Silicones are useful in a variety of applications due to their diverse properties. The materials gain additional value when the basic constituents, oils and elastomers, are combined to create silicone gels. These materials possess excellent tunable properties such as moldability, tack, and adhesion, which are useful in certain circumstances. Only linear oils are currently used to make commercial silicone gels. While the materials initially possess desirable properties, over time the linear silicone oil can bleed out, and naturally, this is problematic for a variety of reasons. Among other things, the physical properties of the gel change and the oil that leaches out can be problematic. We test in this thesis the hypothesis that the use of branched silicone oils, as opposed to linear materials, in a gel could lead to lower levels of bleed (or slower release). There is currently very little research in the literature on the effect of adding branches to linear silicone polymers.
This thesis explores the synthesis of branched structures (dendrons) synthesized using the Piers Rubinsztajn reaction. These compounds were subsequently grafted onto linear SiH bearing silicone polymers at different frequencies through a hydrosilylation reaction. The branched silicones were characterized by NMR and the viscosity of the various oils was measured; the latter property correlated with the frequency of branching. The viscosity increased in a linear fashion until a maximum viscosity was observed, at which point further branching led to a slight decrease in viscosity; this trend was observed with silicone backbones at three molecular weights.
The branched silicone oils, capped with vinylpentamethyldisiloxane to remove remaining SiH sites, were then incorporated into gels. The Young’s modulus was measured and bleed measurements were collected twice over a ten-day period. Both measurements demonstrated that branching silicone polymers influenced the properties relative to linear silicone oils of comparable molecular weight. We discuss the possible origins of these differences. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22856 |
| Date | January 2018 |
| Creators | Morgan, Jennifer |
| Contributors | Brook, Michael A., Chemistry and Chemical Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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