Poly(dimethylsiloxane) (PDMS) and similar polymers have proved to be of widespread interest for use in microfluidic and similar microanalytical devices. Surface modification of PDMS is required to extend the range of applications for devices made of this polymer, however. Here we report on the grafting of perfluorooctyltriethoxysilane via hydrolysis onto an oxidized PDMS substrate in order to form a fluorinated microchannel. Such a fluorinated device could be used for separating fluorous tagged proteins or peptides, similar to that which has been recently demonstrated in a capillary electrophoresis system, or in an open tubular capillary column. The modified polymer is characterized using chemical force titrations, contact angle measurements and X-ray photoelectron spectroscopy (XPS). We also report on a novel means of performing electroosmotic measurements on this material to determine the surface zeta potential. As might be expected, contact angle and chemical force titration measurements indicate the fluorinated surface to be highly hydrophobic. XPS indicates that fluorocarbon groups segregate to the surface of the polymer over a period of days following the initial surface modification, presumably driven by a lower surface free energy. One of the most interesting results is the zeta potential measurements, which show that significant surface charge can be maintained across a wide range of pH on this modified polymer, sufficient to promote electroosmotic flow in a microfluidic chip. Matrix-assisted time of flight mass spectrometry (MALDI-TOF MS) measurements show that a fluorous-tagged peptide will selectively adsorb on the fluorinated PDMS in aqueous solution, demonstrating that the fluorinated polymer could be used in devices designed forenrichment or enhanced detection of fluorous-labeled proteins and peptides. However, the non-specific adsorption of other proteins may interfere with the test results. The adsorption of four different proteins (cytochrome-C, carbonic anhydrase, insulin and ubiquitin) onto the unmodified, oxidized and fluorinated PDMS surfaces respectively was studied here with MALDI-TOF MS measurements. The results showed us that when rinsed in water/methanol solutions of high methanol concentration, cytochrome-C strongly adheres to the fluorinated surface. Carbonic anhydrase shows the opposite trend. Retention of ubiquitin on the surface shows relatively little sensitivity to either the nature of the substrate or the solution composition. Finally, the results using insulin demonstrated that this protein adheres relatively strongly to the oxidized PDMS surface as compared to the fluorinated or unmodified PDMS and showed a relative independence on the composition of the washing solution. The influence of the hydrophilicity of the protein, the surface and solvents, stability and size of proteins are discussed in the context of these observations. / Thesis (Master, Chemistry) -- Queen's University, 2008-05-12 16:49:23.672

Linear thermoplastic polyesters are commonly used in high volume applications such as food containers, films and textile fibers. The physical and mechanical properties of these materials are well documented and are a function of chemical structure and morphology (e.g. semi-crystalline, amorphous, etc.). Polyesters, as are many organic polymers, are quite flammable. Polydimethylsiloxane homopolymer exhibits low mechanical strength and, even at high molecular weight, exists as a viscous fluid rubbery gum due to its low glass transition temperature of approximately -123°C. However, one of the many attractive properties of this polymer is its relatively low flammability and if properly designed, organic "sand-like" silicates are produced in oxidizing atmospheres at elevated temperatures (e.g. 500-700°C). This thesis discusses the synthesis and characterization of novel, high molecular weight cycloaliphatic and aromatic polyester/ poly(dimethylsiloxane) segmented copolymers. The cycloaliphatic copolymers were synthesized via a melt process using a high trans content 1,4 dimethylcyclohexanedicarboxylate, and 1,4 butanediol or cyclohexanedimethanol, while the partially aromatic systems were synthesized using dimethyl terephthalate and butanediol. Primary and secondary aminopropyl terminated poly(dimethylsiloxane) oligomers of controlled molecular weight were endcapped with excess diester to form an amide linked diester terminated oligomer. The latter was then incorporated into the copolymer via melt transesterification to afford a multiphase segmented copolymer. Selected compositions showed enhanced ductility and hydrophobic surface modification. The polysiloxane segment was effeciently incorporated into the copolymers and was unaffected by the transesterification catalyst under typical reaction conditions. The homopolymers and copolymers were characterized by solution, thermal, and mechanical, and surface techniques. The segmented copolymers were demonstrated to be microphase separated as determined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission electron microscopy. The surface of the copolymers was enriched with the polysiloxane segment as evidenced by contact angle analysis. Thermal gravimetric analysis of the segmented copolymers containing identical amounts of PDMS, but varying in the primary or secondary nature of their amide linkages, exhibited quantitatively identical char yields and weight loss behavior. The segmented copolymers exhibited char yields in air superior to those of their respective homopolymers. Additionally, aromatic poly(tetramethyleneoxide) (PTMO) based polyether/polyester segmented copolymers were modified with poly(dimethylsiloxane). DMA revealed an apparent shift (higher Tg) of the PTMO segment reflecting an increase in phase mixing with the "hard" polyester segment, possibly induced by the hydrophobic PDMS phase. / Master of Science

