The consolidation of emulsion templating and thiol-ene click chemistry as a route to degradable polyhipes for biomedical applications : doktorska disertacijaViola Hobiger
, 2022, doktorska disertacija
Opis: Thiol-ene click chemistry has been on the rise for the past two decades. In the past years, it has also found its way into the synthesis of porous polymers from emulsion templating (polyHIPEs) due to its versatility and convenience. It is an especially attractive pathway for scaffolds intended for biomedical purposes since the resulting materials are often biocompatible and degradable due to hydrolyzable ester bonds introduced via the thiol monomers.
The overall aim of this dissertation was to bring thiol-ene click chemistry with a focus on photopolymerization to the forefront of polyHIPE research, highlighting the great potential in combining the preparation technique of emulsion templating together with thiol-ene click chemistry. A study to understand the mechanisms of emulsion stability with a focus on already established thiol-ene formulations was conducted. It was possible to study and synthesize materials with a bicontinuous pore morphology within this project. Compared to the typical cellular pore morphology of a polyHIPE, a bicontinuous structure could be especially useful for separation applications. Furthermore, it was possible to induce a phase inversion, leading to small polymer particles.
One part of the dissertation focused on synthesizing hydrophilic polyHIPEs from poly(ethylene glycol) monomers and a hydrophilic thiol through an oil-in-water high internal phase emulsion. The resulting materials exhibited high porosity and small average pore diameters of 2.2 µm. Water uptake and degradation studies were performed. The potential of the material for drug release was demonstrated with the chosen model drug salicylic acid.
Furthermore, a HIPE formulation based on the acrylate 1,6-hexanediol diacrylate and thiol tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate was developed. For the developed poly(acrylate-co-thiol) polyHIPEs, the effect of oxidation thioethers present in the polymer network on the material properties was explored. This investigation was performed firstly to tune material properties, e.g. increase the glass transition temperature and tensile strength, and secondly, to highlight the oxidation properties of thioether-containing polymer networks. The oxidation responsiveness should be considered when a biomedical application is envisioned since inflammatory processes lead to oxidative stress in an organism. The formulation was also investigated for its additive manufacturing potential. The emulsion composition had to be adjusted to obtain a printable emulsion. Furthermore, it was possible to exclude harmful solvents, making the overall printing process more environmentally friendly and less hazardous for operators.
A polyHIPE from the biobased vinyl ester O,O‘-(hexahydrofuro[3,2-b]furan-3,6-diyl) divinyl diadipate (GDVA), which was especially promising as a biocompatible and biodegradable scaffold for tissue engineering, was prepared together with different thiol chain-transfer agents. The synthesis of cellular interconnected polyHIPEs from these starting materials proved challenging. However, the first synthesis of a biobased vinyl ester polyHIPE could be reported.
A final project was conducted in collaboration with Lithoz GmbH. In collaboration, it was possible to establish the first 3D printed ceramics from high internal phase emulsion precursors. For this purpose, trimethylolpropantriacrylte and the thiol trimethylolpropane tris(3-mercaptopropionate) were employed as monomers together with alumina particles to form a composite polyHIPE which would then be submitted to sintering, resulting in an intrinsically porous printed ceramic, allowing for high customization and complex porous morphologies.
Ključne besede: polyHIPE, thiol-ene, photopolymerization, additive manufacturing
Objavljeno v DKUM: 07.10.2022; Ogledov: 99; Prenosov: 26
Celotno besedilo (12,79 MB)
Priprava poroznih polimerov na osnovi celuloze z uporabo emulzij z visokim deležem notranje faze : bachelor thesisPaula Estévez Recio
, 2021, diplomsko delo
Opis: Namen tega dela je razložiti sintezo poliHIPE, ki vsebujejo celulozo. PoliHIPE so bili pripravljeni z uporabo emulzij olja v vodi (O/W). Vodna (kontinuirana) faza je bila sestavljena iz akrilne kisline (AA), karboksimetilceluloze (CMC), N,N′-metilenbisakrilamida (MBA), površinsko aktivne snovi in ustreznih iniciatorjev, medtem ko je bila oljna (notranja) faza toluen. Polimerizacija je potekala termično pri 60 ºC 24 ur. Dobljeni polimeri so imeli diskontinuitetno morfologijo poliHIPE z različnimi premeri, odvisno od stopnje zamreženja in količine CMC. Zanimivo je, da sta prisotnost CMC in višja stopnja zamreženja (30 %) povzročila nastanek večjih por, ki so v bistvu oblikovale material s tremi stopnjami poroznosti - primarno, sekundarno in terciarno. Velikost por je bila od približno 32 μm (0 % CMC) do 260 μm (1 % CMC), površina BET pa se je gibala od približno 1,3 m2/g do 3,9 m2/g. PoliHIPE smo uporabili tudi za adsorpcijo metilen modrega (MB). Pokazalo se je, da prisotnost CMC poveča adsorpcijo MB, vendar se pri višjih koncentracijah CMC adsorpcija zmanjša, kar kaže, da je idealna količina CMC pod 2,5 % (raztopina CMC).
