPE) and other is a multilayer co extruded low-density polyethylene (LDPE), ethylene vinyl alcohol (EVOH), polyamide (PA) based film (LDPE/EVOH/PA). Film samples were irradiated with doses up to 30 kGy, at room temperature and in the presence of air with gamma rays using a 60Co facility and electron beam from 1.5 MeV electrostatic accelerator. Alterations of these properties were detected according to the dose applied initially eight day after irradiation took place and new alterations of these values when the properties were evaluate two to three months after irradiation process. The results showed that scission reactions are higher than cross-linking process for both studied films, irradiated with gamma rays and electron beam. The evaluated properties of the irradiated films were not affected significantly with the dose range and period studied. The monolayer Unipac PE-60 and the multilayer Lovaflex CH 130 films can be used as food packaging materials for food pasteurization and in the sterilization process of by ionizing radiation using a gamma facilities and electron beam accelerators in commercial scale.

No presente trabalho foram estudadas as propriedades mecâncias (resistência à tração e porcentagem de alongamento na ruptura e resistência à perfuração), propriedades ópticas, permeabilidade ao gás oxigênio e ao vapor d\'água, migração total em simulante aquoso (ácido acético 3%) e gorduroso (n- heptano), e a formação de produtos voláteis da radiólise, com vistas à avaliar o efeito da radiação ionizante (raios gama e feixe de elétrons) em filmes flexíveis mono e multicamadas comerciais, fabricados no Brasil para a indústria de produtos cárneos. Os filmes estudados foram: um monocamada de polietileno de baixa densidade (LDPE) e um multicamadas coextrusado composto de polietileno de baixa densidade (LDPE), copolímero de etileno e álcool vinílico (EVOH) e poliamida (PA), ou seja, a estrutura: LDPE/EVOH/PA. As irradiações foram realizadas em uma fonte de 60Co do tipo Gammacell e em um acelerador de elétrons do tipo eletrostático (l,5MeV), com doses de até 30 kGy, na temperatura ambiente e presença de ar. As alterações nas propriedades foram avaliadas de acordo com a dose de radiação aplicada, oito dias após a irradiação e novamente, dois a três meses após a irradiação. Os resultados mostraram que as reações de cisão predominaram sobre as reações de reticulação para ambos os filmes estudados, irradiados com raios gama ou com feixe de elétrons. As variações observadas em função da irradiação, nas propriedades avaliadas não limitam a aplicação final desses filmes, uma vez que não ultrapassaram o limite de segurança especificado pelo fabricante em nenhuma dose e período em que foram estudadas. Concluiu-se que os filmes estudados podem ser utilizados, sob o ponto de vista das propriedades avaliadas, como embalagens para produtos pasteurizáveis por radiação e radioesterilizáveis usando irradiadores gama ou aceleradores de elétrons, nas doses de radiação estudadas. / In this study the mechanical properties (tensile strength and percentage elongation at break and penetration resistance), optical properties, gas oxygen and water vapor permeability, the overall migration tests into aqueous food simulant (3% aqueous acetic acid) and fatty food simulant (n-heptane), as well as the formation of volatile radiation product tests were used to evaluate the effects of ionizing radiation (gamma irradiation or electron-beam irradiation) on commercial monolayer and multilayer flexible plastics packaging materials. These films are two typical materials produced in Brazil for industrial meat packaging, one of them is a monolayer low-density polyethylene (LDPE) and other is a multilayer co extruded low-density polyethylene (LDPE), ethylene vinyl alcohol (EVOH), polyamide (PA) based film (LDPE/EVOH/PA). Film samples were irradiated with doses up to 30 kGy, at room temperature and in the presence of air with gamma rays using a 60Co facility and electron beam from 1.5 MeV electrostatic accelerator. Alterations of these properties were detected according to the dose applied initially eight day after irradiation took place and new alterations of these values when the properties were evaluate two to three months after irradiation process. The results showed that scission reactions are higher than cross-linking process for both studied films, irradiated with gamma rays and electron beam. The evaluated properties of the irradiated films were not affected significantly with the dose range and period studied. The monolayer Unipac PE-60 and the multilayer Lovaflex CH 130 films can be used as food packaging materials for food pasteurization and in the sterilization process of by ionizing radiation using a gamma facilities and electron beam accelerators in commercial scale.

Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2017-03-10T14:39:39Z No. of bitstreams: 1 22066.pdf: 9119613 bytes, checksum: 0b28a0c36e553b4d7b70c8a8a0d8d601 (MD5) / Made available in DSpace on 2017-03-10T14:39:39Z (GMT). No. of bitstreams: 1 22066.pdf: 9119613 bytes, checksum: 0b28a0c36e553b4d7b70c8a8a0d8d601 (MD5) / O polímero Acrilonitrila Butadieno Estireno (ABS) é um dos polímeros mais versáteis disponíveis nos dias de hoje. Atualmente o Brasil não produz o ABS, o que limita a indústria brasileira de plásticos a utilizar as variações deste polímero importadas, ofertadas no mercado nacional por distribuidores locais. Este estudo avaliou os efeitos da adição das argilas Cloisite Na® e Branca de Cubati na matriz polimérica ABS e também os efeitos decorrentes do tratamento por radiação ionizante no ABS e nos compósitos ABS/Argila como formas de modificação de um ABS convencional. Visando avaliar a diferença entre uma argila organofílica e uma organofóbica, a argila Branca de Cubati foi organofilizada e a argila Cloisite Na® foi utilizada como recebida. Foram preparados, utilizando uma extrusora dupla rosca, concentrados a 30 % em massa da argila Branca de Cubati, previamente organofilizada e da Cloisite Na® em Estireno Acrilonitrila (SAN). Os concentrados foram adicionados ao ABS a 1, 3 e 5 % em massa das argilas e foram injetados corpos de prova. Parte dos corpos de prova foi submetida à irradiação por feixe de elétrons à uma dose de 600 kGy. Os compósitos irradiados e não irradiados foram caracterizados por meio de ensaios de resistência a tração, resistência a flexão, resistência ao impacto, temperatura de distorção térmica, ponto de amolecimento Vicat, análise de termogravimétrica (TG), difração de raios X e microscopia eletrônica de varredura com emissão de campo (MEVFEG) e a correlação entre os resultados foi discutida. Foram observadas melhorias nas propriedades mecânicas, exceto resistência ao impacto, nos materiais aditivados com as argilas, sendo os melhores resultados obtidos com a argila Branca de Cubati. O tratamento por radiação ionizante favoreceu o processo de reticulação do ABS. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

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.

The main motivation of this thesis is derived from the fact that physics of disordered systems like conjugated polymer has yet not achieved as concrete understanding as ordered and crystalline systems such as inorganic semiconductors. Through the work done in this thesis, several efforts have been made in order to understand basic charge transport (hopping, current injection) phenomena and photo-physical properties (photoluminescence quenching, absorption, photoconductivity) in conjugated polymer and their hybrid composites. The thesis consists of 7 chapters. Chapter 1 discusses the background knowledge and information of the general properties of conjugated polymers, quantum dots and their hybrid nanocomposites. Chapter 2 deals with the sample preparation and experimental techniques used in this thesis. Chapter 3 elaborates the temperature and field dependent anisotropic charge transport in polypyrrole. Chapter 4 presents an idea to probe and correlate disorder and transport properties using impedance and Raman spectroscopy. Chapter 5 mainly talks about the doping level dependent photophysical and electrical properties of poly(3-hexylthiophene). Chapter 6 reveals the charge transport phenomena in hybrid composites of poly(3,4-ethyldioxythiophene):polysterene sulfonate (PEDOT:PSS) and cadmium telluride quantum dots. Chapter 1: Conjugated polymers and their hybrid systems are easily processible and cost effective material having huge scope for advanced materials of the future. Although variable range hopping (VRH) is widely accepted to model charge transport in π-conjugated systems, but at very low temperatures, high fields, high carrier concentrations one need to explore other models. Conjugated polymers are anisotropic intrinsically. Therefore, anisotropic charge transport can provide basic insights about the physics of charge hopping. Quantum dots, and their hybrid nanocomposites with semiconducting polymers receiving a huge attention for light emission and photovoltaic purposes. It is important to learn about the charge injection,barrier heights, etc. in order to achieve efficient hybrid devices. Chapter 2: Synthesis of the samples, both conjugated polymers and quantum dots, and fabrication of hybrid devices is an important and integral part of this thesis. An Electropolymerization technique is used for making polymer samples on conducting substrates. This is quite interesting because one can tune doping level, disorder and thickness simultaneously. Hydrothermal process is adopted to get highly aqua-dispersible quantum dots. Samples are characterized by different techniques like Raman spectroscopy, energy dispersive spectroscopy. Photoluminescence, UV-Vis absorption, transmission electron microscopy and atomic force microscopy are used to explore several properties of the polymer and hybrid nanocomposites. Chapter 3: It is known that conjugated polymers are intrinsically one–dimensional materials. Therefore it is important to learn anisotropic behavior of these complex systems. Hence, a comparison of electronic transport to their morphology has been carried out and role of carrier density and disorder is discussed further. Both in-plane and out-of-plane charge transport is studied in electrochemically deposited polypyrrole on platinum. Strong anisotropy is observed in the system which is correlated to granular morphology. Field dependence of anisotropic conductivity is also explored. Field scaling analysis shows that all field dependent curves of conductance at different temperatures can fall on to single master curve. Glazman – Matveev model is used to describe nonlinear conduction in field dependence and nonlinearity exponent is estimated. Disorder and carrier density along with the morphological structure like length and orientation of polymer chains with stacking arrangement of different layers in PPy films play an important role in governing the anisotropy in transport properties. Chapter 4: Two different techniques, namely impedance and Raman spectroscopies are used to probe disorder and transport properties in the polypyrrole. An effort is made to correlate the transport properties to the morphology by probing disorder via two different spectroscopic techniques. Frequency dependence of both real and imaginary part has shown that disorder and inhomogeneity varies in different PPy devices, which thus affect the transport properties like conductivity and mobility. Mobility values along the thickness direction for each sample reveal the impact of disorder on out-of¬plane geometry. A circuit based on consideration of the distributed relaxation times, is successfully used to obtain the best fit for the Cole–Cole plot of various PPy devices. FWHM of the de-convoluted peaks of Raman spectra is attributed to the change in distribution of the conjugation length in the PPy films. Chapter 5: The main focus of this chapter is the qualitative exploration of different photo-physical and electrical properties of electropolymerized poly(3-hexylthiophene) and their dependence on doping level. Photoluminescence quenching, band edge shifting in absorption spectra, electrochromic effect, significant enhancement in photocurrent at optimum doping level, two relaxation behaviors in reactance spectra and presence of negative capacitance at low frequencies are distinct features which are observed in poly(3-hexylthiophene) in this work. Quenching in photoluminescence intensity is attributed to charge transfer occurring between polymer chains and dopant ions. Two semicircles in the Cole-Cole plots refer to two type of relaxation process occurring in bulk layer and at interface. Frequency response of capacitance at higher bias and lo side of frequency shows a negative capacitance due to the relaxation mechanism associated with the space-charge effect. Chapter 6: Synthesis of quantum dots and fabrication of hybrid devices is one of the catchy parts of this chapter. Huge quenching photoluminescence intensity and very high increment (~ 400 %) in photocurrent clearly depict the charge transfer at molecular level. Temperature dependent current–voltage characteristics show the absence of thermionic emission since the barrier height is more than the thermal energy of the carriers. Further analysis confirms that the charge carrier injection of ITO/PPCdTe3/Al device is controlled by tunneling processes. The hybrid system has shown a peculiar transition from direct tunneling to Fowler–Nordheim tunneling mechanism which is because of the change in shape of the barrier height from trapezoidal to triangular type with increase in applied electric field. Chapter 7: The conclusions of the different works presented in this thesis are coherently summarized in this thesis. Thoughts and prospective for future directions are also summed up.