Orientador: Carol Hollingworth Collins / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-08T23:26:20Z (GMT). No. of bitstreams: 1 SilvaJunior_EliasSeveroda_M.pdf: 1708075 bytes, checksum: 992e31e82bde038aa81939043b9dd1a7 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho foram feitos estudos de otimização das condições de preparo de fases estacionárias para uso em Cromatografia Líquida de Alta Eficiência em fase reversa (CLAE-FR) da mistura de poli(dimetilsiloxano) (PDMS) e poli(metiloctadecilsiloxano) (PMODS), sorvidos e imobilizados por tratamento térmico (em atmosfera inerte) na superfície de sílica Kromasil (esférica, 5 mm). As fases estacionárias foram avaliadas por testes químicos, físicos, cromatográficos e de estabilidade em fases móveis em condições agressivas. As melhores condições de preparo das fases estacionárias foram: sorção de 25 % PMODS e 25 % PDMS sobre sílica, mantendo 15 dias de repouso, e imobilizados a 128 °C durante 8 horas e 40 minutos. As fases estacionárias preparadas nas melhores condições apresentaram eficiências de 60000 e 38000 pratos m, respectivamente, para os compostos naftaleno e N,N-dimetilanilina, além de picos simétricos mesmo para compostos ácidos (fenol) e básicos (N,N-dimetilanilina). O estudo de caracterização através das misturas-teste de Tanaka indicou a presença de silanóis residuais, mas os resultados dos parâmetros avaliados foram razoáveis, principalmente comparados a fases PMODS, PDMS e algumas comerciais. Quanto aos testes de estabilidade, a FE manteve-se estável durante 250 volumes de coluna para o teste básico apresentando queda significativa da eficiência (60%) para o naftaleno e pequena variação na assimetria para os compostos naftaleno e N,N-dimetilanilina, já no teste ácido a FE manteve-se estável por 950 volumes de coluna apresentando uma queda suave na eficiência (10%) e variações na assimetria a partir de 400 volumes de coluna, ambos para o acenafteno, porém o fator de retenção caiu nos dois testes indicando a perda de parte da mistura polimérica / Abstract: In this work the conditions for the preparation of a stationary phase of use in reverse phase high performance liquid cromatography (RP-HPLC) with a mixture of poly(dimethylsiloxane) (PDMS) and poly(methyloctadecilsiloxane) (PMODS) sorbed and immobilized by thermal treatment (in an inert atmosphere) on Kromasil silica (spherical, 5 mm) were optimized. The stationary phases were evaluatied by chemical, physical and chromatographic tests and for stability in mobile phases having agressive conditions. The best conditions for preparation of the stationary phases were: sorption of 25 % PMODS and 25 % PDMS on to the silica, storing for 15 days and then immobilizing at 128 °C for 8 hours and 40 minutes. The stationary phases from these conditions showed efficiencies of 60000 and 38000 plates m for naphthalene and N,N-dimethylaniline and symmetrical peaks for acidic (phenol) and basic (N,N-dimethylaniline) compounds. A characterization study using Tanaka's test-mixture indicated the presence of residual silanols, but evaluation parameters were still resonable, compared to PMODS, PDMS and some commercials phases. In the stability tests the stationary phase was for stable 250 column volumes in the basic test, showing a decrease of efficiency (60 %) for naphthalene but little change in asymmetry for naphthalene and N,Ndimethylaniline. In the acid test the stationary phase maintained efficiency for 950 column volumes with some decrease in efficiency (10 %) but showed a small change in asymmetry after 400 column volumes for acenaphtene. However, the retention factor fell in both tests, showing partical loss of the polymeric mixture without changing the coverage of the support / Mestrado / Quimica Analitica / Mestre em Química

