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This work demonstrates our effort to develop stimuli responsive cellulose films for the detection of dimethyl amines, a biogenic amine, released during food decomposition. Herein, we demonstrate that thin layer deposition of polydiacetylene‐zinc oxide nanosheets (PDA‐ZnO) on cellulose (CE) paper yields a stimuli responsive strip exhibiting strong thermochromism and solvatochromism against dimethyl amine. The incorporation of Zn nanoclusters within the composite plays an essential role in achieving reversible thermochromism while strong intermolecular interactions promote adsorption of PDA‐ZnO on cellulose paper. X‐ray diffraction and infrared spectroscopy reveal that the Zn2+ ions intercalate with PDA bilayer and strongly interact with the carboxylate headgroup of PDA. Furthermore, the reversible thermochromism persist when the nanosheets are deposited on cellulose (CE) paper when assembling PDA‐ZnO−CE paper. In addition, PDA‐ZnO−CE displayed selective solvatochromism allowing the utilization of the paper in the detection of dimethyl amine as it displayed a distinct and remarkable purple to orange colour transition. In particular, the response of the PDA‐ZnO−CE paper in several other organic solvents was poor as no transitions were observed hence its selectivity towards dimethylamine. In conclusion, the incorporation of PDA‐ZnO on cellulose paper is a step forward towards designing of a stimuli responsive packaging material that can detect biogenic amines released during food decomposition thereby preventing food poisoning. [ABSTRACT FROM AUTHOR]

Functional membranes based on stimuli-responsive block copolymers have attracted significant attention in the field of membrane separations, which can adjust the pore sizes and the surface properties in response to environmental stimuli. However, it was inconvenient to synthesize stimuli-responsive block copolymers due to the complexity and inefficiency of the synthesis process. In this work, pH- and thermal-responsive triblock copolymers were synthesized by the one-pot method to modify PVDF membranes. The modified membranes exhibit good hydrophilicity, and the contact angle of M2 decreased from 74° to 0° within 20 s. Surprisingly, the water flux of the blend membrane is approximately 24 times and 33 times higher than that of the pure membrane, respectively. Besides, the modified membranes also exhibit good pH and thermal response, and superior fouling-tolerant performance. Overall, these multi-responsive block copolymers synthesized by a simple one-pot method have enormous potential for controlled size separation, flux regulation, and many other fields. [ABSTRACT FROM AUTHOR]

Hydrogels based on dynamic covalent bonds have unique properties and are competent in many biomedical fields. However, critical issues such as biocompatibility, mechanical properties, and stimulus responsiveness are required to be solved. It is also expected to develop a simple preparation method with mild conditions. Based on these objectives, chitosan (CS), sodium alginate (SA) and 2‐formylphenylboronic acid (2‐FPBA) are used to prepare the dynamic covalent bond hydrogels within minutes neither chemical medications nor severe conditions. Benefiting from the imine borate and boronic ester bonds both formed in the hydrogels, the hydrogels are stable, injectable, and of efficient self‐healing properties. The damage‐recovery process can be repeated for more than 6 cycles. The microstructure of the hydrogels recoded by atomic force microscopy (AFM) is consistent with the mechanical properties and both of them could be affected by the concentrations of SA and 2‐FPBA. Moreover, the dynamic hydrogels are responsive to pH values and oxidative environment. When the model drug 5‐fluorouracil (5‐FU) is loaded in the dynamic hydrogels, the release profiles are sustainable and present significant differences with various stimuli. These dynamic covalent bond hydrogels have a promising prospect in tissue engineering and drug delivery. [ABSTRACT FROM AUTHOR]

Development of efficient and low cost electrocatalysts has been an important area of research in the field of materials chemistry. In this regard metal‐organic gels (MOGs) are one of the promising materials and they are being utilized for various materials applications including energy conversion and storage. Electrochemical applications of the MOGs are still in its infancy and further studies are required for exploration of structure‐property correlation that is crucial for targeted and efficient materials design. Herein we report multi stimuli responsive MOGs containing a tris‐tetrazole‐tri‐amido based organic ligand. The self‐assembly of the threefold symmetric ligand with Co(II)/Ni(II) acetates results in the MOGs with distinct morphological and structural characteristics, regardless of containing the same organic ligand. These MOGs were synthesized by direct mixing of the precursors under ambient conditions. The xerogels of these MOGs (Co‐MOG′ and Ni‐MOG′) exhibit excellent OER performance as the Co‐MOG′ and Ni‐MOG′ shows the overpotential of 312 mV and 418 mV at 10 mA/cm2 in an alkaline electrolyte. Electrocatalytic performance of the xerogels were correlated to their structural features like distinct morphology and porosity of the material that facilitates the mass transfer and maximum exposure to the electrochemical active sites. Importantly, this work demonstrates the functional application of MOGs as electrocatalysts for OER and the effect of metal ion, porosity and morphology on their overall performance. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive or smart materials have recently shown a significant impact on the frontier of material science and engineering. The exponential development of synthetic host molecules (SHMs) over the last decades and their corresponding host–guest chemistry, have empowered researchers with new opportunities to design and construct tailored or guest‐specific smart materials. In this Minireview, we present the recent advancements in synthetic host based smart materials, ranging from the fabrication strategies to the state‐of‐art applications including adsorption, separation, luminescence, self‐healing and actuation. The role that the host–guest chemistry plays in these systems is highlighted throughout to give a better prospective of the available possibilities for emerging materials of future economies. [ABSTRACT FROM AUTHOR]

The last decade has seen a meteoric rise in studies investigating polymeric aggregates as nanocarriers. When it comes to morphology, size, functionality, and immunostability, polymeric nanocarriers (PNCs) are unparalleled. With characteristics such as large surface area to volume ratio, amphiphilic nano‐environment, non‐toxic components, chemically modifiable composition, external surface alteration potential, uniform particle size, and stimuli‐dependent self‐assembly, PNCs have emerged as strong candidates for therapeutic applications. The article reviews the latest research on different challenges and strategies for targeted drug delivery and shall serve as guide to the researchers in designing site‐specific nanocarriers for application in future. The review systematically discusses the fundamental structural variation of the nanocarriers with emphasis on the influence of chemical alterations and the resulting effects on functionality; addresses the difficulties encountered with modes of administration; target selectivity and stimulus response. [ABSTRACT FROM AUTHOR]

