Hartley, Scott
http://hdl.handle.net/2374.MIA/6241
Dr. Scott Hartley - Professor, Chemistry & Biochemistry2024-03-29T14:30:59ZData archive for "Transient Polymers through Carbodiimide-driven Assembly"
http://hdl.handle.net/2374.MIA/6956
Data archive for "Transient Polymers through Carbodiimide-driven Assembly"
Saha, Nirob K.; Salvia, William S.; Konkolewicz, Dominik; Hartley, C. Scott
Biochemical systems make use of out-of-equilibrium polymers generated under kinetic control. Inspired by these systems, abiotic supramolecular polymers driven by chemical fuel reactions have recently been reported. Conversely, polymers based on transient covalent bonds have received little attention, although they have the potential to complement supramolecular systems by generating transient structures based on stronger bonds and offering a straightforward approach to tuning the reaction kinetics. In this study, we show that simple aqueous dicarboxylic acids give poly(anhydrides) when treated with the carbodiimide EDC. Transient covalent polymers with molecular weights exceeding 15,000 are generated which decompose over the course of days. Disassembly kinetics can be controlled using simple substituent effects in the monomer design. The impact of solvent polarity, carbodiimide concentration, and monomer concentration on polymer properties and lifetimes has been investigated. The results reveal substantial control over polymer assembly and disassembly kinetics, highlighting the potential for fine-tuned kinetic control in nonequilibrium polymerization systems.
Data archive for "Carbodiimide-driven toughening of interpenetrated polymer networks"
http://hdl.handle.net/2374.MIA/6918
Data archive for "Carbodiimide-driven toughening of interpenetrated polymer networks"
Rajawasam, Chamoni W. H.; Tran, Corvo; Sparks, Jessica L.; Krueger, William; Hartley, C. Scott; Konkolewicz, Dominik
Recent work has demonstrated that temporary crosslinks in polymer networks generated by chemical “fuels” afford materials with large, transient changes in their mechanical properties. This can be accomplished in carboxylic-acid-functionalized polymer hydrogels using carbodiimides, which generate anhydrides with lifetimes on the order of minutes to hours. Here, the impact of the polymer architecture on the mechanical properties of materials was explored. Single networks (SNs) were compared to interpenetrated networks (IPNs). Notably, semi-IPN precursors that give IPNs on treatment with the carbodiimide gave much higher fracture energies (i.e., resistance to fracture) and superior resistance to compressive strain compared to other network structures. A precursor semi-IPN material featuring acrylic acid in only the free polymer chains yields, on treatment with carbodiimide, an IPN with a fracture energy of 2400 J/m2, a fourfold increase compared to an analogous semi-IPN precursor that yields a SN. This resistance to fracture enables the formation of macroscopic complex cut patterns, even at high strain, underscoring the pivotal role of polymer architecture in mechanical performance.
Data archive for "Carbodiimide-induced formation of transient polyether cages"
http://hdl.handle.net/2374.MIA/6850
Data archive for "Carbodiimide-induced formation of transient polyether cages"
Hossain, Mohammad Mosharraf; Jayalath, Isuru M.; Baral, Renuka; Hartley, C. Scott
The use of “fuel” compounds to drive chemical systems out of equilibrium is currently of interest because of the potential for temporally controlled, responsive behavior. We have recently shown that transiently formed crown ethers exhibit counterintuitive templation effects when generated in the presence of alkali metal cations: “matched” cations, such as K+ with an 18-crown-6 analogue, suppress the formation of the macrocycles (negative templation). In this work, we describe two macrocyclic diacids that, on treatment with carbodiimides, give transient macrobicyclic cages analogous to polyether cages. Negative templation effects are observed for the smaller cage when generated in the presence of K+ and Na+, but there is a weak, but reproducible, positive templation effect in the presence of Li+. The larger cage behaves similarly in the presence of Li+, K+, Rb+, and Cs+, but differently with Na+, which appears to bind to both the cage and the initial macrocycle.
Data archive for "Engineering chiral induction in centrally functionalized ortho-phenylenes"
http://hdl.handle.net/2374.MIA/6835
Data archive for "Engineering chiral induction in centrally functionalized ortho-phenylenes"
Peddi, Sumalatha; Livieri, Juliana M.; Vemuri, Gopi Nath; Hartley, C. Scott
Work on foldamers, non-biological oligomers that mimic the hierarchical structure of biomacromolecules, continues to yield new architectures of ever increasing complexity. o-Phenylenes, a class of helical aromatic foldamers, are well-suited to this area because of their structural simplicity and the straightforward characterization of their folding in solution. However, combining multiple foldamer subunits into single species requires, by definition, control over folding handedness to obtain well-defined species. Control over o-phenylene twist sense is currently lacking. While chiral induction from groups at their termini has been demonstrated, it would be useful to instead direct twisting from internal positions in order to leave their ends free. Here, we explore chiral induction in a series of o-phenylenes with chiral imides at their centers. Conformational behavior has been studied by NMR and CD spectroscopies and DFT calculations. Chiral induction in otherwise unfunctionalized o-phenylenes is generally poor. However, strategic functionalization of the helix surface with trifluoromethyl and methyl groups allows it to better interact with the imide groups, greatly increasing diastereomeric excesses. The sense of chiral induction is consistent with computational models that suggest that it primarily arises from a steric effect.