Nanoscale patterning of organic molecules has received considerable attention in current nanoscience for a broad range of technological applications. In order to provide a viable approach, this thesis describes catalytic stamp lithography, a novel soft-lithographic process that can easily produce sub-100 nm patterns of organic monolayers on surfaces. Catalytic stamps were fabricated through a two-step procedure in which the nanoscale patterns of transition metal catalysts are first produced on SiOx/Si surfaces via the use of self-assembled block-copolymers, followed by the production of the poly(dimethylsiloxane) (PDMS) stamps on top of the as-patterned metals. Simply peeling off the as-formed PDMS stamps removes the metallic nanostructures, leading to the functional stamps. A number of different patterns with various metals were produced from a commercially available family of block copolymers, polystyrene-block-poly-2-vinylpyridine, by controlling the morphology of thin-film templates through the modulation of molecular weights of polymer blocks or solvent vapor annealing. Using these catalytic stamps, hydrosilylation-based catalytic stamp lithography was first demonstrated. When terminal alkenes, alkynes, or aldehydes were utilized as molecular inks, the metallic (Pt or Pd) nanopatterns on catalytic stamps were translated into corresponding molecular arrays on H-terminated Si(111) or Si(100) surfaces. Since localized catalytic hydrosilylations took place exclusively underneath the patterned metallic nanostructures, the pattern formations were not affected by ink diffusion and stamp deformation even at the sub-20 nm scale, while maintaining the advantages of the stamp-based patterning (i.e., large-area, high-throughput capabilities, and low-cost). The concept of catalytic stamp lithography was further extended with other catalytic reactions, and successful nanoscale patterning was performed using hydrogenation (on azide-terminated SiOx surfaces) and the Heck reaction (on alkene- or bromphenyl-terminated SiOx surfaces). A range of nanopatterned surfaces with different chemical functionalities, including thiol, amine, and acid, were created, and they were further modified through appropriate chemical reactions. The potential utility of this simple approach for the construction of a higher degree of nanoarchitectures was suggested.

No description available.

Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 1.9 in2/sec (~1200 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.

Cells have the ability to sense the rigidity of the extracellular matrix which directly affects the control of cellular functions in development, wound healing and malignant transformation. Polydimethylsiloxane elastomers are useful model biomaterials for mechanotransduction studies because they possess several advantages including ease of fabrication, tunable elasticity and modifiable surface chemistry. In this work, we are investigating the influence of matrix stiffness on adhesion strength and the mechanosensory structures that regulate these processes. In addition, the effect of surface modifications to this elastic substrate system on other physical properties such as local stiffness and topography will be analyzed. Based on previous research, we hypothesized that cell adhesion dependent processes will be regulated by matrix stiffness, but that surface chemistry influences on protein adsorption could provide overriding regulatory signals. The results of this research will provide insight into the interconnected processes of mechanosensing and cell adhesion strengthening, and reveal criteria for designing instructive biomaterials with specific mechanical and chemical properties.

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / As the field of separation science evolves so do the techniques, tools and capabilities of the discipline. The introduction of microfluidics stemmed from a desire to perform traditional analyses faster and on a much smaller scale. The small device sizes exploited in microfluidics permits the investigation of very small volumes of very dilute samples yielding information inaccessible by traditional macroscale techniques. All of the chapters presented in this dissertation illustrate attempts to supplement current microscale techniques with new tools, techniques and analysis schemes for looking at biologically relevant analyses. In chapter two I present the development and characterization of an amphiphilic polymer that has potential as a material for the fabrication of microfluidic devices. This material is composed of a poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer and is dramatically more hydrophilic than the other polymeric materials currently used for the fabrication of microfluidic templates, mainly poly(dimethylsiloxane). Biomolecules such as proteins are notoriously hydrophobic and will tend to adsorb to other hydrophobic surfaces thus the use of a hydrophilic material may serve to reduce or eliminate this problem. The amphiphilic material is of a suitable durability for micromolding and molded channel architectures can be sealed between two layers of the material by simple conformal contact permitting the execution of high speed electrophoretic separations. Chapter three contains initial results obtained while investigating the fluorescent labeling and electrophoretic separation of ecdysteroids. Ecdysteroids are hormones found in insects that are responsible for controlling the process of molting. Here we attempted to analyze these molecules by employing a reactive fluorescent probe, BODIPY FL® hydrazide, that would target the α,β-unsaturated ketone group on the steroid, permitting its analysis by capillary electrophoresis with laser induced fluorescence detection. While optimistic initial results were obtained with the labeling and analysis of similar functional groups on model compounds such as progesterone, labeling of the ecdysteroid molecules was never achieved to a degree that would permit reliable analysis. In chapter four I report the development and use of a microimmunoaffinity column for the analysis of insect serine protease inhibitors, or serpins. These proteins play a very important role in the regulation of insect immune responses and their activity may play an integral role in the effective transmission of the malaria parasite by the mosquito Anopheles gambiae. A microimmunoaffinity column was constructed from magnets, poly(dimethylsiloxane), fused silica capillary and Protein A coated magnetic microspheres. In these initial studies, purified antibodies to serpin protein, as well as purified serpin protein, were used to prepare and investigate the ability to isolate, preconcentrate, and elute serpin proteins for subsequent analysis. By implementing this miniaturized system which incorporates very small fluid volumes we hoped to extend this technique to the analysis of very small samples, and eventually to the analysis of individual small insects. Our work indicates that it is possible to isolate, elute, and detect serpin protein on a traditional western blot membrane. Chapter five presents the development of a novel polymer blend for the fabrication of paper-based microfluidic devices and use of these devices in the performance of diagnostically relevant clinical assays. We took the concept of paper-based microfluidic devices and improved upon the current photoactive polymers used for their fabrication by developing a polymer blend using an acryloxy modified siloxane polymer as well as a commercially available photoactive adhesive, Norland Optical Adhesive 74. This blended polymer resulted in a dramatic reduction in fabrication time as well as improved resolution permitting the reliable patterning of small feature sizes. We also report for the first time a demonstration of these devices performing a two-step spatially separated online chemical derivatization facilitating the analysis of urinary ketones. These devices are predominantly used for the analysis of urine, and their application was extended to the quantitation of nitrite in saliva for the purposes of hemodialysis monitoring. While varied in application, all of the data presented in this dissertation exploits the power of miniaturization to improve current methods of analysis and to extend macroscale techniques to trace biological analytes.