Deoxyribonucleic acid (DNA) hydrogels are a unique class of programmable, biocompatible materials able to respond to complex stimuli, making them valuable in drug delivery, analyte detection, cell growth, and shape‐memory materials. However, unmodified DNA hydrogels in the literature are very soft, rarely reaching a storage modulus of 103 Pa, and they lack functionality, limiting their applications. Here, a DNA/small‐molecule motif to create stiff hydrogels from unmodified DNA, reaching 105 Pa in storage modulus is used. The motif consists of an interaction between polyadenine and cyanuric acid—which has 3‐thymine like faces—into multimicrometer supramolecular fibers. The mechanical properties of these hydrogels are readily tuned, they are self‐healing and thixotropic. They integrate a high density of small, nontoxic molecules, and are functionalized simply by varying the molecule sidechain. They respond to three independent stimuli, including a small molecule stimulus. These stimuli are used to integrate and release DNA wireframe and DNA origami nanostructures within the hydrogel. The hydrogel is applied as an injectable delivery vector, releasing an antisense oligonucleotide in cells, and increasing its gene silencing efficacy. This work provides tunable, stimuli‐responsive, exceptionally stiff all‐DNA hydrogels from simple sequences, extending these materials' capabilities. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive polymer networks like microgels and hydrogels possess a variety of properties that need to be analyzed for their rational design and successful application in the targeted field of interest. Nanoscale characterization of gels can be achieved by highly selective and sensitive techniques including high‐resolution NMR spectroscopy, relaxometry, and diffusometry. This review is focusing on recent results using 1H and 13C 1D and 2D NMR techniques, which give chemically site‐selective information about the polymer network revealing the interplay between structure and dynamics of polymer networks at the nanoscale level. By that, NMR can allow to obtain information about i) internal structure, ii) stimuli‐induced phase transition, iii) mesh size, and iv) aggregation of microgels and hydrogels. The rational design of responsive microgels and hydrogels with application in drug delivery, cell carrier systems, catalysis, actuators, and as antibacterial agent can be made, if crucial polymer network properties can be correlated with cross‐linking density, type of cross‐link interactions, electrical charges, hydrophobic nano‐structuring, and dispersion concentration. [ABSTRACT FROM AUTHOR]

Electromerism is a very well‐known phenomenon in transition metal chemistry. In main group chemistry, this concept has only started getting attention recently. We report stimuli responsive low‐valent silicon compounds exhibiting electromerism. A mixed‐valent silaiminyl‐silylene 1, [LSi−Si(NDipp)L] (L=PhC(NtBu)2), was synthesized in a single step from amidinate‐chlorosilylene. Compound 1 has two interconnected Si atoms in formally +I and +III oxidation states. Upon treatment with Lewis acidic CuIX (X=mesityl, Cl, Br, I), electron redistribution occurs resulting in the formation of [{LSi(NDipp)Si(L)}−CuX], in which both silicon atoms are in the +II formal oxidation state. Removal of the copper center from [{LSi(NDipp)Si(L)}−CuX] by using a Lewis basic carbene led to reformation of the precursor [LSi−Si(NDipp)L]. Thus, the process is fully reversible. This showcases the first example of Lewis acid/base‐induced reversible electromerism in silicon chemistry. [ABSTRACT FROM AUTHOR]

Design and fabrication of freestanding chiro‐photonic crystal film with the ability to change color over the whole visible light spectrum is appealing for anticounterfeiting technology and smart labels. Utilizing a newly synthesized light‐responsive molecular motor functionalized with cholesterol (chol‐MM) on the rotor, novel light‐controlled photonic crystal is prepared by doping the novel chol‐MM into liquid crystals (LCs). Thanks to the liquid crystalline cholesterol substituent, the chol‐MM can be triggered by visible light (420 nm). At the same time, the miscibility of chol‐MM in LC matrix is significantly enhanced. Integrating the chol‐MM with thermochromic hydrogen‐bonded LC matrix, thermal and light dual‐responsive cholesteric LC (CLC) material is prepared, in which the nanoscale helical pitch is tunable by photo‐induced molecular motions of chol‐MM. More importantly, utilizing UV‐initiated polymerization of the visible light‐modulated CLC material, structural colored photonic crystal films with arbitrary colorful patterns are fabricated. Such freestanding helical nanostructured labels have potential in the application of encrypted communication and anticounterfeiting. [ABSTRACT FROM AUTHOR]

Recently, we presented a strategy for packaging peptides as side‐chains in high‐density brush polymers. For this globular protein‐like polymer (PLP) formulation, therapeutic peptides were shown to resist proteolytic degradation, enter cells efficiently and maintain biological function. In this paper, we establish the role charge plays in dictating the cellular uptake of these peptide formulations, finding that peptides with a net positive charge will enter cells when polymerized, while those formed from anionic or neutral peptides remain outside of cells. Given these findings, we explored whether cellular uptake could be selectively induced by a stimulus. In our design, a cationic peptide is appended to a sequence of charge‐neutralizing anionic amino acids through stimuli‐responsive cleavable linkers. As a proof‐of‐concept study, we tested this strategy with two different classes of stimuli, exogenous UV light and an enzyme (a matrix metalloproteinase) associated with the inflammatory response. The key finding is that these materials enter cells only when acted upon by the stimulus. This approach makes it possible to achieve delivery of the polymers, therapeutic peptides or an appended cargo into cells in response to an appropriate stimulus. [ABSTRACT FROM AUTHOR]

