Showing papers in "Macromolecular Rapid Communications in 2017"
TL;DR: This study presents here a strategy to capitalize on a series of medical imaging modalities to construct a printable shape memory endoluminal device, exemplified by a tracheal stent.
Abstract: The convergence of additive manufacturing and shape-morphing materials is promising for the advancement of personalized medical devices. The capability to transform 3D objects from one shape to another, right off the print bed, is known as 4D printing. Shape memory thermosets can be tailored to have a range of thermomechanical properties favorable to medical devices, but processing them is a challenge because they are insoluble and do not flow at any temperature. This study presents here a strategy to capitalize on a series of medical imaging modalities to construct a printable shape memory endoluminal device, exemplified by a tracheal stent. A methacrylated polycaprolactone precursor with a molecular weight of 10 000 g mol-1 is printed with a UV-LED stereolithography printer based on anatomical data. This approach converges with the zeitgeist of personalized medicine and it is anticipated that it will broadly expand the application of shape memory-exhibiting biomedical devices to myriad clinical indications.
268 citations
TL;DR: All synthetic approaches that have been reported for the synthesis of SCPs are discussed and categorized, and the characterization tools, properties, and potential applications of these new polymers are described herein.
Abstract: Over the last ten years, the development of synthetic polymers containing controlled monomer sequences has become a prominent topic in fundamental and applied polymer science. This emerging area is particularly broad and combines classical polymer chemistry tools with techniques imported from other domains such as biology, biochemistry, organic synthesis, engineering, and bioanalytics. Consequently, it also generates new structures, terminologies, and applications that are not within the traditional scope of polymer science. The term "sequence-controlled polymers" (SCPs) was recently proposed as a generic name to describe all these recent trends. However, since the field of SCPs has been growing very rapidly in recent literature, it is urgent to accurately define its scientific frontiers. In this important context, this review is an attempt to define, rationalize, and classify the field of SCPs. In particular, all synthetic approaches that have been reported for the synthesis of SCPs are discussed and categorized. In addition, the characterization tools, properties, and potential applications of these new polymers are described herein. Overall, this review serves as a reference guide for understanding the burgeoning field of SCPs.
204 citations
TL;DR: The development of brush block copolymers as photonic crystals that can reflect visible to near-infrared wavelengths of light is highlighted.
Abstract: Brush block copolymers are a class of comb polymers that feature polymeric side chains densely grafted to a linear backbone These polymers display interesting properties due to their dense functionality, low entanglement, and ability to rapidly self-assemble to highly ordered nanostructures The ability to prepare brush polymers with precise structures has been enabled by advancements in controlled polymerization techniques This Feature Article highlights the development of brush block copolymers as photonic crystals that can reflect visible to near-infrared wavelengths of light Fabrication of these materials relies on polymer self-assembly processes to achieve nanoscale ordering, which allows for the rapid preparation of photonic crystals from common organic chemical feedstocks The characteristic physical properties of brush block copolymers are discussed, along with methods for their preparation Strategies to induce self-assembly at ambient temperatures and the use of blending techniques to tune photonic properties are emphasized
169 citations
TL;DR: An innovative self-healing polydimethylsiloxane (PDMS) elastomer, namely, PDMS-TFB, is reported by incorporating the reversibly dynamic imine bond as the self- healing points into the PDMS networks, showing a promising outlook for broader applications.
Abstract: An innovative self-healing polydimethylsiloxane (PDMS) elastomer, namely, PDMS-TFB, is reported by incorporating the reversibly dynamic imine bond as the self-healing points into the PDMS networks. The PDMS-TFB elastomer features good optical transmittance (80%) in full visible light region, high stretchability (≈700%), and excellent autonomous self-healing ability at room temperature. Surprisingly, the self-healing behavior can take place in water and even at a temperature as low as -20 °C in air, showing a promising outlook for broader applications. As a proof-of-concept, this study demonstrates the use of the PDMS-TFB elastomer for preparing anticorrosion coating and adhesive layer, and also the use of such an elastomer to be the platform for fabricating the flexible interconnector and chemical sensor. Remarkably, no significant difference is observed between the pristine and healed samples. Taking full advantage of these unique properties, it is anticipated that such a PDMS-TFB elastomer shows wide applications in the fields of materials science, electronics, biology, optics, etc.
