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An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels
Thesis (MSc)--Stellenbosch University, 2020.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2020
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| _version_ | 1867613970845663232 |
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| access_status_str | Open Access |
| author | Eaby, Alan |
| author2 | Barbour, Leonard J. |
| author_browse | Barbour, Leonard J. Eaby, Alan |
| author_facet | Barbour, Leonard J. Eaby, Alan |
| author_sort | Eaby, Alan |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2020. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/108390 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:44:36.436Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/108390 An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels Eaby, Alan Barbour, Leonard J. Esterhuysen, Catharine Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Smart materials, supramolecular chemistry, crystals, mechanical testing, hydrochromism UCTD Thesis (MSc)--Stellenbosch University, 2020. ENGLISH ABSTRACT: Stimuli-responsive materials have become topical in the field of supramolecular chemistry in the last 20 years. Their applications include coatings, fibres, actuators, sorbents and conductors, amongst others, owing to their unique ability to adapt to their environment. Within this class are organic crystals that have demonstrated responses to pH, temperature, electromagnetic radiation, mechanical force, solvent and so on. These responses can be observed on a macroscopic level, such as chromism or mechanical motion, extending the application of molecular crystals beyond the molecular level. Developing these materials and the tools to study them should be the focal point of materials design. This work presents two molecular systems whose properties adapt to their external environment and the methods that were used to observe, characterise and utilise these properties. The first system is a series of inclusion compounds that crystallise with 2,7-dimethyl-octa-3,5- diyne-2,7-diol (1) as the host, forming 1-D channels for smaller guest molecules to occupy. These crystals grow as long needles that exhibit elastic flexibility under mechanical stress. The guest molecules can be selectively exchanged without significant change to the packing of the host. However, the crystal habits differ in size and cross-sectional shape. The aim was to determine whether the flexibility of each crystal could be altered by selectively exchanging the guest molecule in the channel, with the difference between inclusion compounds attributed to specific supramolecular interactions. An instrument was developed to determine the Young’s modulus as a measure of the relative flexibility between crystal analogues, where the difference in crystal shape and size could be taken into account with in-house developed software. The second system studied is a trianglimine compound (2) that crystallises with large, onedimensional channels. Crystals of 2 exhibit reversible hydrochromism that only occurs at relative humidities (RH) in excess of 55% RH. The colour change stems from a proton shift in the Schiff base moiety that favours the ketoenamine tautomer at high humidities. In addition to chromism, 2 also demonstrates rare water vapour sorption capabilities. With almost no water adsorption at humidities below 55% RH, adsorption to 9 wt. % occurs rapidly at the threshold RH and is indicated with the change in colour. Remarkably, desorption across this threshold RH is also rapid with no pressureinduced hysteresis. This reduces the energy cost of desorption, which often is the primary limitation for desiccant regeneration. The rapid adsorption is related to the prototropy, as these hydroxyl groups are the primary nucleation sites during adsorption. AFRIKAANSE OPSOMMING: Materiale wat as gevolg van 'n stimulus reageer het die afgelope 20 jaar in die gebied van supramolekulêre chemie belangstelling gewek. Toepassings sluit onder andere beskermingslae, vesels, aktuators, absorberend materiale en geleiers in, weens hul unieke vermoëns om by hul omgewing aan te pas. Binne hierdie klas is organiese kristalle wat reaksies op pH, temperatuur, elektromagnetiese bestraling, meganiese krag, oplosmiddel en so meer toon. Hierdie reaksies kan waarneembare veranderinge op 'n makroskopiese vlak wys, soos chromisme of meganiese beweging. Die ontwikkeling van hierdie materiale en die instrumente om dit te bestudeer, is die fokuspunt van die ontwerp van materiale. Hierdie werk bied twee molekulêre stelsels waarvan die eienskappe aanpas by hul eksterne omgewing aan asook die metodes wat gebruik is om hierdie eienskappe te waar te neem, karakteriseer en te benut. Die eerste is 'n reeks-insluitingsverbindings wat kristaliseer met 2,7-dimetiel-okta-3,5-diyne2,7-diol (1) as gasheer wat 1-D-kanale vorm om kleiner gasmolekules te akkommodeer. Hierdie kristalle groei as lang naalde wat 'n elastiese buigsaamheid onder meganiese spanning toon. Die gasmolekules kan selektief uitgeruil word sonder dat die molekulêre struktuur van die gasheer wesenlik verander, alhoewel die kristalvorms verskil in grootte en deursnit. Die doel was om te bepaal of die buigsaamheid van die kristalle verander kon word deur die gasmolekuul in die kanaal selektief te verruil, met die verskil in buigsaamheid tussen insluitingverbindings toegeskryf aan spesifieke supramolekulêre interaksies. 'n Instrument is ontwikkel om die Young se modulus te bepaal as 'n maatstaf van die relatiewe buigsaamheid tussen kristalanaloë, waar die verskil in kristalvorm en -grootte in ag geneem kan word met in-huis ontwikkelde sagteware. Die tweede sisteem is ‘n trianglimienverbinding wat kristaliseer (2) en vertoon omkeerbare hidrochromisme in die teenwoordigheid van water. Chromisme in 2 is vinnig en kom slegs voor by humiditeite van meer as 55% relatiewe humiditeit (RH). Die kleurverandering spruit uit 'n protonverskuiwing in die Schiff-basisgroep wat die ketoenamien-tautomeer by hoë humiditeite bevoordeel. Benewens chromisme, toon 2 ook seldsame waterdampsorpsievermoë. Met byna geen water-adsorpsie by humiditeite onder 55% RH, vinnige adsorpsie tot 9 wt. % kom by die drempel RH vinnig voor en word gekenmerk deur die kleurverandering. Merkwaardiglik vind desorpsie oor hierdie drempel RH ook vinnig plaas sonder dat histerese deur die druk veroorsaak word. Dit verlaag die energiekoste van desorpsie, wat dikwels die primêre beperking vir hergenerasie van droogmiddels is. Die vinnige adsorpsie hou verband met die prototropie, aangesien die hidroksielgroepe die primêre nukleasiepunt tydens adsorpsie is. Masters 2020-02-20T08:43:51Z 2020-04-28T15:11:51Z 2020-02-20T08:43:51Z 2020-04-28T15:11:51Z 2020-02 Thesis http://hdl.handle.net/10019.1/108390 en_ZA Stellenbosch University 106 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Smart materials, supramolecular chemistry, crystals, mechanical testing, hydrochromism UCTD Eaby, Alan An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels |
| title | An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels |
| title_full | An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels |
| title_fullStr | An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels |
| title_full_unstemmed | An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels |
| title_short | An investigation of the solvent-mediated properties of organic crystals with one-dimensional channels |
| title_sort | investigation of the solvent mediated properties of organic crystals with one dimensional channels |
| topic | Smart materials, supramolecular chemistry, crystals, mechanical testing, hydrochromism UCTD |
| url | http://hdl.handle.net/10019.1/108390 |
| work_keys_str_mv | AT eabyalan aninvestigationofthesolventmediatedpropertiesoforganiccrystalswithonedimensionalchannels AT eabyalan investigationofthesolventmediatedpropertiesoforganiccrystalswithonedimensionalchannels |