In an effort to be able to use photoinitiators to their maximum potential, the sequence of events that occurs in an ink formulation during the UV curing process has have been studied and information presented to allow more effective formulation. Emphasis has been placed on highlighting the variables that have the greatest impact both on photoinitiator efficiency and on the suitability of individual photoinitiators and synergists for use in particular applications. These variables were found to be photoinitiator thermal stability, UV light utilisation, reaction mechanisms and cure reactivity. A wide range of photoinitiators and synergists were investigated using thermogravimetric analysis (TGA) and thermogravimetric analysis-mass spectroscopy (TGA-MS) to define both their thermal stability and whether under heating they thermally decompose or merely evaporate. Differential photocalorimetry (DPC) was used to determine which wavelengths from a typical medium pressure mercury curing lamp are the most important for providing cure, with both theoretical and practical methods being used to define the extent to which these wavelengths penetrate into pigmented and non-pigmented coatings. A procedure was devised and validated for this purpose. The reaction mechanism and photodecomposition products of a range of photoinitiators were investigated using gas chromatography-mass spectroscopy (GC-MS) and radical trapping experiments. The reaction mechanisms are discussed in terms of available literature knowledge. Evidence is also presented suggesting that, with only particular exceptions, cleavage photoinitiators can also react by a hydrogen abstraction mechanism in the presence of an amine synergist. A real time infrared spectrometer (RTIR) was set up and a method validated for following the UV curing reaction through changes in the acrylate double bond concentration. The advantages and disadvantages of this instrument are discussed in terms of other similar instruments reported in the literature, and the technique subsequently used to measure the reaction rates of a wide range of photoinitiators. Other factors such as photoinitiator concentration, amine synergist type I level and formulation viscosity were also investigated to determine their influence on the cure process.

No description available.

Foi estudado o processo de fotopolimerização iniciado através de misturas dos fotoiniciadores, acilfosfínicos (MAPO e BAPO), com canforquinona (CQ). Também foi investigada a existência de um possível efeito sinérgico durante a fotoiniciação. A eficiência de polimerização das duas misturas, MAPO/CQ e BAPO/CQ, foi determinada por actinometria. A fotodilatometria foi a técnica utilizada para o acompanhamento das cinéticas de polimerização. A adição do co-iniciador EDB não apresentou efeito nas velocidades de polimerização iniciadas pelos fotoiniciadores acilfosfínicos. Do ponto de vista do rendimento quântico de polimerização, um efeito antagonístico foi observado devido a transferência de energia a partir dos fotoiniciadores mais eficientes (MAPO ou BAPO) para o menos eficiente, canforquinona (CQ). / The photopolymerization processes involving two different photoinitiators: acylphosphine oxides (MAPO and BAPO) and camphorquinone (CQ) were studied in order to determine possible synergistic effects. The polymerization efficiency of the two mixtures, MAPO/CQ and BAPO/CQ, was studied using actinometry. The polymerization kinetics was followed by photodilatometry. The presence of the coinitiator EDB had no effect in the polymerization rate initiated by the acylphosphine oxides. From the point of view of photopolymerization quantum yields, an antagonistic effect is observed due to the energy transfer from the more efficient initiator (MAPO or BAPO) to the less efficient (CQ).

Foi estudado o processo de fotopolimerização iniciado através de misturas dos fotoiniciadores, acilfosfínicos (MAPO e BAPO), com canforquinona (CQ). Também foi investigada a existência de um possível efeito sinérgico durante a fotoiniciação. A eficiência de polimerização das duas misturas, MAPO/CQ e BAPO/CQ, foi determinada por actinometria. A fotodilatometria foi a técnica utilizada para o acompanhamento das cinéticas de polimerização. A adição do co-iniciador EDB não apresentou efeito nas velocidades de polimerização iniciadas pelos fotoiniciadores acilfosfínicos. Do ponto de vista do rendimento quântico de polimerização, um efeito antagonístico foi observado devido a transferência de energia a partir dos fotoiniciadores mais eficientes (MAPO ou BAPO) para o menos eficiente, canforquinona (CQ). / The photopolymerization processes involving two different photoinitiators: acylphosphine oxides (MAPO and BAPO) and camphorquinone (CQ) were studied in order to determine possible synergistic effects. The polymerization efficiency of the two mixtures, MAPO/CQ and BAPO/CQ, was studied using actinometry. The polymerization kinetics was followed by photodilatometry. The presence of the coinitiator EDB had no effect in the polymerization rate initiated by the acylphosphine oxides. From the point of view of photopolymerization quantum yields, an antagonistic effect is observed due to the energy transfer from the more efficient initiator (MAPO or BAPO) to the less efficient (CQ).