Microbial growth and fluctuations in environmental conditions have been shown to cause microbial contamination and deterioration of food. Thus, it is paramount to develop reliable strategies to effectively prevent the sale and consumption of contaminated or spoiled food. Responsive packaging systems are designed to react to specific stimuli in the food or environment, such as microorganisms or temperature, then implement an informational or corrective response. Informative responsive packaging is aimed at continuously monitoring the changes in food or environmental conditions and conveys this information to the users in real time. Meanwhile, packaging systems with the capacity to control contamination or deterioration are also of great interest. Encouragingly, corrective responsive packaging attempting to mitigate the adverse effects of condition fluctuations on food has been investigated. This packaging exerts its effects through the triggered release of active agents by environmental stimuli. In this review, informative and corrective responsive packaging is conceptualized clearly and concisely. The mechanism and characteristics of each type of packaging are discussed in depth. This review also summarized the latest research progress of responsive packaging and objectively appraised their advantages. Evidently, the mechanism through which packaging systems respond to microbial contamination and associated environmental factors was also highlighted. Moreover, risk concerns, related legislation, and consumer perspective in the application of responsive packaging are discussed as well. Broadly, this comprehensive review covering the latest information on responsive packaging aims to provide a timely reference for scientific research and offer guidance for presenting their applications in food industry. [ABSTRACT FROM AUTHOR]

Developing safe and efficient delivery systems for therapeutic biomacromolecules is a long‐standing challenge. Herein, we report a newly developed combinatorial library of cholesteryl‐based disulfide bond‐containing biodegradable cationic lipidoid nanoparticles. We have identified a subset of this library which is effective for protein and mRNA delivery in vitro and in vivo. These lipidoids showed comparable transfection efficacies but much lower cytotoxicities compared to the Lpf2k in vitro. In vivo studies in adult mice demonstrated the successful delivery of genome engineering protein and mRNA molecules in the skeletal muscle (via intramuscular injection), lung and spleen (via intravenous injection), and brain (via lateral ventricle infusion). [ABSTRACT FROM AUTHOR]

Synthetic materials that mimic the ability of natural occurring features to self‐actuate in response to different stimuli have wide applications in soft robotics, microdevices, drug delivery, regenerative medicine, and sensing. Here, unexpected and counter‐intuitive findings are presented in which a strongly polyelectrolytic hydrogel repels from strong polar solvents upon partial exposure (e.g., partial hydration by water). This repulsion drives the actuation and self‐folding of the gel, which results in rapid formation of different three‐dimensional shapes by simply placing the corresponding two‐dimensional films on water. A detailed investigation into the role of hydrogel chemistry, pH, and morphology on hydration‐triggered actuation behavior of the gels and their nanocomposites is described. Finally, a computational model is developed in order to further elucidate mechanisms of actuation. Modeling partial hydration as a repulsive driving force, it tracks the evolution of the shape of the thin film that results from restoring elastic forces. Taken together, the results indicate that an interplay between elastic and Coulombic repulsive forces leads to seemingly unexpected behavior of actuation of strongly polyelectrolytic gels away from polar solvents, leading to a novel and simple fabrication strategy for diverse 3D devices. [ABSTRACT FROM AUTHOR]

Proteinosome, characterized by an inner aqueous cavity wrapped by membrane with embedded protein, is one of the most attractive structures, has huge potential applications on drug delivery, tissue engineering, catalysis, synthetic biology, artificial cells, engineering of the biomachines, biosensors, and biodevices, etc. Here, inspired by polyphenol chemistry, a facile and universal method is presented to fabricate the diverse proteinosomes, with independence on the amino acid sequence, isoelectric points, molecular weight (Mw), wettability, and functional domains of applied proteins. Besides, the materials employed here are green and cost‐effective, and the method developed here is efficient and easily operated without any expensive equipments. The proteinosomes and the mechanism of generating proteinosomes are well characterized and analyzed by various techniques. The permeability of generated proteinosomes is underlined, which not only shows dependence on the applied proteins but also the Mw of diffused molecules. In addition, the permeability can be reversibly switched on/off in 100% by environmental pH. Capitalizing the facility and university of this method, it is believed it paves the way of the proteinosomes to multiple potential applications, such as drug delivery, micro‐/nanoreactors, tissue engineering, catalysis, biosensor, etc. [ABSTRACT FROM AUTHOR]

Chemodynamic therapy (CDT) takes the advantages of Fenton‐type reactions triggered by endogenous chemical energy to generate highly cytotoxic hydroxyl radicals. As a novel modality for cancer treatment, CDT shows minimal invasiveness and high tumor specificity by responding to the acidic and the highly concentrated hydrogen peroxide microenvironment of tumor. The CDT approach for spatiotemporal controllable reactive oxygen species generation exhibits preferable therapeutic performance and satisfying biosafety. In this review article, we summarized the recent advances of stimuli‐activatable nanomedicines for CDT. We also overviewed the strategies for augmenting CDT performance, including increasing the catalytic efficacy through rational design of the nanomaterials, modulating the reaction condition, inputting external energy field, and regulating the tumor microenvironment. Furthermore, we discussed the potential and challenges of stimuli‐activatable nanomedicine for clinical translation and future development of CDT. This article is categorized under:Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic DiseaseNanotechnology Approaches to Biology > Nanoscale Systems in BiologyDiagnostic Tools > In Vivo Nanodiagnostics and Imaging [ABSTRACT FROM AUTHOR]

Self‐assembly of 3D structures presents an attractive and scalable route to realize reconfigurable and functionally capable mesoscale devices without human intervention. A common approach for achieving this is to utilize stimuli‐responsive folding of hinged structures, which requires the integration of different materials and/or geometric arrangements along the hinges. It is demonstrated that the inclusion of Kirigami cuts in planar, hingeless bilayer thin sheets can be used to produce complex 3D shapes in an on‐demand manner. Nonlinear finite element models are developed to elucidate the mechanics of shape morphing in bilayer thin sheets and verify the predictions through swelling experiments of planar, millimeter‐scaled PDMS (polydimethylsiloxane) bilayers in organic solvents. Building upon the mechanistic understandings, The transformation of Kirigami‐cut simple bilayers into 3D shapes such as letters from the Roman alphabet (to make "ADVANCED FUNCTIONAL MATERIALS") and open/closed polyhedral architectures is experimentally demonstrated. A possible application of the bilayers as tether‐less optical metamaterials with dynamically tunable light transmission and reflection behaviors is also shown. As the proposed mechanistic design principles could be applied to a variety of materials, this research broadly contributes toward the development of smart, tetherless, and reconfigurable multifunctional systems. [ABSTRACT FROM AUTHOR]

