A5057076273- Polymer composites and self-healing
- Photochromic and Fluorescence Chemistry
- Advanced Polymer Synthesis and Characterization
- Advanced Materials and Mechanics
- Photopolymerization techniques and applications
- Photoreceptor and optogenetics research
- Electrowetting and Microfluidic Technologies
- Polymer Surface Interaction Studies
- Conducting polymers and applications
- Plant and Biological Electrophysiology Studies
- Porphyrin and Phthalocyanine Chemistry
- Nanofabrication and Lithography Techniques
- Microfluidic and Bio-sensing Technologies
- Additive Manufacturing and 3D Printing Technologies
- Synthesis and properties of polymers
- Luminescence and Fluorescent Materials
- Radical Photochemical Reactions
- Oxidative Organic Chemistry Reactions
- Advanced Sensor and Energy Harvesting Materials
- Polydiacetylene-based materials and applications
- Supramolecular Self-Assembly in Materials
- Synthetic Organic Chemistry Methods
- Epoxy Resin Curing Processes
- DNA and Nucleic Acid Chemistry
- Chemical and Physical Properties of Materials
University of Chicago
2020-2025
Tsinghua University
2024
University of California, Santa Barbara
2017-2022
Santa Barbara City College
2019-2021
Division of Materials Research
2019
University of California System
2017-2019
A class of tunable visible and near-infrared donor-acceptor Stenhouse adduct (DASA) photoswitches were efficiently synthesized in two to four steps from commercially available starting materials with minimal purification. Using either Meldrum's or barbituric acid "acceptors" combination aniline-based "donors", an absorption range spanning 450 750 nm is obtained. Additionally, photoisomerization results complete decoloration for all adducts, yielding fully transparent, colorless solutions...
A novel methodology for printing 3D objects with spatially resolved mechanical and chemical properties is reported. Photochromic molecules are used to control polymerization through coherent bleaching fronts, providing large depths of cure rapid build rates without the need moving parts. The coupling these photoswitches resin mixtures containing orthogonal photo-crosslinking systems allows simultaneous selective curing multiple networks, access chemically mechanically distinct domains. power...
Pluripotency, which is defined as a system not fixed to its developmental potentialities, typically associated with biology and stem cells. Inspired by this concept, we report synthetic polymers that act single "pluripotent" feedstock can be differentiated into range of materials exhibit different mechanical properties, from hard brittle soft extensible. To achieve this, have exploited dynamic covalent networks contain labile, thia-Michael bonds, whose extent bonding thermally modulated...
The effect of catalyst strength on polyester–alcohol dynamic covalent exchange was systematically studied using Brønsted acids and a low-Tg poly(4-methylcaprolactone) vitrimer formulation. Relaxation times, activation energies, Arrhenius prefactors are correlated with pKa. Strong protic induce facile network relaxation at 25 °C the order 104–105 s, significantly faster than Lewis acid alternatives that function only above 100 °C. Activation energies span 49–67 kJ/mol increase as pKa...
A novel library of tunable negative photochromic compounds, donor-acceptor Stenhouse adducts (DASAs), is reported. Tailoring the electron deficient "acceptor" moiety yielded DASAs that can be activated with mild visible and far red light. The effect acceptor composition on reactivity, absorption, equilibrium, cyclability exploited for design high performance photoswitches. structural changes to carbon acid also provide access new, more structurally diverse DASA derivatives by facilitating...
Abstract The fabrication of well‐defined, multifunctional polymer brushes under ambient conditions is described. This facile method uses light‐mediated, metal‐free atom‐transfer radical polymerization (ATRP) to grow with only microliter volumes required. Key the success this strategy dual action N ‐phenylphenothiazine (PTH) as both an oxygen scavenger and catalyst. Use simple glass cover slips results in a high degree spatial temporal control allows for multiple be grown simultaneously....
A signature of photo-mediated controlled polymerizations is the ability to modulate rate polymerization by turning light source ‘on’ and ‘off.’ However, in many reported systems, growth can be reproducibly observed during dark periods. In this study, emerging radical are evaluated with situ 1H NMR monitoring assess their behavior dark. Interestingly, it that Cu-mediated systems undergo long-lived, linear periods organic media. Please note: The publisher not responsible for content or...
Vinylogous urethane (VU
We report a simple procedure for rapid, visible light-mediated, controlled radical polymerization in aqueous solutions. Based on the photoelectron transfer reversible addition–fragmentation chain (PET–RAFT) polymerization, fast propagation at room temperature water was achieved presence of reductant and without prior deoxygenation. A systematic study correlating irradiation intensity kinetics, enabled by situ nuclear magnetic resonance spectroscopy, provided optimized reaction conditions....
A modular synthesis of Donor-Acceptor Stenhouse Adduct (DASA) polymer conjugates is described. Pentafluorophenyl-ester chemistry employed to incorporate aromatic amines into acrylate and methacrylate copolymers, which are subsequently coupled with activated furans generate polymers bearing a range DASA units in manner. The effect glass transition temperature on switching kinetics studied, showing dramatic rate enhancements going from glassy rubbery matrix. Moreover, tuning the absorption...
