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Structure and dynamics of complex materials in the water-poor regime

Gustavsson, Sanna LU (2016)
Abstract (Swedish)
Kolhydratsystem så som alkylglycosider, cellulosa och cyklodextrin är miljövänliga förnybara material som används inom många områden i dagens samhälle; som bärare av aktiva substanser i läkemedelstabletter, matsmältningsfiber, papper, kosmetika och hygienartiklar för att nämna några. De är fasta substanser uppbyggda av molekyler ordnade i en viss struktur. Med tiden, och eventuell yttre påverkan, som t ex. vattenupptag och temperaturförändringar, så kan dessa material ändra sin uppbyggnad och då få helt andra egenskaper. Små upptag av vatten från atmosfären kan leda till stora ändringar i funtionalitet och hållbarhet. Det är därför viktigt att ha detaljerad kunskap om hur molekylstrukturen påverkar dynamiken och stabiliteten samt... (More)
Kolhydratsystem så som alkylglycosider, cellulosa och cyklodextrin är miljövänliga förnybara material som används inom många områden i dagens samhälle; som bärare av aktiva substanser i läkemedelstabletter, matsmältningsfiber, papper, kosmetika och hygienartiklar för att nämna några. De är fasta substanser uppbyggda av molekyler ordnade i en viss struktur. Med tiden, och eventuell yttre påverkan, som t ex. vattenupptag och temperaturförändringar, så kan dessa material ändra sin uppbyggnad och då få helt andra egenskaper. Små upptag av vatten från atmosfären kan leda till stora ändringar i funtionalitet och hållbarhet. Det är därför viktigt att ha detaljerad kunskap om hur molekylstrukturen påverkar dynamiken och stabiliteten samt funtionaliteten av en substans.
Vanligtvis så karakteriserer man denna typ av "torra" system med ljusspridningsteknik (röntgen), gravimetriska tekniker (vägning) och kalorimetri (värmemängdsmätning). Kärnmagnetresonans (NMR) har på senare tid visat sig användbart när man studerar fasta material såväl som halvfasta (flytande kristallina) material. Med denna teknik kan man systematisk undersöka materialegenskaper i form av struktur och dynamik i specifika segment i molekylen som funktion av vattenhalt och temperatur. Det är även viktigt för att optimisera tillverkningsprocessen samt hålla ekonomiska kostnader nere.
Polymerer används flitigt i dagens samhälle. Ett av de områdena är inom förnybar energi där man använder dem i bränsleceller. Bränsleceller är som ett batteri. De är uppbyggda av ett elektriskt ledande material som är placerat mellan två elektroder. Till skillnad från batterier så kräver bränsleceller ingen uppladdning eller något byte. De drivs så länge bränsle och oxidationsmedel tillförs (vanligen syre och väte) utifrån till elektroderna. Fördelen för miljön är att bränsleceller inte har någon förbränning. Däremot så är framställningen av bränslet (väte) inte föroreningsfri. Vi undersöker hur transporten av vatten relaterar till strukturen av polymer membranet och dess egenskaper. Eftersom vatten transporten är viktig för en bränslecells funktionalitet så undersöker vi även diffusionen vid olika vattenhalter och temperaturer för att kunna optimera bränslecellens egenskaper. (Less)
Abstract
In the solid state, molecules are normally ordered in a specific structure. With time, and as a result of influence from the surroundings, solid materials can change their molecular and/or crystal structure and, as a consequence, obtain completely different properties. Water is particularly important in this respect. Adsorption of minuscule amounts of water from the atmosphere may have huge effects on the properties and stability of solid materials. For instance, in pharmaceutics this can lead to harmful consequences if an active substance, with a specific solid-state structure, suddenly changes due to interaction with adsorbed moisture. In processing and during storage, it is therefore important to have a detailed molecular understanding... (More)
In the solid state, molecules are normally ordered in a specific structure. With time, and as a result of influence from the surroundings, solid materials can change their molecular and/or crystal structure and, as a consequence, obtain completely different properties. Water is particularly important in this respect. Adsorption of minuscule amounts of water from the atmosphere may have huge effects on the properties and stability of solid materials. For instance, in pharmaceutics this can lead to harmful consequences if an active substance, with a specific solid-state structure, suddenly changes due to interaction with adsorbed moisture. In processing and during storage, it is therefore important to have a detailed molecular understanding of the material properties and how they depend on water content. The primary aim of this thesis is to investigate the effects of small amounts of adsorbed water on molecular structure and dynamics in complex materials. In this water-poor regime (loosely defined as <5% of water), solid substances are normally investigated by means of X-ray scattering, gravimetric techniques and calorimetry. In the thesis, these conventional techniques are supplemented by solid-state NMR. This opens new possibilities to understand not only the structure, but also the dynamics of the materials. The complex materials investigated in the thesis belong to the two large substance classes of surfactants and polymers. These types of substances are used