Self‐assembly of asymmetric block copolymers (BCPs) around active pore edges has emerged as an important strategy to produce smart membranes with tunable pathways for solute transport. However, thus far, it is still challenging to manipulate pore shape and functionality for directional transformation under external stimuli. Here, a versatile strategy by mesoscale simulations to design stimuli‐responsive pores with various edge decorations in hybrid membranes is reported. Dopant BCPs are used as decorators to stabilize pore edges and extend their function in reconfiguring pores in response to repeated membrane stretching/shrinking caused by external stimuli. The decoration morphologies are predictable since the assemblies of dopant BCPs around pore edges are closely related to their self‐assemblies in solution. The coassembly between different BCPs in the hybrid membrane for the control of pore morphology is featured, and the parameter settings, including block incompatibility and molecular architecture for the construction of a specific pore, are determined. Results show that harnessed dopant BCPs in the hybrid membrane can enhance pore formation and induce directional pore shape and functionality transformation. Diversified pore decorations exhibit potential that can be further explored in selective solute transport and the design of stimuli‐responsive smart nanodevices. [ABSTRACT FROM AUTHOR]

Development of macromolecules provides applicable platforms for the delivery of therapeutics. In this general overview, we focus on the design principles of synthetic polymers, with disulfide bonds located in either the polymer backbone or side chains. We also discuss the role of disulfide bonds, as well as the remaining questions to better understand their applications in therapeutic delivery systems. [ABSTRACT FROM AUTHOR]

The many postpolymerization modification opportunities of biocompatible poly(2‐alkyl/aryl‐2‐oxazoline)s (PAOx), such as thiol–ene/thiol–yne, azide–alkyne cycloadditions, amidation, and transesterification, are one of the most appealing features of this polymer class for its popularity in biomedicine. Inspired by recent reports on guanidine‐catalyzed transesterification and amidation reactions of methyl ester substrates, we explored the use of guanidines as a reactant for the modification of methyl ester functional PAOx, to obtain the respective acyl guanidines. The obtained acyl guanidines functional polymers display reactivity toward α‐haloketones, yielding imidazole functional PAOx. The obtained polymer structures are protonated in a broad pH range, and the acyl guanidine moiety is demonstrated to be a cleavable linker under basic conditions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2616–2624 [ABSTRACT FROM AUTHOR]

Biologically occurring non‐canonical di‐α‐amino acids were converted into new di‐N‐carboxyanhydride (di‐NCA) monomers in reasonable yields with high purity. Five different di‐NCAs were separately copolymerized with tert‐butyl‐l‐glutamate NCA to obtain covalently crosslinked copolypeptides capable of forming hydrogels with varying crosslinker density. Comparison of hydrogel properties with residue structure revealed that different di‐α‐amino acids were not equivalent in crosslink formation. Notably, l‐cystine was found to produce significantly weaker hydrogels compared to l‐homocystine, l‐cystathionine, and l‐lanthionine, suggesting that l‐cystine may be a sub‐optimal choice of di‐α‐amino acid for preparation of copolypeptide networks. The di‐α‐amino acid crosslinkers also provided different chemical stability, where disulfide crosslinks were readily degraded by reduction, and thioether crosslinks were stable against reduction. This difference in response may provide a means to fine tune the reduction sensitivity of polypeptide biomaterial networks. Biologically occurring non‐canonical di‐α‐amino acids were converted into new di‐N‐carboxyanhydride, di‐NCA, monomers in reasonable yields with high purity. These new building blocks enabled synthesis of covalent copolypeptide biomaterial hydrogels with tunable properties. [ABSTRACT FROM AUTHOR]

The cavities of metallosupramolecular cages can be used to mimic the central spaces of naturally occurring proteins and bind a wide variety of molecular guests. A range of potential applications have arisen from this capacity for host–guest chemistry. However, to truly harness the opportunities thus afforded, methodologies to controllably allow the release and reuptake of guests from the cavities of metallosupramolecular cages are required. Methods to accomplish this have centered upon reversibly altering the character of either the guest or host. This minireview outlines the current approaches used to carry out the binding and release of guests from metallosupramolecular hosts using important examples from the field. The cavities of metallosupramolecular cages can be used to mimic the central spaces of naturally occurring proteins and bind a wide variety of molecular guests. However, in order to more fully mimic Nature mechanisms that allow for the binding and release of guest molecules are required. This minireview outlines the current approaches used to carry out the binding and release of guests from metallosupramolecular hosts. [ABSTRACT FROM AUTHOR]

Abstract: The design and synthesis of a series of zwitterionic ionic liquids (ZILs) to understand the structure–property relationship towards an increase of the thermal stability, a variation of the glass transition temperature, the shape‐tuning of nanostructured aggregates and the tuning of the stimuli responsiveness are demonstrated. The substitution reaction of imidazole with various aliphatic and aromatic bromides followed by the reaction of the corresponding substituted imidazoles with bromoalkyl carboxylic acids of varying spacer length produces the ZILs. In aqueous solution, a ZIL molecule either exist in its ionic liquid (substituted imidazolium bromide) form or its zwitterionic (substituted imidazolium alkyl carboxylate) form with an isoelectric point (pI) depending on the pH value of the solution. Upon changing the pH to near or above the pI, the aqueous ZIL solution undergoes transition from a transparent to a turbid phase due to the formation of insoluble hierarchical nanostructured aggregates of various morphologies, such as spheres, tripods, tetrapods, fern‐like, flower‐like, dendrites etc. depending on the pH of the solution and the nature of the alkyl/vinyl/aryl substituents. Upon heating the solution a phase transition occurs from turbid to transparent, exhibiting a distinct reversible upper critical solution temperature (UCST)‐type cloud point (Tcp). It is observed that the cloud point varies with the nature of the substituent, an increase of the concentration of the ZIL as well as with changes of the pH of the solution. [ABSTRACT FROM AUTHOR]

