Academic literature on the topic 'PIMS (Polymerization Induced Micro-phase Separation)'

Polymerization-induced phase separation is comparatively applied to fabricating a superhydrophobic micro/nano surface by microwave and ultraviolet (UV) irradiation. The monolithic coatings can be tailored easily on different substrates with excellent chemical and mechanical stability in rigid conditions. Importantly, the patterned filter paper is successfully used for the colorimetric detection of nitrite handily.

The shape and porosity of polymeric colloids are two properties that highly influence their ability to accomplish specific tasks. For micro-sized colloids, the control of both properties was demonstrated by the photo-induced phase separation of droplets of NOA81—a thiol-ene based UV-curable adhesive—mixed with acetone, water, and polyethylene glycol. The continuous phase was perfluoromethyldecalin, which does not promote phase separation prior to UV activation. A profound influence of the polymer concentration on the particle shape was observed. As the photo-induced phase separation is triggered by UV radiation, polymerization drives the extracted solution out of the polymeric matrix. The droplets of the extracted solution coalesce until they form a dimple correlated to the polymer concentration, significantly changing the shape of the formed solid colloids. Moreover, control could be gained over the porosity by varying the UV intensity, which governs the kinetics of the reaction, without changing the chemical composition; the number of nanopores was found to increase significantly at higher intensities.

Herein, a novel strategy to fabricate haze films employing liquid crystal (LC) technology for photovoltaic (PV) applications is reported. We fabricated a high optical haze film composed of low-molecular LCs and polymer and applied the film to improve the energy conversion efficiency of PV module. The technique utilized to fabricate our haze film is based on spontaneous polymerization-induced phase separation between LCs and polymers. With optimized fabrication conditions, the haze film exhibited an optical haze value over 95% at 550 nm. By simply attaching our haze film onto the front surface of a silicon-based PV module, an overall average enhancement of 2.8% in power conversion efficiency was achieved in comparison with a PV module without our haze film.

AbstractDiffractive approaches are needed when refractive microlenses reach their focusing limit at the micron-scale in visible light. Previously, we have reported on micron-sized optical lenses based on the diffraction of metallic nanowires. Here, we extend our study to lenses based on pairs of subwavelength dielectric scatterers. Using simulations by two-dimensional finite element method, we demonstrate that focusing holds for pair spacings as small as the wavelength-size. For pairs with distances between inner walls larger than about 1.2λ, the scattered waves generate a quadratic phase modulation on the total propagating field leading to a diffraction-limited focusing i.e. an effective optical lens effect with high numerical aperture. In addition, they have low sidelobe intensities, long depths of focus, and they have a low sensitivity with polarization. For pairs with inner wall distances smaller than about 1.2λ, the focusing phase modulation is accumulated during the propagation through the dielectric pair structure. In this work, we report only on the experimental demonstration for the case of larger wall separation to emphasize on the scattered wave effect on micro-focusing. A pair of parallel polymer lines (cylindrical lens), and a grid of polymer lines (square microlens array) with 2 μm-spacing were fabricated by two-photon induced polymerization. Their focal lengths are comparable to their separating distances, their spot-sizes are 0.37 μm and 0.28 μm at wavelength 530 nm, and their focusing efficiencies are 70% and 60%, respectively.

