Showing papers in "ACS Macro Letters in 2019"
TL;DR: Alternative PISA protocols are paid particular attention to, which allow the preparation of nanoparticles with improved control over copolymer morphology and functionality, and have been optimized via high-throughput polymerization and recently evaluated within flow reactors for facile scale-up syntheses.
Abstract: In this Perspective, we summarize recent progress in polymerization-induced self-assembly (PISA) for the rational synthesis of block copolymer nanoparticles with various morphologies. Much of the PISA literature has been based on thermally initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. Herein, we pay particular attention to alternative PISA protocols, which allow the preparation of nanoparticles with improved control over copolymer morphology and functionality. For example, initiation based on visible light, redox chemistry, or enzymes enables the incorporation of sensitive monomers and fragile biomolecules into block copolymer nanoparticles. Furthermore, PISA syntheses and postfunctionalization of the resulting nanoparticles (e.g., cross-linking) can be conducted sequentially without intermediate purification by using various external stimuli. Finally, PISA formulations have been optimized via high-throughput polymerization and recently evaluated within flow reactors for facile scale-up syntheses.
339 citations
TL;DR: In this article, a disulfide-containing carboxylic acid is applied as a curing agent to synthesize epoxy vitrimers with simultaneous Disulfide metathesis and carboxylate transesterification.
Abstract: Vitrimers make up a class of polymeric materials combining the advantages of thermosets and thermoplastics, because they can be reprocessed while being at the same time permanently cross-linked. However, a long heating duration or an elevated temperature is necessary for most vitrimers to relax the stress from deformation and exhibit malleability. Herein, a disulfide-containing carboxylic acid is applied as a curing agent to synthesize epoxy vitrimers with simultaneous disulfide metathesis and carboxylate transesterification. The insoluble networks exhibit rapid stress relaxation and have relaxation times ranging from 1.5 s (200 °C) to 5500 s (60 °C), while the temperature of malleability is as low as 65 °C. Moreover, this vitrimer can be efficiently reprocessed at 100 °C in 1 h with full recovery of mechanical strength for at least four cycles. Additionally, such a material is simply synthesized from commercially available chemicals and may have potential applications in the electronics industry where a ...
178 citations
TL;DR: In this paper, a type of polyurethane elastomer with excellent self-healing ability has been fabricated through digital light processing 3D printing, which is a new technique for 3D printings.
Abstract: A type of polyurethane elastomer with excellent self-healing ability has been fabricated through digital light processing 3D printing. First, a type of polyurethane acrylate containing disulfide bo...
155 citations
TL;DR: It is demonstrated that the integration of sacrificial bonds into a vitrimeric network can remarkably enhance the overall mechanical properties while facilitating network rearrangement.
Abstract: Vitrimers are a class of covalently cross-linked polymers that have drawn great attention due to their fascinating properties such as malleability and reprocessability. The state of art approach to...
146 citations
TL;DR: In this paper, surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization (SI-PET-RAFT) is introduced, which affords functionalization of surfaces with spatiotemporal control and provides oxygen tolerance under ambient conditions.
Abstract: In this communication, surface-initiated photoinduced electron transfer-reversible addition–fragmentation chain transfer polymerization (SI-PET-RAFT) is introduced. SI-PET-RAFT affords functionalization of surfaces with spatiotemporal control and provides oxygen tolerance under ambient conditions. All hallmarks of controlled radical polymerization (CRP) are met, affording well-defined polymerization kinetics, and chain end retention to allow subsequent extension of active chain ends to form block copolymers. The modularity and versatility of SI-PET-RAFT is highlighted through significant flexibility with respect to the choice of monomer, light source and wavelength, and photoredox catalyst. The ability to obtain complex patterns in the presence of air is a significant contribution to help pave the way for CRP-based surface functionalization into commercial application.
101 citations
TL;DR: Methods to achieve hydrogels that simultaneously mimic the hydration, strength, and stiffness of soft and load-bearing tissues have the potential to be used in a much broader range of biomedical applications.
Abstract: Hydrogels are frequently used biomaterials due to their similarity in hydration and structure to biological tissues. However, their utility is limited by poor mechanical properties, namely, a lack ...
94 citations
TL;DR: In this paper, a photoresponsive azobenzene-containing polymer (azopolymer) is developed for photocontrolled adhesion, which exhibits photoinduced reversible solid-to-liquid transitions due to trans-cis photoisomerization.
