Search

The inability to synthesize hierarchical structures with independently tailored nanoscale and mesoscale features limits the discovery of next-generation multifunctional materials. We present a programmable molecular self-assembly strategy to craft nanostructured materials with a variety of phase-in-phase hierarchical morphologies. The compositionally anisotropic building blocks employed in the assembly process are formed by multi-component graft block copolymers (GBCPs) containing sequence-defined side chains. The judicious design of various structural parameters in the GBCPs enables broadly tunable compositions, morphologies, and lattice parameters across the nanoscale and mesoscale in the assembled structures. Our strategy introduces new design principles for the efficient creation of complex hierarchical structures and provides a facile synthetic platform to access nanomaterials with multiple precisely integrated functionalities.

Multicomponent nanostructured materials assembled from molecular building blocks received wide attention due to their precisely integrated multifunctionalities. However, discovery of these materials with desirable composition and morphology was limited by their low synthetic scalability and narrow structural tuning window with given building blocks. Here, we report a scalable and diversity-oriented synthetic approach to hierarchically structured nanomaterials based on a few readily accessible building blocks. Mixed-graft block copolymers containing sequence-defined side chains were prepared through ring-opening metathesis copolymerization of three or four types of macromonomers. Intramolecularly defined interfaces promoted the formation of ordered hierarchical structures with lattice sizes tunable across multiple length scales. The same set of macromonomers were arranged and combined in different ways, providing access to diverse morphologies in the resultant structures.

Block copolymer self-assembly is a powerful tool for 2D nanofabrication; however, its extension to complex 3D network structures, which would be useful for a range of applications, is limited. Here, we report a simple method to generate unprecedented 3D mesh morphologies through intrinsic molecular confinement self-assembly. We designed triblock bottlebrush polymers with two Janus domains: one perpendicular and one parallel to the polymer backbone. The former enforces a lamellar superstructure that intrinsically confines the intra-layer self-assembly of the latter, giving rise to a mesh-like monoclinic M15 network substructure with excellent long-range order. Dissipative particle dynamics simulations show that the spatial constraints exerted on the polymer backbone drive the emergence of M15, as well as a tetragonal T131 in the strong segregation regime. This work demonstrates intrinsic molecular confinement as a path to bottom-up assembly of new geometrical phases of soft matter, extending the capabilities of block copolymer nanofabrication.

Transmembrane protein channels, including ion channels and aquaporins that are responsible for fast and selective transport of water, have inspired membrane scientists to exploit and mimic their performance in membrane technologies. These biomimetic membranes comprise discrete nanochannels aligned within amphiphilic matrices on a robust support. While biological components have been used directly, extensive work has also been conducted to produce stable synthetic mimics of protein channels and lipid bilayers. However, the experimental performance of biomimetic membranes remains far below that of biological membranes. In this review, we critically assess the status and potential of biomimetic desalination membranes. We first review channel chemistries and their transport behavior, identifying key characteristics to optimize water permeability and salt rejection. We compare various channel types within an industrial context, considering transport performance, processability, and stability. Through a re-examination of previous vesicular stopped-flow studies, we demonstrate that incorrect permeability equations result in an overestimation of the water permeability of nanochannels. We find in particular that the most optimized aquaporin-bearing bilayer had a pure water permeability of 2.1 L m-2 h-1 bar-1, which is comparable to that of current state-of-the-art polymeric desalination membranes. Through a quantitative assessment of biomimetic membrane formats, we analytically show that formats incorporating intact vesicles offer minimal benefit, whereas planar biomimetic selective layers could allow for dramatically improved salt rejections. We then show that the persistence of nanoscale defects explains observed subpar performance. We conclude with a discussion on optimal strategies for minimizing these defects, which could enable breakthrough performance.