Abstract Elevated fetal hemoglobin (HbF) expression ameliorates the clinical severity of sickle cell disease (SCD) by inhibiting hemoglobin S polymerization. Differences in HbF levels are attributed to inherited DNA genetic variations that regulate γ-globin transcription; however the role of microRNA (miRNA) genes in HbF regulation has not been investigated using clinical samples. miRNAs are small non-protein-coding RNA molecules that negatively regulate gene expression through inhibition of mRNA translation. Our goal is to identify miRNA genes with altered expression in sickle cell patients with elevated HbF levels, to elucidate mechanisms of γ-globin gene regulation. After IRB approval, peripheral blood was collected from SCD patients (not on hydroxyurea therapy), followed in the pediatric and adult Sickle Cell Clinics at Georgia Regents University. HbF levels measured by high performance liquid chromatography and complete blood and reticulocyte counts were obtained. Twelve blood samples, six each from SCD subjects with high HbF (19.9±2.1%) or low HbF (4.4±0.9%) levels were analyzed. We observed more severe anemia and higher reticulocyte counts in the low HbF group. After Histopaque separation, red blood cells were processed on a MACS column with anti-CD71 antibody to isolate reticulocytes, followed by total RNA extraction using Trizol. RNA (750ng) was hybridized to a genome-wide miRCURY LNA microRNA Array (Exiqon) containing 1,921 human probes. The microarray raw data were collected on an Agilent G2565BA Microarray Scanner System and normalized by Model-Based Background Correction and Principle Component Analysis. Characterization of miRNA profiles for low HbF compared to high HbF groups identified 327 differentially expressed genes including multiple miR-144 isoforms. We subsequently explored the function of miR-144 because it targets Nrf2 which mediates drug-induced HbF expression and Nrf2 has an antioxidant protective effect in SCD. Therefore, we conducted supervised learning of the normalized microarray data based on miR-144 expression. Interestingly, in the low HbF group we observed two subphenotypes: 1) associated with 8-fold increased miR-144 expression (3 subjects) and 2) associated with no change in miR-144 level (3 subjects) when compared to the high HbF group suggesting a role of miR-144 in HbF regulation. In the supervised learning analysis, there were 62 up-regulated and 33 down-regulated miRNAs (>2-fold; p<0.05) in the first subphenotype. We hypothesized that miRNAs up-regulated in the low HbF group might silence known γ-globin trans-activators. By TargetScan and Miranda analysis 7 miRNAs were predicted to target γ-globin including miR-96 a known negative regulator. There were 4 miRNAs predicted to target Nrf2 and 12 miRNAs that target other transcription factors such as KLF1, KLF4, BCL11A, and GATA2. To define a functional role of miR-144 we conducted studies in adult CD34+ stem cells grown in a two-phase culture system containing Stem Cell Factor (50ng/mL), Interleukin-3 (10ng/mL) and Erythropoietin (4IU/mL). At day 8 in culture, miR-144 mimic, miR-144 antagomir (inhibitor) or scrambled control (100nM, 200nM, and 300nM) were transfected using a Nucleofector System. After 72 hr incubation, RT-qPCR was conducted to measure γ-globin and Nrf2 mRNA levels. miR-144 mimic or antagomir at 100-300nM concentrations had no significant effect on γ-globin mRNA levels. By contrast, flow cytometry analysis using a FITC-anti-γ-globin antibody in erythroid cells treated with miR-144 mimic, produced a 30-70% decrease in HbF positive cells (p<0.05). On the contrary, we observed a 1.8-fold increase in HbF positive cells mediated by 300nM miR-144 antagomir. Evidence that miR-144 targets Nrf2 was established when antagomir treatment increased Nrf2 expression 1.4-fold (p<0.05). Final studies using day 8 erythroid progenitors treated with Nrf2 siRNA demonstrated a 40% decrease in γ-globin mRNA supporting a role of Nrf2 on γ-gene expression. In summary, the miRNA profiles associated with HbF expression in SCD patients combined with functional studies in human primary erythroid progenitors, support a role for miR-144 in γ-globin regulation. These findings will be expanded to a pre-clinical SCD mouse model to develop miR-144 as a potential therapeutic option. Disclosures No relevant conflicts of interest to declare.

