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Functional light-emitting materials of platinum, zinc and boron for organic optoelectronic devices郭子中, Kwok, Chi-chung. January 2005 (has links)
published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy
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Desenvolvimento de microrreator para síntese de polímeros biorreabsorvíveis (PLLA) utilizados como implantes biomédicos / Development of microreactor for bioresorbable polymer synthesis (PLLA) used as biomedical implantsLopes, Milena Savioli, 1985- 26 August 2018 (has links)
Orientador: Rubens Maciel Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T08:53:26Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014 / Resumo: Atualmente, o conceito de sustentabilidade vem ganhando cada vez mais espaço e com ele os desafios de melhorar os processos industriais. O uso dos microrreatores surge como uma opção atraente e com potencial para atender às diversas e crescentes exigências ambientais e econômicas. Por outro lado, o mau funcionamento ou a perda de funções totais ou parciais de um órgão ou tecido resultante de doenças ou traumas, é um dos mais importantes e preocupantes problemas de saúde pública, atingindo um número significativo de pessoas em todo o mundo. Dessa forma, o principal objetivo dessa tese foi o desenvolvimento, fabricação e avaliação de microrreator capaz de realizar a síntese de polimerização do poli (L-ácido láctico) (PLLA) utilizado como implantes biomédicos. Para o cumprimento desse objetivo, foi necessário avaliar separadamente as condições de síntese e as rotas de obtenção do PLLA. O rota escolhida de polimerização para ser desenvolvida em microrreator foi a policondensação direta. Os produtos foram gerados e caracterizados por diferentes técnicas de análise. Os resultados mostraram semelhança entre os dois produtos e sua avaliação citotóxica permitiu confirmar sua aplicação com biomaterial. Pode-se concluir que o microrreator proposto apresentou-se com grande potencial na realização da polimerização do PLLA por policondensação direta do ácido láctico / Abstract: Currently, the concept of sustainability has been gaining more space and with it the challenges of improving industrial processes. The use of microreactors emerges as an attractive and potential option to meet the diverse and growing environmental and economic requirements. Furthermore, the malfunction or loss of total or partial functions of an organ or tissue resulting from disease or trauma is a major concern and public health problems, achieving a significant number of people worldwide. Thus, the main objective of this thesis was the development, manufacture and evaluation of microreactor capable of performing the synthesis of polymerization of poly (L-lactic acid) (PLLA) used as biomedical implants. To fulfill this objective, it was necessary to separately evaluate the conditions of synthesis and routes of obtaining the PLLA. The route chosen for polymerization with microreactor to be developed was in direct polycondensation. The products were generated and characterized by different analysis techniques. The results showed similarity between the two products and their cytotoxic evaluation confirmed their application with biomaterial. It can be concluded that the idea of microreactor proposed has been presented with great potential in fulfilment of the polymerization of the PLLA by direct polycondensation of lactic acid / Doutorado / Desenvolvimento de Processos Químicos / Doutora em Engenharia Quimica
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An investigation into the synthesis, characterisation and some applications of novel metal-containing polymers and dendrimers of transition metalsSmith, Gregory Stuart January 2003 (has links)
Philosophiae Doctor - PhD / metal-containing complexes, that exhibit enhanced chemical and physical properties. This thesis describes the synthesis of new metal-containing linear polymers and dendritic molecules.
Chapter 1 presents an overview of the field of metal-containing polymers, with particular attention to the synthesis of polymers via condensation polymerisation. This review
includes the various types of metal-containing condensation polymers and the applications of these materials, where available. This discussion is followed by a brief summary of
metal-containing dendrimers, which includes a concise description of their structure and applications in general.
There are two routes to preparing metal-containing polymers. Chapter 2 describes the synthesis of three bifunctional organometallic monomers, of the general type [M]-O-{2,6-(CH2OH)2-4-CH3-C6H2}, where [M] represents the various metal-containing moieties, (η5-C5H5)(CO)2 Fe(CH2)3 (25), (η5-C5H4-CH2CH2CH2-)Re(CO)3 (26) and Fpdendr
(27). These monomers were prepared using 2,6-bis(hydroxymethyl)-p-cresol as the key reagent. The monomers were used in classical polycondensation reactions with
terephthaloyl chloride using ambient temperature solution techniques. This yielded new low molecular weight oligomeric polyesters, that were characterised using FTIR and 1HNMR
spectroscopy, differential scanning calorimetry, thermogravimetric analysis and sizeexclusion
chromatography. In Chapter 3, an alternate route to metal-containing polymers is described. In this case, bifunctional organic monomers were polymerised to give preformed organic polymers. Two types of organic polymers were prepared, viz. polyesters (with pendant vinyl moieties) and polyimines (with α-diimine units along the polymer backbone).