Este trabalho aborda a síntese, caracterização e estudo dos processos fotoquímicos e fotofísicos de materiais distintos baseados em corante/biopolímero e corante/argila. Os resultados e a discussão obtidos com estes materiais foram distribuídos em três capítulos, os quais foram intitulados: (i) Macrofotoiniciador biopolimérico baseado em quitosana e derivado de tioxantona; (ii) Fotoiniciador híbrido orgânico-inorgânico baseado em argila mineral e derivado de tioxantona e (iii) Híbridos orgânico-inorgânicos: fotofísica no estado sólido dos corantes auramina O e isocianina adsorvidos em argilas. O capítulo 1 descreve a preparação de um novo macrofotoiniciador baseado em quitosana e um derivado de tioxantona. A fim de compreender os processos elementares, este macrofotoiniciador foi caracterizado por diferentes técnicas espectroscópicas, tais como espectroscopia de absorção no ultravioleta-visível, fluorescência estacionária e resolvida no tempo, fotólise por pulso de laser na escala de nano- e femtosegundos. Já sua eficiência como fotoiniciador foi testada frente à fotopolimerização de um monômero acrílico e na síntese de nanopartículas metálicas de ouro e prata. No capítulo 2 é abordada a preparação, caracterização e aplicação de fotoiniciador híbrido orgânico-inorgânico baseado em derivado de tioxantona ligado covalentemente em argila. A eficiência deste fotoiniciador também foi testada frente a reações de polimerização. Ainda abordando os híbridos orgânico-inorgânicos, o capítulo 3 discute as propriedades fotofísicas no estado sólido de híbridos de dois corantes catiônicos, auramina O e isocianina, adsorvidos em argilas. Neste capitulo discutiu-se os efeitos da concentração dos corantes e do tipo de argila, utilizados como matriz sólida na preparação dos híbridos, nas propriedades fotofísicas do material híbrido e na agregação das moléculas de corante. / In the present work describe the synthesis, characterization and the study of the photochemical and photophysical processes for distinct materials based on dye/biopolymer and dye/clay. The results and discussion obtained for these materials were divided into three chapters, which were entitled: (i) Biopolymeric macrophotoinitiator based on chitosan and thioxanthone derivative; (ii) Organic-inorganic hybrid photoinitiator based on clay mineral and thioxanthone derivative; and (iii) Organic-inorganic hybrids: photophysics in solid state of auramine O and isocyanine dyes adsorbed on clays. Chapter 1 describes the preparation of a novel macrophotoinitiator based on chitosan and a thioxanthone derivative. In order to understand the elemental processes, this macrophotoinitiator was characterized by different spectroscopic techniques, such as ultraviolet-visible absorption spectroscopy, stationary and time resolved fluorescence, flash-photolysis on the nano- and femtosecond scale. The photoinitiator efficiency was tested against photopolymerization of an methacrylic monomer and in the synthesis of gold and silver nanoparticles. In Chapter 2 the preparation, characterization and application of organic-inorganic hybrid photoinitiator based on thioxanthone derivative covalently bound in clay is discussed. The efficiency of this photoinitiator was also tested against polymerization reactions. The chapter 3 discusses the photophysical properties in solid state of organic-inorganic hybrids of two cationic dyes, auramine O and isocyanine, adsorbed on clays. In this chapter it is discussed the effects of dye concentration and clay type, used as a solid matrix in the preparation of the hybrids, in the photophysical properties of the hybrid material and in the aggregation of the dye molecules.

