Type of Document Dissertation Author Lee, Minjae URN etd-08192010-223814 Title Design, Synthesis and Self-Assembly of Polymeric Building Blocks and Novel Ionic Liquids, Ionic Liquid-Based Polymers and Their Properties Degree PhD Department Chemistry Advisory Committee
Advisor Name Title Gibson, Harry W. Committee Chair Carlier, Paul R. Committee Member Esker, Alan R. Committee Member Tanko, James M. Committee Member Turner, S. Richard Committee Member Keywords
- Host-Guest Complexation
- Polymeric Building Block
- Structure-Property Relationship
- Dicationic Imidazolium Salt
- Ionic Liquid
- Supramolecular Chemistry
- End-Functional Polymer
Date of Defense 2010-08-02 Availability unrestricted AbstractThe convergence of supramolecular and polymer sciences has led to the construction of analogs of traditional covalently-constructed polymeric structures and architectures by supramolecular methods. Host-guest complexations of polymers are also possible through well-defined synthesis of polymeric building blocks, for novel supramolecular polymers.
Monotopic polymeric building blocks were synthesized by controlled radical polymerizations with a crown or paraquat initiator. The combinations of terminal and central functionalities of host and guest polymeric building blocks provided chain-extended and tri-armed homopolymers, and diblock and tri-armed copolymers.
A supramolecular graft copolymer was formed from a main-chain poly(ester crown ether) and a paraquat terminated polystyrene. This comb-like copolymer was characterized by a large viscosity increase. A four-armed polystyrene-b-poly(n-butyl methacrylate) was synthesized from a pseudorotaxane macroinitiator derived from a complex of a crown-centered polystyrene and a dufunctional paraquat compound. A single peak with higher molecular weight from size exclusion chromatography proved the copolymer formation.
Supramolecular interactions enhance the ionic conductivity of semi-crystalline ionic polymers; the ionic conductivity of a C6-polyviologen and dibenzo-30-crown-10 mixture was 100 times higher than the polyviologen itself. However, ionic conductivities of amorphous polyviologens with polyethers were influenced only by glass transition temperature changes.
New imidazolium ionic liquid monomers and imidazolium based polymers were synthesized for potential applications in electroactive devices, such as actuators. Structure-property relationships for pendant imidazolium polyacrylates and main-chain imidazolium polyesters were investigated. Terminal ethyleneoxy moeties enhanced ionic conduction 2~3 times; however, the alkyl chain length effect was negligible. For the imidazoium polyesters, higher ion conductivities result from 1) mono-imidazolium over bis-imidazolium, and 2) bis(trifluoromethanesulfonyl)imide polymers over hexafluorophosphate analogs. A semi-crystalline hexafluorophosphate polyester with C10-sebacate-C10, displayed 400-fold higher ionic conductivity than the amorphous C6-sebacate-C6 analogue, suggesting the formation of a biphasic morphology in the former polyester.
New dicationic imidazolium salts have interesting features. 1,2-Bis[N-(N’-alkylimidazoilum)]ethane salts stack well in the solid state and possess multiple solid-solid phase transitions. They complex with dibenzo-24-crown-8 and a dibenzo-24-crown-8 based pyridyl cryptand with Ka = ~30 and 360 M-1, respectively. Some of these dicationic imidazolium salts have low entropies of fusion, typical of plastic crystals.
These newly discovered imidazolium homopolymers have ionic conductivities up to 10-4 (S cm-1); however, better properties are still required. Well-designed block copolymers should provide both good electrical and mechanical properties from bicontinuous morphologies, such ion channels.
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