Graft copolymers offer a versatile platform for the design of self-assembling materials; however, simple strategies for precisely and independently controlling the thermomechanical and morphological properties of graft copolymers over wide property windows remain elusive. Here, using a library of 92 systematically varied polynorbornene-graft-polydimethylsiloxane (PDMS) copolymers, we discover a versatile backbone-pendant sequence control strategy that overcomes this challenge. We find that small structural variations of aliphatic pendant groups, e.g., cyclohexyl versus n-hexyl, of small molecule comonomers have dramatic impacts on the order-to-disorder transitions, glass transitions, mechanical properties, and self-assembled morphologies of statistical and block silicone-based graft copolymers, providing an exceptionally broad palette of designable materials properties, e.g., elastic moduli that vary over 9 orders-of-magnitude. For example, statistical graft copolymers with very high PDMS volume fractions yielded unbridged body-centered cubic (BCC) morphologies that behaved as ultra-soft, shear-thinning, plastic crystals. By contrast, lamellae-forming statistical graft copolymers provided robust, stiff, yet reprocessable silicone thermoplastics (TPs) with transition temperatures spanning over 160 °C and elastic moduli as high as 150 MPa, which is much greater than commercial silicone thermosets. Altogether, this study reveals a new pendant-mediated assembly strategy that simplifies graft copolymer synthesis and enables access to a diverse family of silicone materials, setting the stage for the broader development of self-assembling materials with tailored performance specifications.

An atom transfer radical polymerization-based sequential “graft-from” approach was developed to synthesize molecular brush-on-brush (MBoB)-based hierarchically branched polymers with readily tunable backbone grafting density, lengths of backbone and primary/secondary side chains, and monomer type. The hierarchically branched structure was visualized, and the stability of the giant MBoB macromolecules was studied by atomic force microscopy. The robust approach enabled the versatile combination of chemical functionality and MBoB structure.

Although poly(ethylene glycol) (PEG) is commonly used in nanoparticle design, the impact of surface topography on nanoparticle performance in biomedical applications has received little attention, despite showing significant promise in the study of inorganic nanoparticles. Control of the surface topography of polymeric nanoparticles is a formidable challenge due to the limited conformational control of linear polymers that form the nanoparticle surface. In this work, we establish a straightforward method to precisely tailor the surface topography of PEGylated polymeric nanoparticles based on tuning the architecture of shape-persistent amphiphilic bottlebrush block copolymer (BBCP) building blocks. We demonstrate that nanoparticle formation and surface topography can be controlled by systematically changing the structural parameters of BBCP architecture. Furthermore, we reveal that the surface topography of PEGylated nanoparticles significantly affects their performance. In particular, the adsorption of a model protein and the uptake into HeLa cells were closely correlated to surface roughness and BBCP terminal PEG block brush width. Overall, our work elucidates the importance of surface topography in nanoparticle research as well as provides an approach to improve the performance of PEGylated nanoparticles.

The application of positively charged polymers is a common treatment strategy for the sorption and separation of dissolved hexavalent chromium Cr(VI). In particular, polyethylenimine (PEI) has been demonstrated as an effective polymer for Cr treatment due to abundant amine groups and cost-effectiveness. However, PEI as a photoactive polymer has not been previously explored for Cr treatment. Toward this, we demonstrate the significant photoactive potential of PEI for Cr sorption and reduction [to Cr (III)], delineating amine structure-function relationships. Overall, Cr(VI) photoreduction is enhanced dramatically as a function of amine group density. Additionally, among the types of amine groups evaluated, tertiary amines are observed to be the most reactive followed by secondary and primary amines. When PEI is incorporated onto graphene oxide (GO) as a stabilizing scaffold, mass loading of PEI is a key variable for Cr(VI) treatment performance, which is observed to be a function of PEI molecular weight and oxidation extent of GO. Finally, when combined with magnetic nanomaterials, low energy, high efficiency separation, and reuse are demonstrated. For these, sorption-based separation processes maintained excellent performance over five cycles. Taken together, this work demonstrates that PEI can serve as highly effective, multifunctional material coating(s) not only for chromium treatment but potentially for other oxidized aqueous species as well.