AbstractThe distribution of molecular weights in polymers, known as the molecular weight distribution (MWD), plays a significant role in dictating the behavior of polymer self‐assembly and influencing the characteristics of the resulting materials. This study investigates how MWD of macromolecular chain‐transfer agents (macroCTAs) impact internal nanostructures in materials prepared by polymerization‐induced microphase separation (PIMS) 3D printing. In the aim of elucidating this relationship, the study initially harnessed the precision offered by narrow‐MWD macroCTAs, which provide precise control over phase separation, as assessed by atomic force microscopy (AFM) and small‐angle X‐ray scattering (SAXS) measurements. Through systematic variation of macroCTA molecular weights, the dimensions of the distinct domains were precisely tuned from 10 to 90 nanometers and a decrease of materials stiffness was observed with increased domain size. In contrast, the utilization of a broader MWD, achieved by blending two distinct macroCTAs, resulted in increased domain size dispersity and reduced interface sharpness, without significantly affecting the mechanical properties of the 3D‐printed materials. Overall, this approach expands the strategies for manipulating the nanoscale architecture of 3D‐printed PIMS materials, opening new possibilities for printing advanced engineering materials with tailorable properties.

ABSTRACTWe have analyzed the micro-phase separation during photo-polymerization in the liquid crystal/polymer composite films for a variety of light-control applications. The photo-polymerization induced phase separation process is remarkably affected by the reactivity in diacrylates and the fraction volume in liquid crystals. It is presumed that the nematic transition in a liquid crystal-rich phase and the reactivity play an important role to determine the morphology.

Le but de ce travail de thèse a été d’élaborer une résine permettant le procédé PIMS (Polymerization Induced Micro-phase Separation) en photopolymérisation sous l’irradiation des longueurs d’onde du visible, applicable à l’impression 3D et donnant accès à des matériaux thermoplastiques aisément recyclables. Cette thèse s’est donc articulée autour de 3 axes principaux. Tout d’abord, de nouveaux photoamorceurs de Type I, permettant une photopolymérisation efficace sous l’irradiation du visible, ont été développés. Pour ce faire, les propriétés physico-chimiques d’une centaine de composés dérivés des oxydes de phosphines ont été calculées par modélisation moléculaire et les candidats les plus prometteurs ont été synthétisés. L’efficacité de ces nouveaux photoamorceurs a ensuite été évaluée en photopolymérisation et ceux avec les meilleures réactivités ont été utilisés avec succès en impression 3D. Dans une seconde partie, le macro-amorceur Flexibloc, fourni par Arkema, a été introduit dans des résines photosensibles, avec des compositions variées, afin de permettre le procédé PIMS. Différentes stratégies d’amorçages photochimiques ont aussi été étudiées. Néanmoins, en présence du Flexibloc, il n’a pas été possible d’obtenir un copolymère à blocs et le procédé PIMS. Par conséquent, de nouveaux macro-(co)amorceurs, fonctionnalisés avec des amines tertiaires, ont été synthétisés pour remplacer le Flexibloc dans les résines photopolymérisables. Finalement, ces nouveaux composés ont permis une photopolymérisation et une impression 3D efficaces. En outre, grâce à ces nouveaux macro-coamorceurs, il a été possible d’obtenir des copolymères et le procédé PIMS en photopolymérisation
The aim of this thesis was to develop a resin enabling the PIMS process (Polymerization Induced Micro-phase Separation) in photopolymerization under the irradiation of visible lights, applicable to 3D printing and giving access to easily recyclable thermoplastic materials. For this purpose this thesis was structured around 3 main axis. First, new Type I photoinitiators have been developed, enabling efficient photopolymerization under visible light irradiation. For this purpose, the physico-chemical properties of a hundred compounds derived from phosphine oxides were calculated by molecular modeling, and the most promising candidates were synthesized. The efficiency of these new photoinitiators was then evaluated in photopolymerization, and those with the best reactivities were successfully used in 3D printing. In the second part, the Flexibloc macro-initiator, supplied by Arkema, was introduced into photosensitive resins with various compositions to enable the PIMS process. Multiple photochemical initiation strategies have also been studied. However, with the Flexibloc, it was not possible to obtain a block copolymer or the PIMS process. As a result, new macro-(co)initiators, functionalized with tertiary amines, have been synthesized to substitute the Flexibloc in photosensitive resins. Finally, these new compounds enabled efficient photopolymerization and 3D printing. In addition, these new macro-coinitiators made it possible to obtain copolymers and the PIMS process in photopolymerization