SYNTHESIS AND FUNCTIONALIZATION OF 1,4-POLYKETONES AND ENANTIOSELECTIVE POLYESTER CATALYST DEVELOPMENT USING MOLECULAR LEGO SCAFFOLDS

Abstract

Objectives of the present study are aimed towards improving upon alternating copolymerization techniques for polyketones and aliphatic polyesters, and the majority of this work is focuses on post-polymerization modifications to alternating polyketones. These materials are currently under studied in the literature, but the aptly spaced, repeating carbonyl functionality creates an easily functionalized material. Complimentary work described herein relates to efforts currently underway to prepare highly enantioselective catalysts for the alternating copolymerization of epoxides with cyclic anhydrides. Aliphatic polyesters currently suffer from a lack of chemical diversity, and, with greener chemistries on the forefront of research efforts, polyesters made from environmentally benign and/or renewable materials are desirable. Additional limitations of aliphatic polyesters include difficulty obtaining stereoregular polyesters. In collaboration with the Schafmeister laboratory we are developing catalysts for the alternating copolymerization of polyesters to address these limitations. The model catalysts are carefully designed scaffolds of spiroligomers encasing a Lewis acidic transition metal at its center ([spiro]MX). The spiroligomer bulk around the metal center imparts significant chirality onto the catalyst thereby controlling which enantiomer of a given monomer is polymerized leading to stereoregular polyesters. Additionally, the use of more than one monomer increases the available chemical space with which to create novel polyesters. To date, three [spiro]MX catalysts have been prepared all of which are catalytically active for poly(propylene maleate) synthesis. A core objective of this work is the study of functionalization methods to create novel materials from an inexpensive polyketones. The chemical modifications performed on polyketones to date have been limited, and the utility of the functionalized materials often goes unmentioned. Efforts to functionalize polyketones in this study were aimed at creating electrically conducting polymeric materials which would be used as hole transport materials in photovoltaic devices. Polyketones were decorated with pendant (tri)arylamine functionality creating several novel polymeric materials, and electrochemical experiments supported the formation of radical cations at the triarylamine nitrogen of the pendants. Further, the functionalization of the polyketones provided enhanced ultraviolet stability of the functionalized polymers. Concurrent to the functionalization of polyketones, we investigated the effects Lewis acids had on the synthesis of the polyketone itself. Through previous research conducted in the Dobereiner laboratory we know that a Lewis acid will interact with carbonyls of molecules during catalytic reactions. The addition of Lewis acids to the synthesis of the polyketones is thought to have similar interactions altering the polymerization. This study explored the bulk properties of the polyketone synthesized in the presence of several Lewis acids. As a result of this study specific polymer properties (e.g. molecular weight) could be targeted through careful selection of the Lewis acid and the amount added during polymerization.