Thesis (PhD)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Finding use for byproducts from the chemical industry holds many advantages for a country's economy. Synthesis of new monomers from such byproducts adds value to otherwise otherwise low-value material. The synthesis of a new olefin-modified acrylate monomer, 1-methyl-1-propyl-hexyl acrylate (1-MPHA), derived from 1-pentene, is reported. Homopolymerisation of the monomer 1-MPHA was carried out in both benzene and in toluene. The products of full-conversion of the homopolymer poly-(1-MPHA) were characterised by GPC, NMR, TGA and DMA. Kinetic studies of the homopolymerisation process of 1- MPHAwere also undertaken. The monomer 1-methyl-1-propyl-hexyl acrylate (1-MPHA) was copolymerised with methyl methacrylate (MMA). Samples obtained from full conversion copolymerisations at various 1-MPHAIMMAfeed ratios were characterised by GPC, NMR, TGA and DMA. Reactivity ratios of the two monomers were obtained from in situ 1H NMR kinetic studies. 1-MPHA was also copolymerised with vinyl acetate (VAc). Samples obtained from full conversion copolymerisation with a 1-MPHA content ranging from 2 to 16 wt% were characterised by GPC, NMR, TGA and DMA. The solubility parameter and the hydrophobicity of the VAc/1-MPHA copolymers were also determined. Reactivity ratios of the two monomers were obtained from in situ 1HNMR kinetic studies. Further copolymerisation studies with styrene and glycidyl methacrylate as comonomers were undertaken. The chemical analysis and thermogravimetric analysis of the copolymers are reported. In conclusion, the use of 1-methyl-1-propyl-hexyl acrylate as a comonomer results in a reduction in the glass transition temperature, better thermal stability, increased hydrophobicity with an insignificant loss in stiffness of the copolymers. These properties are due to the long and branched chain structure of the 1-MPHA monomer. / AFRIKAANSE OPSOMMING: Gebruik van byprodukte van die chemiese nywerheid hou groot voordele in vir die land se ekonomie. Sintese van nuwe monomere vanuit sulke byprodukte dra by tot waardetoevoeging tot andersins lae-waarde byprodukte. Die sintese van 'n nuwe olefien-gewysigde akrilaatmonomeer afkomstig van 1-penteen, naamlik 1-metiel-1-propiel-heksielakrilaat (1-MPHA), word hier beskryf. Homopolimerisasie van die monomeer 1-MPHA is uitgevoer in beide benseen en tolueen. Die produkte van die volledige omskakeling van die homopolimeer is met behulp van GPC, KMR, TGA en DMA gekarakteriseer. Die reaksiekinetika van die homopolimerisasie van 1-MPHA is ook ondersoek. Die monomeer 1-MPHA is met metielmetakrilaat (MMA) gekopolimeriseer. Monsters van die volledig omgeskakelde kopolimere met verskeie 1- MPHNMMA voerverhoudings is m.b.v. GPC, KMR,' TGA en DMA gekarakteriseer. Die reaktiwiteitsverhoudings van die twee monomere is vanaf 1HKMR-studies bepaat. 1-MPHA is ook met vinielasetaat (VAc) gekopolimeriseer. Monsters van die produk van die volledige kopolimerisasie met 1-MPHA , met 'n inhoud van 2- 16 massa 0/0, is ook m.b.v. GPC, KMR, TGA en DMA gekarakteriseer. Die 1- MPHA het die hidrofobisiteit van VAc/1-MPHA aansienlik verhoog. Die reaktiwiteitsverhoudings van die twee monomere is vanaf in situ 1H KMRstudies bepaal. Verdere kopolimerisasiestudies met stireen en glisidielmetakrilaat as komonomere is onderneem. Chemiese- en termogravimetriese analises van die kopolimere is gedoen en gerapporteer. Ter afsluiting, die gebruik van 1-metiel-1-propiel-heksielakrilaat as komonomeer het 'n verlaging in die glasoorgangstemperatuur, verhoogde termiesestabiliteit, verhoogde hidrofobisiteit, en 'n klein verlies in die stewigheid (Eng. stiffness) van die kopolimeer tot gevolg. Hierdie eienskappe is as gevolg van die lang, vertakte kettingstruktuur van die 1-MPHA monomeer.

Controlled free radical polymerization facilitates the production of polymers with highly defined microstructures like traditional ionic polymerization; but in contrast allows for previously unattainable monomer combinations such as acrylic acid in its non-protected form. Incorporation of acrylic acid into styrene was done by random copolymerization of acrylic acid (directly and in its protected form as tert-butyl acrylate) with styrene. Styrene/tert-butyl acrylate (S/t-BuA) as well as styrene/acrylic acid (S/AA) mixtures were copolymerized to form tapered or gradient copolymers. Using an alkoxyamine unimolecular initiator, 2-[N- tert-butyl-2,2-(dimethylpropyl)aminooxy] propionic acid (BlocBuilder RTM), along with additional free nitroxide (SG1), the effect of acid protection on polymerization kinetics and copolymer composition was determined. Adding 4.5 mol% SG1/BlocBuilderRTM greatly improved the control of S/t-BuA copolymerization with low polydispersities (1.14-1.22) whereas the S/AA required higher levels of SG1 to produce polymers with low polydispersities that were comparatively still broader compared to the S/t-BuA system (polydispersities ∼ 1.3-1.4 at 9 mol% SG1/BlocBuilderRTM). S/AA copolymerization required higher SG1 concentrations to compensate for degradation of SG1 by attack from the acrylic acid monomer.

