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The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels
Thesis (MSc)--Stellenbosch University, 2021.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2021
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| _version_ | 1867614039242178560 |
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| access_status_str | Open Access |
| author | Garbonova, Gabriela Ventsislavova |
| author2 | Klumperman, Bert |
| author_browse | Garbonova, Gabriela Ventsislavova Klumperman, Bert |
| author_facet | Klumperman, Bert Garbonova, Gabriela Ventsislavova |
| author_sort | Garbonova, Gabriela Ventsislavova |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2021. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/110338 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:41.741Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/110338 The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels Garbonova, Gabriela Ventsislavova Klumperman, Bert Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Hydrogels Crosslinked polymers Polyvinylpyrrolidone Triblock copolymers UCTD Thesis (MSc)--Stellenbosch University, 2021. ENGLISH ABSTRACT: The focus of this study was to synthesize physically crosslinked hydrogels based on the polymer poly(N-vinylpyrrolidone) (PVP). To achieve this, a triblock copolymer system comprising of PVP as a permanently hydrophilic block and poly(N-isopropyl acrylamide) (PNIPAm) as a tuneable hydrophobic block was designed. PNIPAm undergoes a reversable transition from hydrophilic to hydrophobic upon reaching its lower critical solution temperature (LCST). The amphiphilic character of this system, upon reaching the LCST, induces self-assembly morphologies ranging from micelles to worms and at relatively high concentrations, physically crosslinked hydrogels. This system was envisioned to be used in polymer therapeutics as thermoresponsive injectable hydrogel. Uniformity of polymer characteristics is a prerequisite for biomedical and nanotechnology applications. To achieve this, reversable activation-fragmentation transfer (RAFT) polymerization was conducted using two difunctional xanthate-based RAFT agents. The RAFT agents differed in terms of their R-groups, where RAFT 1 was more prone to hydrolysis under extreme conditions while RAFT 2 was hydrolytically stable. The order of block addition is also an important consideration. For this project, we chose PVP as the starting block followed by chain extension with NIPAm such that the middle block was permanently hydrophilic while the outer blocks were thermoresponsive. This was done to obtain a flower-like morphology upon self-assembly. Both RAFT agents were successful in controlling the polymerization of NVP. Chain extensions were conducted in organic and aqueous media, with particular focus on aqueous media polymerization at temperatures above the LCST of PNIPAm. Two series of block copolymers with varying molecular weights but similar hydrophilic fractions (fPVP) throughout the groups were synthesized. The effect of copolymer composition, molecular weight, and concentration on the thermoresponsive and gelation properties of the triblock copolymers, PNIPAm-b-PVP-b-PNIPAm, was investigated. Visual analysis showed that the critical gelation concentration was dependent on the fPVP and molecular weight. Quantitative investigations conducted using UV/vis spectroscopy showed that the cloud point temperature (TCP) and fPVP were directly related, while the concentration was inversely related. Moreover, a two-phase behaviour was detected for samples of higher concentrations and lower fPVP. Rheology studies showed the same two-phase behaviour which was hypothesized to be because of a change in morphology from solvated polymers to flower-like micelles connected through hydrophilic bridges and finally fused micelles capable of supporting a hydrogel network. The morphology was further investigated using transmission electron microscopy (TEM). TEM images showed the onset of micelle fusion with an increase in concentration and decrease in fPVP, suggestive of the two-phase behaviour detected with UV/vis spectroscopy and rheology. AFRIKAANSE OPSOMMING: Die fokus van hierdie studie was