Les nanocomposites à matrice polymère et plus particulièrement les élastomères chargés intéressent depuis de nombreuses années la communauté scientifique du fait notamment de leurs bonnes propriétés mécaniques. Il est établi que l'amélioration des propriétés mécaniques observées dans les élastomères renforcés par des charges nanoscopiques est principalement due à des effets de structure (dispersion des charges) et à des effets d'interface (interactions charges/matrice). Afin d'alimenter la discussion sur l'origine du renforcement dans les élastomères chargés, cette étude s'intéresse à la synthèse et à la caractérisation de nanocomposites modèles pour lesquels les interactions charges/matrice et la microstructure sont maîtrisées. En parallèle, ce travail propose également une analogie entre ces systèmes et les ionomères, matériaux constitués de macromolécules sur lesquelles des groupements ioniques sont greffés. Ces matériaux ionomère présentent des propriétés originales et permettent la création de nœuds de réticulation réversibles avec la température / In polymer-based nanocomposites macroscopic properties are driven by one specific feature: the huge interfacial area developed by nanofillers, leading to a strong improvement in mechanical properties. Even though the molecular origins of this reinforcement are still not well understood, its amplitude appears to be strongly related to two main effects: a structural effect (dispersion state) and an interfacial effect (filler/matrix interactions). The present project aims at developing and studying organic-inorganic nanocomposite materials based on an elastomeric matrix and spherical nanoparticles. A specific attention is paid to get tailored interactions and microstructures, different model nanocomposites are obtained with interesting and original thermo-mechanical properties. In parallel, this work also gives an analogy between these nanocomposite and ionomers, polymer chains on which ionic groups are grafted. These ionomer materials show original mechanical properties and allow creating reversible crosslink nodes with temperature

Commonly used thermoplastic biodegradable polymers are generally brittle and lack appreciable elasticity at physiological temperature and thereby fail to mimic the elastic nature of many human soft tissues such as blood vessels. Thus, there is a need for biomaterials which exhibit elasticity. Biodegradable elastomers are promising candidates whose elasticity more closely parallels that of soft tissues. In this research, we developed hybrid biodegradable elastomers comprised of organic and inorganic polymer components in a block copolymer system: poly(e-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), respectively. A block structure maintains the distinct properties of the PCL and PDMS components. These elastomers may be useful for the tissue engineering of soft tissues as well as for shape memory polymer (SMP) devices. Tri-block macromers of the form PCLn-block-PDMSm-block-PCLn were developed to permit systematic variations to key features including: PDMS block length, PCL block length, PDMS:PCL ratio, and crosslink density. The macromer was capped with acrylating groups (AcO) to permit their photochemical cure to form elastomers. Thus, a series of biodegradable elastomers were prepared by photocrosslinking a series of macromers in which the PCL blocks varied (n = 5, 10, 20, 30, and 40) and the PDMS block was maintained (m = 37). All elastomers displayed hydrophobic surface properties and high thermal stability. These elastomers demonstrated systematic tuning of mechanical properties as a function of PCL block length or crosslink density. Notable was strains at break as high as 814% making them suitable for elastomeric bioapplications. Elastomers with a critical PCL block length (n = 30 or 40) exhibited shape memory properties. Shape memory polymers based on an organic-inorganic, photocurable silicon-containing polymer system is a first of its kind. This SMP demonstrated strain fixity of 100% and strain recovery near 100% after the third thermomechanical cycle. Transition from temporary to permanent shape was quite rapid (2 sec) and at temperatures near body temperature (60 degrees C). Lastly, porous analogues of the biodegradable elastomers were created using a novel porogen - salt leaching technique. Resulting porous elastomers were designed for tissue engineering scaffolds or shape memory foams.