Self-assembly of PS-PVP block copolymers and their complexes at the air/water interface

Une compréhension approfondie et un meilleur contrôle de l'auto-assemblage des copolymères diblocs (séquencés) et de leurs complexes à l'interface air/eau permettent la formation contrôlée de nanostructures dont les propriétés sont connues comme alternative à la nanolithographie. Dans cette thèse, des monocouches obtenues par les techniques de Langmuir et de Langmuir-Blodgett (LB) avec le copolymère dibloc polystyrène-poly(4-vinyl pyridine) (PS-PVP), seul ou complexé avec de petites molécules par liaison hydrogène [en particulier, le 3-n-pentadécylphénol (PDP)], ont été étudiées. Une partie importante de notre recherche a été consacrée à l'étude d'une monocouche assemblée atypique baptisée réseau de nanostries. Des monocouches LB composées de nanostries ont déjà été rapportées dans la littérature mais elles coexistent souvent avec d'autres morphologies, ce qui les rend inutilisables pour des applications potentielles. Nous avons déterminé les paramètres moléculaires et les conditions expérimentales qui contrôlent cette morphologie, la rendant très reproductible. Nous avons aussi proposé un mécanisme original pour la formation de cette morphologie. De plus, nous avons montré que l'utilisation de solvants à haut point d’ébullition, non couramment utilisés pour la préparation des films Langmuir, peut améliorer l'ordre des nanostries. En étudiant une large gamme de PS-PVP avec des rapports PS/PVP et des masses molaires différents, avec ou sans la présence de PDP, nous avons établi la dépendance des types principaux de morphologie (planaire, stries, nodules) en fonction de la composition et de la concentration des solutions. Ces observations ont mené à une discussion sur les mécanismes de formation des morphologies, incluant la cinétique, l’assemblage moléculaire et l’effet du démouillage. Nous avons aussi démontré pour la première fois que le plateau dans l'isotherme des PS-PVP/PDP avec morphologie de type nodules est relié à une transition ordre-ordre des nodules (héxagonal-tétragonal) qui se produit simultanément avec la réorientation du PDP, les deux aspects étant clairement observés par AFM. Ces études ouvrent aussi la voie à l'utilisation de films PS-PVP/PDP ultraminces comme masque. La capacité de produire des films nanostructurés bien contrôlés sur différents substrats a été démontrée et la stabilité des films a été vérifiée. Le retrait de la petite molécule des nanostructures a fait apparaître une structure interne à explorer lors d’études futures.Deeper understanding and control of the self-assembly of diblock copolymers and their complexes at the air/water interface allow the formation of nanopatterns with known properties to provide a competitive substitute to nanolithography. In this dissertation, Langmuir and Langmuir-Blodgett (LB) monolayers obtained from polystyrene-poly(4-vinyl pyridine) diblock copolymers (PS-PVP), alone and hydrogen-bonded by various small molecules [particularly, 3-n-pentadecylphenol (PDP)], have been extensively investigated. A major part of the research was devoted to the study of an uncommon monolayer pattern that we term the nanostrand network. LB monolayers consisting of nanostrands have sometimes been reported in the literature, but are often coexistent with other morphologies, which is not useful for potential applications. We have determined the molecular parameters and experimental conditions that control this morphology, making it highly reproducible, and have proposed a novel mechanism for the formation of this morphology. In addition, we have shown that the use of high-boiling spreading solvents, not usually used for Langmuir film preparation, can improve the nanostrand order. By investigation of a wide range of PS-PVP’s with various block ratios and molecular weights, with and without PDP present, we have established the composition dependence of the main LB morphology types (planar, nanostrand, nanodot) and the influence of each type on spreading solution concentration. This led to an extensive discussion concerning the mechanisms of morphology formation, including kinetic, molecular association, and dewetting contributions. We have also shown that the isotherm plateau transition for nanodot-forming PS-PVP/PDP is related to an order–order transition that occurs simultaneously with PDP reorientation, both aspects being clearly observed by AFM. These studies also form the basis for the use of ultrathin PS-PVP/PDP films as templates. The ability to produce well-controlled nanopatterned films on various substrates has been demonstrated, and film stability has been verified. Removal of small molecules from the nanostructures has revealed the appearance of new substructure of interest for further study

Threshold-like Complexation of Conjugated Polymers with Small Molecule Acceptors in Solution within the Neighbor-Effect Model

