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http://hdl.handle.net/11375/22857
Title: | CONTROLLING SILICONE-SACCHARIDE INTERFACES THROUGH BORONIC ACID MODIFICATION OF SILICONE POLYMERS |
Authors: | Macphail, Benjamin |
Advisor: | Brook, Michael |
Department: | Chemistry |
Publication Date: | 2018 |
Abstract: | Silicone elastomers, which are normally crosslinked using metal catalysts, are traditionally reinforced with mineral fillers to achieve desired mechanical properties. When alternate, hydrophilic materials are used as fillers the silicone must be modified using amphiphilic moieties to mitigate phase separation. Herein it is reported that renewable saccharides can be used to both crosslink and reinforce silicones. The grafting of boronic acids, which bind to saccharides, to silicone polymers gives materials that, when added to aqueous solutions of mono- or polysaccharides, without catalysts, generated elastomers via the boronic acid interaction with saccharides. The efficiency of crosslinking, as shown by Young’s moduli, depended strongly on the specific saccharide and the density of boronic acid groups on the silicone. Simple silicones normally phase separate in water saccharide mixtures. However, pretreatment of silicone boronates with the saccharide phytoglycogen, followed by exposure to water, led to stable aqueous phytoglycogen/silicone dispersions (pastes). The different outcomes arising from the order of addition are attributed to better dispersion of the silicone and saccharide in the latter case. Rheological studies of the pastes showed that, unlike the elastomers, viscosities depended more on the fraction of silicone in saccharide; number of boronic acid contact points between the silicone and saccharide was only a minor contributor. The equilibrium concentration of sugar/boronate contacts, which stabilize the water/oil interfaces, remains high even at high concentrations of water and even when the specific binding constant for an individual saccharide is low. Additionally, the ability of the surfaces of these modified silicones to adsorb saccharides was investigated. Silicone boronic acids (SiBA) with and without permanent (non-hydrolyzable links), were prepared by hydrosilyation of a tartrate-protected styrylboronate. Hydrolysis led to free boronic acids at the interface to which the saccharides sorbitol, pullulan, casein and phytoglycogen, and the glycosylated protein, mucin, chemisorbed. Surface active proteins like albumin and casein adsorbed on such surfaces too, but only on the SiBA surfaces would (poly)saccharides and the glycosylated proteins adsorb; HSA was an exception. It was not possible to exchange polysaccharides like phytoglycogen from the surface, even when using sorbitol, a monosaccharide with a better binding constant to boronic acid. The behaviors of these surfaces are reported. |
URI: | http://hdl.handle.net/11375/22857 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Macphail_Benjamin_J_FinalSubmission_2017December_MSc.pdf | Thesis | 2.75 MB | Adobe PDF | View/Open |
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