Structure of plasma (re)polymerized polylactic acid films fabricated by plasma-assisted vapour thermal deposition

Plasma polymer films typically consist of very short fragments of the precursor molecules. That rather limits the applicability of most plasma polymerisation/plasma-enhanced chemical vapour deposition (PECVD) processes in cases where retention of longer molecular structures is desirable. Plasma-assisted vapour thermal deposition (PAVTD) circumvents this limitation by using a classical bulk polymer as a high molecular weight “precursor”. As a model polymer in this study, polylactic acid (PLA) has been used. The resulting PLA-like films were characterised mostly by X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR) spectroscopy. The molecular structure of the films was found to be tunable in a broad range: from the structures very similar to bulk PLA polymer to structures that are more typical for films prepared using PECVD. In all cases, PLA-like groups are at least partially preserved. A simplified model of the PAVTD process chemistry was proposed and found to describe well the observed composition of the films. The structure of the PLA-like films demonstrates the ability of plasma-assisted vapour thermal deposition to bridge the typical gap between the classical and plasma polymers. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Czech Science FoundationGrant Agency of the Czech Republic [GA17-10813S]; Charles University [SVV 260 579-2020]Univerzita Karlova v Praze, UK; Grantová Agentura České Republiky, GA ČR: GA17-10813

Plasma polymers as targets for laser-driven proton-boron fusion

Laser-driven proton-boron (pB) fusion has been gaining significant interest for energetic alpha particles production because of its neutron-less nature. This approach requires the use of B- and H-rich materials as targets, and common practice is the use of BN and conventional polymers. In this work, we chose plasma-assisted vapour phase deposition to prepare films of oligoethylenes (plasma polymers) on Boron Nitride BN substrates as an advanced alternative. The r.f. power delivered to the plasma was varied between 0 and 50 W to produce coatings with different crosslink density and hydrogen content, while maintaining the constant thickness of 1 μm. The chemical composition, including the hydrogen concentration, was investigated using XPS and RBS/ERDA, whereas the surface topography was analyzed using SEM and AFM. We triggered the pB nuclear fusion reaction focusing laser pulses from two different systems (i.e., the TARANIS multi-TW laser at the Queen’s University Belfast (United Kingdom) and the PERLA B 10-GW laser system at the HiLASE center in Prague (Czech Republic)) directly onto these targets. We achieved a yield up to 108 and 104 alpha particles/sr using the TARANIS and PERLA B lasers, respectively. Radiative-hydrodynamic and particle-in-cell PIC simulations were performed to understand the laser-target interaction and retrieve the energy spectra of the protons. The nuclear collisional algorithm implemented in the WarpX PIC code was used to identify the region where pB fusion occurs. Taken together, the results suggest a complex relationship between the hydrogen content, target morphology, and structure of the plasma polymer, which play a crucial role in laser absorption, target expansion, proton acceleration and ultimately nuclear fusion reactions in the plasma

Multikomponentní plazmové polymery s prostorově řízenými vlastnostmi

Title: Multicomponent plasma polymers with spatially controlled properties Author: MSc. Pavel Pleskunov Department / Institute: Department of Macromolecular Physics/Charles University Supervisor of the doctoral thesis: Prof. Ing. Andrey Shukurov, PhD, Department of Macromolecular Physics / Charles University Abstract: Mixing of two (or more) polymers often leads to phase separation and to the formation of nanoscale architecture, which can be highly attractive in various applications including controllable drug delivery, fabrication of separation and solid electrolyte membranes, gas storage, etc. Different wet-chemistry techniques already exist to produce nanophase-separated polymers; however, capturing the resultant polymeric structure in a predictable manner remains a challenging task. In this thesis, a low-temperature plasma-based strategy is investigated for the production of multicomponent thin films of plasma polymers with spatially discriminated nanoscale domains. Gas aggregation cluster source is used for the fabrication of nanoparticles of plasma polymerized acrylic acid, whereas Plasma-Assisted Vapor Phase Deposition is used for the deposition of thin films of poly(ethylene oxide) plasma polymer. Embedding of nanoparticles into matrices of thermodynamically incompatible plasma polymer as well as...Název práce: Multikomponentní plazmové polymery s prostorově řízenými vlastnostmi Author: Mgr. Pavel Pleskunov Katedra/Ústav: Katedra Makromolekulární Fyziky/Univerzita Karlova Vedoucí doktorské práce: Prof. Ing. Andrey Shukurov, PhD Abstrakt: Směšování dvou či více polymerů často vede k jejich fázové separaci a ke vzniku nanostruktur, které jsou atraktivní pro využití v různých aplikacích včetně řízeného podávání léčiv, přípravy separačních membrán, membrán s pevným elektrolytem, skladování plynů atd. Ačkoliv již byly vyvinuty nejrůznější metody přípravy nanofázově separovaných polymerů, které jsou založeny na "mokré" chemii, řízení a předpověditelné ovlivňování jejich finální struktury doposud představuje obtížný vědecký problém. V předkládané disertační práci je zkoumána možnost přípravy vícesložkových tenkých vrstev plazmových polymerů s prostorově odlišitelnými nanodoménami pomocí metod založených na využití nízkoteplotního plazmatu. Nanočástice plazmových polymerů jsou připravovány pomocí plynových agregačních zdrojů, zatímco matrice plazmových polymerů (plazmově polymerizovaný polyetylénoxid) jsou nanášeny v podobě tenkých vrstev pomocí plazmatem podporované depozici z plynné fáze. Je zkoumáno zabudovávání nanočástic do termodynamicky nekompatibilního plazmového polymeru i ko- depozice dvou...Katedra makromolekulární fyzikyDepartment of Macromolecular PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Multicomponent plasma polymers with spatially controlled properties

