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A laboratory experiment was developed that connects the interpretation of computer-generated models to the self-assembly of macrocycles. Students compare the reactions of terephthalaldehyde and isophthalaldehyde by reacting each with (R,R)-(-)-1,2-diaminocyclohexane. These isomeric systems serve as the foundation for a discussion about the impact of entropy and enthalpy on macrocycle formation. This experiment requires students to use multiple data sources to develop evidence-based explanations about the impact of the startingmaterial geometry on macrocyclization. Results from laboratory implementation indicate that a majority of students were able to successfully demonstrate competency of the learning goals.

Biochemical systems make use of out‐of‐equilibrium polymers generated under kinetic control. Inspired by these systems, many abiotic supramolecular polymers driven by chemical fuel reactions have been reported. Conversely, polymers based on transient covalent bonds have received little attention, even though they have the potential to complement supramolecular systems by generating transient structures based on stronger bonds and by offering a straightforward tuning of 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 then decompose over the course of hours to weeks. Disassembly kinetics can be controlled using simple substituent effects in the monomer design. The impact of solvent polarity, carbodiimide concentration, temperature, pyridine 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. [ABSTRACT FROM AUTHOR]

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 anhydride crosslinks with lifetimes on the order of minutes to hours. Here, the impact of the polymer network architecture on the mechanical properties of transiently crosslinked materials was explored. Single networks (SNs) were compared to interpenetrated networks (IPNs). Notably, semi‐IPN precursors that give IPNs on treatment with carbodiimide give much higher fracture energies (i.e., resistance to fracture) and superior resistance to compressive strain compared to other network architectures. 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. [ABSTRACT FROM AUTHOR]

Although stereochemistry is an important topic in second-year undergraduate organic chemistry, there are limited options for laboratory activities that allow direct visualization of macroscopic chiral phenomena. A novel, guided-inquiry experiment was developed that allows students to explore chirality in the context of cholesteric liquid crystals. As part of the experiment, which requires no specialized equipment, students visually distinguish two enantiomers. A chiral imine is synthesized in one step from an assigned (but unknown to students) enantiomer of 1-phenylethylamine and then dissolved in a nematic liquid crystal host, inducing a helical structure. The resulting cholesteric liquid crystalline material selectively reflects circularly polarized light with a handedness that depends on the absolute configuration of the starting amine, easily detected using circularly polarizing filters from disposable 3D glasses. Working in teams, students examine the behavior of both dopant enantiomers and the racemic mixture. Analysis of our students' responses to post-lab questions indicates comprehension of most of the ideas introduced in lab.

Dynamic NMR spectroscopy and computational chemistry are utilized to study in detail the conformational behavior of series of o-phenylenes, which represent a fundamental class of conjugated polymers. The o-phenylene motif could find significant potential for organizing arenes into predictable three-dimensional arrangements.

A robust synthetic approach is developed to monodisperse ortho-phenylene oligomers that are shown by preparing a homologous series up to the dodecamer. The series have displayed long-range delocalization and the oligomers have shown an unusual hypsochromic shift in their fluorescence spectra with increasing length.

Studies have shown a sequence-directed, dynamic covalent approach to unsymmetrical macrocycles by using imine formation and exchange. A series of potentially useful side-chain patterns, including monofunctionalized and Janus-type structures, are described.

Dynamic covalent chemistry (DCC) is used to show that complimentary m-phenylene ethynylene (mPE) oligomers will self-assemble into [n]-rung molecular ladders (n = 3 - 6). The gel permeation chromatography (GPC) has indicated that the yield has decreased as a greater proportion of higher molecular weight material is observed and these structures have shown the use of discrete oligomers as components for two-dimensional nanostructure assembly.