An overview on polyacrylonitrile (PAN)-derived carbon nanomaterials is presented. Controlled synthesis of well-defined PAN by reversible deactivation radical polymerization (RDRP) techniques is discussed as a route to tailored carbon precursors of various architectures, such as block copolymers (BCPs) and organic-inorganic hybrids. Primary examples of different approaches to templating include the use of PAN-containing BCPs self-assembled on planar surfaces or in solution to yield: (i) bulk carbon films, (ii) discrete nano-objects and (iii) mesoporous copolymer-templated nanocarbons (CTNCs). Inorganic templates or electrospinning as a viable approach to ordered mesoporous carbons or carbon nanofibers are also discussed. Special attention is devoted to nitrogen doping in PAN-derived partially graphitic carbons and to the evaluation of nitrogen-enriched nanocarbons in energy conversion and storage applications such as supercapacitors, lithium-sulfur batteries, electrocatalysts, solar cells or CO2 sorbents.

Hydrogel-composite membranes fabricated using poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) hydrogel and a polyethersulfone (PES) support present a promising avenue toward developing self-healing membranes—membranes that autonomously heal from physical damage without any external intervention. The previously developed pore-filled structure, however, suffers from low water permeability, since the hydrogel spans the depth of the PES substrate. This study explores a new asymmetric architecture in which the hydrogel layer is asymmetrically confined to the top several tens of micrometers of a single side of the substrate. We present an approach to achieve this configuration based on controlling the viscosity of the acrylamido-2-methylpropanesulfonic acid (AMPS) monomer solution used during membrane fabrication. The asymmetric PAMPS composite membranes exhibited improved water permeability compared to their pore-filled counterparts, as well as nearly equal self-healing performance following the same mechanism of self-healing. The results of this study collectively suggest that asymmetric hydrogel composite membranes are a more promising route to developing practical water filtration membranes with self-healing capability.

Micro RNA-146 (miR-146) is involved in mediating many innate and adaptive immune and inflammatory responses in the body. It is associated with a variety of systemic inflammation or autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and type 2 diabetes. In recent years, microRNAs (miRNAs) and nanotechnology have become research hotspots in cardiovascular pathology. The close relationship between host miRNAs and coxsackie virus B3 has gradually been discovered by scientists, which may provide new directions for the treatment and prevention of viral myocarditis. At the same time, recent studies have also found that nano-α-linolenic acid and its metabolites can inhibit the production of inflammatory cytokines such as TNF-α and IL-17; At the same time, they also have anti-lipid peroxidation effects. Therefore, in order to further explore the role of miR-146 and nano-α-linolenic acid in the occurrence and development of viral myocarditis, in this study, a mouse model of viral myocarditis was used to establish a VMC mouse model using coxsackie virus B3. Intervention with different doses of nano-α-linolenic acid, the control group was injected with the same amount of sodium chloride buffer, and the changes in cardiac function and inflammation indexes were compared to evaluate the role in the pathogenesis of viral myocarditis. The results showed that this study suggested that serum miR-146 concentration in viral myocarditis mice is increased and is positively correlated with serum IL-17 and TNF-α concentrations. This suggest that miR-146 in the circulation may be involved in the pathogenesis of viral myocarditis through IL-17 and TNF-α, providing a theoretical basis for the role of miR-146 in viral myocarditis, but its specific mechanism of action needs to be further studied. At the same time, the research in this experiment showed that nano-α-linolenic acid significantly improves the survival rate of CVB3 infected mice and reduces myocardial damage. And with the increase of the dosage of nano-α-linolenic acid, the effect is more significant, showing a significant dose-effect relationship.