Abstract: Layer‐by‐layer (LbL) films of micelles of poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly[(2‐(diethylamino)ethyl methacrylate)] (PDMA‐b‐PDEA) and poly(sodium 4‐styrenesulfonate) (PSS) with remarkably different pH‐stability and release properties are obtained via tuning film deposition conditions in a narrow pH and temperature range. Multilayers constructed at pH 8.5/25 °C or pH 8/30 °C completely disintegrate at physiologically related conditions, whereas film deposition at pH 8/25 °C produces stable films under the same conditions. Importantly, despite their stability, pH 8/25 °C multilayers release a considerable amount of pyrene at moderately acidic pH due to disintegration of the micellar cores. The amount of pyrene increases significantly at body temperature due to lower critical solution temperature (LCST)‐type phase behavior of PDMA coronal chains. The difference in properties of multilayers is explained by the extent of association among the layers which can be tuned by film deposition conditions in a narrow pH and temperature range due to dual responsive, that is, pH and temperature behavior of PDMA‐b‐PDEA micelles. [ABSTRACT FROM AUTHOR]

Construction of supramolecular polymers, in which functional monomer components are held together by noncovalent interactions, is considered as a promising design principle for functional materials. Linear fluorescent supramolecular polymer assembled on account of electrostatic attractions based host-guest interaction is synthesized and illustrated here. 1H NMR was involved to ensure the structure of guest and polymer, UV-vis and fluorescent spectra were recorded to be a readout signal to investigate the assemble process of polymer. TEM and AFM measurements were carried out to confirm the homogeneous nanometer-sized molecular assembly. It shows the way to be used as remote readout fluorescent functional material in the future. [ABSTRACT FROM AUTHOR]

In this study, a fabrication route towards functional capsule particles was successfully developed by means of a self-templating shell-selective cross-linking strategy that enables us to prepare shell-cross-linked hollow polymer particles directly from homogeneous spherical polymer particles. To prepare redox-responsive degradable capsule particles, a newly designed monomer bearing a photoinduced post-cross-linking group (cinnamoyl group) and a redox-environment-responsive cleavable group (disulfide group), N-cinnamoyl- N′-methyacryloylcystamine (MCC), was synthesized. Redox-responsive degradable capsule particles were successfully prepared from homogeneous spherical poly(MCC)-based particles by a self-templating shell-selective photoinduced cross-linking approach. Moreover, the cargo loading capability of the shell-cross-linked hollow particles was confirmed through a solvent exchange procedure using dyes, polymer precursors and anticancer reagents. Furthermore, redox-responsive degradability of the capsule polymer particles was also confirmed by adding a reducing agent for cleavage of the disulfide linkage. We hope that the efficient fabrication route of functional capsule particles directly from spherical polymer particles opens efficient routes for the fabrication of a wide range of capsule particles; in particular, this technique is robust, productive, and facile because neither additional sacrificial template particles nor toxic solvents are required. [ABSTRACT FROM AUTHOR]

Aggregation-induced emission luminogens (AIEgens) have become an emerging field since the concept of AIE was proposed in 2001. Recently, AIEgens have attracted considerable attention due to their abnormal non-emissive fluorescent behavior in solution but strongly emissive behavior in the aggregate state. By utilizing the inherent hydrophobicity, AIEgens can be used to monitor the crystal formation and dewetting behavior in the self-assembly process. More importantly, some stimuli-responsive AIE-active surfaces have been successfully fabricated. In this perspective review, we outline the advances of surface wettability of AIEgens and its applications. [ABSTRACT FROM AUTHOR]

A unique pressure-induced Cu−N bond breaking/bond forming reaction is reported. The variation of pressure on a single crystal of a one-dimensional copper- (II)-containing coordination polymer (Cu2L2(1-methylpiperazine)2] n, where H2L is 1,1′-(1,3-phenylene)-bis(4,4-dimethylpentane-1,3-dione)), was monitored using single crystal X-ray diffraction with the aid of a diamond anvil cell. At a very low elevated pressure (≈0.05 GPa) a remarkable reversible phase change was observed. The phase change results in the depolymerization of the material through the cleavage and formation of axial Cu−N bonds as well as 'ring flips' of individual axially coordinated 1-methylpiperazine ligands. Overall, the pressure-induced phase change is associated with a surprising (and non-intuitive) shift in structure-from a 1-dimensional coordination polymer to a discrete dinuclear complex. [ABSTRACT FROM AUTHOR]

Intelligence of living and nonliving systems is often characterized by the ability to communicate through signal and response. In the polymer science community, this intelligence is realized through the reaction of a material construct to environmental triggers. These smart materials are modeled after natural materials, which utilize matrix-fiber architectures to detect stimuli, release small molecules, or alter their macroscopic morphology in response to stimuli. As such, researchers have designed matrix-fiber composites, which function as release vehicles, sensors or switches, and actuators. Through the examination of the architecture and environmental triggering of these natural muses, the fundamental design parameters necessary for functional response in matrix-fiber composites and the ability to utilize these composites in targeted applications are highlighted. Opportunities for innovation in composite design are also discussed. [ABSTRACT FROM AUTHOR]

