Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
NMR studies on the mechanism of iodine mediated polymerisation
Thesis (MSc)--Stellenbosch University, 2011.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA |
| Published: |
Stellenbosch : Stellenbosch University
2011
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613971528286208 |
|---|---|
| access_status_str | Open Access |
| author | Wright, Trevor |
| author2 | Pasch, Harald |
| author_browse | Pasch, Harald Wright, Trevor |
| author_facet | Pasch, Harald Wright, Trevor |
| author_sort | Wright, Trevor |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2011. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/17967 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:44:37.487Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2011 |
| publishDateRange | 2011 |
| publishDateSort | 2011 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/17967 NMR studies on the mechanism of iodine mediated polymerisation Wright, Trevor Pasch, Harald Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Iodine Radical polymerization Nuclear magnetic resonance spectroscopy Dissertations -- Polymer science Theses -- Polymer science Chemistry and Polymer Science Thesis (MSc)--Stellenbosch University, 2011. ENGLISH ABSTRACT: In reverse iodine transfer polymerisation (RITP), chain transfer agents (CTAs) are generated in situ from the reaction between 2,2’-azobis(isobutyronitrile) (AIBN) and molecular iodine. This stage of RITP is the inhibition period, which ends when all iodine has been consumed. The evolution of CTAs was studied for the polymerisation reactions of n-butyl acrylate and styrene respectively. RITP of n-butyl acrylate was performed at 70 °C. In situ 1H nuclear magnetic resonance (NMR) experiments were carried out to study the evolution of CTAs during the inhibition period of n-butyl acrylate polymerisation and the structures A-I and A-Mn-I (where A represents the moiety originating from AIBN, M represents the monomer unit and n is the mean number degree of polymerisation) were observed. A polymer with the general structure A-Mm-I is formed. The molecular weight of poly(n-butyl acrylate) (PnBA) was evaluated with size exclusion chromatography (SEC) and NMR. Structural analysis of PnBA was done using NMR spectroscopy and matrix-assisted laser desorption/ionisation time-of-flight (MALDI-ToF) mass spectrometry. Similar conditions to those used for n-butyl acrylate polymerisation were used for RITP of styrene. The evolution of CTAs during the inhibition period of styrene polymerisation was studied using in situ 1H NMR. The inhibition period of styrene polymerised by RITP was much shorter than expected. This is due the consumption of iodine in the reaction between styrene and iodine which reversibly forms 1,2-diiodo-ethyl benzene. The CTAs A-I and A-Mn-I are formed, as well as 1-phenylethyl iodide (1-PEI). The molecular weight of polystyrene (PS) was determined using SEC and NMR and the functionality was evaluated using 1H NMR. The structure of PS was confirmed with 1H NMR and MALDI-ToF mass spectrometry. By increasing the temperature of the reaction, the inhibition period can be shortened. Both polymerisation systems retain control over molecular weight with an increase in temperature, however, n-butyl acrylate is limited due to the possible formation of mid-chain radicals. The formation of an A–Mm–A population (direct combination of the initiator and styrene) in RITP of styrene results in more initiator being consumed than for n-butyl acrylate, despite limited conversion of styrene to polymer. AFRIKAANSE OPSOMMING: In omgekeerde-jodium-oordrag polimerisasie, is die kettingoordragagente gegenereer in situ van die reaksie tussen 2,2’-azobis(isobutironitriel) (AIBN) en molekulêre jodium. Hierdie fase van RITP is die inhibisie tydperk wat eindig wanneer alle jodium verbruik is. Die evolusie van kettingoordragagente is vir die polimerisasiereaksies van butielakrilaat en stireen onderskeidelik bestudeer. Omgekeerde-jodium-oordrag polimerisasie van butielakrilaat was uitgevoer by 70 °C. In situ 1H kernmagnetieseresonans (KMR) eksperimente is uitgevoer om die evolusie van die kettingoordragagente te bestudeer tydens die inhibisie van butielakrilaat polymerisasie en die strukture A-I en A-Mn-I (waar A die gedeelte voorstel wat afkomstig is van AIBN, M die monomeer-eenheid en n die gemiddelde aantal polymerisasiegraad verteenwoordig) is ge-identifiseer. 'n Polimeer met die algemene struktuur A-Mm-I is gevorm. Die molekulêre gewig van poli(butielakrilaat) (PnBA) was geëvalueer deur grootte-uitsluitings chromatografie en KMR spektroskopie. Strukturele ontleding van PnBA is gedoen deur die KMR spektroskopie en matriks ge-assisteerde laser desorpsie/ionisasie tyd-van-vlug massaspektroskopie. Soortgelyke kondisies as dié wat gebruik word vir butielakrilaat polymerisasie, is gebruik vir omgekeerde-jodium-oordrag polimerisasie van stireen. Die evolusie van die ketting oordrag agente gedurende die inhibisie periode van stireen polymerisasie is deur in situ 1H KMR bestudeer en die inhibisie periode is baie korter as verwag. Dit is as gevolg van die opname van jodium in die reaksie tussen stireen en jodium wat omkeerbare stireen-di-jodied tot gevolg hê. Die ketting oordrag agente A-I en A-Mn-I is gevorm, sowel as 1-feniel-etiel jodied. Die molekulêre massa van polistireen (PS) is bepaal met behulp van grootte-uitsluitings chromatografie en KMR spektroskopie en die funksioneering is geëvalueer met behulp van 1H KMR. Die struktuur van PS is bevestig deur 1H KMR en matriks ge-assisteerde laser desorpsie/ionisasie tyd-vanvlug massaspektroskopie. Deur die verhoging van die temperatuur van die reaksie, kan die inhibisie periode verkort word. Beide polimerisasie sisteme behou beheer oor die molekulêre massa met 'n toename in temperatuur, alhoewel butielakrilaat beperk word as gevolg van die moontlike vorming van middel kettingradikale. Die vorming van die A-Mm-A spesie (direkte kombinering van AIBN en stireen) in omgekeerdejodium- oordrag polimerisasie van stireen veroorsaak dat meer AIBN verbruik word as butielakrilaat, ten spyte van die beperkte omskakeling van stireen tot polimeer. 2011-11-17T09:52:29Z 2011-12-05T13:15:52Z 2011-11-17T09:52:29Z 2011-12-05T13:15:52Z 2011-11-17T09:52:29Z 2011-12 Thesis http://hdl.handle.net/10019.1/17967 en_ZA Stellenbosch University application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Iodine Radical polymerization Nuclear magnetic resonance spectroscopy Dissertations -- Polymer science Theses -- Polymer science Chemistry and Polymer Science Wright, Trevor NMR studies on the mechanism of iodine mediated polymerisation |
| title | NMR studies on the mechanism of iodine mediated polymerisation |
| title_full | NMR studies on the mechanism of iodine mediated polymerisation |
| title_fullStr | NMR studies on the mechanism of iodine mediated polymerisation |
| title_full_unstemmed | NMR studies on the mechanism of iodine mediated polymerisation |
| title_short | NMR studies on the mechanism of iodine mediated polymerisation |
| title_sort | nmr studies on the mechanism of iodine mediated polymerisation |
| topic | Iodine Radical polymerization Nuclear magnetic resonance spectroscopy Dissertations -- Polymer science Theses -- Polymer science Chemistry and Polymer Science |
| url | http://hdl.handle.net/10019.1/17967 |
| work_keys_str_mv | AT wrighttrevor nmrstudiesonthemechanismofiodinemediatedpolymerisation |