Programming Supramolecular Polymer Structure and Function Using Covalently-Fixed Monomers

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With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Ronald Castellano of the University of Florida (UF) will develop a new class of synthetic supramolecular polymers that are made from novel molecular building blocks, monomers, that are cyclic and chiral. Structure-property investigations will exploit the robustness of the design to control supramolecular polymer thermodynamics, mechanism, and optoelectronic properties relevant to potential downstream applications. In the broadest sense, this research aims to contribute to a fundamental understanding of how to control the 3D structure of organic matter at the nano-/mesoscale to accelerate development of next-generation materials. Broader impacts with respect to education and training come from (1) graduate and undergraduate students being exposed to synthetic and physical organic chemistry, spectroscopy, computation, and polymer characterization; (2) introducing aspects of the science to the community through outreach activities in partnership with the UF ACS POLY/PMSE student chapter, the UF Chemistry Club, and a local retirement community; (3) broadening the participation of members of underserved groups in scientific research. This research aims to develop homochiral 1D supramolecular polymers through the covalent bridging of two otherwise independently self-assembling monomers (“covalent-fixation”) to create a planar chiral structure, reduce conformational degrees of freedom, and establish strong, persistent transannular hydrogen bonding. The primary vehicles to be used in the work are [n.n]paracyclophanes ([n.n]pCps), where the design involves introduction of complementary hydrogen-bonding groups in a cross pattern on the paracyclophane scaffold. The [n.n]pCps intimately transfer chemical and stereochemical information to their neighbors within a growing assembly. Extensive structure-property studies, involving both experiment and theory, will be conducted to (1) develop deck-differentiated cyclophanes to control supramolecular polymer assembly thermodynamics and mechanism through electronically complementary intra- and inter-deck interactions, (2) expand the cyclophane decks to useful chromophores, and (3) examine minimalist monomers capable of self-folding and then 1D supramolecular polymerization. The structure-property studies seek to provide information that will allow investigators to achieve new levels of atomic level control of supramolecular assembly thermodynamic and kinetic outcomes in designing these and related systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.