Functionalisation of these preformed organic polymers with various metal sources was attempted. Hydrozirconation reactions of the vinyl polyesters with Schwartz’s reagent,
Cp2Zr(H)Cl, were attempted and were largely unsuccessful. Competing reactions with the ester functionality prevailed, preventing the desired reaction. Reaction of the polyimines
with PdCl2(COD) yielded insoluble, intractable metal-containing oligomers. Partial characterisation of the complexes is described. The synthesis of new poly(propylene imine) iminopyridyl metallodendrimers is described
in Chapter 4. Schiff-base condensation reaction of the commercially available DAB dendrimers with 2-pyridinecarboxaldehyde, gave the dendrimers 51, 52, and 53, with four, eight and sixteen pyridylimine functionalities respectively on the periphery. Successful complexation reactions with PdCl2(COD), PtCl2(COD) and CuCl2 produced the corresponding metal-containing dendrimers, with either PdCl2 (54, 55, 56), PtCl2 (57) or CuCl2 (58) moieties bound on the periphery. The metallodendrimers were insoluble in the
more common organic solvents, and were characterised by IR and 1H-NMR spectroscopy and microanalysis where possible. Dendrimers with salicylaldiminato ligands on the periphery were prepared by reacting the DAB dendrimers with salicylaldehyde. These ligands were reacted with various metal acetates in an attempt to prepare new metalcontaining
salicylaldimine dendrimers. This work yielded either paramagnetic metal complexes or insoluble, intractable compounds. Chapter 5 describes the applications of the catalyst precursors (54, 55, 56, 57, 58), discussed in Chapter 4, in the polymerisation of ethylene and the use of complexes 54 and 55 as Heck cross-coupling catalyst precursors. The complexes all showed catalytic activity toward ethylene polymerisation. A discussion of their activity, the polyethylene molecular weight and microstructure is presented in this chapter. The precursors 54 and 55 are also effective catalysts in the Heck reactions, coupling iodobenzene with methyl acrylate, styrene and 1-octene in high conversions. / South Africa
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Complexation of metal salts with phosphorus-containing poly(arylene ether)sBonaplata Revilla, Elena 21 July 2009 (has links)
Poly(arylene ether phosphine oxide)s (PEPO) are a recently identified subset of an important macromolecular series which includes industrially important high performance thermoplastics, such as the polysulfones, e.g. UDEL@ and polyether ketones, e.g. PEEK@, PEKK@, etc. The PEPO materials show an elevated glass transition temperature, high thermal and oxidative stability, improved solubility, and increased flame resistance. It has been demonstrated that a variety of metal salts including metals such as iron, zinc, cobalt, and copper, can be complexed at a molecular level with the phosphoryl group in films of these polymers producing novel transparent metal/polymer "composites". A procedure for obtaining homogeneous films from solutions of the metal halide complexed polymers has been developed. FTIR experiments as well as Tl phosphorus
(31 P) NMR measurements were conducted to demonstrate the existance of metal complexation in the solid state. The effect of the chemical composition of the chain, type of metal salt, molar concentration of the metal salt, and heating cycle were investigated and found to influence properties of the films such as solubility, glass transition temperature, thermal stability, and storage mexiulus.