156 citations
TL;DR: This review describes different synthetic strategies towards sequence-defined, monodisperse macromolecules, which are built up by iterative approaches and lead to linear non-natural polymer structures.
Abstract: This review describes different synthetic strategies towards sequence-defined, monodisperse macromolecules, which are built up by iterative approaches and lead to linear non-natural polymer structures. The review is divided in three parts: solution phase-, solid phase-, and fluorous- and polymer-tethered approaches. Moreover, synthesis procedures leading to conjugated and non-conjugated macromolecules are considered and discussed in the respective sections. A major focus in the evaluation is the applicability of the different approaches in polymer chemistry. In this context, simple procedures for monomer and oligomer synthesis, overall yields, scalability, purity of the oligomers, and the achievable level of control (side-chains, backbone, stereochemistry) are important benchmarks.
148 citations
TL;DR: In this review, some important strategies for enhancing stereocomplex crystallization in practical processing operations are presented and recently developed processing technologies for SC-PLA are highlighted, such as low-temperature sintering.
Abstract: Over the past two decades, biomass-derived and biodegradable polylactide (PLA) has sparked tremendous attention as a sustainable alternative to traditional petroleum-derived polymers for diverse applications. Unfortunately, the current applications of PLA have been mainly limited to biomedical and commodity fields, mostly because the poor heat resistance (resulting from low melting temperature) and hydrolysis stability make it hard to use as an engineering plastic. Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) opens a new avenue toward PLA-based engineering plastics with improved properties. The formation, crystal structure, properties, and potential applications of stereocomplex-type PLA (SC-PLA) are summarized by some research groups. However, since it is challenging to achieve full stereocomplexation from high-molecular-weight PLLA/PDLA blends and to avoid serious thermal degradation of the PLAs after complete melting, the advances and progress in the processing of SC-PLA into useful products are quite rare in open publication. In this review, some important strategies for enhancing stereocomplex crystallization in practical processing operations are presented and recently developed processing technologies for SC-PLA are highlighted, such as low-temperature sintering. Furthermore, major challenges and future developments are briefly discussed. This review is expected to potentially open up new research activities in the processing of SC-PLA.
123 citations
TL;DR: The use of photocatalysts and catalyst-free approaches to mediate polymerization upon photoexcitation and the existing challenges in polymer chemistry that could be overcome by further development of light-mediated polymerization techniques are highlighted.
Abstract: Recently, visible-light-regulated polymerization has been gaining popularity, as it opens a range of new opportunities for the synthesis of functional polymers and materials Here, the most recent developments in this field are summarized, which is the use of photocatalysts and catalyst-free approaches to mediate polymerization upon photoexcitation These catalysts can transfer an electron or energy to activate an initiator The recent achievements in light-regulated atom-transfer radical polymerization, reversible addition-fragmentation chain-transfer polymerization, ring-opening metathesis polymerization, cobalt-mediated radical polymerization, iodine-mediated radical polymerization, and living cationic polymerization are reviewed Recent development in these fields have solved important challenges in polymer chemistry, such as the development of oxygen-tolerant polymerization, polymerization mediated by near-infrared, metal-free polymerization, and spatial-, temporal-, and sequence-controlled polymerization Some applications of these techniques will be discussed, such as adapting the current photocatalytic systems to synthesize heterogeneous photocatalysts that act as recyclable photocatalysts and novel light-mediated approaches for surface functionalization of hybrid materials and living cells Finally, the existing challenges in polymer chemistry that could be overcome by further development of light-mediated polymerization techniques are highlighted along with the future directions of this field
120 citations
TL;DR: Analysis of the proposed mechanism gives insight into the relevant photophysical and chemical properties that determine catalyst performance, leading to a set of design principles for O-ATRP catalysts.
Abstract: The recent development of organocatalyzed atom transfer radical polymerization (O-ATRP) represents a significant advancement in the field of controlled radical polymerizations. A number of classes of photoredox catalysts have been employed thus far in O-ATRP. Analysis of the proposed mechanism gives insight into the relevant photophysical and chemical properties that determine catalyst performance. Discussion of each of the classes of O-ATRP catalysts highlights their previous uses, their roles in the development of O-ATRP, and the distinctive properties that govern their polymerization behavior, leading to a set of design principles for O-ATRP catalysts. Remaining challenges for O-ATRP are presented, as well as prospects for further improvement in the application scope of O-ATRP.
