A5091361929- Polymer composites and self-healing
- Advanced Polymer Synthesis and Characterization
- Fluorine in Organic Chemistry
- Photochromic and Fluorescence Chemistry
- Radical Photochemical Reactions
- Luminescence and Fluorescent Materials
- Porphyrin and Phthalocyanine Chemistry
- X-ray Diffraction in Crystallography
- Polymer Nanocomposites and Properties
- Crystallization and Solubility Studies
- Synthetic Organic Chemistry Methods
- Synthesis and Catalytic Reactions
- Hydrogels: synthesis, properties, applications
- Pickering emulsions and particle stabilization
- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- Covalent Organic Framework Applications
- biodegradable polymer synthesis and properties
- Carbon dioxide utilization in catalysis
- Photoreceptor and optogenetics research
- Chemistry and Chemical Engineering
- Organic Chemistry Cycloaddition Reactions
- Supramolecular Self-Assembly in Materials
- Microplastics and Plastic Pollution
- Molecular Sensors and Ion Detection
Northwestern University
2018-2024
Northwestern University
2023
Duke University
2021
Institute for Soldier Nanotechnologies
2015-2017
Massachusetts Institute of Technology
2015-2017
Princeton University
2010-2016
Columbia University
2012
An enantioselective method for the synthesis of beta-fluoroalcohols by catalytic nucleophilic fluorination epoxides is described. Mild reaction conditions and high selectivity are made possible use benzoyl fluoride as a soluble, latent source anion. A chiral amine Lewis acid serve cooperative catalysts desymmetrizations five- through eight-membered cyclic epoxides, affording products in up to 95% ee. The cocatalytic protocol also effective kinetic resolutions racemic terminal which proceed...
Longer and stronger; stiff but not brittle Hydrogels are highly water-swollen, cross-linked polymers. Although they can be deformed, tend to weak, methods strengthen or toughen them reduce stretchability. Two papers now report strategies create tough deformable hydrogels (see the Perspective by Bosnjak Silberstein). Wang et al . introduced a toughening mechanism storing releasable extra chain length in part of double-network hydrogel. A high applied force triggered opening cycling strands...
Having a compact yet robust structurally based identifier or representation system is key enabling factor for efficient sharing and dissemination of research results within the chemistry community, such systems lay down essential foundations future informatics data-driven research. While substantial advances have been made small molecules, polymer community has struggled in coming up with an system. This because, unlike other disciplines chemistry, basic premise that each distinct chemical...
Current vitrimer technology uses only a handful of distinct reactions for cross-linking. New dynamic can diversify functionality and properties. In this paper, reversible cross-links formed by conjugate addition–elimination thiols with Meldrum’s acid derivative enable compression–remolding silicone elastomers. After 10 remolding cycles, there is no discernible deterioration mechanical properties (Young’s modulus, Tg, rubbery plateau E’), nor change in stress relaxation activation energy....
Micro-scale optical components play a crucial role in imaging and display technology, biosensing, beam shaping, switching, wavefront-analysis, device miniaturization. Herein, we demonstrate liquid compound micro-lenses with dynamically tunable focal lengths. We employ bi-phase emulsion droplets fabricated from immiscible hydrocarbon fluorocarbon liquids to form responsive that can be reconfigured focus or scatter light, real virtual images, variable Experimental demonstrations of dynamic...
This report describes mechanistic studies of the (salen)Co- and amine-cocatalyzed enantioselective ring opening epoxides by fluoride. The kinetics reaction, as determined in situ (19)F NMR analysis, are characterized apparent first-order dependence on (salen)Co. Substituent effects, nonlinear reactivity with a linked (salen)Co catalyst provide evidence for rate-limiting, bimetallic ring-opening step. To account these divergent data, we propose mechanism wherein active nucleophilic fluorine...
By controlling the stability of dynamic covalent crosslinks with adjacent photoswitches, stiffness an adaptable hydrogel is tuned reversibly.
The rate of stress relaxation in a vitrimer can be modulated by changing solely the structure cross-linker electrophile.