Biological materials have evolved to combine a number of functionally relevant properties. They are sensitive to chemical and mechanical signals and respond to these signals in a highly specific manner. Many biological hydrogels possess the ability to stress-stiffen, a property that is difficult to mimic in synthetic systems. A novel synthetic hydrogel is described that possesses stress-stiffening behavior in the biologically relevant stress regime and, at the same time, contains DNA cross-links as stimuli-responsive elements. The hydrogel scaffold is composed of oligo(ethylene glycol)-functionalized polyisocyanopeptides (PIC), which show a sol-to-gel transition upon increasing the temperature. It is shown that the mechanical properties of the hybrid hydrogel depend on DNA cross-linker concentration and temperature. At high temperature, a hydrophobically bundled stress-stiffening PIC network forms. By contrast, gel formation is controlled by DNA cross-linking at temperatures below the PIC sol-to-gel transition. The DNA cross-linked hydrogel also exhibits stress-stiffening behavior and its properties are controlled by the DNA cross-linker concentration. The hydrogel properties can further be tuned when using DNA cross-linkers with different melting temperature or when breaking cross-links by strand displacement. This clearly shows the potential of DNA cross-links as stimuli-responsive elements, highlighting the possible applications of this hybrid hydrogel as a new sensor. [ABSTRACT FROM AUTHOR]

ABSTRACT In recent years, significant progress has been made in polymeric materials, which alter shape upon external stimuli, suggesting potential applications in robotics, biomedical engineering, and optical devices. These stimuli-responsive materials may be categorized into two classes: (i) shape-changing materials in which a specific type of shape-shifting is encoded in the original material structure and (ii) shape-memory materials, which do not possess any predetermined shape-shifting as prepared, yet allow programming of complex shape transformations on demand. While shape alterations in shape-changing materials are intrinsically reversible, shape memory is usually a one-way transformation from a metastable (programmed) to an equilibrium (original) state. Recently, different principles for both one-way reversible and two-way reversible shape memory have been developed. These offer a powerful combination of reversibility and programmability, which significantly expands the range of potential applications. The goal of this review is to highlight recent developments in reversible shape-shifting by introducing novel mechanisms, materials, and applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1365-1380 [ABSTRACT FROM AUTHOR]

Elastomeric, robust, and biocompatible hydrogels are rare, while the need for these types of biomaterials in biomedical-related uses remains high. Here, a new family of genetically engineered silk-elastin-like proteins (SELPs) with encoded enzymatic crosslinking sites is developed for a new generation of stimuli-responsive yet robust hydrogels. Input into the designs is guided by simulation and realized via genetic engineering strategies. The avoidance of gamma irradiation or chemical crosslinking during gel fabrication, in lieu of an enzymatic process, expands the versatility of these new gels for the incorporation of labile proteins and cells. In the present study, the new SELP hydrogels offer sequence-dependent, reversible stimuli-responsive features. Their stiffness covers almost the full range of the elasticity of soft tissues. Further, physical modification of the silk domains provides a secondary control point to fine-tune mechanical stiffness while preserving stimuli-responsive features, with implications for a variety of biomedical material and device needs. [ABSTRACT FROM AUTHOR]

Self-assembled lipidic amphiphile systems can create a variety of multi-functional soft materials with value-added properties. When employing natural reagents and following biocatalytic syntheses, self-assembling monomers may be inherently designed for degradation, making them potential alternatives to conventional and persistent polymers. By using non-covalent forces, self-assembled amphiphiles can form nanotubes, fibers, and other stimuli responsive architectures prime for further applied research and incorporation into commercial products. By viewing these lipid derivatives under a lens of green principles, there is the hope that in developing a structure-function relationship and functional smart materials that research may remain safe, economic, and efficient. A review of various soft materials comprises self-assembled amphiphilic lipids derived from natural renewable resources. These assemblies are reviewed under a green perspective to assess the viability of incorporating these value-added multifunctional assemblies into soft materials. Amphiphilic systems derived from cardanol, short, medium, and long chain mono-, and di-fatty acids, acetaminophen, ascorbic acid, open-chain sugar alcohols, and closed-chain sugars are examined both as monomers and in their secondary architectures that arise upon assembly in certain solvents. [ABSTRACT FROM AUTHOR]

The article discusses a study which demonstrates that rational engineering of external stimuli, such as electrostatic and capillary cues, can lead to the formation of nanoscopically alternating and microscopically corrugated T-rGO reduced graphene oxide (rGO) hybrid photoanodes with energetically favorable and structurally durable interfaces. The high-resolution scanning electron microscopy (HRSEM) and corresponding EDX mapping confirms the results of the study.

A series of [Au2(nixantphos)2](X)2 (nixantphos=4,6-bis(diphenylphosphino)-phenoxazine; X=NO3, 1; CF3COO, 2; CF3SO3, 3; [Au(CN)2], 4; and BF4, 5) complexes that exhibit intriguing anion-switchable and stimuli-responsive luminescent photophysical properties have been synthesized and characterized. Depending on their anions, these complexes display yellow ( 3), orange ( 4 and 5), and red ( 1 and 2) emission colors. They exhibit reversible thermo-, mechano-, and vapochromic luminescence changes readily perceivable by the naked eye. Single-crystal X-ray studies show that the [Au2(nixantphos)2]2+ cations with short intramolecular Au ⋅⋅⋅Au interactions are involved as donors in an infinite NH ⋅⋅⋅X (X=O and N) hydrogen-bonded chain formation with CF3COO− ( 2 C) and aurophilically linked [Au(CN)2]− counterions ( 4 C). Both crystals show thermochromic luminescence; their room temperature red ( 2 C) and orange ( 4 C) emission turns into yellow upon cooling to 77 K. They also exhibit reversible mechanochromic luminescence by changing their emission color from red to dark ( 2 C), and orange to red ( 4 C). Compounds 1- 5 also display reversible mechanochromic luminescence, altering their emission colors between orange ( 1) or red ( 2) to dark, as well as between yellow ( 3) or orange ( 4 and 5) to red. Detailed photophysical investigations and correlation with solid-state structural data established the significant role of NH ⋅⋅⋅X interactions in the stimuli-responsive luminescent behavior. [ABSTRACT FROM AUTHOR]