111 citations
TL;DR: In this new method, flat polymer sheets can be cured by a light field from a commercial projector with varying intensity, and the self-folding process is triggered by desolvation in water, which can be used for responsive actuators and the fabrication of 3D electronic devices.
Abstract: Self-folding origami is of great interest in current research on functional materials and structures, but there is still a challenge to develop a simple method to create freestanding, reversible, and complex origami structures. This communication provides a feasible solution to this challenge by developing a method based on the digit light processing technique and desolvation-induced self-folding. In this new method, flat polymer sheets can be cured by a light field from a commercial projector with varying intensity, and the self-folding process is triggered by desolvation in water. Folded origami structures can be recovered once immersed in the swelling medium. The self-folding process is investigated both experimentally and theoretically. Diverse 3D origami shapes are demonstrated. This method can be used for responsive actuators and the fabrication of 3D electronic devices.
110 citations
TL;DR: This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects and emerging applications and future research directions of this "smart" nanoparticle behavior are reviewed.
Abstract: Polymerization-induced self-assembly (PISA) is an extremely versatile method for the in situ preparation of soft-matter nanoparticles of defined size and morphologies at high concentrations suitable for large-scale production. Recently, certain PISA-prepared nanoparticles have been shown to exhibit reversible polymorphism (“shape-shifting”), typically between micellar, worm-like, and vesicular phases (order–order transitions), in response to external stimuli including temperature, pH, electrolytes, and chemical modification. This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects. Reversible pH-responsive behaviour is rationalised in terms of increased solvation of reversibly ionised groups. Temperature-triggered order–order transitions, conversely, do not rely on inherently thermo-responsive polymers, but are explained based on interfacial LCST or UCST behaviour that affects the volume fractions of the core and stabilizer blocks. Irreversible morphology transitions, on the other hand, can result from chemical post-modification of reactive PISA-made particles. Emerging applications and future research directions of this ‘smart’ nanoparticle behaviour are reviewed.
104 citations
TL;DR: This review aims to provide an introductory perspective on the basic synthetic methods of star-shaped polymers, the properties which can be controlled by the unique architecture, and also recent advances in drug delivery applications related to these star candidates.
Abstract: With the advancement of polymer engineering, complex star-shaped polymer architectures can be synthesized with ease, bringing about a host of unique properties and applications. The polymer arms can be functionalized with different chemical groups to fine-tune the response behavior or be endowed with targeting ligands or stimuli responsive moieties to control its physicochemical behavior and self-organization in solution. Rheological properties of these solutions can be modulated, which also facilitates the control of the diffusion of the drug from these star-based nanocarriers. However, these star-shaped polymers designed for drug delivery are still in a very early stage of development. Due to the sheer diversity of macromolecules that can take on the star architectures and the various combinations of functional groups that can be cross-linked together, there remain many structure-property relationships which have yet to be fully established. This review aims to provide an introductory perspective on the basic synthetic methods of star-shaped polymers, the properties which can be controlled by the unique architecture, and also recent advances in drug delivery applications related to these star candidates.
TL;DR: It is emphasised how these features can interplay and add synergistically to affect antifouling and fouling-release against common, widespread marine micro- and macro-fouling organisms.
Abstract: A range of amphiphilic polymers with diverse macromolecular architectures has been developed and incorporated into films and coatings with potential for marine antibiofouling applications, without resorting to addition of currently used biocidal, toxic agents. Novel "green" chemical technologies employ different building blocks to endow the polymer film with surface activity, functionality, structure, and reconstruction according to the outer environment as a result of a tailored amphiphilic character of the polymer platform. We emphasise how these features can interplay and add synergistically to affect antifouling and fouling-release against common, widespread marine micro- and macro-fouling organisms.
TL;DR: The design and synthesis of novel PET-based copolyesters with flame-retardant and antidripping performance are highlighted and three approaches are used: "ionic aggregation," "smart self-cross-linking," and "rearrangement at high temperatures."
Abstract: Poly(ethylene terephthalate) (PET) is a fiber-forming polymer with the largest output and widest usage. Its flame retardation is well-achieved via a mechanism of promoting the melt dripping while ignited. However, the melt dripping leads to secondary damage and an immediate empyrosis during fire. How to address the contradiction between the flame retardation and the melt-dripping behavior of PET via an inherent flame-retardant approach becomes a real challenge. This feature article highlights the design and synthesis of novel PET-based copolyesters with flame-retardant and antidripping performance. Three approaches are used to design these copolyesters: "ionic aggregation," "smart self-cross-linking," and "rearrangement at high temperatures." Some new conceptions are proposed accordingly. The synthesis, structure characterization, and properties of those copolyesters are discussed together with the ongoing challenges and limitations at this frontier.