The fundamentals of the photopolymerization process are not well understood. As a result, issues affecting the cure speed and overall quality of the final product (shape, size, and surface finish) of photopolymerization impose significant limitations on applications that require fast processing and high spatial resolution. To address this issue, microrheology was employed to perform in-situ monitoring of the liquid-to-gel transition during free-radical photopolymerization. Photosensitive acrylate and hydrogel resins were exposed to ultraviolet light, while the Brownian motion of micrometer sized, inert fluorescent tracer particles was tracked via optical videomicroscopy. Statistical analysis of particle motion yielded the rheological properties of the embedding medium as a function of time and location, thereby relating UV exposure to the progress of polymerization and gelation. The microrheological setup enabled a detailed study of three-dimensional gelation profiles; other experimental parameters that were initially varied include photoinitiator concentration, monomer composition, and light intensity. Significant changes in gelation time were observed with varying UV intensity and UV penetration depth into the sample. In addition, oxygen inhibition was found to significantly impact the cure speed of monomeric resins. The preliminary results were used to test the accuracy of the energy threshold model, which is often used to empirically predict the outcome of photopolymerization reactions. By using lithographic masks to generate well-defined UV illumination patterns with characteristic dimensions of tens of micrometers, it could be shown unambiguously that the diffusion of oxygen, an inhibitor, plays a critical role in the polymerization reaction. The experiments are in excellent agreement with a simple two-step model of oxygen consumption followed by polymerization. The use of high-speed electronic shutters in the UV light path enabled us to control the illumination time of the samples with high precision. Microrheological analysis could be used to reconstruct three-dimensional profiles of partially polymerized samples. Traditional photorheometry is not capable of resolving the evolution of sample rheology with such spatial resolution. In addition, experiments with pulsed illumination were used to quantify the role of dark reactions due to residual free radicals after termination of UV illumination.

Made available in DSpace on 2014-10-09T12:34:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:02Z (GMT). No. of bitstreams: 1 17900.pdf: 755420 bytes, checksum: b49381f0e220377f0173530306d2ddf1 (MD5) / Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia) / IPEN/D-MPLO / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP; Faculdade de Odontologia, Universidade de São Paulo, São Paulo

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Dans le but d'augmenter l'utilisation du bois dans les bâtiments, il est important de repousser les limites de ses propriétés. Dans le secteur des produits du bois d'intérieur, la résistance mécanique de surface est le paramètre clé à optimiser. Concernant les couvre-planchers en bois, la résistance à l'abrasion et aux égratignures est indispensable, car ils subissent des agressions mécaniques à répétition. C'est le système de finition sans solvant à base d'acrylates photopolymérisables aux UV qui assure ce rôle de protection des couvre-planchers en bois. Malgré ses performances, l'apparition d'égratignures après une agression mécanique est inévitable. Une nouvelle approche est envisagée pour augmenter leur durée de vie, celle de conférer au système de finition la propriété d'autoréparation. Deux technologies sont étudiées au cours de cette thèse. La première est l'étude de nouvelles formulations d'acrylates contenant des liaisons hydrogène. Pour cela, des formulations de monomères et oligomères acrylates portant des groupements hydroxyles ont été développées. Pour répondre aux exigences de l'application aux couvre-planchers en bois, la dureté et le taux de polymérisation des revêtements ont été évalués, ainsi que leurs propriétés physico-chimiques. L'efficacité d'autoréparation a été évaluée sur différents types d'égratignures et plusieurs formulations prometteuses ont été développées. Elles combinent une autoréparation de plus de 90 %, une densité de réticulation élevée, et un stimulus thermique de réparation inférieur à 100 °C, grâce à des composants à faible encombrement stérique. La seconde est la synthèse de capsules contenant un agent autoréparateur. Plusieurs systèmes ont été expérimentés, tels que les capsules urée-aldéhyde, les capsules de polyuréthane sans isocyanate, et la synthèse d'isocyanates biosourcés afin d'en faire des capsules de polyuréthane biosourcé. Cependant, malgré des avancées importantes comme la synthèse d'un polyuréthane sans isocyanate, aucune capsule n'a été obtenue. / In order to increase the use of wood in buildings, it is important to push the limits of its properties. In the indoor wood products sector, surface mechanical resistance is the key parameter to optimize. Regarding wood flooring, abrasion and scratch resistance is essential because they are subject to repeated mechanical aggressions. It is the solvent-free finishing system based on UV photopolymerized acrylates that ensures this role of protecting wood flooring. Despite its performance, the appearance of scratches after mechanical aggression is unavoidable. A new approach is envisaged to increase their service life, giving to the finishing system the self-healing property. Two technologies are studied during this thesis. The first is the development of new acrylate formulations containing hydrogen bonds. For this, acrylate formulations have been developed with monomers and oligomers carrying hydroxyl groups. To meet the requirements of wood flooring application, the hardness and polymerization rate of the coatings were evaluated, as well as their physicochemical properties. Self-healing efficiency has been evaluated on different types of scratches and several promising formulations have been developed. They combine a self-healing of more than 90 %, a high cross-linking density, and a thermal repair stimulus of less than 100 °C, thanks to components with a small steric hindrance. The second is the synthesis of capsules containing a self-healing agent. Several systems have been tested, such as urea-aldehyde capsules, isocyanate-free polyurethane capsules, and the synthesis of bio-based isocyanates to make bio-based polyurethane capsules. However, despite important advances such as the synthesis of an isocyanate-free polyurethane, no capsule has been obtained.