In some donor-acceptor blends based on conjugated polymers, a pronounced charge-transfer complex (CTC) forms in the electronic ground state. In contrast to small-molecule donor-acceptor blends, the CTC concentration in polymer: acceptor solution can increase with the acceptor content in a threshold-like way. This threshold-like behavior was earlier attributed to the neighbor effect (NE) in the polymer complexation, i.e., next CTCs are preferentially formed near the existing ones; however, the NE origin is unknown. To address the factors affecting the NE, we record the optical absorption data for blends of the most studied conjugated polymers, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene) (P3HT), with electron acceptors of fluorene series, 1,8-dinitro-9,10-antraquinone (DNAQ), and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in different solvents, and then analyze the data within the NE model. We have found that the NE depends on the polymer and acceptor molecular skeletons and solvent, while it does not depend on the acceptor electron affinity and polymer concentration. We conclude that the NE operates within a single macromolecule and stems from planarization of the polymer chain involved in the CTC with an acceptor molecule; as a result, the probability of further complexation with the next acceptor molecules at the adjacent repeat units increases. The steric and electronic microscopic mechanisms of NE are discussed

Exceptionally Strong Effect of Small Structural Variations in Functionalized 3,4-Phenylenedioxythiophenes on the Surface Nanostructure and Parahydrophobic Properties of Their Electropolymerized Films

Electropolymerization of electron-rich aromatics/heteroaromatics to form conducting polymers is an easy and powerful technique to form surfaces of different nanostructures and hydrophobicity/wettability. Understanding the factors governing the growth of the polymer nanostructures and controlling the surface morphology are the big challenges for the surface and materials science. In this paper, we report the design and synthesis of a series of 3,4-phenylenedioxythiophenes (PheDOTs) substituted at the benzene ring with 2-naphthylmethyl-, 1-naphthylmethyl-, and 9-anthracenylmethyl-groups (2Na-PheDOT, 1Na-PheDOT, and 9Ant-PheDOT). They have been electropolymerized in either potentiostatic or potentiodynamic conditions to form the polymer surfaces of different morphologies. Even small changes in the structure of PheDOT monomers by varying the side groups (2-/1-naphthyl-or 9-anthracenyl-) result in the formation of very different polymer surface nanostructures: From monodirectionally growing (one-dimensional) vertically aligned nanotubes for 2Na-PheDOT to ribbonlike nanostructures (two-dimensional) for 1Na-PheDOT, and a mixture of these two structures for 9Ant-PheDOT. Moreover, the surfaces of the p[2Na-PheDOT] polymer, electrodeposited from the monomer 2Na-PheDOT and the dimer (2Na-PheDOT)2 (which have different solubilities and the reactivities on electropolymerization, but formally lead to the polymer of the same chemical structure), show very different nanostructures. In contrast to 2Na-PheDOT, which forms vertically aligned nanotubes of the polymer on the surface, the polymerization of (2Na-PheDOT)2 leads to spherical particles [three-dimensional (3D)] when Bu4NClO4 is used as an electrolyte and a membrane structure with spherical holes (3D) in the case of more hydrophobic Bu4NPF6. The importance of water for gas bubble formation (O2 and H2) during electropolymerization and creation of the surface nanostructures has been demonstrated and discussed. The formation of these different nanostructures is accompanied by different wettability of the surface, from hydrophilic (with an apparent water droplet contact angle of θw ∼40-70°) to highly hydrophobic (θw up to 129-134°). The sticky, parahydrophobic surface formed from 1Na-PheDOT showed high adhesion to water, with no water droplets moving after inclination of the surface to 90° (rose-petal effect). Copyright © 2019 American Chemical Society.Government Council on Grants, Russian FederationThe authors thank the Center Commun de Microscopie Appliquée (CCMA, Univ. Nice Sophia Antipolis) for the realization of the SEM images. E.L.K. thanks the Russia President Ph.D. Scholarship for studying abroad to visit Bangor University and also thanks Act 211 Government of the Russian Federation for financial support (contract No. 02.A03.21.0006). I.S. thanks the Erasmus+ student mobility program for supporting her internship at Bangor University. I.F.P. thanks SIFE-NPU for generous startup funding

Synthesis and Properties New Derivatives of 3,4-Phenylenedioxythiophene

This work was supported by the Russian President PhD Scholarship for studying abroad and by an Act 211 Government of the Russian Federation for financial support (contract No 02.A03.21.0006)

3,4-Phenylenedioxythiophene (PheDOT): a novel platform for the synthesis of planar substituted pi-donor conjugated systems