Ključne besede: PolyHIPE, akrilna kislina, celuloza, adsorpcija, poroznost
Objavljeno v DKUM: 22.09.2021; Ogledov: 459; Prenosov: 44
Celotno besedilo (10,55 MB)
Porous beads from multiple emulsions with thiol-ene polymerisation : magistrsko deloStanko Kramer
, 2019, magistrsko delo
Opis: This thesis aims to explain the process of porous bead synthesis. The porous beads were prepared from a multiple emulsion water-in-oil-in-water (W/OW) system. The W/O/W multiple emulsion was made up of a High Internal Phase Emulsion (HIPE (primary emulsion)) and a suspension phase. The HIPE consisted of pentaerythritol tetrakis (3 mercaptopropionate) (TT) in combination with either divinyl adipate (DVA) or trimethylolpropane triacrylate (TMPTA) and an internal phase volume fraction of 80 %. The suspension phase consisted of an aqueous phase with dissolved surfactants which stabilised the secondary emulsion. The surfactants which stabilised the secondary emulsion were polyvinylpyrrolidone K30 (PVP K30) and polyvinylpyrrolidone K90 (PVP K90).
The polymerisation was carried out thermally at first for 24 hours and later under UV light and daylight, as the thermally initiated polymerisation was unsuccessful due to coalesence. The beads that were obtained using the photoinitiated polymerisation were porous with a mostly bicontinuous structure and varying diameters. The viscosity of the primary emulsion (HIPE) had the greatest influence on the stability of the entire W/O/W emulsion. By adding more than 5 wt. % of toluene to the primary emulsion, the emulsion broke down and did not successfully polymerise. Another important factor was the ratio of the functional groups in the case of TT-co-TMPTA, which greatly affected the yield and structure of the obtained beads.
The diameters of the spherical particles were dependent on the viscosity, monomer ratio and surfactant used in the suspension phase. The inner structure of the beads was mostly bicontinuous with occasional pores that resembled a polyHIPE structure.
The obtained beads had a yield of up to 80 % in the case of TT-co-DVA and a yield of up to 90 % in the case of TMPTA-co-DVA
Ključne besede: polyHIPE, thiol-ene, suspension polymerisation, porous beads, HIPE
Objavljeno v DKUM: 17.09.2019; Ogledov: 1020; Prenosov: 168
Celotno besedilo (3,56 MB)
Tkivni inženiring hrustančnega tkiva na biosintetičnem polimernem polyHIPE nosilcuJakob Naranđa
, 2017, doktorsko delo/naloga
Opis: Tkivni inženiring hrustančnega tkiva še vedno nudi številne možnosti za izboljšavo, navkljub intenzivnim raziskovalnim naporom v zadnjem času. Razvoj umetnih materialov in 3-D celičnih nosilcev ima pomembno vlogo pri regeneraciji hrustančnega tkiva. Zanimiv pristop pri izdelavi celičnih nosilcev predstavlja izgradnja s pomočjo emulzij. Nastali material, imenovan polyHIPE (PHP), je sintetični visoko porozen polimer, ki ga pripravimo s polimerizacijo visokega deleža notranje faze emulzij (HIPEs – high internal phase emulsions).
Glavni cilj te doktorske disertacije je raziskati možnosti za tvorbo hrustančnega tkiva znotraj celičnih nosilcev pripravljenih iz PHP materiala. Proizvodnjo PHP nosilcev smo posebej prilagodili tkivnemu inženiringu hrustanca, tako da smo pripravili porozne (85 %) strukture s primarno velikostjo por v območju 50–170 m. Pokazali smo, da je PHP material biokompatibilen s človeškimi sklepnimi hondrociti, kar smo ovrednotili s pomočjo testa za preživetje celic (Live/Dead kit) in histološko analizo. Opazovali smo hondrocite z okroglimi jedri, ki so bili organizirani v večceličnih plasteh na površini PHP nosilca in so rastli približno 300 m v notranjost nosilca. Kopičenje kolagena tipa 2 smo dokazali s pomočjo imunohistokemije, molekularna analiza je pokazala izražanje hrustančno specifičnih genov z ugodnim razmerjem kolagena tipa 2 in tipa 1. Dodatno so bili PHP vzorci biološko razgradljivi, njihove osnovne mehanske lastnosti pa primerljive z nativnim sklepnim hrustancem.
Izsledki raziskave dokazujejo, da je zasnovan PHP celični nosilec primeren za nadaljnjo uporabo v tkivnem inženiringu hrustančnega tkiva.