Polyelectrolyte multilayer membranes (PEMs) produced by the sequential, layer-by-layer deposition of polyelectrolytes on porous supports have been shown to significantly reject ions in dilute saline solutions. However, polyelectrolyte thin films are susceptible to swelling or detachment from the substrate in higher salinities and extreme pH conditions, such that their performance is highly dependent on feed water composition. In this study, we introduce tethered electrolyte active-layer membranes (TEAMs), whereby charged block copolymers are covalently grafted-from a porous support, in aim of reducing the stimuli response of layered polyelectrolyte membranes under variable solution conditions. Cellulose support layers were modified using surface-initiated atom transfer radical polymerization of neutral precursor polymers, which were then converted into charged blocks after polymerization. An ultrathin layer of a single negative or positive block with a degree of polymerization (DP) ≥ 770 exhibited ∼15–20 L m-2 h-1 bar-1 pure water permeability, 45–60% rejection of monovalent co-ions, and ∼75% rejection of divalent co-ions. In mixed feed solutions, selectivity of monovalent over divalent co-ions with single-block TEAMs fell within the range of 2–4. Single-block TEAMs slightly shrank under high salt concentration, contrary to the typical substantial swelling of PEMs. As such, this new form of polyelectrolyte membrane may provide greater stability than conventional PEMs and may have potential applications in water softening and salinity reduction of surface waters.

Fast lithium ion (Li+) transport in solid-state polymer-matrix conductors is in desperate demand in a wide range of room-temperature scenarios but remains a formidable challenge. Herein, we designed a class of solid-state electrolytes based on mixed-graft block copolymers (mGBCPs) containing short poly(ethylene oxide) (PEO) and polydimethylsiloxane (PDMS) side chains. The strong immiscibility of PEO and PDMS resulted in the formation of ordered phase-separated nanostructures. Diverse morphologies, including double gyroids, hexagonally perforated lamellae, hexagonally packed cylinders, and lamellae, were observed at different volume fractions of PEO/PDMS blocks. The impact of chain mobility of PEO on Li+ transport was investigated by varying the length of PEO side chains and blending with free PEO chains. We demonstrated that physically blending mGBCPs with free amorphous PEO chains significantly facilitated the Li+ conduction, and a solid-state electrolyte with room-temperature conductivity up to 2.0 × 10−4 S/cm was prepared.

The graft-through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self-assembly of GBCPs resulted in ordered nanostructures with ultra-small domain sizes down to 2.8 nm (half-pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self-assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.

Controlling the molecular structure of amorphous cross-linked polymeric materials is a longstanding challenge. Herein, we disclose a general strategy for precise tuning of loop defects in covalent polymer gel networks. This "loop control" is achieved through a simple semibatch monomer addition protocol that can be applied to a broad range of network-forming reactions. By controlling loop defects, we demonstrate that with the same set of material precursors it is possible to tune and in several cases substantially improve network connectivity and mechanical properties (e.g., ∼600% increase in shear storage modulus). We believe that the concept of loop control via continuous reagent addition could find broad application in the synthesis of academically and industrially important cross-linked polymeric materials, such as resins and gels.

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinduced single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized., Living additive manufacturing via photoredox catalyzed controlled radical polymerization is developed. Under blue LED light, monomers from solution can be repeatedly inserted into “parent” gels to produce “daughter” gels with diverse properties.

Zinc oxide (ZnO) is a wide bandgap semiconductor material that has attracted widespread interest as particle filler in polymer nanocomposite materials. However, its applications have been hindered by the limited dispersibility and surface-modification techniques. Herein, three distinct approaches for the synthesis of polymer-tethered ZnO hybrid materials are compared in terms of uniformity and yield of the particle-brush product: “grafting-from”, “grafting-onto”, and “grafted-copolymer template” methods. In the “grafting-from” method, pristine ZnO nanoparticles (NP) were first functionalized with atom transfer radical polymerization (ATRP) initiators followed by grafting-from process to form poly(methyl methacrylate) (PMMA) or poly(styrene-co-acrylonitrile) (PSAN) tethered polymer chains. In the “grafting-onto” method, PMMA-b-PAA (poly[acrylic acid]) and PSAN-b-PAA diblock copolymers were prepared and attached onto the surface of ZnO NPs using sonication bath. For the “grafted-copolymer template” method, PSAN-b-PtBA-Br (poly[tert-butyl acrylate]-Br) macroinitiators were crosslinked with divinylbenzene (DVB) to form PSAN-b-PtBA-PDVB core-shell star polymers. After hydrolysis to form PSAN-b-PAA-PDVB star polymers, the functional stars were used as polymer templates for the synthesis of ZnO NPs within the PAA-core of the stars. Core-shell molecular bottlebrushes with PAA-b-PS block-copolymer side chains were also used as anisotropic analogues of star template to prepared worm-like ZnO particles. Several ZnO precursors, zinc nitrite, zinc 2-ethylhexanoate, and zinc acetate were evaluated as precursors of ZnO. Conditions were identified that enable the synthesis of polymer-tethered ZnO with excellent size uniformity and dispersion characteristics using the star-template method.

