6,064 research outputs found
Micropatterning polymer brushes on confined surfaces using two-photon-initiated RAFT polymerisation
No full textWhen biological systems come in contact with materials, precise control over the materials’ surface properties is required to ensure desired functionality. Polymer brushes are excellent candidates to modify surface properties on demand, finding applications in biosensors, microelectronic parts, tissue engineering substrates, or microfluidic devices [1]. Already established ways to produce such brushes include use of photomasks, direct laser writing and more. However, the achievable pattern resolution is limited. In this work, polymer brushes were photopatterned on confined glass substrates via two photon initiated reversible addition fragmentation chain transfer, 2PRAFT [2]. The biocompatible and hydrophilic monomer N acryloylmorpholine (NAM) was chosen for the synthesis of the polymer brushes. To establish the composition of the polymerisation mixture, the system was initially optimised using RAFT polymerization and blue light irradiation. The glass wafers were covalently modified with RAFT agent 4-cyano-4-(((dodecylthio)carbonothioyl)thio)pentanoic acid (CDTPA) via a two-step procedure, using Ivocerin as the photoinitiator. Firstly, the kinetics of the polymer brushes formation were monitored. Ellipsometry was used for brush thickness measurements, observing a maximum of 10.4 ± 1.5 nm. X ray photoelectron spectroscopy (XPS) was utilised to determine the chemical composition of the brushes. Finally, the established system was further expanded and applied on 2PRAFT, using an established 2P fabrication initiator. The patterned brushes and their morphology were characterised using confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). The possibilities of this method were further highlighted not only by the ability to print patterns of various colours, but also by the ability to print on vertically stacked surfaces.
Funding by the Christian Doppler Research Association within the framework of a Christian Doppler Laboratory for “Advanced Polymers for Biomaterials and 3D Printing” and the financial support by the Austrian Federal Ministry for Digital and Economic Affairs and the National foundation for Research, Technology and Development are gratefully acknowledged.
References:
[1]Zoppe, J.O.; Ataman, N.C.; Mocny, P.; Wang, J.; Moraes, J.; Klok, H.A. Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes. Chem. Rev. 2017, 117, 1105–1318, DOI:10.1021/acs.chemrev.6b00314
[2] Helfert, S.; Zandrini, T.; Rohatschek, A.; Rufin, M.; Machata, P.; Zahoranová, A.; Andriotis, O.G.; Thurner, P.J.; Ovsianikov, A.; Liska, R.; Baudis, S.; Micropatterning of Confined Surfaces with Polymer Brushes by Two‐Photon‐Initiated Reversible Addition–Fragmentation Chain‐Transfer Polymerization. Small Science, 5(1), p.2400263, DOI: 10.1002/smsc.20240026
Micropatterning Confined Surfaces with Polymer Brushes via Two-Photon-Initiated RAFT Polymerization
Full text linkTo ensure their intended functionality, exact control over material surface properties is necessary when biological systems are in contact with them. Excellent options for on-demand surface modification include polymer brushes which are used in tissue engineering substrates, microelectronic components, biosensors, and microfluidic devices.[1] Existing brush fabrication methods include photomasks and direct laser writing, but are limited in patterning resolution. In this study, polymer brushes were photopatterned on confined glass substrates using two-photon initiated reversible addition fragmentation chain transfer, 2PRAFT.[2] The biocompatible and hydrophilic monomer N-acryloylmorpholine was chosen to synthesise the polymer brushes. The system was first optimised via RAFT polymerisation and blue light irradiation to establish polymerisation solution composition. Glass wafers were covalently modified with RAFT agent 4-cyano-4-(((dodecylthio)carbonothioyl)thio)pentanoic acid (CDTPA) via a two-step procedure, using Ivocerin as the photoinitiator. Brush formation kinetics were monitored, and brush thickness was measured by ellipsometry, with a maximum of 10.4 ± 1.5 nm. X-ray photoelectron spectroscopy (XPS) was used for the determination of the brushes’ chemical composition. The developed system was further extended to two-photon-initiated RAFT (2PRAFT) polymerisation, utilising a well-known 2P fabrication initiator. The patterned polymer brushes and their morphology were analysed using confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). This method demonstrated its versatility through the capability to print multicoloured patterns and also to print on vertically stacked surfaces.
Funding by the Christian Doppler Research Association within the framework of a Christian Doppler Laboratory for “Advanced Polymers for Biomaterials and 3D Printing” and the financial support by the Austrian Federal Ministry for Digital and Economic Affairs and the National foundation for Research, Technology and Development are gratefully acknowledged.