Este trabalho aborda a síntese, caracterização e estudo dos processos fotoquímicos e fotofísicos de materiais distintos baseados em corante/biopolímero e corante/argila. Os resultados e a discussão obtidos com estes materiais foram distribuídos em três capítulos, os quais foram intitulados: (i) Macrofotoiniciador biopolimérico baseado em quitosana e derivado de tioxantona; (ii) Fotoiniciador híbrido orgânico-inorgânico baseado em argila mineral e derivado de tioxantona e (iii) Híbridos orgânico-inorgânicos: fotofísica no estado sólido dos corantes auramina O e isocianina adsorvidos em argilas. O capítulo 1 descreve a preparação de um novo macrofotoiniciador baseado em quitosana e um derivado de tioxantona. A fim de compreender os processos elementares, este macrofotoiniciador foi caracterizado por diferentes técnicas espectroscópicas, tais como espectroscopia de absorção no ultravioleta-visível, fluorescência estacionária e resolvida no tempo, fotólise por pulso de laser na escala de nano- e femtosegundos. Já sua eficiência como fotoiniciador foi testada frente à fotopolimerização de um monômero acrílico e na síntese de nanopartículas metálicas de ouro e prata. No capítulo 2 é abordada a preparação, caracterização e aplicação de fotoiniciador híbrido orgânico-inorgânico baseado em derivado de tioxantona ligado covalentemente em argila. A eficiência deste fotoiniciador também foi testada frente a reações de polimerização. Ainda abordando os híbridos orgânico-inorgânicos, o capítulo 3 discute as propriedades fotofísicas no estado sólido de híbridos de dois corantes catiônicos, auramina O e isocianina, adsorvidos em argilas. Neste capitulo discutiu-se os efeitos da concentração dos corantes e do tipo de argila, utilizados como matriz sólida na preparação dos híbridos, nas propriedades fotofísicas do material híbrido e na agregação das moléculas de corante. / In the present work describe the synthesis, characterization and the study of the photochemical and photophysical processes for distinct materials based on dye/biopolymer and dye/clay. The results and discussion obtained for these materials were divided into three chapters, which were entitled: (i) Biopolymeric macrophotoinitiator based on chitosan and thioxanthone derivative; (ii) Organic-inorganic hybrid photoinitiator based on clay mineral and thioxanthone derivative; and (iii) Organic-inorganic hybrids: photophysics in solid state of auramine O and isocyanine dyes adsorbed on clays. Chapter 1 describes the preparation of a novel macrophotoinitiator based on chitosan and a thioxanthone derivative. In order to understand the elemental processes, this macrophotoinitiator was characterized by different spectroscopic techniques, such as ultraviolet-visible absorption spectroscopy, stationary and time resolved fluorescence, flash-photolysis on the nano- and femtosecond scale. The photoinitiator efficiency was tested against photopolymerization of an methacrylic monomer and in the synthesis of gold and silver nanoparticles. In Chapter 2 the preparation, characterization and application of organic-inorganic hybrid photoinitiator based on thioxanthone derivative covalently bound in clay is discussed. The efficiency of this photoinitiator was also tested against polymerization reactions. The chapter 3 discusses the photophysical properties in solid state of organic-inorganic hybrids of two cationic dyes, auramine O and isocyanine, adsorbed on clays. In this chapter it is discussed the effects of dye concentration and clay type, used as a solid matrix in the preparation of the hybrids, in the photophysical properties of the hybrid material and in the aggregation of the dye molecules.

No description available.