Elasticity, one of the most important properties of a soft material, is difficult to quantify in polymer networks because of the presence of topological molecular defects in these materials. Furthermore, the impact of these defects on bulk elasticity is unknown. We used rheology, disassembly spectrometry, and simulations to measure the shear elastic modulus and count the numbers of topological "loop" defects of various order in a series of polymer hydrogels, and then used these data to evaluate the classical phantom and affine network theories of elasticity. The results led to a real elastic network theory (RENT) that describes how loop defects affect bulk elasticity. Given knowledge of the loop fractions, RENT provides predictions of the shear elastic modulus that are consistent with experimental observations.

Star polymers with block copolymer arms were prepared by atom transfer radical polymerization (ATRP) via an arm-first method. Several macroinitiators based on block copolymers (MIs), PBA-b-PtBA–Br, PtBA-b-PBA–Br, PSAN-b-PBA–Br, and PBA-b-PtBA–Br, were prepared by activators regenerated by electron transfer (ARGET) ATRP to maintain high chain-end functionality. Then the MIs were reacted with divinylbenzene as a cross-linker to form star-shaped polymers via ARGET ATRP. Several parameters including concentration of reducing agent, copper catalyst concentration, degree of polymerization (DP) of MIs, and composition of MIs were investigated. A high level of control was achieved by sequential feeding of the reducing agents for DPMI ≤ 100. Stars in >95% yield and with narrow molecular weight distributions (Mw/Mn < 1.3) were obtained under the optimized polymerization condition.

We report the synthesis of Janus bottlebrush block copolymers by graft-through polymerization of branched diblock macromonomers. Self-assembly of the bottlebrushes was characterized by small-angle X-ray scattering, atomic force microscopy, and scanning electron microscopy. Phase separation and packing models of the bottlebrushes were computed, and their self-assembly behavior was corroborated experimentally in bulk and in thin films. Lamellar, hexagonal cylinder, and gyroid phases were observed and modeled. The A-branch-B Janus bottlebrush structure provides several unique advantages in the context of bottlebrush polymer assembly, including access to the first examples of gyroid phases.

Mixed-graft block copolymers (mGBCPs) consist of two or more types of polymeric side chains grafted on a linear backbone in a random, alternating, or pseudo-alternating sequence. They can phase-separate with the backbone serving as the interface of the blocks, and the side chains dominate their self-assembly behavior. mGBCPs are an accessible polymer architecture for exploring the idea of encoding polymer properties through the macromolecular architecture, as there are two distinct structural components that can be tuned: the backbone and the side chains. In this Concept article, the current literature on the synthesis of mGBCPs is reviewed, and the advantages and disadvantages of each synthetic method are noted. The self-assembly of mGBCPs is also discussed where possible. Finally, directions for future research on mGBCP synthesis and self-assembly are suggested.

Controlled/living radical polymerization was developed to synthesize branched polyacrylates and polystyrene with tunable degrees of branching and low dispersities. This method is based on a polymerization-induced branching process that occurs when n-butyl α-bromoacrylate is copolymerized under atom transfer radical polymerization conditions. This novel branching polymerization demonstrates excellent synthetic versatility, enabling the preparation of complex macromolecular architectures constructed from branched-polymer building blocks.

