Stereoelective polymerization of propylene oxide with a chiral aluminum alkoxide initiator.
Item
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Title
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Stereoelective polymerization of propylene oxide with a chiral aluminum alkoxide initiator.
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Identifier
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AAI9315496
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identifier
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9315496
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Creator
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Panchalingam, Vaithilingam.
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Contributor
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Advisers: Howard Haubenstock | George Odian
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Polymer
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Abstract
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The polymerization of propylene oxide (PO) was studied with an initiator prepared by the reaction of R-{dollar}(-){dollar}-3,3-dimethyl-1,2-butanediol (DMBD) with aluminum hydride. When mixed with an equimolar amount of zinc chloride, the initiator was found to be highly reactive and also stereoelective in the polymerization of PO, preferentially incorporating R-(+)-PO into the polymer chain. Analysis of the polymer structure by {dollar}\sp{13}{dollar}C-NMR spectroscopy showed that chlorine, hydroxy, and one type of alkoxy end groups derived from the initiator were present in the polymer prepared in bulk at 80{dollar}\sp\circ{dollar}C. An additional alkoxy end group was identified in the polymer prepared at room temperature. Fractionation of poly(propylene oxide) (PPO) in acetone at {dollar}-30\sp\circ{dollar}C gave about 10% insoluble PPO shown to be isotactic by {dollar}\sp{13}{dollar}C-NMR. The soluble, largely atactic fraction contained irregular head-to-head (h,h) and tail-to-tail (t,t) structures. In the absence of coinitiator zinc chloride the PPO product was completely soluble at {dollar}-30\sp\circ{dollar}C and contained a greater proportion of irregular h,h and t,t structures. The {dollar}\sp{13}{dollar}C-NMR peak assignments were made for the methine and methylene carbons in the irregular h,h and t,t linkages in PPO by the use of DEPT (Distortionless Enhancement by Polarization Transfer) experiment.;An attempt was made to fit the stereoelective behavior of this initiator system to a kinetic scheme. It was found that the system follows a second order monomer consumption. An initiator prepared by the reaction of aluminum hydride and N-methyl-1-ephedrine in a 1:3 molar ratio was also used for the polymerization of PO to check its stereoelective potential. This initiator system was found to be poor and its efficiency was not improved very much even by the use of zinc chloride as a coinitiator. However, this initiator preferentially elected the S-enantiomer from the racemic PO as opposed to the preferential election of R-enantiomer by the initiator derived from DMBD.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