References:
[1] Zoppe, J.O.; Ataman, N.C.; Mocny, P.; Wang, J.; Moraes, J.; Klok, H.A. Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes. Chem. Rev. 2017, 117, 1105–1318, DOI:10.1021/acs.chemrev.6b00314 [2] Helfert, S.; Zandrini, T.; Rohatschek, A.; Rufin, M.; Machata, P.; Zahoranová, A.; Andriotis, O.G.; Thurner, P.J.; Ovsianikov, A.; Liska, R.; Baudis, S.; Micropatterning of Confined Surfaces with Polymer Brushes by Two-Photon-Initiated Reversible Addition–Fragmentatio
Revolutionary Sn-based photoinitiators: how to combine long wavelengths with reactivity and stability
Full text linkPhotopolymerization finds applications in a wide variety of fields, such as coatings,[1] 3D printing,[2] dental materials[3] and many more.[4] The limitation of the thickness of the curable layers is the wavelength of the used light, as light with longer wavelengths can penetrate deeper into materials than light with shorter wavelengths.[5]
Therefore, photoinitiators (PI) with red-shifted absorbance are favourable as they enable the use of light with longer wavelengths and therefore higher curing depths. This can be achieved for instance by the introduction of heteroatoms as central atom, typically P or Ge. Generally, the bathochromic shift is higher the bigger the central atom is, as can be seen for stannanes compared to Ge-based PIs.[6]
In our work, we synthesized a novel tetraacylstannane with absorbance up to 560 nm, about 70 nm longer than the commercial state-of-the-art PI. Reactivity and photobleaching behaviour were also tested and resulted in outstanding properties at 460 nm compared to three reference compounds. One of the most crucial parameters is the stability, as so far, no literature-known Sn-based PI is stable enough in formulations to make it into industrial application. With our novel tetraacylstannane, we found the first Sn-based PI that is as stable as the current state-of-the-art Ge-based PI and hence fulfills all criteria for industrial photopolymerization processes
Potenzial, Herausforderungen und Zukunftschancen
No full textDie additive Fertigung, besser bekannt als 3D-Druck, hat sich als eine transformative Technologie etabliert, bei der Objekte schichtweise aus digitalen Designs aufgebaut werden. Im Gegensatz zu herkömmlichen Fertigungsmethoden ermöglicht die additive Fertigung eine individuelle, präzise und effiziente Herstellung komplexer Strukturen. Diese neugewonnene Gestaltungsfreiheit hat dazu geführt, dass sich die additive Fertigung längst in verschiedene Branchen etabliert hat. Darunter vor allem in der Medizintechnik, wo ihr Potenzial bereits heute genutzt und in Zukunft eine entscheidende Rolle spielen wird.
An der Technischen Universität Wien forscht die Gruppe 3D-Druck und Additive Fertigungstechnologien unter der Leitung von Prof. Jürgen Stampfl seit über einem Jahrzehnt intensiv an der Entwicklung von additiven Fertigungstechnologien auf Basis der Photopolymerisation. Dabei handelt es sich um einen Prozess, bei dem flüssige Photopolymere durch Licht ausgehärtet und schichtweise zu einem Objekt aufgebaut werden. Der Prozess überzeugt durch eine hohe Präzision und Auflösung, sowie ein breites Spektrum an Materialien, welche verarbeitet werden können. Diese Fortschritte haben bereits zu mehreren erfolgreichen Ausgründungen geführt, die weltweit Anerkennung finden.
Eines der größten Potenziale der additiven Fertigung liegt in der personalisierten Medizin zur Herstellung von patientenspezifischen Implantaten, Prothesen und Medikamenten. Diese können auf die individuelle Anatomie und die spezifischen Anforderungen des Patienten zugeschnitten werden. So werden die Erfolgsraten von Behandlungen erhöht und die Genesungszeiten verkürzt. Ein weiterer Vorteil der additiven Fertigung in der Medizintechnik ist die Vielfalt der verwendbaren Materialien, wie zum Beispiel biokompatible Polymere, Biokeramiken oder Metalllegierungen. Zahnprothesen aus Keramik, Implantate aus Metall oder Keramik und Zahnschienen aus Polymeren werden bereits erfolgreich additiv gefertigt und eingesetzt.
Bis zum erfolgreichen Einsatz im medizinischen Alltag müssen jedoch zahlreiche Hürden überwunden werden. Die Zulassung neuer Produkte und Verfahren auf dem Markt unterliegt höchsten regulatorischen Standards, um das Patientenwohl zu gewährleisten. Diese hohen Standards sind unerlässlich, um die Sicherheit neuer medizinischer Geräte oder Implantate für die Patienten zu garantieren. Gleichzeitig erschweren sie jedoch Innovationen und Weiterentwicklungen erheblich, da die Zulassungsverfahren immer zeit- und kostenintensiver werden.