Abstract: The development of switchable adhesives for reversible bonding and debonding can overcome the problems associated with conventional adhesives in separating, recycling, and repairing glued surfaces. Here, a photoresponsive azobenzene-containing polymer (azopolymer) is developed for photocontrolled adhesion. The azopolymer P1 (poly(6-(4-(p-tolyldiazenyl)phenoxy)hexyl acrylate)) exhibits photoinduced reversible solid-to-liquid transitions due to trans–cis photoisomerization. Trans P1 is a solid that glues two substrates with a stiffness comparable to that of conventional adhesives. UV light induces trans-to-cis isomerization, liquefies P1, weakens the adhesion, and facilitates the separation of glued substrates. Conversely, visible light induces cis-to-trans isomerization, solidifies P1, and enhances the adhesion. P1 enables photocontrolled reversible adhesion for various substrates with different wettability, chemical compositions, and surface roughness. P1 can also be implemented in both dry and wet enviro...
88 citations
TL;DR: In this article, three quinoxaline-based conjugated polymers, named PE61, PE62, and PE63, were used to investigate the effect of introducing fluorine and sulfur atoms into the thiophene side chains.
Abstract: Three quinoxaline-based “D−π–A” conjugated polymers, named as PE61, PE62, and PE63, are utilized to investigate the effect of introducing fluorine and sulfur atoms into the thiophene side chains on...
82 citations
TL;DR: Sonication of gallium or gallium-based liquid metals in an aqueous solution of vinyl monomers leads to rapid free radical polymerization (FRP) without the need for conventional molecular initiator as discussed by the authors.
Abstract: Sonication of gallium or gallium-based liquid metals in an aqueous solution of vinyl monomers leads to rapid free radical polymerization (FRP), without the need for conventional molecular initiator...
75 citations
TL;DR: In this paper, a polymer network of strong bonds is used to achieve high fracture toughness on the basis of one physical principle. But, as a crack advances in such a hydrogel, the strength of the polymer network weakens.
Abstract: Hydrogels of numerous chemical compositions have achieved high fracture toughness on the basis of one physical principle. As a crack advances in such a hydrogel, a polymer network of strong bonds r...
74 citations
TL;DR: In this paper, photo-initiated polymerization-induced self-assembly (photo-PISA) based on aqueous visible light-induced reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization at room temperature is presented.
Abstract: Aqueous emulsion polymerization is one of the most commonly used techniques in industry for the production of polymer latexes. In this contribution, we present photoinitiated polymerization-induced self-assembly (photo-PISA) based on aqueous visible light-induced reversible addition–fragmentation chain transfer (RAFT)-mediated emulsion polymerization at room temperature. A wide range of morphologies including spheres, worms, and vesicles have been achieved at room temperature by modulating reaction parameters. Additionally, this method enables access to inorganic nanoparticles-loaded vesicles by adding inorganic nanoparticles at the beginning of the polymerization. Finally, an oxygen-tolerant RAFT-mediated emulsion polymerization has been developed, allowing the synthesis of polymer nano-objects at low volumes (e.g., in a 96-well plate). This study is expected to expand the scope of photo-PISA for the preparation of various block copolymer nano-objects in water at room temperature.
TL;DR: Polymerization-induced self-assembly (PISA) is regarded as one of the most important strategies in macromolecular nanotechnology, as it can create a wide range of nanoparticles at high concentratio.
Abstract: Polymerization-induced self-assembly (PISA) is regarded as one of the most important strategies in macromolecular nanotechnology, as it can create a wide range of nanoparticles at high concentratio...
TL;DR: It is shown that agarose, that is, a common linear polysaccharide, forms helical fibrillar bundles upon cooling from aqueous solution and the hydrogels with these semiflexible fibrils show pronounced strain-stiffening.
Abstract: Strain-stiffening is one of the characteristic properties of biological hydrogels and extracellular matrices, where the stiffness increases upon increased deformation. Whereas strain-stiffening is ...
TL;DR: In this article, SiO2g-PMMAMA with grafted poly(methyl methacrylate) brushes was prepared via activator regeneration by electron transfer (target) atom transfer radical polymerization (ATRP).
Abstract: Silica particles with grafted poly(methyl methacrylate) brushes, SiO2-g-PMMA, were prepared via activator regeneration by electron transfer (ARGET) atom transfer radical polymerization (ATRP). The ...
TL;DR: In this paper, the authors present a technique that allows for oxygen-tolerant polymerizations and the preparation of polymers with low dispersity and high end-group fidelity.
