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You searched for +publisher:"Clemson University" +contributor:("Dr. William Pennington"). Showing records 1 – 2 of 2 total matches.

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1. Poh, Claire Kway. The Development of Polyurethane-based Solid-to-Solid Phase Change Materials for Thermal Energy Storage Applications.

Degree: PhD, Materials Science and Engineering, 2016, Clemson University

This work investigated and characterized the structure-property relationship of a polyurethane-based block copolymer and the thermal energy storage properties obtained through the solid-to-solid phase transition of a PCM polyol polymer that undergoes a thermal transition at low temperatures. The chemical and physical factors that influence or dictated the microphase separation between the urethane “hard” segment block and the polyol “soft” segment block of conventional polyurethanes how the resulting changes in phase morphology effects the crystallization behavior of the “soft” component, which in this dissertation is analogous to the PCM polymer component was analyzed. Theurethane HS group behaves as a cross-link and restricts PCM polymer chain mobility, thereby the PCM can no longer translate freely and instead exhibits a solid-to-solid phase transition. The introduction of HS cross-link exhibits a behavior known as the HS chain-end effect, in which HS constrictions cause the PCM polymer to become partially crystalline. The extent to which PCM crystallization is limited by the HS chain end effect can vary depending on HS structural factors, such molecular architecture and HS composition. The HS chain end effect was quantified for the following HS structural variables; HS cross-link nature, diisocyanate molecular geometry, HS chain length to characterize and compare how each factor limits PEG PCM polymer crystallization. By doing so in a systematic manner, the optimal configuration for an effective PU-SSPCM can be determined. To examine HS cross-link nature, an analogous linear and a non-linear PU-SSPCM polymer, were compared to determine differences in final thermal energy storage properties. The effects of diisocyanate molecular geometry was investigated by comparing the thermal energy storage properties of a series of PU-SSPCMs varied only by its diisocyanate component. The considered diisocyanates were selected based on specific structural moieties that affect the structural regularity, rigidity, and symmetry of the HS. The chain length of the hard segment component influence on thermal energy storage properties was also investigated by varying the proportions of urethane HS concentration and PCM polymer concentrations. HS cross-link nature, the HS diisocyanate component, and HS chain length are considered chemical level factors since they can be controlled during synthesis. On the physical level, the possibility of a connection between the degree of phase separation and thermal energy storage properties were explored. This relationship was investigated by measuring thermal energy storage properties of PU-SSPCMs with a high, medium, and low degree of phase separation. Varying HS crystallization by cooling rates from a homogeneous melt state was used to obtain different levels of phase separation. Thermal energy storage properties were measured using Differential Scanning Calorimetry experiments. Supplemental information about the chemical structure of the synthesized polyurethane-based solid-to-solid phase… Advisors/Committee Members: Dr. Philip J. Brown, Dr. Olin Thompson Mefford, IV, Dr. Vincent Blouin, Dr. William Pennington.

…from Clemson University. July 7, 2016. It is vitally indispensable that modern society… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Poh, C. K. (2016). The Development of Polyurethane-based Solid-to-Solid Phase Change Materials for Thermal Energy Storage Applications. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1708

Chicago Manual of Style (16th Edition):

Poh, Claire Kway. “The Development of Polyurethane-based Solid-to-Solid Phase Change Materials for Thermal Energy Storage Applications.” 2016. Doctoral Dissertation, Clemson University. Accessed October 28, 2020. https://tigerprints.clemson.edu/all_dissertations/1708.

MLA Handbook (7th Edition):

Poh, Claire Kway. “The Development of Polyurethane-based Solid-to-Solid Phase Change Materials for Thermal Energy Storage Applications.” 2016. Web. 28 Oct 2020.

Vancouver:

Poh CK. The Development of Polyurethane-based Solid-to-Solid Phase Change Materials for Thermal Energy Storage Applications. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2020 Oct 28]. Available from: https://tigerprints.clemson.edu/all_dissertations/1708.

Council of Science Editors:

Poh CK. The Development of Polyurethane-based Solid-to-Solid Phase Change Materials for Thermal Energy Storage Applications. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1708

2. Amoah, Emmanuel. Conjugate Addition of Grignard Reagents to Dienones and Thioldienoates, and Copper-Mediated Allylic Substitutions.