Dieser Vortrag gibt Ihnen einen Überblick über additive Fertigungstechnologien in der Medizintechnik. Das Potenzial, die aktuellen Herausforderungen und die zukünftigen Möglichkeiten der additiven Fertigung werden dabei kritisch beleuchtet. Es wird aufgezeigt, welche Technologien und Materialien bereits in der Medizin zum Einsatz kommen und welche aktuellen Forschungsarbeiten an der TU Wien durchgeführt werden. Anschließend laden wir Sie herzlich ein, sowohl die technischen als auch die ethischen Aspekte dieser zukunftsweisenden Technologie zu diskutieren
The Future of 3D Printing: Investigation of a Novel Sn-based Photoinitiator with High Stability
No full textPhotopolymerization finds applications in a wide variety of fields, such as coatings, 3D printing, dental materials and many more. The limitation of the thickness of the curable layers is the wavelength of the used light, as light with longer wavelengths can penetrate deeper into materials than light with shorter wavelengths.
Therefore, photoinitiators (PI) with red-shifted absorbance are favourable as they enable the use of light with longer wavelengths and therefore higher curing depths. This can be achieved for instance by the introduction of heteroatoms as central atom, typically P or Ge. Generally is the bathochromic shift higher the bigger the central atom is, as can be seen for stannanes compared to Ge-based PIs.
In our work, we synthesized a novel tetraacylstannane with absorbance up to 560 nm, about 70 nm longer than the commercial state-of-the-art PI. Reactivity and photobleaching behaviour were also tested and resulted in outstanding properties at 460 nm compared to three reference compounds. One of the most crucial parameters is the stability, as so far, no literature-known Sn-based PI is stable enough in formulations to make it into industrial application. With our novel tetraacylstannane, we found the first Sn-based PI that is as stable as the current state-of-the-art Ge-based PI and hence fulfills all criteria for industrial photopolymerization processes
Investigation of Novel Long Wavelength Photoinitiators for Radical Polymerization
Full text linkPhotoinitiators (PI) for free radical polymerization have been modified using heteroatoms in the α-position to the benzoyl chromophore since the 1980s.1 At that time, acylphosphine oxides were introduced, originally for an application in the coating industry. Further investigations led to the discovery of Ge-based PIs, with diacylgermanes showing particularly good properties.2 These molecules show the desired bathochromic shift in the absorption spectra, what enables the use of light with longer wavelength. This red-shifted light is important for enhancing the curing depth of formulations. The current state-of-the-art PI is also located in the diacylgermane family with the trade name Ivocerin®. Additional advantages of Ivocerin® are thermal stability and low toxicity. Nevertheless, Ge-based PIs are higher in price compared to e.g. phosphorus based PIs, and therefore not for every application suitable. One way to overcome this disadvantage are Sn-based PIs, as this substance class is known to reach excellent bathochromic shifts in their absorbance as well as high reactivity.3 The only drawback is the poor storage stability of the so far known Sn-based PIs. In this work, novel Ge as well as Sn-based PI were successfully synthesized and photochemically investigated including UV/Vis measurements, photo-DSC measurements and steady state photolysis experiments in order to compare their photochemical properties as well as stability with literature known Sn-based PIs. Funding by the Christian Doppler Research Association (Christian Doppler Laboratory for Advanced Polymers for Biomaterials and 3D Printing), the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development is gratefully acknowledged. Additionally, this work was supported by Lithoz GmbH, Karl Leibinger Medizintechnik GmbH & Co. KG and Trauma Care Consult
Expanding the limits of aliphatic photoinitiators based on α-ketoesters for free radical photopolymerization
No full textTowards High-Performance Thermosets from Renewable Resources: Development of a Sustainable Material Platform using Epoxy-Alcohol Polyaddition
No full textOver the last decades, increasing industrial and scientific research focused on sustainable alternatives to replace petroleum-based epoxy resins. Furthermore, evermore social emphasis is shifted towards the environmental impact of such materials, as crosslinked polymers bear a large carbon footprint and are inherently non-recyclable or (bio)degradable.
Epoxy-alcohol polyaddition represents a novel type of step-growth polymerization, which yields polymer networks with regulated and homogeneous architectures and tunable mechanical properties. By variation of the core structure and functionality of epoxy monomers, high-performance thermosets with a tunable glass transition temperature and high tensile toughness were obtained while simultaneously achieving high conversions of sustainable monomers. Additionally, high storage stability at room temperature enables to the industrial use of bio-renewable resins (e.g. coating technologies)
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