TL;DR: This study focuses on developing a facile approach to prepare biocompatible poly(vinyl alcohol) (PVA) composite hydrogels containing polydopamine particles (PDAPs) with ultrafast near-infrared light-triggered shape memory and self-healing capability.
Abstract: This study focuses on developing a facile approach to prepare biocompatible poly(vinyl alcohol) (PVA) composite hydrogels containing polydopamine particles (PDAPs) with ultrafast near-infrared (NIR) light-triggered shape memory and self-healing capability. The PVA-PDAPs composite hydrogels with excellent mechanical properties can be achieved after freezing/thawing treatment, and the formation of physically cross-linked networks from the hydrogen bonding (H-bonding) between PVA and PDAPs. Due to the excellent photothermal effect of polydopamine, the composited hydrogel can achieve rapid shape recovery and efficient self-healing properties under NIR light exposure in a short time. With the excellent shape memory performance, good biocompatibility, and self-healing property, this hydrogel should have great potential in biomedical fields such as tissue engineering, arthrodial cartilage, and artificial skin.
TL;DR: This minireview highlights the fruitful combination of these two topics for the preparation of sequence-controlled oligomeric and macromolecular structures and showcases the vast number of publications in this field within a relatively short span of time.
Abstract: During the previous decade, many popular chemical reactions used in the area of "click" chemistry and similarly efficient "click-inspired" reactions have been applied for the design of sequence-defined and, more generally, sequence-controlled structures. This combination of topics has already made quite a significant impact on scientific research to date and has enabled the synthesis of highly functionalized and complex oligomeric and polymeric structures, which offer the prospect of many exciting further developments and applications in the near future. This minireview highlights the fruitful combination of these two topics for the preparation of sequence-controlled oligomeric and macromolecular structures and showcases the vast number of publications in this field within a relatively short span of time. It is divided into three sections according to the click-(inspired) reaction that has been applied: copper-catalyzed azide-alkyne cycloaddition, thiol-X, and related thiolactone-based reactions, and finally Diels-Alder-chemistry-based routes are outlined, respectively.
TL;DR: This article surveys the decade of progress accomplished in the application of isoconversional methods to thermally stimulated processes in polymers and discusses basic principles for understanding the variations in the activation energy and the possibility of using models for linking such variations to the parameters of individual kinetic steps.
Abstract: This article surveys the decade of progress accomplished in the application of isoconversional methods to thermally stimulated processes in polymers. The processes of interest include: crystallization and melting of polymers, gelation of polymer solutions and gel melting, denaturation (unfolding) of proteins, glass transition, polymerization and crosslinking (curing), and thermal and thermo-oxidative degradation. Special attention is paid to the kinetics of polymeric nanomaterials. The article discusses basic principles for understanding the variations in the activation energy and emphasizes the possibility of using models for linking such variations to the parameters of individual kinetic steps. It is stressed that many kinetic effects are not linked to a change in the activation energy alone and may arise from changes in the preexponential factor and reaction model. Also noted is that some isoconversional methods are inapplicable to processes taking place on cooling and cannot be used to study such processes as the melt crystallization.
TL;DR: Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible-light irradiation and the CO2 -responsive property of the obtained vesicles is investigated by dynamic light scattering, visual appearance, and transmission electron microscope.
Abstract: Carbon dioxide (CO2)-responsive polymer nano-objects are prepared by photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of 2-hydroxypropyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) in water at room temperature using a poly(poly(ethylene glycol) methyl ether methacrylate) macromolecular chain transfer agent. Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible-light irradiation (405 nm, 0.5 mW cm−2). The effect of DMAEMA on the polymerization is studied in detail, and pure higher order morphologies (worms and vesicles) are prepared by this particular formulation. Finally, CO2-responsive property of the obtained vesicles is investigated by dynamic light scattering, visual appearance, and transmission electron microscope.
TL;DR: There is increasing evidence that stimuli-responsive nanomaterials have become significantly critical components of modern materials design and technological developments and there are opportunities for developing novel synthetic approaches facilitating controllable recognition, signaling, or sequential responses.