N-Isopropylacrylamide and vinyl imidazole copolymer, P(NIPAM-co-VI), was synthesized by free radical emulsion polymerization. Then, the copolymer and silver nanoparticle composite, P(NIPAM-co-VI)-Ag, was prepared by in situ reduction of AgNO3 with NaBH4. Due to the coexistence of thermal-responsive PNIPAM and pH-responsive PVI, P(NIPAM-co-VI) and P(NIPAM-co-VI)-Ag exhibited both thermal and pH responsibility, their size would change while altering the temperature or pH of the circumvent. Their thermal and pH dual responsive properties were studied by dynamic light scattering (DLS). P(NIPAM-co-VI)-Ag could be stably dispersed in water at a pH range from 3.0 to 9.3, which is favorable to use P(NIPAM-co-VI)-Ag as a catalyst in the reduction reaction of p-nitrophenol. The reaction rate constant (kapp) increased with the decrease of pH or the increase of VI content in the copolymer. [ABSTRACT FROM AUTHOR]

A charge transfer (CT) mediated two-component, multistimuli responsive supergelation involving a L-histidine-appended pyrenyl derivative (PyHisOMe) as a donor and an asymmetric bolaamphiphilic naphthalene-diimide (Asym-NDI) derivative as an acceptor in a 2:1 mixture of H2O/MeOH was investigated. Asym-NDI alone self-assembled into pH-responsive vesicular nanostructures in water. Excellent selectivity in CT gel formation was achieved in terms of choosing amino acid appended pyrenyl donor scaffolds. Circular dichroism and morphological studies suggested formation of chiral, interconnected vesicular assemblies resembling "pearls-on-a-string" from these CT mixed stacks. XRD studies revealed the formation of monolayer lipid membranes from these CT mixed stacks that eventually led to the formation of individual vesicles. Strong cohesive forces among the interconnected vesicles originate from the protrusion of the oxyethylene chains from the surfaces of the chiral vesicles. [ABSTRACT FROM AUTHOR]

Three multi-responsiveness supramolecular metal-organic gels (MOGs) have been prepared upon Ba(OAc)2, CdSO4·8H2O and Pb(NO3)2 with a simple ligand (G17) based on a carboxyl-functionalized benzimidazole derivative in alcoholic-water solutions. The MOGs display the formation of well-developed nanofibrillar networks composed of intertwined fibers which provide stability to gels structures through coordination, hydrogen bonding and π- π interactions characterized by using field emission scanning electron microscopy (FESEM), the fourier transform infrared (FT-IR) spectroscopy and powder X-ray diffraction (XRD) techniques. MOG-1 shows good stimuli responsiveness toward the changes in K2CrO4, both MOG-2 and MOG-3 do good job toward the changes in Na2S. Moreover, because these MOGs were formed easily by gelator with some heavy metal ion, such as Cd(II) and Pb(II), it might provide the basis for heavy metal ion capture and removal. [ABSTRACT FROM AUTHOR]

Most anticancer drugs cause severe side effect due to the lack of selectivity for cancer cells. In recent years, new strategies of micellar systems, which design for specifically target anticancer drugs to tumors, are developed at the forefront of polymeric science. To improve efficiency of delivery and cancer specificity, considerable emphasis has been placed on the development of micellar systems with passive and active targeting. In this review article, we summarized various strategies of designing multifunctional micellar systems in the purpose of improving delivery efficiency. Micellar systems compose of a multifunctional copolymer or a mixture of two or more copolymers with different properties is a plausible approach to tuning the resulting properties and satisfied various requirements for anticancer drug delivery. It appears that multifunctional micellar systems hold great potential in cancer therapy. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2024-2038, 2014. [ABSTRACT FROM AUTHOR]

Inflammatory pathologies are a growing burden for developed societies, and the tools offered by medicinal chemistry/biotechnology have provided us with an armamentarium of active principles. Unfortunately, most of them are marred by very significant side effects that can be summarized by two words: poor targeting (of cells, of tissues, etc.). This review provides a broad overview of the approaches and of the materials used to obtain an inflammation-responsive or inflammation-targeted behavior, which can be used to improve anti-inflammatory therapies. Here, we first define the biochemical factors that may allow both to recognize and to target an inflamed environment, for example, the leakiness of capillaries, the presence of oxidants (reactive oxygen species), or of upregulated receptors/enzymes. We then review the systems that have shown the possibility to accumulate in inflamed tissues, respond to its stimuli, or bind to activated inflammatory cells, separately discussing payload/carrier (guest/host) systems and macromolecular prodrugs/conjugates. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Teaching an old dog new tricks: Ferrocene–dipeptide conjugates capable of forming gels in response to various external signals including sound, thermal, redox, and mechanical stress are reported (see figure). Interesting examples of how ferrocene–peptide conjugates can be exploited for the construction of organometallic gelators are demonstrated. [ABSTRACT FROM AUTHOR]

The present study deals with preparing stimuli-responsive poly N-isopropyl acryl amide/chitosan (PNCS) nano hydrogel and looks into their effects as a surface modifying system of cotton fabric. The semi-batch surfactant-free emulsion polymerization method was proposed to reduce the size of particle and synthesis of PNCS nano particles. Fourier transform infrared, nuclear magnetic resonance, differential scanning calorimetry, scanning electron microscopy and dynamic light scattering methods confirmed the nano size of synthesized PNCS particles and sensitivity of these nano particles to the different temperature and pH, respectively. The water retention capacity (WRC) and carboxyl content of modified cotton with PNCS nano particles were assessed through the central composite design. The bounded PNCS nano particles to the surface of cotton fabrics made them responsive to these dual stimuli. The results demonstrated the dual effect of BTCA amount on WRC. Increase of the amount of BTCA itself led to the decrease of the WRC of modified cotton, but in the presence of PNCS, WRC was significantly increased. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The cooperative self‐assembly of chiral zinc porphyrins is regulated by a photoresponsive phenylazopyridine ligand (1; see picture). Porphyrin stacks depolymerize into dimers upon axial ligation and the strength of the coordination is regulated by its photoinduced isomerization, which shows more than 95 % conversion ratio for both photostationary states. [ABSTRACT FROM AUTHOR]