Abstract: Photo-ATRP has recently emerged as a powerful technique that allows for oxygen-tolerant polymerizations and the preparation of polymers with low dispersity and high end-group fidelity. However, the...
TL;DR: In this paper, a bicomponent metal-free catalyst comprising a mild phosphazene base and triethylborane was used to copolymerize polyethylene and propylene/ethylene oxide.
Abstract: Phthalic anhydride and propylene/ethylene oxide are copolymerized at room temperature by a bicomponent metal-free catalyst comprising a mild phosphazene base and triethylborane. Provided with prope...
TL;DR: A recently emerged reversible shape memory effect greatly extends the capability of shape memory polymers and their practical potential as discussed by the authors, and physical confinement and chemical fixation are individually individually individually performed by the shape memory polymer.
Abstract: A recently emerged reversible shape memory effect greatly extends the capability of shape memory polymers and their practical potential. Physical confinement and chemical fixation are individually ...
TL;DR: In this article, a strategy for the synthesis of multiblock copolymers based on methacrylates is presented, which is a class of polymeric materials with a range of potential applications.
Abstract: Multiblock copolymers are a class of polymeric materials with a range of potential applications. We report here a strategy for the synthesis of multiblock copolymers based on methacrylates. Reversi...
TL;DR: Heterogenous reversible deactivation radical polymerization (RDRP) has become an important method for the preparation of a diverse set of well-defined polymer materials in dispersed systems.
Abstract: Heterogenous reversible deactivation radical polymerization (RDRP) has become an important method for the preparation of a diverse set of well-defined polymer materials in dispersed systems. Conduc...
TL;DR: The results show that the double-folded ring polymers are significantly less threaded compared to their counterparts at equilibrium, and these findings are robust, being based on universal (model-independent) observables as the average fraction of threaded length or the total penetrations between close-by rings and the corresponding distribution functions.
Abstract: Unconcatenated ring polymers in concentrated solutions and melt are remarkably well described as double-folded conformations on randomly branched primitive trees. This picture though contrasts recent evidence for extensive intermingling between close-by rings in the form of long-lived topological constraints or threadings. Here, we employ the concept of ring minimal surface to quantify the extent of threadings in polymer solutions of the double-folded rings vs rings in equilibrated molecular dynamics computer simulations. Our results show that the double-folded ring polymers are significantly less threaded compared to their counterparts at equilibrium. Second, threadings form through a slow process whose characteristic time-scale is of the same order of magnitude as that of the diffusion of the rings in solution. These findings are robust, being based on universal (model-independent) observables as the average fraction of threaded length or the total penetrations between close-by rings and the correspondi...
TL;DR: In this paper, the viability and increasing variety of functionalized polypentenamers as unique and valuable materials created through enthalpy-driven ring-opening metathesis polymerization (ROMP) of low ring strain cyclopentene monomers.
Abstract: This Viewpoint highlights the viability and increasing variety of functionalized polypentenamers as unique and valuable materials created through enthalpy-driven ring-opening metathesis polymerization (ROMP) of low ring strain cyclopentene monomers. The terms “low ring strain” and “enthalpy-driven” are typically conflicting ideologies for successful ROMP; however, these monomers possess a heightened sensitivity to reaction conditions, which may be leveraged in a number of ways to provide performance elastomers with good yield and precise functional topologies. Over the last several years, a rekindled interest in these systems has led to a renaissance of research aimed at improving their synthesis and exploring their potential. Their chemistry, applications, and future outlook are discussed.
TL;DR: In this paper, the authors proposed a method to use polymer hydrogels with intense yet tunable fluorescence for biological imaging, sensing, information storage, etc., and showed that the convent...
Abstract: Polymer hydrogels with intense yet tunable fluorescence are of great research interest due to their wide potential use in biological imaging, sensing, information storage, etc. However, the convent...
TL;DR: This work presents a method to achieve biocompatible, covalent adhesion, without requiring any functional groups from the wet materials, using two hydrogels as model adherends that have covalENT polymer networks, but have no functional groups for adhesion
Abstract: Tough adhesion between wet materials (i.e., synthetic hydrogels and biological tissues) is undergoing intense development, but methods reported so far either require functional groups from the wet ...
TL;DR: The ability to perform multiple chemical reactions independently (orthogonally) in a single reaction vessel can allow simplified reaction protocols for intricate chemical syntheses as mentioned in this paper, which can be used for many applications.
Abstract: The ability to perform multiple chemical reactions independently (orthogonally) in a single reaction vessel can allow simplified reaction protocols for intricate chemical syntheses. Light is an esp...