widely in everyday products, such as pharmaceutics, paper, textiles, cosmetics and hygiene products. The results in the thesis show that solid-state NMR can be used to construct the equilibrium phase diagram of surfactant systems, in this case tetradecylmaltoside/H_2O in the water-poor regime, and also to determine the regions of metastability of the non-equilibrium solid phases. The combination of solid-state NMR and X-ray scattering is a powerful tool to elucidate the structure and molecular dynamics of crystalline carbohydrates, exemplified by cyclodextrins, upon hydration. Similarly, solid-state NMR was used to extract information about molecular structure and dynamics in different stages of cellulose dissolution. The solid and dissolved cellulose was investigated in aqueous dissolution media together with cosolutes sodium hydroxide or tetrabutylammonium hydroxide. Another area of application of polymers is within renewable power energy where they are used in polymer electrolyte membrane fuel cells. As a way of optimizing the functionality we used NMR-based diffusometry to investigate transport behaviour as a function of polymer membrane structure, temperature and water content. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Malmsten, Martin, Department of Pharmacy, Uppsala University, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Hydration, cellulose , dissolution, sugar surfactant, hydrated crystals, structure, dynamics, phase diagram, fuel cell, pulsed-field-gradient (PFG) spin-echo NMR, Polarization Transfer solid state NMR, PXRD, GVS, TGA, amphiphilic
pages
94 pages
publisher
Lund University, Faculty of Science, Department of Chemistry, Division of Physical Chemistry
defense location
the Center for chemistry and chemical engineering, lecture hall B, Naturvetarvägen 14 (former Getingevägen 60), Lund
defense date
2016-06-10 9:00
ISBN
978-91-7422-449-8
language
English
LU publication?
yes
id
50262b16-522d-4691-9729-9e81a293cd70
date added to LUP
2016-05-13 11:11:48
date last changed
2016-09-19 08:45:20
@phdthesis{50262b16-522d-4691-9729-9e81a293cd70,
  abstract     = {In the solid state, molecules are normally ordered in a specific structure. With time, and as a result of influence from the surroundings, solid materials can change their molecular and/or crystal structure and, as a consequence, obtain completely different properties. Water is particularly important in this respect. Adsorption of minuscule amounts of water from the atmosphere may have huge effects on the properties and stability of solid materials. For instance, in pharmaceutics this can lead to harmful consequences if an active substance, with a specific solid-state structure, suddenly changes due to interaction with adsorbed moisture. In processing and during storage, it is therefore important to have a detailed molecular understanding of the material properties and how they depend on water content. The primary aim of this thesis is to investigate the effects of small amounts of adsorbed water on molecular structure and dynamics in complex materials. In this water-poor regime (loosely defined as &lt;5% of water), solid substances are normally investigated by means of X-ray scattering, gravimetric techniques and calorimetry. In the thesis, these conventional techniques are supplemented by solid-state NMR. This opens new possibilities to understand not only the structure, but also the dynamics of the materials. The complex materials investigated in the thesis belong to the two large substance classes of surfactants and polymers. These types of substances are used widely in everyday products, such as pharmaceutics, paper, textiles, cosmetics and hygiene products. The results in the thesis show that solid-state NMR can be used to construct the equilibrium phase diagram of surfactant systems, in this case tetradecylmaltoside/H_2O in the water-poor regime, and also to determine the regions of metastability of the non-equilibrium solid phases. The combination of solid-state NMR and X-ray scattering is a powerful tool to elucidate the structure and molecular dynamics of crystalline carbohydrates, exemplified by cyclodextrins, upon hydration. Similarly, solid-state NMR was used to extract information about molecular structure and dynamics in different stages of cellulose dissolution. The solid and dissolved cellulose was investigated in aqueous dissolution media together with cosolutes sodium hydroxide or tetrabutylammonium hydroxide. Another area of application of polymers is within renewable power energy where they are used in polymer electrolyte membrane fuel cells. As a way of optimizing the functionality we used NMR-based diffusometry to investigate transport behaviour as a function of polymer membrane structure, temperature and water content.},
  author       = {Gustavsson, Sanna},
  isbn         = {978-91-7422-449-8},
  keyword      = {Hydration,cellulose ,dissolution,sugar surfactant,hydrated crystals,structure,dynamics,phase diagram,fuel cell,pulsed-field-gradient (PFG) spin-echo NMR,Polarization Transfer solid state NMR,PXRD,GVS,TGA,amphiphilic},
  language     = {eng},
  pages        = {94},
  publisher    = {Lund University, Faculty of Science, Department of Chemistry, Division of Physical Chemistry},
  school       = {Lund University},
  title        = {Structure and dynamics of complex materials in the water-poor regime},
  year         = {2016},
}