Additionally, linear poly(arylene ether phosphine oxide)s were reduced to different extents to the corresponding phosphine containing polymers. Properties such as intrinsic One of these phosphine polymers was subsequently used in the generation of a rhodium catalyst for the hydroformylation of octene-l. The utilization of polymer-supported catalysts has important advantages such as catalyst recovery and the ease of separation of the product. The catalyst activity of the polymeric rhodium complex was studied as a function of reaction time as well as ligand to rhodium ratio. For a phosphorus/rhodium ratio of two these heterogeneous catalysts suffer in tenns of reaction rate in relation to their homogeneous counterparts. However, at phosphorus/rhodium ratios of approximately eight the reaction is almost quantitative after three hours, and the selectivity is greatly improved over that of monomeric homogeneous catalysts for the same P/Rh ratio. / Master of Science
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Continuous synthesis of metal-organic frameworks under high pressureLi, Yong J. (Yong Jun) 05 March 2012 (has links)
Metal Organic Framework (MOF) materials, consisting of metal ions with organic linkers, have a functional cavity structure which can be utilized in applications such as catalyst, micro sensing, and gas absorption. Due to MOF materials' selective gas adsorption property, interest in MOF materials has intensified in the last few years, particularly for CO, CO₂, N₂, CH₄, and H₂. MOF materials are typically synthesized by reaction under hydrothermal conditions which yields a highly crystalline product. However, reaction under solvothermal condition typically requires long reaction times - from 8 hours up to several days depending upon the particular MOF material and the reaction conditions, such as solvent, temperature, and concentration. Other synthesis methods that have been developed to address these issues include microwave synthesis, sonochemical synthesis, and mechanochemical synthesis. Reaction time can be reduced to minutes under the high energy conditions of a microwave synthesis method. A solvent free synthesis can be achieved using the mechanochemical synthesis. The sonochemical synthesis method provides an environmentally friendly process.
However, all of these synthesis methods above are batch processes and meet several difficulties in scalability and controllability. Herein, we introduce a new synthesis method for MOF materials which utilizes a continuous flow reactor process. To reduce the reaction time and solvent usage, and to maintain a high degree of the crystallinity are the goals of this study. Cu-BTC (BTC = Benzene, -1,3,5-Tricarboxylate ) or HKUST-1 Metal Organic Framework material was chosen to demonstrate the continuous flow reactor process since it has a simple MOF structure, consisting of Cu⁺² ions and BTC linkers, and has been widely studied for catalyst applications. The continuous flow synthesis method shows successful results of reduced residence time as low as 5 minutes, high crystal quality obtained, size control, and high yield with recycle solvent cooperation. The particle size control of MOF material has been shown crucial contributions in absorption application and is accomplished by adjusting the system temperature, flow rate, and solvent composition ratio. A water/ethanol mixture as the solvent in Cu-BTC synthesis reaction is environmentally friendly and easy to separate from the MOF product. In addition, the composition of water in solvent is the most influential factor to the crystal growth rate specifically in crystallization rate and nucleation rate. BTC is used in excess to achieve a production yield of about 97% based on Cu ion consumption. Since the Cu-BTC particles have a low solubility in the ethanol/water solution, they can be obtained easily using a dispersion/sonication method. The BTC rich supernatant can be recycled for use in the feed stream to maintain a high production rate, which can be beneficial for quick economic production in laboratory, as well as, commercial scale applications. / Graduation date: 2012
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Capturing molecules with templated materials: analysis and rational design of molecularly imprinted polymersWei, Shuting 09 July 2007 (has links)
Advantages such as chemical, mechanical and thermal stability together with high selectivity for the templated analyte render molecularly imprinted polymers MIPs interesting alternatives to routinely applied separation materials or antibodies. Nevertheless, many factors such as the choice of functional monomer, cross-linker, and porogenic solvent, as well as the ratio between template, functional monomer, and cross-linker will affect the resulting imprinting efficiency and polymer particle size and morphology. The research described in this thesis contributes to the development of new synthetic strategies for the generation of imprinted micro- and nanospheres for 17beta-estradiol (E2) focusing on accurate control and optimization of the governing parameters for precipitation polymerization, including the polymerization temperature and the cross-linker, yielding a one-step synthetic approach with superior control on the bead diameter, shape, monodispersity and imprinting efficiency. Thus synthesized imprinting materials for E2 were successfully applied in HPLC separation, solid phase extraction and radioligand binding assays. As the optimization of imprinted materials is based on fundamental understanding of the binding site properties, the investigations is aimed at establishing a more rational basis for further tailoring imprinted materials to the desired analytical application. The relationships between the particle porosity and rebinding properties were detailed, providing useful guidelines for controlling the particle properties for the desired application including, SPE pre-concentration, HPLC separations, and biomimetic binding assays. Furthermore, analytical techniques (1H-NMR and IR, etc.) and molecular modeling were combined in this thesis to facilitate advanced understanding of the fundamental principles governing selective recognition of molecularly imprinted polymers at a molecular level. The molecular interactions involved in the templating process of molecularly imprinted polymers based on the self-assembly approach were simulated in molecular dynamic simulation model by building a modeling system include all the imprinting components with correct ratio, which has never been reported before. Molecular level interactions such as hydrogen bonding, π-π stacking interactions as well as the free energy governing complex formation of E2 with the functional monomers 4-vinylpyridine (4VP) and methacrylic acid (MAA), and the cross-linker divinylbenzene (DVB) were discussed.