TL;DR: Tensile drawing of the conjugated polymer poly(3-hexylthiophene) (P3HT) is employed to create free-standing films with a high degree of uniaxial alignment, giving rise to robustfree-standing materials that are of interest for the design of flexible thermoelectric devices.
Abstract: The thermoelectric power factor of a broad range of organic semiconductors scales with their electrical conductivity according to a widely obeyed power law, and therefore, strategies that permit th...
TL;DR: Inverse vulcanization is the method by which molten sulfur can be combined with comonomers to form stable polymers termed organically modified chalcogenide or “ORMOCHALC” polymers as mentioned in this paper.
Abstract: Inverse vulcanization is the method by which molten sulfur can be combined with comonomers to form stable polymers termed “organically modified chalcogenide” or “ORMOCHALC” polymers. One advantage to ORMOCHALC polymers is that they can possess important optical properties, such as high refractive index and strong infrared (IR) transmission, while being easier to fabricate than glass materials with similar optical properties. In the present work, a new ORMOCHALC is fabricated by using tetravinyltin as a comomoner with sulfur. This is the first example of an organometallic molecule being used as a comonomer to develop ORMOCHALCs. The result is an ORMOCHALC polymer that has the highest refractive index reported for a “sulfur and comonomer” polymer and that demonstrates unprecedented transmission in the IR region.
TL;DR: The utilization of chemical sequence control in polymeric materials is key to enabling material design on par with biomacromolecular systems and one important avenue for scalable sequence-controlled p...
Abstract: The utilization of chemical sequence control in polymeric materials is key to enabling material design on par with biomacromolecular systems. One important avenue for scalable sequence-controlled p...
TL;DR: The synthesis of functional poly(2-alkyl-2-oxazoline) copolymers with complex nanoarchitectures using a graft-through ring-opening metathesis polymerization (ROMP) approach is described, with results promising as organic radical contrast agents for metal-free magnetic resonance imaging (MRI).
Abstract: The synthesis of functional poly(2-alkyl-2-oxazoline) (PAOx) copolymers with complex nanoarchitectures using a graft-through ring-opening metathesis polymerization (ROMP) approach is described. First, well-defined norbornene-terminated poly(2-ethyl-2-oxazoline) (PEtOx) macromonomers (MM) were prepared by cationic ring-opening polymerization. ROMP of these MMs produced bottlebrush copolymers with PEtOx side chains. In addition, PEtOx-based branched MMs bearing a terminal alkyne group were prepared and conjugated to an azide-containing bis-spirocyclohexyl nitroxide via Cu-catalyzed azide–alkyne cycloaddition (CuAAC). ROMP of this branched MM, followed by in situ cross-linking, provided PEtOx-based brush-arm star polymers (BASPs) with nitroxide radicals localized at the core–shell interface. These PEtOx-based nitroxide-containing BASPs displayed relaxivity values on par with state-of-the-art polyethylene glycol (PEG)-based nitroxide materials, making them promising as organic radical contrast agents for meta...
TL;DR: In this article, 1D glycocylinders and 2D diamond-shaped glyco-platelets are produced, where the underlying formation mechanism is revealed by dissipative particle dynamics simulations.
Abstract: Two-dimensional (2D) materials are of great significance to the materials community as a result of their high surface area and controllable surface properties. However, controlled preparation of biodegradable 2D structures with biological activity is difficult. In this work we demonstrate that by careful selection of building block structures and assembly conditions it is possible to use crystallization-driven self-assembly (CDSA) to assemble well-defined 2D nanostructures from poly(l-lactide) (PLLA)-based diblock glycopolymers. 1D glyco-cylinders and 2D diamond-shaped glyco-platelets are produced, where the underlying formation mechanism is revealed by dissipative particle dynamics simulations. Furthermore, we demonstrate that assembly of the polymers under mild degradation provides a straightforward route to hollow-cored platelets, a morphology that has previously proven laborious to access. The well-defined sizes and shapes of the glyco-platelets allow us to investigate macrophage activation efficiency...
TL;DR: In this article, an aqueous electrochemically mediated atom transfer radical polymerization (eATRP) was performed in a small volume solution (75 μL) deposited on a screen-printed electrode (SPE).
Abstract: An aqueous electrochemically mediated atom transfer radical polymerization (eATRP) was performed in a small volume solution (75 μL) deposited on a screen-printed electrode (SPE). The reaction was o...