Abstract: There is increasing evidence that stimuli-responsive nanomaterials have become significantly critical components of modern materials design and technological developments. Recent advances in synthesis and fabrication of stimuli-responsive polymeric nanoparticles with built-in stimuli-responsive components (Part A) and surface modifications of functional nanoparticles that facilitate responsiveness (Part B) are outlined here. The synthesis and construction of stimuli-responsive spherical, core-shell, concentric, hollow, Janus, gibbous/inverse gibbous, and cocklebur morphologies are discussed in Part A, with the focus on shape, color, or size changes resulting from external stimuli. Although inorganic/metallic nanoparticles exhibit many useful properties, including thermal or electrical conductivity, catalytic activity, or magnetic properties, their assemblies and formation of higher order constructs are often enhanced by surface modifications. Section B focuses on selected surface reactions that lead to responsiveness achieved by decorating nanoparticles with stimuli-responsive polymers. Although grafting-to and grafting-from dominate these synthetic efforts, there are opportunities for developing novel synthetic approaches facilitating controllable recognition, signaling, or sequential responses. Many nanotechnologies utilize a combination of organic and inorganic phases to produce ceramic or metallic nanoparticles. One can envision the development of new properties by combining inorganic (metals, metal oxides) and organic (polymer) phases into one nanoparticle designated as "ceramers" (inorganics) and "metamers" (metallic).
TL;DR: The polymerization kinetic study, multiple controlled "on-off" light switching cycle regulation, and chain extension experiment confirm the "living"/controlled features of this promising photoinduced metal-free ATRP system with good molecular weight control in the presence of ppm level photocatalyst 4CzIPN.
Abstract: It is well known that the recently developed photoinduced metal-free atom transfer radical polymerization (ATRP) has been considered as a promising methodology to completely eliminate transition metal residue in polymers However, a serious problem needs to be improved, namely, large amount of organic photocatalysts should be used to keep the controllability over molecular weights and molecular weight distributions In this work, a novel photocatalyst 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) with strong excited state reduction potential is successfully used to mediate a metal-free ATRP of methyl methacrylate just with parts per million (ppm) level usage under irradiation of blue light emitting diode at room temperature, using ethyl α-bromophenyl-acetate as a typical initiator with high initiator efficiency The polymerization kinetic study, multiple controlled "on-off" light switching cycle regulation, and chain extension experiment confirm the "living"/controlled features of this promising photoinduced metal-free ATRP system with good molecular weight control in the presence of ppm level photocatalyst 4CzIPN
TL;DR: The dynamic covalent characteristics of oxime and boronate ester bonds have been explored and the tannic acid cross-linking network is selectively degraded returning the hydrogel storage modulus to its initial value and providing a means for the synthesis of materials with tunable mechanical properties.
Abstract: The dynamic covalent characteristics of oxime and boronate ester bonds have been explored. A small excess of a competing aldehyde under acidic conditions resulted in oxime polymer degradation from high molecular weights (30 kDa) to low molecular weight oligomers (2.2 kDa). The dynamic nature of oxime bonds imparts oxime cross-linked hydrogels with self-healing properties and the incorporation of phenyl boronic acid groups into the hydrogel network provides a platform for hydrogel functionalization. The addition of a polyphenol (tannic acid) proves a facile means to incorporate a second, dynamic covalent cross-linking network through boronate ester formation which, owing to the increase in the degree of cross-linking, is found to be nearly double the hydrogel strength (storage modulus increased from 4.6 to 8.5 kPa). Finally, the tannic acid cross-linking network is selectively degraded returning the hydrogel storage modulus to its initial value and providing a means for the synthesis of materials with tunable mechanical properties.
TL;DR: In this short review, methods for the preparation of metal-containing polymer hydrogels are introduced and an overview of these hydrogel with various functionalities is given.
Abstract: Metal-containing polymer hydrogels have attracted increasing interest in recent years due to their outstanding properties such as biocompatibility, recoverability, self-healing, and/or redox activity In this short review, methods for the preparation of metal-containing polymer hydrogels are introduced and an overview of these hydrogels with various functionalities is given It is hoped that this short update can stimulate innovative ideas to promote the research of metal-containing hydrogels in the communities
TL;DR: This review focuses on the most commonly used pH-sensitive polymers and their applications in insulin delivery systems and the relationship between the chemical structure of the polymeric systems and their insulin delivery performance is discussed.
