Development of S-13G-type coatings as engineering materials Final report, 1 Sep. 1966 - 31 Aug. 1968

S-13G type thermal control coatings for space application

Direct visualization of pyrrole reactivity by confined oxidation in a Cyclodextrin Metal‐Organic Framework

Metal-organic frameworks can be used as porous templates to exert control over polymerization reactions. Shown here are the possibilities offered by these crystalline, porous nanoreactors to capture highly‐reactive intermediates for a better understanding of the mechanism of polymerization reactions. By using a cyclodextrin framework the polymerization of pyrrole is restricted, capturing the formation of terpyrrole cationic intermediates. Single‐crystal X‐ray diffraction is used to provide definite information on the supramolecular interactions that induce the formation and stabilization of a conductive array of cationic complexes

Waterborne Acrylic/CeO2 Nanocomposites for UV Blocking Clear Coats

The encapsulation of inorganic nanoparticles into polymer particles opens the door to countless applications taking advantage of the properties of both phases. In this chapter the UV absorbing capacity of CeO2 nanoparticles and the film forming capacity of acrylic polymers are combined. A synthetic route to produce waterborne acrylic/CeO2 hybrid nanocomposites for UV absorbing coatings applications is presented. This strategy leads to encapsulated morphology of the CeO2 nanoparticles into the polymer particles and therefore to the lack of agglomeration during film formation. A mathematical model developed for inorganic/organic hybrid systems is able to explain the morphology evolution from the initial monomer droplet to the polymer particles. The films cast from these latexes are transparent and show excellent UV absorption that increases with the amount of cerium oxide nanoparticles in the hybrid latex. Finally, the photoactivity behavior that the CeO2 nanoparticles may have on the polymeric matrix is studied, discarding additional effects on the acrylic polymer matrix

Chapter Waterborne Acrylic/CeO2 Nanocomposites for UV Blocking Clear Coats

The encapsulation of inorganic nanoparticles into polymer particles opens the door to countless applications taking advantage of the properties of both phases. In this chapter the UV absorbing capacity of CeO2 nanoparticles and the film forming capacity of acrylic polymers are combined. A synthetic route to produce waterborne acrylic/CeO2 hybrid nanocomposites for UV absorbing coatings applications is presented. This strategy leads to encapsulated morphology of the CeO2 nanoparticles into the polymer particles and therefore to the lack of agglomeration during film formation. A mathematical model developed for inorganic/organic hybrid systems is able to explain the morphology evolution from the initial monomer droplet to the polymer particles. The films cast from these latexes are transparent and show excellent UV absorption that increases with the amount of cerium oxide nanoparticles in the hybrid latex. Finally, the photoactivity behavior that the CeO2 nanoparticles may have on the polymeric matrix is studied, discarding additional effects on the acrylic polymer matrix

Comb-like acrylic-based polymer latexes containing nano-sized crystalline or liquid crystalline domains

306 p.Conventional (meth)acrylate polymer latexes have been widely used for coatings, adhesives, paper and textile finishes, cement additives and other applications. These polymers exhibit useful properties such as adhesion to relatively polar substrates (steel, aluminum, tin, glass and wood), durability, weather resistance, flexibility in composition and glass transition temperature, and compatibility with many polar polymers and inorganic components. However, since these polymers are generally amorphous, they cannot compete in demanding applications where polymers with some degree of crystallinity performed well; e.g., they do not adhere well to most non-polar substrates such as polyolefins, they do not exhibit good mechanical properties (toughness) and they are inferior to olefins in terms of water resistance, barrier properties and durability. Therefore, there is a need of polymer compositions which provide better mechanical and barrier properties, adhesion to polar and non-polar substrates, water and weather resistances and durability. Crystalline and liquid crystalline domains are known to impart improved mechanical and barrier properties of polymers; therefore, the introduction of crystalline and/or liquid crystalline domains in amorphous (meth)acrylate polymer matrix may be a good solution for the above mentioned purpose.This work focus on both coating and adhesive applications of waterborne (meth)acrylic-based copolymer latexes containing crystalline domains and liquid crystalline polymers. The polymer latexes were synthesized via 2-step seeded miniemulsion copolymerization of a crystallizable long side chain acrylate monomer (stearyl acrylste, SA) (first method) or side chain liquid crystalline monomer (SCLCM) (second method) with short side chain (meth)acrylates. Thermal characterization of the films prepared from these latexes indicated that the heat of fusion and crystallinity of the copolymer latexes increased with SA or SCLCM content. The performance of coating films showed that the presence of poly(SA) crystalline and/or liquid crystalline domains reinforced the mechanical properties of polymer films. Conversely, the amorphous domains of poly(SA) and side chain liquid crystalline polymers had plasticizing effects and decreased the mechanical properties of the copolymers. Moreover, the presence of poly(SA) and side chain liquid crystalline polymers improved the barrier and water sensivity of the polymer films. Additionally, for pressure sensitive adhesives (PSAs) it was found that shear resistance, peel resistance and loop tack of soft acrylic-based PSAs increased with crystalline content. Moreover, the PSAs containing crystalline domains showed thermo-responsive behavior