Abstract Polymeric ionic liquids (PILs) have attracted considerable attention as electrolytes with high stability and mechanical durability. Light‐responsive materials are enabling for a variety of future technologies owing to their remote noninvasive manipulation, spatiotemporal control, low environmental impact. To address this potential, responsive PIL based on diarylethene units were designed undergo light‐mediated conductivity changes. Key modulation is tuning the cationic character...
External regulation of controlled polymerizations allows for controlling the kinetics polymerization and gaining spatial or temporal control over polymer growth. In photoinduced atom transfer radical (ATRP), light irradiation (re)generates copper catalyst to switch on. However, removing does not immediately inactivate catalyst, nor rate become zero as chains may grow in dark because continued activation by residual activator regeneration Cu dark. this paper, effect components on ATRP was...
Dynamic covalent networks comprised of tunable thia-Michael bonds result in phase separated with tailorable mechanical and adaptive properties.
Although the catalyst-free dynamic thia-Michael (tM) reaction has been leveraged for a range of significant applications in materials science and pharmaceutical development, exploiting its full potential limited by relatively low equilibrium constants. To address this shortcoming, new series catalyst-free, room-temperature acceptors bearing an isoxazolone motif were developed utilized to access both covalent networks linear polymers. By leveraging generation aromaticity upon thiol addition...
A strategy to efficiently synthesize thermally reprogrammable but mechanically stable liquid crystalline elastomers (LCEs) is reported by investigating the catalytic effects of para-substituted phenols on dynamic aza-Michael reactions. The synthesis LCEs was optimized based a study catalyzed small-molecule reactions, where presence an electron-withdrawing substituent significantly improved reactivity system. catalysts were then screened their exchange adducts. Catalysts with substituents...
Abstract Developing mechanically flexible composite materials with high electrical conductivity is currently hindered by the need to use loading of conductive filler, which severely limits flexibility. Here, acoustic focusing used control arrangement particles in photopolymer matrices create composites both tunable and Acoustophoresis patterns filler into highly efficient percolated networks utilize up 97% composite, whereas inefficient stochastic conventional dispersed‐fiber < 5%. These...
Strong and well-engineered interfaces between dissimilar materials are a hallmark of natural systems but have proven difficult to emulate in synthetic materials, where often act as points failure. In this work, curing reactions that triggered by exposure different wavelengths visible light used produce multimaterial objects with tough, well-defined chemically distinct domains. Longer-wavelength (green) selectively initiates acrylate-based radical polymerization, while shorter-wavelength...
High-Tg, epoxy-amine networks are used ubiquitously across various industries as lightweight adhesives; however, a cross-cutting need is improved ductility in these glassy materials. Tailoring the location of photoactive azobenzene moieties (interstitial, pendent, or at cross-link) within high-Tg elucidated several structural relationships to mechanical responses and improvements ductility. Within linear viscoelastic regime, probed using dynamic analysis, changes during irradiation were...
The thia-Michael reaction, i.e., the addition of a thiol to an α,β-unsaturated carbonyl moiety, has recently gained significant attention within field dynamic covalent chemistry. Interestingly, including additional electron-withdrawing group at α-position Michael acceptor can result in room temperature (rt), catalyst-free reactions. Importantly, electronic nature be used tune equilibrium constant (Keq) these Herein we report how sterics enhance Keq rt bonds. A series benzalcyanoacetate,...
Abstract A simple, inexpensive, and modular method to directly illuminate NMR samples for in situ analysis of photochemical transformations is reported. The versatility this technique demonstrated by analyzing the light‐induced propagating front small‐molecule photoswitches kinetics photocontrolled living radical polymerizations. In measurements allow oxygen‐sensitive rapid photoevents be studied detail, leading reliable determination photoswitching quantum yields polymerization rates. By...
Abstract Herein we report the development of a merocyanine‐based photoacid with improved solubility in organic media and enhanced switching kinetics that can be used to impart temporal control over ring opening polymerization. The effect structural modification on solubility, thermal relaxation activation energy were evaluated using 1 H NMR pump‐probe absorption spectroscopies. Overall, new merocyanine based provides access wider range chemical material applications solvent compatibility control.
DNA-mediated assembly of inorganic particles has demonstrated to be a powerful approach for preparing nanomaterials with range interesting optical and electrical properties. Building on this inspiration, we describe generalizable gram-scale method assemble nanoparticles through the formation poly(methyl methacrylate) (PMMA) triple-helices. In work, alkene-terminated syndiotactic (st-) isotactic (it-) PMMA polymers were prepared subsequently functionalized afford nanoparticle ligands....
A series of multistage (pressure-sensitive/hot melt) adhesives utilizing dynamic thia-Michael bonding motifs are reported. The benzalcyanoacetate Michael acceptors used in this work undergo bond exchange under ambient conditions without external catalysis, facilitating pressure-sensitive adhesion. key feature system is the reaction-induced phase separation that lends reinforcement to otherwise weakly bonded materials, enabling weak, repeatable adhesion and strong when processed as a hot melt...
The non-Newtonian behaviors of dense suspensions are central to their use in technological and industrial applications arise from a network particle-particle contacts that dynamically adapt imposed shear. Reported herein studies aimed at exploring how dynamic covalent chemistry between particles the polymeric solvent can be used tailor such stress-adaptive contact networks, leading unusual rheological behaviors. Specifically, room temperature thia-Michael bond is employed rationally tune...