Photopolymerization is the basis of several multi-million dollar industries including films and coating, inks, adhesives, fiber optics, and biomaterials. The fundamentals of the photopolymerization process, however, are not well understood. As a result, spatial variations of photopolymerization impose significant limitations on applications in which a high spatial resolution is required. To address these issues, microrheology was implemented to study the spatial and temporal effects of free-radical photopolymerization. In this work a photosensitive, acrylate resin was exposed to ultraviolet light, while the Brownian motion of micron sized, inert fluorescent tracer particles was tracked using optical videomicroscopy. Statistical analysis of particle motion yielded data that could then be used to extract rheological information about the embedding medium as a function of time and space, thereby relating UV exposure to the polymerization and gelation of monomeric resins. The effects of varying depth, initiator concentration, inhibitor concentration, composition of the monomer, and light intensity on the gelation process were studied. The most striking result is the measured difference in gelation time observed as a function of UV penetration depth. The observed trend was found to be independent of UV light intensity and monomer composition. The intensity results were used to test the accuracy of energy threshold model, which is used to empirically predict photo-induced polymerization. The results of this research affirm the ability of microrheology to provide the high spatial and temporal resolution necessary to accurately monitor the photopolymerization process. The experimental data provide a better understanding of the photo-induced polymerization, which could lead to expanded use and improved industrial process optimization. The use of microrheology to monitor photopolymerization can also aid in the development of predictive models and offer the ability to perform in-situ quality control of the process.

Dans ce travail, nous présentons une étude originale de l'utilisation des catalyseurs basiques solides dans la réaction de transestérification des acrylates. La réaction de l'acrylate d'éthyle avec le n-hexanol a été choisie comme réaction modèle. Les catalyseurs employés, à base d'alumines modifiées par des ions alcalins, alcalino-terreux ou fluorures, se sont avérés être actifs et sélectifs dans la réaction de transestérification, réalisée en conditions douces, sans solvant, en utilisant un rapport stoéchiométrique des réactifs. Les réactions secondaires ont été identifiées comme étant des réactions d'addition de Michael. Nous avons mis en évidence que la réaction de transestérification se produit sur des sites basiques faibles, le catalyseur Ca(NO3)2/ γ-Al2O3 ayant montré la sélectivité la plus élevée en acrylate d'hexyle (> 90%) pour une conversion supérieure à 60%. L'étude du recyclage du catalyseur nous a permis de déterminer les facteurs les plus influents tels que le contact du catalyseur avec le CO2 et l'eau ainsi que la teneur en fer de l'alumine employée comme support. Ces facteurs sont déterminants pour le recyclage du catalyseur, qui peut alors être recyclé jusqu'à 4 fois dans la réaction de transesterification de l'acrylate d'éthyle par le n-hexanol sans observer de changements significatifs de la conversion et de la sélectivité / We present an original study of the use of solid basic catalysts in the transesterification reaction of acrylates. The reaction of ethyl acrylate with n-hexanol was chosen as model reaction. The catalysts employed, based on alumina modified with alkalin, alkalin earth, and fluoride ions were shown to be active and selective for the reaction of transesterification reaction carried out under mild conditions, without solvent, using a stoechiometric amount of reactants . The secondary reactions were identified as Michael addition reactions. We demonstrated that the transesterification reaction occurs on weak basic sites, the catalyst Ca (NO3)2 /γ-Al2O3 has shown the highest selectivity in the hexyl acrylate (> 90%) for conversion greater than 60%. The study of the catalyst recycling allowed to determine the most influential factors such as the catalysts contact between CO2 and water as well as the iron content of the alumina support. These factors are critical to the success of the catalyst recycling, which was done four times in the reaction of transesterification of ethyl acrylate with n-hexanol without observing significant changes in the conversion and selectivity