We report a stepwise assembly strategy for the integration of metal-organic cages (MOCs) into block copolymers (BCPs). This approach creates "block co-polyMOC" (BCPMOC) materials whose microscopic structures and mechanical properties are readily tunable by adjusting the size and geometry of the MOCs and the composition of the BCPs. In the first assembly step, BCPs functionalized with a pyridyl ligand on the chain end form star-shaped polymers triggered by metal-coordination-induced MOC assembly. The type of MOC junction employed precisely determines the number of arms for the star polymer. In the second step, microphase separation of the BCP is induced, physically cross-linking the star polymers and producing the desired BCPMOC networks in the bulk or gel state. We demonstrate that large spherical M12L24 MOCs, small paddlewheel M2L4 MOCs, or a mixture of both can be incorporated into BCPMOCs to provide materials with tailored branch functionality, phase separation, microdomain spacing, and mechanical properties. Given the synthetic and functional diversity of MOCs and BCPs, our method should enable access to BCPMOCs for a wide range of applications.

Studies on the phase segregation of unimolecular block copolymers (BCPs) are limited by a lack of reliable, versatile methods for the synthesis of such polymers on the preparative scale. Herein, we describe an advancement of Iterative Exponential Growth (IEG) wherein chiral allyl-based IEG oligomers are subjected to thiol-ene reactions and converted into unimolecular BCPs. With this strategy we have synthesized uniform BCPs with molar masses up to 12.1 kDa on ∼1 g scale. BCPs composed of decane-based side chains and either triethyleneglycol- or thioglycerol-based side chains phase-segregate into hexagonal cylinder morphologies. The assembly is not driven by side-chain crystallization, but is instead the result of amorphous BCP assembly.

Acrylonitrile (AN) was polymerized by initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP). The effect of the ligand, tris(2-pyridylmethyl)amine (TPMA) and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), in the Cu-based catalyst, the amount of catalyst, several alkyl halide initiators, targeted degree of polymerization, and amount of azobisisobutyronitrile (AIBN) added were studied. It was determined that the best conditions utilized 50 ppm of CuBr2/TPMA as the catalyst and 2-bromopropionitrile (BPN) as the initiator. This combination resulted in 46% conversion in 10 h and polyacrylonitrile (PAN) with the narrowest molecular weight distribution (Mw/Mn = 1.11–1.21). Excellent control was maintained after lowering the catalyst loading to 10 ppm, with 56% conversion in 10 h, experimental molecular weight closely matching the theoretical value, and low dispersity (Mw/Mn

Through the use of macromolecular design and efficient chemical reactions it is now possible to control the composition of polymer networks and gels with excellent precision. In contrast, topological defects are still impossible to avoid and are generally difficult to quantify. For example, primary loops that form when a bifunctional monomer (A2) reacts twice with the same f functional (f > 2) monomer (Bf) during formation of an end-linked A2 + Bf network represent a pervasive defect that has a detrimental effect on mechanical integrity. Methods for the quantitative analysis of primary loops in such materials have recently emerged; however, these methods have only been applied to the simplest network structure: A2 + B3. Herein, we report strategies for counting primary loops in tetrafunctional (A2 + B4) networks and networks with mixed tri- and tetrafunctional (A2 + B3/B4) junctions. We apply these strategies to the quantitative analysis of primary loops in a series of end-linked poly(ethylene glycol) hyd...

Gels formed via metal-ligand coordination typically have very low branch functionality, f, as they consist of ∼2-3 polymer chains linked to single metal ions that serve as junctions. Thus, these materials are very soft and unable to withstand network defects such as dangling ends and loops. We report here a new class of gels assembled from polymeric ligands and metal-organic cages (MOCs) as junctions. The resulting 'polyMOC' gels are precisely tunable and may feature increased branch functionality. We show two examples of such polyMOCs: a gel with a low f based on a M2L4 paddlewheel cluster junction and a compositionally isomeric one of higher f based on a M12L24 cage. The latter features large shear moduli, but also a very large number of elastically inactive loop defects that we subsequently exchanged for functional ligands, with no impact on the gel's shear modulus. Such a ligand substitution is not possible in gels of low f, including the M2L4-based polyMOC.