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Multi-functionalized side-chain supramolecular polymers: a methodology towards tunable functional materialsNair, Kamlesh Prabhakaran 01 October 2008 (has links)
"Multi-functionalized Side-chain Supramolecular Polymers:A Methodology Towards Tunable Functional Materials".
Even as we see a significant growth in the field of side-chain supramolecular polymers in the last ten years, systems employing multiple non-covalent interactions have been scarcely studied. Non-covalent multi-functionalization provides unique advantages such as rapid optimization via reversible functionalization as well as for the tuning of materials properties by exploiting the differences in the nature of these reversible interactions.
This thesis involves the design principles, synthesis & methodology of side-chain multi-functionalized polymers. The combination of the principles of a functionally tolerant & a controlled polymerization technique such as ROMP with multiple noncovalent interactions such as hydrogen bonding, metal coordination & Coulombic self-assembly has been used to synthesize multi-functionalized polymers. Furthermore, the orthogonality between hydrogen bonding, metal coordination & ionic self-assembly in random/block copolymers has been studied in detail.
In order to validate the viability of this multi-functionalization methodology towards materials design non-covalent crosslinking of polymers was used as a potential application. Three classes of crosslinked networks have been studied: complementary multiple-hydrogen bonded networks, multiple-metal crosslinked networks, & multi-functionalized hydrogen bonded & metal coordinated networks.
By using non-covalent multi-functionalization, important materials properties & its responsiveness towards chemical agents have been tuned & controlled to yield novel materials which would be difficult to be obtained via traditional covalent techniques or by using single non-covalent interactions.
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Poly(norbornene) supported side-chain coordination complexes: an efficient route to functionalized polymersCarlise, Joseph Raymond 11 April 2006 (has links)
This thesis begins with a brief overview of current strategies used in the synthesis of side-chain functionalizad polymers and materials. The discussion then focuses more explicitly on transition metal-based motifs and methodologies that are employed in polymer functionalization and continues with a more detailed overview of this field.
The primary hypothesis that is addressed herein is that combining the versatility and strength of metal-ligand interactions with the efficiency and functional group tolerance of ROMP comprises a useful method of generating a variety of functionalized polymers and materials via side-chain metal coordination. Thus, the goal is to test this hypothesis by synthesizing functionalized polymers with a range of useful properties to demonstrate the relevance and importance of this methodology, by employing several different strategies to show the synthetic ease by which the materials can be realized.
The strategies and methods discussed in the synthesis of side-chain functionalized polymers are divided into three subgroups: (1) pre-polymerization functionalization, in which all of the modifications take place on the monomer with polymerization as the last step, (2) post-polymerization functionalization, in which the polymer itself is subsequently modified, and (3) combinations of the first two strategies.
It is shown that useful functional polymers and materials can be synthesized by any of the above strategies, and representative examples of each are given in both the introduction and in the body of work presented.
Modes of functionalization are all based on transition metal coordination, and polymerizations are primarily carried out via ROMP. Metal coordination is shown to be a useful technique for functionalizing polymers, to creating supported emissive complexes, to modulating solution viscosity.
Finally, conclusions are drawn regarding the various strategies presented herein, and potential future directions are discussed.