Title: Multicomponent plasma polymers with spatially controlled properties Author: MSc. Pavel Pleskunov Department / Institute: Department of Macromolecular Physics/Charles University Supervisor of the doctoral thesis: Prof. Ing. Andrey Shukurov, PhD, Department of Macromolecular Physics / Charles University Abstract: Mixing of two (or more) polymers often leads to phase separation and to the formation of nanoscale architecture, which can be highly attractive in various applications including controllable drug delivery, fabrication of separation and solid electrolyte membranes, gas storage, etc. Different wet-chemistry techniques already exist to produce nanophase-separated polymers; however, capturing the resultant polymeric structure in a predictable manner remains a challenging task. In this thesis, a low-temperature plasma-based strategy is investigated for the production of multicomponent thin films of plasma polymers with spatially discriminated nanoscale domains. Gas aggregation cluster source is used for the fabrication of nanoparticles of plasma polymerized acrylic acid, whereas Plasma-Assisted Vapor Phase Deposition is used for the deposition of thin films of poly(ethylene oxide) plasma polymer. Embedding of nanoparticles into matrices of thermodynamically incompatible plasma polymer as well as..

Study of Wettability of Polyethylene Membranes for Food Packaging

In this study, the wettability of PET membranes (prepared with different pore sizes) treated by UV irradiation, thermal annealing or doping with metal nanoparticles was investigated. The wettability was studied using the contact angle method based on the optical microscopy. The membranes were analyzed before and after pore etching, and after each applied treatment. It turned out that membranes with different pore sizes exhibit different wetting behavior. Of particular interest are membranes with 0.53 μm pores. When pristine, they show high hydrophobicity (a high contact angle), but after treatment (some of which can be considered as an accelerated aging), their wetting characteristics swap between a hydrophobic and hydrophilic state. Interactions between packaging material and food and the external environment through fine control of wettability could have a major impact on maintaining product quality

Etching and Doping of Pores in Polyethylene Terephthalate Analyzed by Ion Transmission Spectroscopy and Nuclear Depth Profiling

This work is devoted to the study of controlled preparation and filling of pores in polyethylene terephthalate (PET) membranes. A standard wet chemical etching with different protocols (isothermal and isochronous etching for different times and temperatures and etching from one or both sides of the films) was used to prepare the micrometric pores. The pores were filled with either a LiCl solution or boron deposited by magnetron sputtering. Subsequent control of the pore shape and dopant filling was performed using the nuclear methods of ion transmission spectroscopy (ITS) and neutron depth profiling (NDP). It turned out that wet chemical etching, monitored and quantified by ITS, was shown to enable the preparation of the desired simple pore geometry. Furthermore, the effect of dopant filling on the pore shape could be well observed and analyzed by ITS and, for relevant light elements, by NDP, which can determine their depth (and spatial) distribution. In addition, both non-destructive methods were proven to be suitable and effective tools for studying the preparation and filling of pores in thin films. Thus, they can be considered promising for research into nanostructure technologies of thin porous membranes

Advances and challenges in the field of plasma polymer nanoparticles

This contribution reviews plasma polymer nanoparticles produced by gas aggregation cluster sources either via plasma polymerization of volatile monomers or via radio frequency (RF) magnetron sputtering of conventional polymers. The formation of hydrocarbon, fluorocarbon, silicon- and nitrogen-containing plasma polymer nanoparticles as well as core@shell nanoparticles based on plasma polymers is discussed with a focus on the development of novel nanostructured surfaces

Sebeuspořádání polyolefinů deponovaných z plynné fáze na rozhraní vakua a pevné látky