A systematic study was performed on two triazolium ionic liquid isomers which included examination of thermal, physical, and electrochemical properties. It was found that a minor change in structure significantly influences physical and thermal properties of ionic liquids.

In this report, we demonstrate the superior performance of dye-sensitized solar cells (DSSCs) with novel, metal-free counter electrodes (CEs) comprised of copolymer-templated nitrogen-enriched nanocarbons (CTNCs) with well-controlled morphology, nanoporosity, and nitrogen content. This superior performance is due to the high catalytic activity of CTNCs toward the reduction of Co(bpy)32+/3+, as evidenced by unusually low charge transfer resistance (RCT) at the CE–electrolyte interface. The observed activity is attributed to the combination of the high surface area of CTNCs afforded by a three-dimensional, hierarchical pore structure, and to their unique electronic properties stemming from the presence of nitrogen heteroatoms located on the edges of nanographitic domains. Altogether, the use of CTNC CEs enhanced the efficiency and fill factor (FF) of JK-306 dye, Co(bpy)32+/3+ redox couple based DSSCs at one sun illumination up to 10.32% and 73.5%, respectively, suggesting the considerable promise of these materials as an attractive alternative to costly Pt-based CEs. Interestingly, the use of CTNCs did not lead to the analogous beneficial lowering of RCT in I−/I3− redox couple based N719-sensitized DSSCs, limiting their FF and short circuit current density (JSC). This chemical specificity indicates that the type of nitrogen bonding configurations, rather than the total N-content, is the key factor determining the catalytic activity.

Cubosomes are micro- and nanoparticles with a bicontinuous cubic two-phase structure, reported for the self-assembly of low molecular weight surfactants, for example, lipids, but rarely formed by polymers. These objects are characterized by a maximum continuous interface and high interface to volume ratio, which makes them promising candidates for efficient adsorbents and host-guest applications. Here we demonstrate self-assembly to nanoscale cuboidal particles with a bicontinuous cubic structure by amphiphilic poly(ionic liquid) diblock copolymers, poly(acrylic acid)-block-poly(4-vinylbenzyl)-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide, in a mixture of tetrahydrofuran and water under optimized conditions. Structure determining parameters include polymer composition and concentration, temperature, and the variation of the solvent mixture. The formation of the cubosomes can be explained by the hierarchical interactions of the constituent components. The lattice structure of the block copolymers can be transferred to the shape of the particle as it is common for atomic and molecular faceted crystals., Generally cubosomes are formed by the self-assembly of surfactants such as lipids and are used as adsorbents or in host-guest applications. Here the authors have shown that an amphiphilic block copolymer can form nanoscale cuboidal particles with a bicontinuous cubic phase.

Atom transfer radical polymerization (ATRP) of dimethyl(methacryloyloxymethyl) phosphonate (DMMAMP, also referred to as MAPC1) with a copper/2,2′-bipyridine based catalytic system in DMSO resulted in a homopolymer with narrow molecular weight distribution. Initiators for continuous activator regeneration (ICAR) ATRP of this monomer was also successful when using tris[(2-pyridyl)methyl]amine as ligand and azobisisobutyronitrile as supplementary initiator for the regeneration of the CuI activator. Normal ATRP provided better control compared to ICAR ATRP. Differential scanning calorimetry measurements of the resulting poly(DMMAMP) revealed a glass transition temperature (Tg = 63 °C), lower than that of poly(methyl methacrylate). Chain extension of the poly(dimethyl(methacryloyloxymethyl) phosphonate) macroinitiator with styrene was successfully achieved with a high fraction of block copolymer.