Abstract: Since diabetes mellitus has become one of the most serious threats to human health, researchers have been designing new drugs and developing new technologies to control the blood glucose level (BGL) while improving patient compliance. In addition to the traditional subcutaneous injection method, alternative routes of insulin delivery have been investigated and tested, including oral, pulmonary, transdermal, and nasal. The final goal of all these technologies is to develop a system that releases insulin in a controlled manner depending on the BGL. pH-Sensitive polymers appear to be good candidates to achieve this goal because they exhibit a conformational transition when the pH in the surrounding medium fluctuates, which changes the solubility of the polymers and leads to the swelling of hydrogels. Many pH-sensitive polymers, such as poly(2-dimethylamino)ethylmethacrylate) and natural biopolymers such as chitosan, have been used in different delivery systems. This review focuses on the most commonly used pH-sensitive polymers and their applications in insulin delivery systems. In particular, the relationship between the chemical structure of the polymeric systems and their insulin delivery performance is discussed.
TL;DR: The utilizing of host-guest macro-crosslinking approach manifests the as-prepared hydrogel reversible and light-switchable self- healing property, which would broaden the potential applications of self-healing polymers.
Abstract: A self-healing hydrogel is prepared by crosslinking acrylamide with a host-guest macro-crosslinker assembled from poly(β-cyclodextrin) nanogel and azobenzeneacrylamide. The photoisomerizable azobenzene moiety can change its binding affinity with β-cyclodextrin, therefore the crosslinking density and rheology property of the hydrogel can be tuned with light stimulus. The hydrogel can repair its wound autonomously through the dynamic host-guest interaction. In addition, the wounded hydrogel will lose its ability of self-healing when exposed to ultraviolet light, and the self-healing behavior can be recovered upon the irradiation of visible light. The utilizing of host-guest macro-crosslinking approach manifests the as-prepared hydrogel reversible and light-switchable self-healing property, which would broaden the potential applications of self-healing polymers.
TL;DR: This study provides a generic method for improving the mechanical properties of nonwoven nanofiber mats, holding great potential in various applications.
Abstract: This communication describes a simple and effective method for welding electrospun nanofibers at the cross points to enhance the mechanical properties of their nonwoven mats. The welding is achieved by placing a nonwoven mat of the nanofibers in a capped vial with the vapor of a proper solvent. For polycaprolactone (PCL) nanofibers, the solvent is dichloromethane (DCM). The welding can be managed in a controllable fashion by simply varying the partial pressure of DCM and/or the exposure time. Relative to the pristine nanofiber mat, the mechanical strength of the welded PCL nanofiber mat can be increased by as much as 200%. Meanwhile, such a treatment does not cause any major structural changes, including morphology, fiber diameter, and pore size. This study provides a generic method for improving the mechanical properties of nonwoven nanofiber mats, holding great potential in various applications.
TL;DR: It is found that the nanoparticle formation process involves covalent copolymerization of monomers, as well as noncovalent self-assembly pathways, and the resulting PNs exhibit better free-radical scavenging activities compared with similar-sized, polydopamine-based synthetic melanin nanoparticles.
Abstract: The constant demand for functional nanomaterials from natural biomass polymers usually requires new "green" synthetic strategies without using any foreign additives. Here, the green fabrication of a series of polyphenol nanoparticles (PNs) only from green tea extraction compounds is reported (i.e., tea polyphenols and theophylline). It is found that the nanoparticle formation process involves covalent copolymerization of monomers, as well as noncovalent self-assembly pathways. Additionally, the resulting PNs exhibit better free-radical scavenging activities compared with similar-sized, polydopamine-based synthetic melanin nanoparticles. This class of biomass-based functional nanoparticles is promising as green and effective antioxidant agents in general.
TL;DR: This feature article focuses on recent strategies that were developed to overcome the contamination problem and includes bifunctional materials with simultaneously presented antimicrobial and protein-repellent moieties; polymer surfaces that can be switched from an antimicrobial, cell-attractive to a cell-repelled state.