The preparation of a new group of functionalized conjugated polymer networks has been described based on spontaneous quaternization polymerization of ethynylpyridines with bis(bromomethyl)arenes. The networks consisted of polyacetylene chains with pyridyl and pyridiniumyl pendants cross-linked with -CH2(arylene)CH2- links. The variation of the ratio of monomer and quaternization agent in the feed modified the ratio of pyridyl and pyridiniumyl groups in the networks (pyridyl/pyridiniumyl ratios from 0 to 1.32). The networks did not exhibit a permanent microporosity that could be confirmed by nitrogen adsorption at 77 K. Nevertheless, all networks were active in capture of CO2 at 293 K (up to 0.73 mmol CO2/g, 750 Torr). It has been hypothesized that CO2 capture reflected formation of a temporary porous texture of the networks through conformational changes of the network segments enabled by the segments mobility at room temperature. The preparation of functionalized conjugated polymer networks with permanent micro/mesoporosity (SBET up to 667 m2 /g) has been described that was based on chain coordination copolymerization of acetylenic monomers. The copolymerization of 1,4-diethynylbenzene or 4,4'-diethynylbiphenyl with mono or diethynylbenzenes bearing NO2 or CH2OH groups has been demonstrated as...

4 ABSTRACT The synthesis has been described yielding a new type of rigid conjugated polymer networks which possess a high content of permanent micropores and macropores and exhibit high surface areas up to 1469 m2/g. The networks have been prepared via chain-growth coordination polymerization catalysed with insertion catalysts based on Rh complexes. This polymerization has been newly applied to bifunctional acetylenic monomers of diethynylarene type (1,4-diethynylbenzene, 1,3-diethynylbenzene and 4,4'-diethynylbiphenyl). The covalent structure of the networks consists of the polyacetylene main chains densely connected by arylene struts. The W and Mo metathesis catalysts have been revealed as inefficient for the synthesis of these networks. The increase in the polymerization temperature and time has been shown to affect positively the content and the diameter (up to 22 nm) of the mesopores in the networks. A mechanism has been proposed that explains the mesopores formation as a result of mutual knitting of small particles of the microporous polymer. The application of emulsion polymerization technique allowed to prepare texturally hierarchical polyacetylene networks possessing interconnected open macropores (diameter up to 4,8 μm) the walls of which exhibited micro/mesoporous texture. It was demonstrated...