<p> 3D printing has established itself as a critical tool for manufacturing in all areas. It has evolved from a purely rapid prototyping technique into a feasible process for large-scale processing. A wide variety of 3D printing processes exist across an extreme range of size, from meters to nanometers. Much of the current technological advances come from pushing fabrication techniques to smaller and smaller scales. For 3D printing this has led to the rise of two-photon polymerization, a direct laser writing process with submicron structuring capabilities. Two-photon polymerization has proven its worth as a nanoscale 3D fabrication technique but is often considered slow and expensive, two undesirable qualities for high throughput manufacturing. Parallelization methods such as projection lithography are potential solutions to increasing the throughput capabilities of two-photon polymerization 3D printing. Additionally, the drive for further reducing the print size has inspired printing resolution enhancing strategies in two-photon polymerization printing by processes such as stimulated emission depletion (STED) and other STED-inspired pathways. This work will explore avenues for improving two-photon polymerization printing throughput and resolution.</p> <p> First, a two-photon polymerization printing system is constructed with a secondary laser for controlling polymerization inhibition. Through a STED process, a 65 nm wide printed line feature was achieved. Alongside this, a characterization and verification methodology for choosing new photoinitiator molecules for similar inhibition lithography processes is presented. Through implementation of tests such as Z-scan, fluorescence depletion, ultrafast transient spectroscopy and UV-Vis absorption and fluorescence measurements a promising new photoinitiator with 5-factor improvement in printing efficiency is found. </p> <p> Second, a projection lithography scheme is developed for rapid two-photon 3D printing. A digital micro-mirror device (DMD) is utilized for dynamic pattern generation and the effects of its dispersion properties are considered. Through a spatiotemporal focusing process, continuous 3D printing is achieved at vertical prints speeds of 1 mm s-1. Simulations performed representing this rapid printing process indicate a ~1 µm layer print feature size for large areas of exposure. Comparably, a printed vertical feature size of ~ 1 µm was achieved. Lateral feature sizes ~200 nm were also demonstrated in fabrication. A variety of complex 3D structures are printed for demonstration of the spatiotemporal focusing projection lithography process including millimeter scale objects with micrometer scale 3D features.</p> <p> Finally, resolution enhancing strategies are implemented into the continuous, projection two-photon lithography technique. An investigation of the inhibition properties of a variety of photoinitiator systems for inhibiting polymerization achieved with low repetition rate laser exposure is presented. A planar polymerization inhibiting region is generated by creating a light sheet propagating perpendicularly to the projection printing plane. </p>