3,4-Phenylenedioxythiophene (PheDOT), a benzenic analogue of 3,4-ethylenedioxythiophene (EDOT), has been synthesized using two different routes namely etherification of 2,5-dicarboethoxy-3,4-dihydroxythiophene with halo-aromatics and transetherification of 3,4-dimethoxythiophene with catechols. Quantum calculations and electrochemical measurements show that replacement of the ethylene bridge of EDOT by a phenyl group leads to an increase of the HOMO level and to a stabilization of the cation radical, making electropolymerization of PheDOT more difficult than that of EDOT. The synthesis of several PheDOT derivatives is described together with preliminary results on their electrochemical polymerization and on the properties of the resulting polymers and copolymers

РОЗВИТОК ЕМПАТІЙНИХ ЗДІБНОСТЕЙ У СТУДЕНТІВ-МЕДИКІВ

The aim of the work – to study the problem of empathy among medical students, cognitive and emotional direction of empathy. The main body. The study of empathy issues in psychology is of rather long history. The empathy is defined as the human ability to respond emotionally to the worries of another person, animal or any anthropomorphized subject; as an exceptionally emotional phenomenon representing the process of mutual worries – sympathy – internal perception; as realization of emotional state of another person, penetration into the worries of another man; as an ability to touch to emotional life of another person sharing his/her worries; as “transformation” into the position of another man, ability to fell in his/her position; as a sensation reproducing moral unity. In order to study possible relations between empathy and experiencing fault and shame, the empirical research was conducted involving 37 fourth-year students from Bukovyna State Medical University applying the methods of V. V. Boiko to diagnose empathy and J. Tangney to assess feelings of fault and shame. Conclusion. The necessity to investigate the level of empathy abilities of medical students and their continuous development is stipulated by the time as an important constituent of high professional and humane qualities of a modern doctor.Мета роботи – вивчити проблему емпатійності у студентів-медиків, когнітивний та емотивний напрямки емпатій. Основна частина. Вивчення проблеми емпатії в психології має досить тривалу історію. Емпатія визначається як здатність людини емоційно відгукуватися на переживання іншої людини, тварини чи будь-якого антропоморфізованого предмета; як суто емоційний феномен, що репрезентує процес співпереживання – співчуття – внутрішнього прийняття; як осягнення емоційного стану  іншого, як проникнення в переживання іншої людини; як здатність прилучатися до емоційного життя іншого, розділяючи його переживання; як “учуття” в позицію іншого, вміння поставити себе на його місце; як почуття, що передає духовне єднання. Ми провели емпіричне дослідження, у якому вибіркою стали 37 студентів ІV курсу Чернівецького медичного університету і використовувалися методики В. В. Бойка для діагностики емпатії та Дж. Тангней для вимірювання почуття провини та сорому. Здатність до емпатії разом з розвитком таких базових і загальнолюдських моральних за характером почуттів, як провини та сорому, що визначають етичну спрямованість самосвідомості особистості, є професійно важливими якостями для представників допомагаючих професій, зокрема медика. Висновок. Велінням часу є необхідність дослідження рівня емпатійних здібностей студентів-медиків та їх постійний розвиток як важлива складова частина високих професійних і медичних якостей сучасного лікаря

Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene

Photolysis (λ \u3e 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N2 at 10 K, yields triplet 3-thienylcarbene (13) and α-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cm–1, |E/hc| = 0.0554 cm–1; |D/hc| = 0.579 cm–1, |E/hc| = 0.0315 cm–1). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding σ orbital between sulfur and the neighboring carbon—an interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (λmax = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C5H4S or C5H4O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively)

Charge Delocalization in Self-Assembled Mixed-Valence Aromatic Cation Radicals

The spontaneous assembly of aromatic cation radicals (D+•) with their neutral counterpart (D) affords dimer cation radicals (D2+•). The intermolecular dimeric cation radicals are readily characterized by the appearance of an intervalence charge-resonance transition in the NIR region of their electronic spectra and by ESR spectroscopy. The X-ray crystal structure analysis and DFT calculations of a representative dimer cation radical (i.e., the octamethylbiphenylene dimer cation radical) have established that a hole (or single positive charge) is completely delocalized over both aromatic moieties. The energetics and the geometrical considerations for the formation of dimer cation radicals is deliberated with the aid of a series of cyclophane-like bichromophoric donors with drastically varied interplanar angles between the cofacially arranged aryl moieties. X-ray crystallography of a number of mixed-valence cation radicals derived from monochromophoric benzenoid donors established that they generally assemble in 1D stacks in the solid state. However, the use of polychromophoric intervalence cation radicals, where a single charge is effectively delocalized among all of the chromophores, can lead to higher-order assemblies with potential applications in long-range charge transport. As a proof of concept, we show that a single charge in the cation radical of a triptycene derivative is evenly distributed on all three benzenoid rings and this triptycene cation radical forms a 2D electronically coupled assembly, as established by X-ray crystallography