A photo-responsive and thermo-responsive poly(ethylene glycol) derivative containing azobenzene group was synthesized. Its photoisomerization kinetics was investigated by the UV-vis spectra, and the pseudo-first-order rate constants ( kt and kc) were determined to be 1.5 × 10−2 and 9.3 × 10−2 s−1, respectively. It is found that the phase transition behavior can be tuned theoretically through photoirradiation between 26.6°C and 36.7°C. Finally, it is worthy to note that the changes of the lower critical solution temperature occur repeatedly upon successive irradiation of UV and visible light. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hydrogels are formed when a three-dimensional polymeric network is loosely crosslinked. They are swollen by water but not dissolved in it. Hydrogels may display reversible sol-gel transitions, induced by changes in the environmental conditions such as temperature, pH, ionic strength, phase separation, wave length of light, crystallinity, etc. Hydrogel is described as smart or intelligent when sharp transition is induced by small change in such conditions. For the shape-memory hydrogels, reversible change in shape may also be induced by such stimuli. The preparation and applications of the molecularly imprinted polymeric hydrogels (MIPs) are illustrated by a few examples. The use of shape sensitive hydrogels in microfluidic is mentioned. Application of hydrogels for chronobiology and chronotherapy is outlined. The conversion of hydrogels into aerogels and their respective properties is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Biomaterials: The Bioinspired Facile Method to Efficiently Generate Diverse Proteinosomes with pH Switchable Permeability (Adv. Keywords: polyphenol; protein materials; proteinosome; stimuli responsive EN polyphenol protein materials proteinosome stimuli responsive 1 1 1 07/29/20 20200723 NES 200723 Inspired by polyphenol chemistry, a facile and universal method is presented to fabricate the diverse proteinosomes, with independence on the amino acid sequence, isoelectric points, molecular weight (Mw), wettability, and functional domains of applied proteins. Polyphenol, protein materials, proteinosome, stimuli responsive. [Extracted from the article]

Stimuli‐responsive soft materials are becoming increasingly important in a wide range of contemporary technologies, and methods by which to promote thermal stimulation remotely are of considerable interest for controllable device deployment, particularly in inaccessible environments such as outer space. Until now, remote thermal stimulation of responsive polymers has relied extensively on the use of nanocomposites wherein embedded nanoparticles/structures are selectively targeted for heating purposes. In this study, an alternative remote‐heating mechanism demonstrates that the dielectric and resistive thermal losses introduced upon application of an alternating current generate sufficient heat to raise the temperature of a neat polyimide by over 70 °C within ≈10 s. Thermal imaging is used here to measure current‐induced temperature changes of polymeric media, and a proposed analytical model yields predictions that compare reasonably well with experimental data, confirming that such remote heating is viable. Conditions permitting a shape‐memory polymer possessing a melting transition and susceptible to dielectric actuation to achieve continuous electrostrain‐temperature cycling are identified. Remote heating is needed for the thermal activation of stimuli‐responsive polymers in inaccessible environments. Dielectric and resistive losses that develop during application of an alternating current generate sufficient heat to raise the temperature of a polymer by >70 °C in ≈10 s. Thermal imaging measures current‐induced temperature changes, and a heat‐transfer model yields predictions that compare favorably with experimental observations. [ABSTRACT FROM AUTHOR]

Superparamagnetic iron oxide nanoparticles (SPIONs) are synthesized through ultrasound based coprecipitation method. SPIONs are coated with poly(2‐isopropyl‐2‐oxazoline) (PIPOX) and tannic acid (TA) in a layer‐by‐layer (LbL) fashion at pH 4 and 25 °C. PIPOX/TA coated SPIONs are then loaded with doxorubicin (DOX) at pH 7.5 and 25 °C. DOX release from LbL‐coated SPIONs is examined at pH 7.5 and pH 6 at 25 °C, 37 °C, and 42 °C. LbL‐coated SPIONs exhibit dual responsive behavior and release the greatest amount of DOX at pH 6 and 42 °C. Increasing layer number decreases the colloidal stability and saturation magnetization. Superparamagnetic behavior of SPIONs retains after coating. Overall, this study shows an alternative strategy to modify the surface of SPIONs with a dual responsive polymer coating which is capable of releasing DOX at moderately acidic pH of 6 within a physiologically related temperature range. Besides, it generates fundamental knowledge for further development of SPIONs‐based drug carriers. Superparamagnetic iron oxide nanoparticles (SPIONs) are layer‐by‐layer (LbL) modified using stimuli‐responsive polymers. These LbL‐coated SPIONs are capable of releasing doxorubicin (DOX) at acidic pH within a physiologically related temperature range. [ABSTRACT FROM AUTHOR]

With the rapid development of nanotechnology, stimuli‐responsive nanomaterials have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. As a new type of porous material, metal–organic frameworks (MOFs) have been widely used in biomedical applications, especially drug delivery systems, owing to their tunable pore size, high surface area and pore volume, and easy surface modification. Here, recent progress in MOF‐based stimuli‐responsive systems is presented, including pH‐, magnetic‐, ion‐, temperature‐, pressure‐, light‐, humidity‐, redox‐, and multiple stimuli‐responsive systems for the delivery of anticancer drugs. The remaining challenges and suggestions for future directions for the rational design of MOF‐based nanomedicines are also discussed. Reaching the advanced drug delivery potential of metal–organic frameworks (MOFs) featuring spatiotemporally controllable properties is of utmost importance. MOFs have the advantages of high drug loading capacities, easy functionalization, and good biocompatibility. The development of MOF‐based stimuli‐responsive drug delivery systems provides a means of designing exciting nanoformulations for clinical translation in future nanomedicines. [ABSTRACT FROM AUTHOR]