Ključne besede: humani sklepni hrustanec, tkivni inženiring, biokompatibilni celični nosilec, sintetični polimer, polyHIPE, diferenciacija hondrocitov
Objavljeno v DKUM: 17.10.2017; Ogledov: 1530; Prenosov: 169
Celotno besedilo (24,38 MB)
Tailoring the mechanical and thermal properties of dicyclopentadiene polyHIPEs with the use of a comonomerE. H. Mert
, Christian Slugovc
, Peter Krajnc
, 2015, izvirni znanstveni članek
Opis: The effect of adding a comonomer to dicyclopentadiene in high internal phase emulsions (HIPEs) on the properties of ring-opening metathesis polymerisation (ROMP) derived polyHIPEs has been investigated. With this aim, dicylopentadiene was copolymerised with norbornene in surfactant stabilized high internal phase emulsions. Morphological, mechanical and thermal properties of the resulting materials were investigated with regard to the monomer ratio. The interconnected pore structure was observed for the resulting poly(dicylopentadiene-co-norbornene) polyHIPEs. Furthermore, the new polyHIPE copolymers were found to have an improved thermal stability compared to the poly(dicylopentadiene) homopolymer.
Ključne besede: mechanical properties, emulsion templating, polyHIPE, dicyclopentadiene, norbornene
Objavljeno v DKUM: 07.08.2017; Ogledov: 964; Prenosov: 350
Celotno besedilo (1,39 MB)
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Polyester type polyHIPE scaffolds with an interconnected porous structure for cartilage regenerationJakob Naranđa
, Maja Sušec
, Uroš Maver
, Lidija Gradišnik
, Mario Gorenjak
, Andreja Vukasović
, Alan Ivković
, Marjan Rupnik
, Matjaž Vogrin
, Peter Krajnc
, 2016, izvirni znanstveni članek
Opis: Development of artificial materials for the facilitation of cartilage regeneration remains an important challenge in orthopedic practice. Our study investigates the potential for neocartilage formation within a synthetic polyester scaffold based on the polymerization of high internal phase emulsions. The fabrication of polyHIPE polymer (PHP) was specifically tailored to produce a highly porous (85%) structure with the primary pore size in the range of 50–170 μm for cartilage tissue engineering. The resulting PHP scaffold was proven biocompatible with human articular chondrocytes and viable cells were observed within the materials as evaluated using the Live/Dead assay and histological analysis. Chondrocytes with round nuclei were organized into multicellular layers on the PHP surface and were observed to grow approximately 300 μm into the scaffold interior. The accumulation of collagen type 2 was detected using immunohistochemistry and chondrogenic specific genes were expressed with favorable collagen type 2 to 1 ratio. In addition, PHP samples are biodegradable and their baseline mechanical properties are similar to those of native cartilage, which enhance chondrocyte cell growth and proliferation.
Ključne besede: polyester, polymerization, polyHIPE
Objavljeno v DKUM: 23.06.2017; Ogledov: 1387; Prenosov: 372
Celotno besedilo (1,24 MB)
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Microcellular open-porous polystyrene-based composites from emulsionsSebastjan Huš
, Mitja Kolar
, Peter Krajnc
, 2014, izvirni znanstveni članek
Opis: Series of cross-linked polystyrene samples were prepared using an emulsion templating approach, where monomers were contained in the continuous phase of the emulsion, while the droplet aqueous phase induced primary pores, connected with a number of secondary pores. Emulsions with a high fraction of the droplet phase (HIPEs) were used and stabilised with a combination of a surfactant (sorbitan monooleate) and various types of particles (charcoal powder, copper powder and carbon nanopowder). The morphology of the resulting porous polymer depends on the type and amount of the particles added to the emulsion; however, in all the cases open-cellular morphology was formed. The size of the primary pores (cavities) ranged from 5 µm to 25 µm, while the size of the secondary interconnecting pores was from 1 µm to 5 µm. The materials were investigated using scanning electron microscopy and nitrogen adsorption/desorption.
Ključne besede: polyHIPE, porous polymers, nanocomposites, porosity, polystyrene
Objavljeno v DKUM: 16.03.2017; Ogledov: 1351; Prenosov: 122
Celotno besedilo (1,06 MB)
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Poly(styrene-co-divinylbenzene-co-2-ethylhexyl)acrilate membranes with interconnected macroporous structureUrška Sevšek
, Silvo Seifried
, Črtomir Stropnik
, Irena Pulko
, Peter Krajnc
, 2011, izvirni znanstveni članek
Opis: A combination of doctor blading and emulsion templating was used to prepare macroporous poly(styrene-co-divinylbenzene-co-2-ethylhexylacrylate) and poly(styrene-co-divinylbenzene) membranes with an interconnected porous structure. Water in oil high internal phase emulsions including monomers in the oil phase were cast onto a glass plate and polymerised at elevated temperature. After purification porous polyHIPE membranes were obtained. The volume ratio of aqueous phase (75 % or 85 %) and the molar ratio of divinylbenzene (2 % or 4 %) were varied, while the addition of chlorobenzene to the oil phase influenced the viscosity of the emulsions. A comonomer, 2-ethylhexylacrylate substantially improved the flexibility of the membranes. All yielding membranes were characterized by measuring their cast thicknesses and flow densities for deionised water. Scanning electron microscopy was used to study the morphological features of the membranes.
Ključne besede: membrane, porous polymers, polyHIPE, emulsions
Objavljeno v DKUM: 10.07.2015; Ogledov: 1727; Prenosov: 150
Celotno besedilo (668,83 KB)
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