Abstract: Contact-active antimicrobial polymer surfaces bear cationic charges and kill or deactivate bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). The exact mechanism of this interaction is still under debate. While cationic antimicrobial polymer surfaces can be very useful for short-term applications, they lose their activity once they are contaminated by a sufficiently thick layer of adhering biomolecules or bacterial cell debris. This layer shields incoming bacteria from the antimicrobially active cationic surface moieties. Besides discussing antimicrobial surfaces, this feature article focuses on recent strategies that were developed to overcome the contamination problem. This includes bifunctional materials with simultaneously presented antimicrobial and protein-repellent moieties; polymer surfaces that can be switched from an antimicrobial, cell-attractive to a cell-repellent state; polymer surfaces that can be regenerated by enzyme action; degradable antimicrobial polymers; and antimicrobial polymer surfaces with removable top layers.
TL;DR: In this review, recent studies on A-π-D- π-A electron-donating small molecules for organic solar cells are introduced and the relationships between molecular properties and device performances are summarized, from which inspiration for the future design of high performance organicSolar cells may be obtained.
Abstract: Organic solar cells based on semiconducting polymers and small molecules have attracted considerable attention in the last two decades. Moreover, the power conversion efficiencies for solution-processed solar cells containing A–π–D–π–A-type small molecules and fullerenes have reached 11%. However, the method for designing high-performance, photovoltaic small molecules still remains unclear. In this review, recent studies on A–π–D–π–A electron-donating small molecules for organic solar cells are introduced. Moreover, the relationships between molecular properties and device performances are summarized, from which inspiration for the future design of high performance organic solar cells may be obtained.
TL;DR: A general procedure of preparing the hydrogels cross-linked by both ionic coordination of Fe3+ and carboxyl group from the gelatin and the quadruple hydrogen bonding interaction from the ureido-pyrimidinone (UPy) dimers is introduced.
Abstract: Self-healing hydrogels have been studied by many researchers via multiple cross-linking approaches including physical and chemical interactions. It is an interesting project in multifunctional hydrogel exploration that a water soluble polymer matrix is cross-linked by combining the ionic coordination and the multiple hydrogen bonds to fabricate self-healing hydrogels with injectable property. This study introduces a general procedure of preparing the hydrogels (termed gelatin-UPy-Fe) cross-linked by both ionic coordination of Fe3+ and carboxyl group from the gelatin and the quadruple hydrogen bonding interaction from the ureido-pyrimidinone (UPy) dimers. The gelatin-UPy-Fe hydrogels possess an excellent self-healing property. The effects of the ionic coordination of Fe3+ and quadruple hydrogen bonding of UPy on the formation and mechanical behavior of the prepared hydrogels are investigated. In vitro drug release of the gelatin-UPy-Fe hydrogels is also observed, giving an intriguing glimpse into possible biological applications.
TL;DR: It is demonstrated that conducting polymerization-induced self-assembly (PISA) at low temperatures is crucial for obtaining colloidal stable PGMA-based diblock copolymer nano-objects.
Abstract: Herein, a novel photoinitiated polymerization-induced self-assembly formulation via photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of glycidyl methacrylate (PGMA) in ethanol-water at room temperature is reported It is demonstrated that conducting polymerization-induced self-assembly (PISA) at low temperatures is crucial for obtaining colloidal stable PGMA-based diblock copolymer nano-objects Good control is maintained during the photo-PISA process with a high rate of polymerization The polymerization can be switched between "ON" and "OFF" in response to visible light A phase diagram is constructed by varying monomer concentration and degree of polymerization The PGMA-based diblock copolymer nano-objects can be further cross-linked by using a bifunctional primary amine reagent Finally, silver nanoparticles are loaded within cross-linked vesicles via in situ reduction, exhibiting good catalytic properties
TL;DR: A continuous electrospinning method for gel fiber preparation is presented without a spinning window and proof of the presence of cross-links as well as pH sensitivity after the transformation of the poly(succinimide)-based material to poly(aspartic acid) acid is presented.
Abstract: Electrospinning is a well-known technique for the preparation of scaffolds for biomedical applications. In this work, a continuous electrospinning method for gel fiber preparation is presented without a spinning window. As proof of concept, the preparation of poly(aspartic acid)-based hydrogel fibers and their properties are described by using poly(succinimide) as shell polymer and 2,2,4(2,4,4)-trimethyl-1,6-hexanediamine as cross-linker in the core of the nozzle. Cross-linking takes place as the two solutions get in contact at the tip of the nozzle. The impact of solution concentrations and feeding rates on fiber morphology, proof of the presence of cross-links as well as pH sensitivity after the transformation of the poly(succinimide)-based material to poly(aspartic acid) is presented.