Doctoral thesis (Dissertations and theses)
Nanosecond Pulsed Plasma-Induced Free-Radical Polymerization of Liquid Methacrylate Monomers for the Synthesis of Hydrogel Films
Azevedo Gonçalves, Ingrid
2024
 

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Abstract :
[en] Hydrogels, as a class of soft materials, consist of hydrophilic three-dimensional polymer networks that swell upon immersion in liquid environments while retaining their structural integrity. Traditionally, these materials have well-established applications in biomedicine, including wound dressing and contact lenses. Nowadays, hydrogels in the form of thin films have found applications in advanced fields such as artificial skins, biosensors, and flexible electronics. As films, their performance and functionality are heavily influenced by the polymeric network structure and thickness. In this context, plasma polymerization is a widely used method to deposit thin films due to its scalability, substrate independence, and being solventless and without the need of chemical initiator. However, several side reactions can yield the loss of the monomer’s functionalities and regularity compared to polymers obtained via wet chemistry polymerization. Recent studies have demonstrated the use of nanosecond-pulsed plasma to minimize fragmentation and recombination reactions in plasma-state polymerization, promoting a conventional free-radical polymerization pathway for depositing functional polymer films. In this context, the plasma polymerization of monomers deposited as liquid layers is a relatively underexplored approach compared to vapor-phase methods and offers the possibility to use low vapor pressure monomers, high molecular weight oligomers, or even solid particles dispersed in a liquid medium to form composite films. This thesis aims to understand the effect of plasma pulse frequency and liquid parameters on the chemistry, growth rate, and properties of hydrogel films. The research specifically examines the use of 2-hydroxyethyl methacrylate (HEMA) as a model hydrophilic monomer. The findings in this study highlight how adjusting the plasma pulse frequency and spray delivery rate influences the retention of monomer functionalities, polymeric growth, and growth rate of the films. Notably, using liquid layers demonstrates a higher chemical structure preservation and deposition rates when compared to the injection of HEMA in the vapor phase using the same reactor. Hydrogel films were further synthesized by copolymerizing methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) using the same setup.The research reported for the first time the influence of plasma pulse frequency to tune the swelling ratios and viscoelastic modulus of the resulting hydrogels. Such hydrogel properties were accessed by quartz crystal microbalance with dissipation monitoring (QCM-D) coupled with spectroscopic ellipsometry (SE). Taking advantage of the versatility of the studied apparatus, plasma-induced free-radical polymerization of a high molecular weight oligomer (polyethylene glycol dimethacrylate (PEGDMA400)) was conducted onto several substrates. The resulting hydrogels exhibited thermo-responsive behavior, as evidenced by QCM-D coupled SE. In-depth characterization of the hydrogel properties through QCM-D and SE showed their suitability for providing insights into the hydrated layer, swelling ratio, and viscoelastic modulus of plasma-polymerized hydrogel films.
Research center :
LIST - Luxembourg Institute of Science & Technology
Disciplines :
Physics
Author, co-author :
Azevedo Gonçalves, Ingrid ;  University of Luxembourg ; LIST - Luxembourg Institute of Science and Technology > Materials Research and Technology Department
Language :
English
Title :
Nanosecond Pulsed Plasma-Induced Free-Radical Polymerization of Liquid Methacrylate Monomers for the Synthesis of Hydrogel Films
Defense date :
05 December 2024
Institution :
Unilu - Université du Luxembourg [Faculty of Science, Technology and Medecine (FSTM)], Luxembourg
Degree :
Docteur en Physique (DIP_DOC_0003_B)
Promotor :
Quintana Vicente, Roberto;  LIST - Luxembourg Institute of Science and Technology > Materials Research and Technology Department
President :
LAGERWALL, Jan  ;  University of Luxembourg > Faculty of Science, Technology and Medicine (FSTM) > Department of Physics and Materials Science (DPHYMS)
Jury member :
Boscher, Nicolas;  LIST - Luxembourg Institute of Science and Technology > Materials Research and Technology Department
Armelin Diggroc, Elaine;  Universitat Politécnica de Catalunya (UPC) > Department of Chemical Engineering
Nonglaton, Guillaume;  CEA - Commissariat à l'Énergie Atomique et aux Énergies Alternatives > Leti (Laboratoire d'électronique et de technologie de l'information)
FnR Project :
FNR13641732 - Deposition Of Multifunctional Coatings With Interpenetrating Hydrogel Networks By Liquid Nanopulsed Plasma Polymerization, 2019 (01/09/2020-31/08/2023) - Roberto Quintana Vicente
Funders :
FNR - Fonds National de la Recherche
Funding number :
C19/MS/13641732
Available on ORBilu :
since 15 January 2025

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