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Supported catalysts, from polymers to gold nanoparticles supportsSommer, William J. 10 July 2007 (has links)
In today s world, the need to limit the use of nonrenewable resources and the importance of recycling has been recognized. One important contribution of chemists toward the general goal of limiting their use is to find catalysts that can be reused and recycled thereby limiting the need for expensive metal precursors and metal waste. Strategies to recycle catalysts are multifold and range from the employment of soluble polymers as catalyst supports to the use of membrane-encapsulated catalyst. The use of soluble polymers as a support not only offers the advantage of being soluble under the catalytic reaction conditions but also, to be removable by changing the conditions of the surrounding media. Despite the great potential of these soluble supported catalysts, their use is very limited in today s synthesis. In addition, no set of rules have been established to guide the synthesis of efficient supported catalysts. In order to establish a tool box for the synthesis of supported catalysts, the study of several parameters such as the choice of the support and the choice and the stability of the catalyst are necessary. To establish this set of rules, a limited number of catalytic transformations, were studied. These catalytic reactions are the Heck-Mizoroki, Suzuki-Miyaura and Sonogashira coupling reactions. These transformations became fundamental for the synthesis of drugs and materials. The first and second chapters provide background information by describing and evaluating the main supports that were previously used for catalysts and the two main catalysts that are used in this thesis, the palladium pincer complex and the palladium N-heterocyclic complex. In chapter 3, the synthesis of a soluble polymer supported catalyst is described. The polymer chosen for the study is poly(norbornene), and the catalyst is a 1,3-disubstituted benzene ligand with sulfurs in the side-chains able to chelate to the metal center, better known as pincer ligand. These ligands are abbreviated by the three atoms that coordinate to the metal center, in this study, SCS. The metal used for the investigation of the activity of this supported pincer is palladium. The importance of the nature of the linkage on the stability of the Pd-SCS pincer complex has been reported in the literature, leading to the synthesis of Pd-SCS pincer complex tethered to the polymer via an ether and an amide linkage. The synthesized poly(norbornene) supported Pd-SCS pincer complexes were evaluated using the Heck transformation of iodobenzene with n-butyl acrylate. Kinetic studies and leaching tests using poly(vinyl pyridine) and mercury were carried out resulting in the conclusion that the active species during the catalysis is not the palladium pincer complex but a leached palladium (0) species. In chapter 4, Pd-PCP pincer complexes with the ether and amide tether were synthesized. Kinetic and poisoning studies were carried out resulting in a similar conclusion. Furthermore, 31P NMR experiments were conducted to investigate the unstability of the complex. Following this study, in-situ XAS as well as computational calculations were carried out. The conclusion from this sinvestigation argues that triethylamine is a key ingredient for the decomposition of the Pd-PCP complex. The overall conclusion from these two different studies is thta Pd(II) pincer complexes decomposes during the Heck reaction when triethylamine is used for the coupling of iodobenzene to n-butyl acrylate in DMF at 120 ºC. Stemming from this investigation, a reported more stable complex, Pd-NHC, was tethered onto poly(norbornene). The system was evaluated using Suzuki-Miyaura, Heck and Sonogashira reactions. Similar poisoning and kinetic studies were utilized to investigate the stability of the supported NHC Pd complexes. The result of this investigation suggests that supported Pd-NHC complexes are stable under Suzuki-Miyaura and Sonogashira but decompose under Heck conditions. However, when the system was recycled, a decrease in activity for the Suzuki-Miyaura transformation and solubility was observed. In chapter 6, gold monolayer protected clusters (MPC) were investigated as potential candidates as supports. To examine the potential of MPC as a support, a NHC-Pd complex was graphted onto the particles. To functionalize the gold nanoparticles, a new method was developed. Using azide moieties added to the gold nanoparticles, the catalyst was added via microwave assisted 1,3 dipolar cycloaddition. The system was evaluated using Suzuki-Miyaura transformations under microwave conditions. The system exhibited quantitative conversions for a variety of substrates. However, when the system was recycled, aggregation of the particles and decrease in catalytic activity was observed. In summary, this thesis describes the synthesis and evaluation of poly(norbornene) supported Pd-pincer and Pd-NHC complexes and of gold nanoparticles supported Pd-NHC complex. It also detail the combination of kinetic and poisoning studies developed to evaluate a potential supported catalyst.