Degree: PhD, Chemistry, 2017, Clemson University

Alkyl Grignard reagents (Et, nBu, iPr, cyclohexyl), with the exception of tBuMgCl, undergo exclusive or exceptionally highly regioselective 1,4-addition reactions to acyclic ,–,-unsaturated ketones, while aryl and heteroaryl Grignard reagents give mixed results ranging from exclusive 1,4-addition (1-naphthyl, 2-N-methylpyrrolyl) to regioselective 1,2-addition (2-furyl, 2:1). All alkyl, aryl, and heteroaryl Grignard reagents examined gave exclusive 1,4-addition reactions with ,–,-unsaturated thiol esters, with the exception of tBuMgCl which gave an 80:20 mixture of 1,4-:1,6-addition products. The high chemo- and regioselectivity observed for these reactions is attributed to a radical or radical-like pathway for the alkyl Grignard reagents and possibly a carbanion pathway for aryl Grignard reagents. The ,-dienyl thiol esters provide for a one-pot tandem 1,4-addition-nucleophilic acyl substitution reaction sequence to afford 3-substituted 4-enone moieties. Allylic opening of functionalized vinyloxiranes has been investigated with Grignard reagents and both catalytic and stoichiometric amounts of copper (I) salts. Specifically, α,β-epoxy-γ,δ-enones were found to undergo allylic opening of the epoxide ring in the presence of either CuCN or CuBr·SMe2 in THF or CH2Cl2 from -55 °C to -78 °C to give δ-substituted-β,γ-unsaturated-α-hydroxyketones in 3 hours. While reactions were conducted with stoichiometric amounts of CuCN, sub-stoichiometric (20 mol%) and catalytic ( 5-10 mol%) amounts of CuBr·SMe2 could be used to effect clean transfer of alkyl Grignard reagents to the substrates. Interestingly, it required two equivalents of the allyl and aryl Grignard reagents with stoichiometric CuBr·SMe2 to effect complete transfer in 3 hours. The CuCN-mediated reaction gave at best 70:30 mixture of the E/Z stereoisomers of the δ-substituted-β,γ-unsaturated-α-hydroxyketones. However, with the use of CuBr·SMe2 only the E-isomer was observed. A tentative model was proposed to rationalize the marked differences in the stereoselection associated with these copper salts. Allowing the reaction to warm to room temperature resulted in the oxidation of the α-hydroxy alcohol to the corresponding δ-substituted-β,γ-unsaturated dione. In the absence of any copper salts, 1,2-addition product arising from nucleophilic attack on the carbonyl carbon was obtained. Alkylmagnesium cuprates and zincates reacted with ethyl 6-bromo-α, β, γ, δ-dienoates to give exclusively the SN2 product while their lithium versions gave mixed results favoring the SN2′ product. When the substrate was changed to ethyl 6-chloro-α, β, γ, δ-dienoates, cuprates and zincates of lithium gave only the SN2′ products while their magnesium versions gave mixed results favoring the SN2′ product. These results suggest that both the leaving group ability of the halide, and the magnesium vs lithium as counter ion in the cuprate or the zincate influenced the regioselectivity of the ethyl… Advisors/Committee Members: Dr. R. Karl Dieter, Advisor and Department Chair, Dr. Daniel C. Whitehead, Dr. William Pennington, Dr. Rhett Smith.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Amoah, E. (2017). Conjugate Addition of Grignard Reagents to Dienones and Thioldienoates, and Copper-Mediated Allylic Substitutions. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1873

Chicago Manual of Style (16th Edition):

Amoah, Emmanuel. “Conjugate Addition of Grignard Reagents to Dienones and Thioldienoates, and Copper-Mediated Allylic Substitutions.” 2017. Doctoral Dissertation, Clemson University. Accessed October 28, 2020. https://tigerprints.clemson.edu/all_dissertations/1873.

MLA Handbook (7th Edition):

Amoah, Emmanuel. “Conjugate Addition of Grignard Reagents to Dienones and Thioldienoates, and Copper-Mediated Allylic Substitutions.” 2017. Web. 28 Oct 2020.

Vancouver:

Amoah E. Conjugate Addition of Grignard Reagents to Dienones and Thioldienoates, and Copper-Mediated Allylic Substitutions. [Internet] [Doctoral dissertation]. Clemson University; 2017. [cited 2020 Oct 28]. Available from: https://tigerprints.clemson.edu/all_dissertations/1873.

Council of Science Editors:

Amoah E. Conjugate Addition of Grignard Reagents to Dienones and Thioldienoates, and Copper-Mediated Allylic Substitutions. [Doctoral Dissertation]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_dissertations/1873

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