Orientador: Mário Fernando de Góes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-18T00:31:21Z (GMT). No. of bitstreams: 1 Antunes_AlbertoNogueiradaGama_D.pdf: 9481155 bytes, checksum: a267a90e105bb7a35b7e5367aa915a36 (MD5) Previous issue date: 2011 / Resumo: O objetivo do estudo foi avaliar a resistência à tração e nanoinfiltração de adesivos autocondicionantes unidos à dentina em função do período de armazenamento em água. Cinquenta molares humanos foram aleatoriamente distribuídos em cinco grupos com 10 dentes cada, de acordo com o adesivo: Single Bond 2, Easy One, Silorane (3M ESPE), Bond Force (Tokuyama) e Adhese One (Ivoclair Vivadent). O esmalte oclusal foi seccionado para obter uma superfície plana em dentina. Os adesivos foram aplicados sobre a superfície da dentina de acordo com as orientações de cada fabricante. Um bloco de resina composta foi construído sobre cada dente, armazenados por 24 horas em água a 37ºC, seguidos pelo seccionamento e obtenção de corpos-de-prova com o formato de palitos com área de secção transversal de 0,8±0,1mm2. Foram usados 5 palitos de cada dente (n=5) em cada período de armazenamento, 24h, 3 e 6 meses, para o teste de resistência à tração (Instron, 0,5mm/minuto). O padrão de fratura foi analisado em microscópio eletrônico de varredura. Três palitos de cada grupo (n=5), em cada período de armazenamento, foram imersos em prata amoniacal para a análise da região da união. Os valores médios obtidos no ensaio de tração (MPa) e nanoinfiltração (%) foram submetidos à Análise de Variância e teste de Fischer (p<0,05). Os valores da resistência à tração (MPa) e nanoinfiltração (%) nos períodos de 24h, 3 e 6 meses foram, respectivamente: Single Bond 2 (48,78, 37,24 e 30,32), (4,78, 4,79 e 6.14); Easy One (48,55, 39,71 e 29,96), (3,22, 2,51 e 4,87); Silorane (41,77, 36,5 e 26,27), (0,77, 0,79 e 2,18); BondForce (39,10, 34,44 e 22,54), (4,28, 4,67 e 13,10); Adhese One (24,65, 24,48 e 16,69), (3,14, 2,93 e 6,74). A resistência à tração do Adhese One foi estatisticamente diferente e inferior aos demais adesivos nos 3 períodos de armazenamento. Single Bond 2, Silorane e BondForce apresentaram resistência à tração estatisticamente diferentes nos períodos de 24h e 6 meses, enquanto que o Easy One e o Adhese One não foram diferentes estatisticamente nos mesmos períodos. O valor médio da nanoinfiltração do Silorane foi inferior e diferente estatisticamente em relação aos demais adesivos, que não apresentaram diferenças entre si no período de 24h. O adesivo BondForce apresentou o maior valor de infiltração de prata em relação aos demais adesivos com a exceção do Adhese One. Os adesivos Single Bond 2, Easy One e Silorane não apresentaram diferenças estatisticamente significantes entre si. O Silorane, BondForce e Adhese One apresentaram valores estatisticamente diferentes em relação ao período de 24h e 6 meses de armazenamento, enquanto que o Single Bond 2 e o Easy One não apresentaram diferenças no mesmo período de tempo. A fratura coesiva na camada de adesivo foi o padrão predominante para os adesivos autocondicionantes nos diferentes tempos de armazenamento. O Single Bond 2 mostrou um padrão de fratura misto, distribuído nas regiões da base da camada híbrida, coesiva no adesivo, dentina, camada híbrida e resina composta nos 3 períodos de armazenamento / Abstract: The aim of this study was to evaluate the tensile strength and nanoleakage of adhesives to dentin surface according to water storage period. Fifty human molars were randomly assigned to five groups of 10 teeth each, according to the adhesive Single Bond 2, Easy One, Silorane (3M ESPE), Bond Force (Tokuyama) and Adhese One (Ivoclair Vivadent). The occlusal enamel was sectioned to obtain a flat dentin surface. The adhesives were applied on the dentin surface according to manufacturer' s instruction. A composite block was built-up on each flat dentin, stored for 24h in water at 37°C, followed by sectioning to obtain beams with crosssectional area of 0.8 ± 0.1mm2. It was used 5 beams from each tooth (n=5) at each storage period - 24h, 3 and 6 months - to evaluate the tensile strength (Instron, 0.5mm/minute). The fracture pattern was analyzed in scanning electron microscope. Three beams of each group (n=5) in each storage period were immersed in ammoniacal silver nitrate to evaluate the nanoleakage. The average values obtained in tensile test (MPa) and nanoleakage (%) were submitted to ANOVA and Fischer's test (p<0.05). The tensile strength (MPa) and nanoleakage (%) values for 24h, 3 and 6 months were: Single Bond 2 (48.78, 37.24 and 30.32), (4.78, 4.79 and 6.14); Easy One (48.55, 39.71 and 29.96), (3.22, 2.51 and 4.87); Silorane (41.77, 36.5 and 26, 27), (0.77, 0.79 and 2.18); BondForce (39.10, 34.44 and 22.54), (4.28, 4.67 and 13.10); Adhese One (24.65, 24.48 and 16.69), (3.14, 2.93 and 6.74). The tensile strength of Adhese One was inferior and statistically different from the other groups on the three periods of storage. Single Bond 2, Silorane Bond Force 24h tensile strength values showed statistically difference to the 6 months groups, while the Easy One and One Adhese were not statistically different in the same periods. The nanoleakage of Silorane was lower and statistically different compared to the other adhesives, which do not differ from each other within 24 hours. The adhesive Bond Force showed the highest infiltration of silver compared to Easy One and Silorane while it was not statistically different from Single Bond 2 and Adhese One other adhesives with the exception of Adhese One and Single Bond 2. The Silorane, BondForce Adhese One showed 6 months nanoleakage values statistically different from 24h, but Single Bond 2 and Easy One presented no differences in the same period. A cohesive failure in adhesive layer was the predominant pattern of self-etching adhesives in three storage periods. The Single Bond 2 showed a mixed fracture pattern, distributed in hybrid layer base, cohesive in adhesive, dentin, hybrid layer and composite resin in three storage periods / Doutorado / Materiais Dentarios / Doutor em Materiais Dentários

Printing of 3-dimensional nanostructures with high-resolution by two-photon polymerization has gained significant attention recently. Isopropyl thioxanthone (ITX) has been studied and used as a photoinitiator because of its unique property in initiating and depleting polymerization, but to further improve the resolution of 3D structures, new photoinitiating materials are necessary to decrease the power requirements especially in industrial world. In this dissertation, different new types of thioxanthone-based photoinitiators were synthesized and our new initiators possessed a clear enhancement in terms of excitation over ITX. To clearly reveal the writing mechanism behind it, the behavior of the initiators was evaluated by several methods such as low temperature phosphorescence spectroscopy and density functional theory (DFT) calculations. The first type of new molecules with alkyne bridge will be discussed in chapter 2 and the further developed initiators with electron donating and withdrawing groups will be discussed in chapter 3. By modifying the structure of ITX, we have revealed and proposed an important pathway to guide future development of photoinitiators in direct laser writing.