om fisiese kruisverbindende hidrogels gebaseer op polimeer poli (N-vinielpirrolidoon) (PVP) te sintetiseer. Om dit te bereik, is 'n triblok-kopolymeerstelsel, bestaande uit PVP as 'n permanent hidrofiliese blok en poli (N-isopropylakrylamied) (PNIPAm) as 'n verstelbare hidrofobiese blok ontwerp. Wanneer die onderste kritieke oplossingstemperatuur (LCST) bereik word ondergaan PNIPAm 'n omkeerbare oorgang van hidrofilies na hidrofobies. By LCST veroorsaak die amfifiele karaktereienskap van hierdie stelsel, dat selfmonterende morfologieë ontwikkel wat wissel van micelle tot wurms en onder relatiewe hoë konsentrasies, fisies kruisverbindende hidrogels tot gevolg het. Die vooruitsig is om hierdie stelsel te gebruik in polimeerterapieë as 'n thermoresponsiewe inspuitbare hidrogel. Aangesien eenvormigheid van polimeer-eienskappe 'n voorvereiste is vir biomediese en nanotegnologiese toepassings is omkeerbare aktivering-fragmentasie-oordrag (RAFT) polimerisasie uitgevoer met behulp van twee difunksionele xanthaat-gebaseerde RAFT-middels. Die RAFT-middels het verskil in terme van hul R-groepe, waar RAFT 1 meer geneig was tot hidrolise onder uiterste toestande, terwyl RAFT 2 hidrolities stabiel was. Die volgorde van bloktoevoeging is ook 'n belangrike oorweging. Vir hierdie projek het ons PVP gekies as die beginblok, gevolg deur kettingverlenging met NIPAm, sodat die middelblok permanent hidrofilies was, terwyl die buitenste blokke thermoresponsief was. Dit is gedoen om 'n blomagtige morfologie te verkry tydens selfversameling. Albei RAFT-middels was suksesvol in die beheer van die polimerisasie van NVP. Kettinguitbreidings is in organiese en waterige media uitgevoer, met ’n streng fokus op waterige media-polimerisasie by temperature bo die LCST van PNIPAm. Twee reeks blokkopolimere met verskillende molekulêre gewigte, maar soortgelyke hidrofiliese breuke (fPVP) in die groepe, is gesintetiseer. Die effek van samepolymeersamestelling, molekulêre gewig en konsentrasie op die termoresponsiewe en geleringseienskappe van die triblok-kopolymere, PNIPAm-b-PVP-b-PNIPAm, is ondersoek. Visuele analise het getoon dat die kritieke geleringskonsentrasie afhanklik was van die fPVP en die molekulêre gewig. Kwantitatiewe ondersoeke wat met behulp van UV/vis spektroskopie gedoen is, het getoon dat die wolkpunt temperatuur (TCP) en fPVP direk verband hou, terwyl die konsentrasie omgekeerd verband hou. Daarbenewens is 'n tweefasige gedrag opgespoor vir monsters van hoër konsentrasies en laer fPVP. Reologie-studies het dieselfde tweefasige gedrag getoon en ondersteun dus die hipotese dat veranderinge in morfologie van opgeloste polimere na blomagtige micelle, verbind deur hidrofiliese brûe en uiteindelik gesmelte micelle, ’n hidrogelnetwerk kan ondersteun. Die morfologie is verder ondersoek met behulp van transmissie-elektronmikroskopie (TEM). TEM-beelde het die aanvang van micellefusie getoon met 'n toename in konsentrasie en afname in fPVP, wat dui op die tweefase-gedrag wat met UV/vis spektroskopie en reologie opgespoor is. Masters 2021-04-22T10:45:59Z 2023-05-03T03:00:12Z 2021-03 Thesis http://hdl.handle.net/10019.1/110338 en Stellenbosch University xiv, 75 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Hydrogels Crosslinked polymers Polyvinylpyrrolidone Triblock copolymers UCTD Garbonova, Gabriela Ventsislavova The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels |
| title | The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels |
| title_full | The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels |
| title_fullStr | The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels |
| title_full_unstemmed | The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels |
| title_short | The synthesis and investigation of Poly(N-vinylpyrrolidone) based hydrogels |
| title_sort | synthesis and investigation of poly n vinylpyrrolidone based hydrogels |
| topic | Hydrogels Crosslinked polymers Polyvinylpyrrolidone Triblock copolymers UCTD |
| url | http://hdl.handle.net/10019.1/110338 |
| work_keys_str_mv | AT garbonovagabrielaventsislavova thesynthesisandinvestigationofpolynvinylpyrrolidonebasedhydrogels AT garbonovagabrielaventsislavova synthesisandinvestigationofpolynvinylpyrrolidonebasedhydrogels |