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Functional Derivatives Of MEHPPV Using The Dithiocarbamate Precursor RouteKolishetti, Nagesh 07 1900 (has links)
Emissive conjugated polymers, namely PPV, PPP, polyfluorenes, etc, have gained
considerable attention in recent times, specifically because of their potential application in the fields of PLED’s, displays, FET’s and sensors. The main target of the present work is the synthesis and utilization of dithiocarbamate (DTC) precursor polymers for: (a) generation of
segmented conjugated polymers of poly[2-methoxy-5-((2'-ethylhexyl)oxy)-1,4-
phenylenevinylene], MEHPPV-x, for color control and the study of their thermal elimination kinetics, (b) modulating phase separation and energy transfer in MEHPPV-x blends, (c) generation of tunable two-color patterns of conjugated polymers and (d) modification of the precursor polymer backbone by grafting and the study of its fluorescence modulation in the presence of different probe molecules.
In the first part of this work, various dithiocarbamate (DTC) precursor copolymers,
MDP-x, containing two types of leaving groups viz. methoxy and diethyldithiocarbamate
with precise control over the DTC composition, were synthesized. Thermal elimination of these precursor polymers generated segmented MEHPPV with controlled conjugation, and hence the tuning of color from green to red is achieved (figure 1). These copolymers were synthesized via a modified Wessling’s route previously developed in our laboratory.1 The
advantage of the DTC precursor over the acetate and xanthate precursor routes was that the elimination can be carried out at lower temperature (160OC) for the generation of segmented MEHPPV-x.2
(Figure 1)
Kinetic parameters, namely activation energy (Ea) and pre-exponential factor (A),
associated with the thermal elimination process of MDP-x to MEHPPV-x were determined in solution and as well as in thin films by following the evolution of the absorption spectra during the elimination process (figure 2). It was seen that the activation energy required for the elimination process was similar in both thin film and solution, whereas the pre-exponential factor was two order magnitude higher in thin films.2 This fact holds good for all the DTC compositions investigated. The thermal degradation products, carbon disulphide and
diethyl amine, were analyzed using a mass spectrometer coupled with TGA instrument,
confirming the selective elimination of the DTC groups.
(Figure 2)
Phase separation and energy transfer characteristics of segmented MEHPPV blends
containing two different distributions of conjugation lengths, namely MEHPPV-8 (LC) and MEHPPV-100 (HC), were investigated using FL, UV and confocal fluorescence microscopic
studies (figure 3). The phase separation and energy transfer in blends of the HC and LC were
(Figure 3)
modulated by addition of selective non-solvent for HC, namely cyclohexane, to the film casting solution. Typically, the extent of energy transfer to HC from LC is reduced in the presence of high volume fraction of cyclohexane.3
A novel way to generate two-color patterned substrates of MEHPPV was developed based on the control of “molecular conjugation length” using standard photo-acid generator
based photolithographic methods (figure 4). This approach relies on the use of a single
precursor containing controllable amounts of two types of thermally eliminatable groups,
only one of which eliminates in the presence of an acid while the other that is labile even in its absence. An important feature of this approach is that the colour of the unexposed regions can be controlled by varying the composition of the MDP-x precursor.
(Figure 4)
Benzyl diethyl dithiocarbamate (BDTC) is known to act as iniferter (initiator-transfer agent and terminator). MDP-x precursor polymers, which contain similar benzyl dithiocarbamate groups, were used as macro-iniferter for grafting various acrylates, viz,
(Figure 5)
methyl acrylate, benzoyloxy ethyl acrylate and t-butyl acrylate, on to the precursor backbone, which resulted in MEHPPV-g-polyacrylate after acid catalyzed thermal elimination of the residual methoxy groups (figure 5).4
The t-butyl acrylate-grafted precursor polymers, namely, MDP-g-PtBA on thermal
elimination in presence of acid underwent simultaneous acid-catalyzed thermal elimination as well as the complete hydrolysis of the t-butyl groups, leading to the formation of water soluble MEHPPV-grafted with polyacrylic acid chains, namely MEHPPV-g-PAA (figure 6). These PAA-grafted MEHPPV’s were shown to respond to various probe molecules and their optical responses were studied using fluorescence spectroscopy. These polymers could sense
methyl viologen at very low concentrations. Single-tail ammonium surfactants and non-ionic surfactant, like triton-X-100, caused a dramatic enhancement of fluorescence in solution, due to the modulation of the conjugated backbone conformation, and as a consequence the break up of intra-chain inter-chromophore excitons (figure 6).
(Figure 6)
Fof figures and molecular formula pl see the original thesis)
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