Understanding the influence of salt/counterion on atom transfer radical polymerization (ATRP) is important to optimize the conditions for ATRP of ionic monomers, such as ionic liquid monomer. This article reports the results of a systematical investigation of the variables associated with ATRP in the presence of different types and amounts of salts, solvents, ligands, and monomers. A series of control ATRP experiments were conducted under various polymerization conditions. The kinetics of the polymerizations, the molecular weight, and molecular weight distribution of the formed polymers were studied by nuclear magnetic resonance and gel permeation chromatography. The results indicated that all of the studied variables influenced the ATRP process to different degrees. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2175–2184

The emergence of flexible and stretchable electronic components expands the range of applications of electronic devices. Flexible devices are ideally suited for electronic biointerfaces because of mechanically permissive structures that conform to curvilinear structures found in native tissue. Most electronic materials used in these applications exhibit elastic moduli on the order of 0.1–1 MPa. However, many electronically excitable tissues exhibit elasticities in the range of 1–10 kPa, several orders of magnitude smaller than existing components used in flexible devices. This work describes the use of biologically derived heparins as scaffold materials for fabricating networks with hybrid electronic/ionic conductivity and ultracompliant mechanical properties. Photo-cross-linkable heparin–methacrylate hydrogels serve as templates to control the microstructure and doping of in situ polymerized polyaniline structures. Macroscopic heparin-doped polyaniline hydrogel dual networks exhibit impedances as low as Z = 4.17 Ω at 1 kHz and storage moduli of G′ = 900 ± 100 Pa. The conductivity of heparin/polyaniline networks depends on the oxidation state and microstructure of secondary polyaniline networks. Furthermore, heparin/polyaniline networks support the attachment, proliferation, and differentiation of murine myoblasts without any surface treatments. Taken together, these results suggest that heparin/polyaniline hydrogel networks exhibit suitable physical properties as an electronically active biointerface material that can match the mechanical properties of soft tissues composed of excitable cells.

A series of porous polymers with different pore volumes, pore sizes, and crosslinking densities were synthesized by high internal phase emulsion (HIPE) polymerization. The crosslinked polymerized HIPEs (polyHIPEs) were formed by the copolymerization of 4-vinylbenzyl chloride and divinylbenzene using water droplets in conventional or Pickering HIPEs as the templates. These porous materials were further modified by quaternization and ion exchange to introduce quaternary ammonium hydroxide groups. The resulting polyHIPEs were utilized as sorbents for reversible CO2 capture from air using the humidity swing. The effect of pore structure on the CO2 adsorption and desorption processes was studied. The polyHIPEs containing large pores and interconnected porous structures showed improved swing sizes and faster adsorption/desorption kinetics of CO2 compared to a commercial Excellion membrane with similar functional groups.

Porous nanocarbons with tunable morphology and pore size were prepared via the carbonization of polyacrylonitrile containing block copolymers. Retention of the nanostructure of the precursor upon pyrolysis was studied for both thin-film and bulk materials. Morphology-dependent preservation of the resulting nanostructure was observed in the latter case.

A facile approach was developed to prepare crosslinked ionic polymer hydrogel films by photo-crosslinking utilizing p-vinylbenzyl trimethylammonium chloride (VBTMACl) or p-vinylbenzyl trimethylammonium hydroxide (VBTMAOH) as the monomer and poly(ethylene oxide) dimethacrylate (PEODMA, Mn = 750) as the crosslinker. The films with different crosslinking degrees (20%, 40%, 60%, 80%, and 100%) were prepared and characterized by swelling measurements, scanning electron microscopy (SEM), UV-visible spectroscopy, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and small-angle X-ray scattering (SAXS). It was found that the mechanical and thermal properties of the films were largely influenced by the contents of the crosslinker in the films. By ion-exchange of the anions in the films with various other anions, the hydrophobicity/hydrophilicity of the films was changed. In addition, fluorescent films were prepared by treatment with fluorescein, and paramagnetic films with FeCl4− as a counter anion showed catalytic activity for Friedel–Crafts alkylation. The ionic films with quaternary ammonium chloride groups displayed antimicrobial activity against Escherichia coli (E. coli) with almost 100% killing efficiency. Multifunctional films with various tunable properties have significant potential for a wide range of applications.