A review on flexible electrochemical biosensors to monitor alcohol in sweat

The continued focus on improving the quality of human life has encouraged the development of increasingly efficient, durable, and cost-effective products in healthcare. Over the last decade, there has been substantial development in the field of technical and interactive textiles that combine expertise in electronics, biology, chemistry, and physics. Most recently, the creation of textile biosensors capable of quantifying biometric data in biological fluids is being studied, to detect a specific disease or the physical condition of an individual. The ultimate goal is to provide access to medical diagnosis anytime and anywhere. Presently, alcohol is considered the most commonly used addictive substance worldwide, being one of the main causes of death in road accidents. Thus, it is important to think of solutions capable of minimizing this public health problem. Alcohol biosensors constitute an excellent tool to aid at improving road safety. Hence, this review explores concepts about alcohol biomarkers, the composition of human sweat and the correlation between alcohol and blood. Different components and requirements of a biosensor are reviewed, along with the electrochemical techniques to evaluate its performance, in addition to construction techniques of textile-based biosensors. Special attention is given to the determination of biomarkers that must be low cost and fast, so the use of biomimetic materials to recognize and detect the target analyte is turning into an attractive option to improve electrochemical behavior.Authors acknowledge the Portuguese Foundation for Science and Technology (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI) and the Portuguese Government (OE) for funding the project PluriProtech—“Desenvolvimentos de soluções multicamada para proteção ativa contra ameaças NBQR”, ref. POCI-01-0247-FEDER-047012. Authors also acknowledge strategic funding of UID/CTM/00264/2020 of 2C2T and by the “plurianual” 2020–2023 Project UIDB/00264/2020

3D correlative single-cell imaging utilizing fluorescence and refractive index tomography

Cells alter the path of light, a fact that leads to well-known aberrations in single cell or tissue imaging. Optical diffraction tomography (ODT) measures the biophysical property that causes these aberrations, the refractive index (RI). ODT is complementary to fluorescence imaging and does not require any markers. The present study introduces RI and fluorescence tomography with optofluidic rotation (RAFTOR) of suspended cells, quantifying the intracellular RI distribution and colocalizing it with fluorescence in 3D. The technique is validated with cell phantoms and used to confirm a lower nuclear RI for HL60 cells. Furthermore, the nuclear inversion of adult mouse photoreceptor cells is observed in the RI distribution. The applications shown confirm predictions of previous studies and illustrate the potential of RAFTOR to improve our understanding of cells and tissues.Comment: 15 pages, 5 figure

Responsive liquid crystal polymer rods

In this dissertation I report on the successful fabrication of anisotropic liquid crystal polymer rods. These polymer rods demonstrated re-orientation by an applied external field. The polymer rods, 200 nm in diameter and a maximum of 60 mum in length, were produced by a template synthesis technique. A reactive liquid crystal monomer was filled into porous Anopore membranes which were used as a confining media. The liquid crystal monomer was polymerized by UV light while the liquid crystal remained in the nematic temperature range. The polymerization process permanently freezes the orientational order of the confined liquid crystal molecules, producing rods that are temperature independent after curing. The curing is kept in the nematic range to ensure proper orientational alignment in the pore of the membrane, where the responsive nature of the rods can be tailored by temperature, external fields, and/or surface treatments. The rods were suspended in low viscosity silicone oil and injected into indium tin oxide coated glass cells.;Both DC and AC electric fields were applied to the electro-optical glass cells, resulting in different types of rod movement. Switching times (time to change orientation from horizontal to vertical) has been observed to be as fast as 0.1 seconds and the threshold voltage has been as low as 5 volts. The switching times of the rods are mainly driven by the strength of the applied field and the molecular orientation of the rods. A model was used to describe the best case scenario of the rod structures and outlines that faster switching times are possible. Translational movement (moving vertical with the rod staying in the horizontal position) was also noted with the DC applied field. AC fields give different types of movement including rotational, vibrating, and swimming motions. The average rotational speed was found to vary linearly with the applied field strength, where the fastest speeds were at the highest field strength. Also, responsive rods were noted to move and push unresponsive rods in and out of the viewing area. The responsive rods are technologically important for possible electro-rheological fluids, magneto-rheological fluids, and components in microfluidic devices

Detection of humidity-treated aged latent prints using cyanoacrylate fuming and a reflected ultraviolet imaging system (RUVIS)

For the past several decades, challenges in the detection and collection of latent prints exposed to harsh environmental conditions have inspired research in pretreatment methods prior to the application of chemical, physical, or optical-based enhancement techniques. Some of the difficulties associated with processing degraded latent prints are attributed to dehydration, alterations in chemical composition, and physical disturbance of ridge detail. This study seeks to investigate the effectiveness of humidity, cyanoacrylate fuming method (CFM), and a reflected ultraviolet imaging system (RUVIS) on the detection and collection of aged latent palmprints. Prints were exposed to air flow and ultraviolet (UV) light for a period of 0 to 28 days, and subsequently treated with either cool or warm humidity and CFM. RUVIS was then utilized to detect and capture friction ridge detail after each treatment step. Improvements in RUVIS detection between treatments were evaluated based on four response factors: minutiae count, percent print recovery, ridge thickness and contrast. By measuring these factors, each latent print photograph was able to be converted to quantifiable data to facilitate statistical analysis of potential differences or improvements between treatments. The results demonstrate that the application of 80% relative humidity successfully revived aged latent palmprints across all factors. The combined effect of humidity followed v by CFM treatment and RUVIS detection was greatest for minutiae count and ridge thickness, while percent print recovery and contrast demonstrated more modest improvements when compared to control prints. Additionally, cool temperature treatments outperformed warm temperature treatments across all factors except contrast. The data therefore suggest that to achieve print rejuvenation and overall improvements in RUVIS detection, combined cool humidity and CFM is more effective than humidity alone. The data also indicate a potential correlation between temperature treatments and latent print age. Warm humidity combined with CFM appeared to best enhance RUVIS images on fresher prints of a few days to one week old, while cool humidity and CFM appeared to maximally enhance RUVIS images on prints of several weeks old