Byly zkoumány interakce mezi polyolefiny a křemíkovými substráty při depozici z plynné fáze ve vakuu. Simulace pomocí molekulární dynamiky ukázaly, že polyolefiny se po adsorpci rozbalí, a že dvě makromolekuly stačí pro vytvoření stabilního zárodku. AFM měření se superostrým hrotem ukázala formování 3,5 nm velkých globulárních klastrů, které se dále transformovaly do 2D ostrůvků. Ostrůvky rostly horizontálně prostřednictvím přidávání nových molekul na jejich okraj při zachování tloušťky. Vývoj velikosti ostrůvků byl charakterizován prostřednictvím diagramu zóny záchytu s využitím generalizovaného Wignerova škálování. Zjištěná kritická velikost ostrůvků byla 1, v souladu se simulacemi pomocí molekulární dynamiky. Delší doby depozice vedly ke srůstání ostrůvků a vyhlazování jejich povrchu s růstovým exponentem γ = –0,33 a dynamickým exponentem 1/z = –0,21. Vyhlazování je doprovázeno krystalizací vedoucí k vytvoření ortorombických polyolefinových krystalů detekovaných pomocí XRD.Interactions between polyolefins and silicon substrates are investigated upon their physical vapor deposition under vacuum. Molecular dynamics simulations show that polyolefins unfold upon adsorption and that two macromolecules suffice to produce a stable nucleus. Supersharp probe AFM measurements reveal the formation of 3.5 nm globular clusters that further transform into two-dimensional islands. The islands grow via attachment-limited aggregation by accepting new molecules from the edge, keeping the thickness constant and expanding laterally. The evolution of the island growth is analyzed within the framework of capture zone distribution analysis using generalized Wigner scaling. The critical island size is found to be 1, confirming the results of molecular dynamics simulations. Upon longer deposition times, the islands coalesce, whereas their surface smoothens with a growth exponent of γ = –0.33 and a dynamic exponent of 1/z = –0.21. Smoothening is accompanied by crystallization phenomena that result in the formation of orthorhombic polyolefin crystals, as detected by XRD

Změna morfologie a struktury vrstev tvořených nanočásticemi vanadu vlivem jejich teplotního ohřevu

Temperature-driven genesis of morphology and structure of vanadium nanoparticle films fabricated by magnetron-based gas aggregation sources has been investigated. Three temperature regions were identified. In the first one which covers the range from room temperature to approximately 200 °C, the increasing temperature results in the gradual oxidation of nanoparticle films and a slight increase of the individual nanoparticles that form the coating. Despite this, the nanoparticle films in this temperature range preserve their highly porous architecture. Above 200 °C, the vanadium nanoparticles undergo rapid oxidation, which is accompanied by an abrupt change in their mass, crystallinity, morphology, and optical properties (absorbance, photoluminescence). According to XRD, an orthorhombic V2O5 phase becomes the only detectable crystalline phase in the films in this temperature range. Furthermore, the individual nanoparticles start to coalesce, rapidly forming rod-like structures. The size of such formed structures, as well as the size of crystallites rapidly increases with the temperature. This lowers the specific surface area of the coatings and causes a shift in the optical band gap from 2.68 eV to 2.48 eV. Finally, the subsequent heating of the nanoparticle films above 650 °C causes the complete collapse of the coatings due to their melting.Článek pojednává o teplotně řízeném vývoji morfologie a struktury vrstev tvořených nanočásticemi vanadu připravených magnetronovým naprašováním s využitím zdroje shluků částic. Byly identifikovány tři teplotní oblasti. První, zahrnující rozsah teplot od pokojové do cca 200 °C, ve které dochází vlivem rostoucí teploty k postupné oxidaci nanočástic ve vrstvě a mírnému nárůstu počtu jednotlivých nanočástic tvořících povlak. Přesto si však vrstvy v tomto teplotním rozmezí zachovávají vysoce porézní strukturu. Při zvýšení teploty nad 200 °C dochází k rychlé oxidaci vanadových nanočástic, což je doprovázeno prudkou změnou jejich hmotnosti, krystalinity, morfologie a optických vlastností, a k vytvoření krystalické orthorombické fáze V2O5. Jednotlivé nanočástice se navíc začnou shlukovat a vytvářet tyčinkovitou strukturu. Velikost této struktury, stejně jako velikost krystalitů, pak rychle roste s rostoucí teplotou. To má za následek snížení specifické plochy na povrchu povlaků a vede k posunu optického zakázaného pásu z 2,68 eV 2,48 eV. Ohřev vrstev nad 650 °C (třetí teplotní interval) má za následek roztavení vrstvy a tedy její úplné zničení