The composition of low-Tg n-butylacrylate-block-(acetoxyaceto)ethyl acrylate block polymers is investigated as a strategy to tune the properties dynamically cross-linked vinylogous urethane vitrimers. As proportion cross-linkable increased, thermorheological properties, structure, and stress relaxation evolve in ways that cannot be explained by increasing cross-link density alone. Evidence presented network connectivity defects such loops dangling ends are increased microphase separation....
Convenient strategies for the deconstruction and reprocessing of thermosets could improve circularity these materials, but most approaches developed to date do not involve established, high-performance engineering materials. Here, we show that bifunctional silyl ether, i.e., R'O-SiR2-OR'', (BSE)-based comonomers generate covalent adaptable network analogues industrial thermoset polydicyclopentadiene (pDCPD) through a novel BSE exchange process facilitated by low-cost food-safe catalyst...
Most photochemistry occurs in the regime of weak light-matter coupling, which a molecule absorbs photon and then performs from its excited state. In strong coupling regime, enhanced interactions between an optical field multiple molecules lead to collective hybrid states called polaritons. This leads fundamental changes nature including multi-molecule delocalized excitations, modified potential energy surfaces, dramatically altered levels relative non-coupled molecules. The effect on...
Vitrimers are associative covalent adaptable networks that undergo reversible bond-exchange reactions while maintaining a fixed cross-linking density with changing temperature. To date, experimental studies rely on macroscopic rheology have not been able to reveal topological changes and microscopic dynamics in these materials. Here, coarse-grained molecular simulations combined Monte Carlo method implemented investigate the structural changes, dynamics, linear of unentangled...
Embedding dynamic covalent bonds into polymer compositions transforms static thermosets active materials with the reprocessability of thermoplastics and bulk properties cross-linked networks. This class next-generation materials, called adaptable networks, shows significant promise in composites, soft optoelectronics, robotics. Herein, we synthesized two oligosiloxane-based epoxy networks that provide fast bond exchange. Oligosiloxane diepoxides were cured stoichiometric amounts...
Lewis base catalysis promotes the in situ generation of amine-HF reagents from benzoyl fluoride and a non-nucleophilic alcohol. The hydrofluorination aziridines to provide β-fluoroamines using this latent HF source is described. This protocol displays broad scope with respect aziridine substitution N-protecting groups. Examples regio- diastereoselective ring opening access medicinally relevant β-fluoroamine building blocks are presented.
Significance A nonfluorescence-based technology is introduced that can lead to visual detection of enzyme activity. These results represent a dramatically different paradigm for creating sensors based on dynamic liquid lenses with general utility.
The copper-catalyzed H–F insertion into α-diazocarbonyl compounds is described using potassium fluoride (KF) and hexafluoroisopropanol. Access to complex α-fluorocarbonyl derivatives achieved under mild conditions, the method readily adapted radiofluorination with [18F]KF. This late-stage strategy provides an attractive route 18F-labeled biomolecules.
Christopher Bowman, Filip Du Prez and Julia Kalow introduce the <italic>Polymer Chemistry</italic> themed collection on chemistry for covalent adaptable networks.
We report a series of azobenzene boronic acids that reversibly control the extent diol binding via photochemical isomerization. When acid is ortho to azo group, thermodynamically favored E isomer binds weakly with diols form esters. The isomerization (E)-azobenzene its Z enhances binding, and magnitude this enhancement affected by structure. 2,6-Dimethoxy show an over 20-fold in upon → isomerization, which can be triggered red light. Competition experiments computational studies suggest...
In dynamic materials, the reversible condensation between boronic acids and diols provides adaptability, self-healing ability, responsiveness to small molecules pH. The thermodynamics kinetics of bond exchange determine mechanical properties polymer networks. Here, we investigate effects diol structure salt additives on rate acid–diol exchange, binding affinity, corresponding We find that proximal amides used conjugate polymers buffering anions induce significant acceleration, consistent...
The transesterification rate of boronate esters with diols is tunable over 14 orders magnitude. Rate acceleration achieved by internal base catalysis, which lowers the barrier for proton transfer. Here we report a photoswitchable catalyst that tunes boronic ester/diol exchange 4 We employed an acylhydrazone molecular photoswitch, forms thermally stable but photoreversible intramolecular H-bond, to gate activity in 8-quinoline ester. photoswitch bidirectional and can be cycled repeatedly....