Search

Bone is a complex tissue with robust mechanical and biological properties originating from its nanoscale composite structure. Although much research has been conducted on designing bioinspired artificial bone, the role of biological macromolecules such as noncollagenous proteins (NCPs) in influencing the formation of biominerals is not fully understood. In this work, we have designed nanofiber shish-kebab (NFSK) structures that can template mineral location by recruiting calcium cations from an ion-rich mineralization solution. Poly(acrylic acid) (PAA) is used as the NCP analogue to understand the role of polyelectrolytes in scaffold mineralization. We demonstrate that the addition of PAA in the mineralization solution suppresses the development of extrafibrillar minerals as well as slows down the accumulation and development of mineral phases within NFSKs. We probe the mechanism behind this effect by monitoring the free calcium ion concentration, investigating the PAA molecular weight effect, and conducting mineralization in membrane-partitioned solutions. Our results suggest the 2-fold effect of PAA as a solution stabilizer and physical barrier on the NFSK surface. This work could shed light on the understanding of the NCP effect in biomineralization.

Crystalsomes are crystalline capsules that are formed by controlling polymer crystallization to break translational symmetry. While recent studies showed that these crystalline capsules exhibit interesting mechanical properties, thermal behavior, and excellent performance in blood circulation, the closed capsule is undesired for drug delivery applications. We report the formation and characterization of porous crystalsomes where porosity is rendered on the crystalline shells. A miniemulsion is formed using two amphiphilic block copolymers (BCP). The competition between controlled crystallization and phase separation of the BCPs at the emulsion surface leads to multiphase crystalsomes. Subsequently removing one BCP produces porous crystalline capsules.

We report herein single-walled carbon nanotube-induced polyethylene crystallization at the curved liquid/liquid interface. A Pickering emulsion system comprised of polyethylene (PE)/single-walled carbon nanotubes (SWCNTs)/1,2-dichlorobenzene (DCB)/water is formed using probe sonication at an elevated temperature. SWCNTs are used as the Pickering agents, and they are bent into nanosized rings by the curved DCB/water interface. Upon cooling, PE crystallizes onto SWCNTs, forming kebab single crystals, and the PE lamellae are orthogonal to the DCB/water interface. The unique structure resembles nanohybrid shish kebab (NHSK) rings.

Recently, hierarchical polymer nanostructures called nanofiber shish-kebabs (NFSKs) have shown great potential in directing the distribution of minerals for biomineralization. In this work, we repo...

One of the grand challenges at the forefront of bionanomaterials is their quick clearance in blood circulation. Progress has been made in understanding nanomaterial-biological system interactions and in developing new strategies to extend the blood circulation time of nanomaterials. Here, we first review interactions between the complement system and nanomaterials as well as clearance pathways in major organs such as the liver, spleen, and kidneys. We then discuss new approaches to prolong the blood circulation of nanomaterials with a focus on grafting polymers and biomimetic camouflages including cell membrane coating and hybrid vesicles. In the end, we provide insights into the pros and cons of these approaches and our perspectives for advancing this field.

Here we reported a hierarchical self-assembly approach toward well-defined superlattices in supramolecular liquid crystals by fullerene-based sphere-cone block molecules. The fullerenes crystallize to form monolayer nanosheets intercalated by the attached soft hydrocarbon cones. The frustration caused by cross-sectional area mismatch between the spheres and the somewhat oversize cones leads to a unique lamellar superlattice whereby each stack of six pairs of alternating sphere-cone sublayers is followed by a cone double layer. While such areal mismatch problems in soft matter are usually solved by interface curvature, the lamellar superlattice solution is best suited to systems with rigid layers. Meanwhile, formation of the superlattice significantly improves the material's transient electron conductivity, with the maximum value being among the highest for π-conjugated organic materials. The design principle of solving steric frustration by forming a superlattice opens a new avenue toward self-assembled optoelectronic materials.

Developing solid polymer electrolytes (SPEs) is a promising approach to realize practical dendrite-free lithium metal batteries (LMBs). Tuning the nanoscale polymer network chemsitry is of critical importance for SPE design. In this work, we took lessons from the rubber chemistry and developed a series of comb-chain crosslinker-based SPEs (ConSPEs) using a preformed polymer as the multifunctional crosslinker. The high-functionality crosslinker increased the connectivity of nanosized cross-linked domains, which led to a robust network with dramatically improved toughness and superior lithium dendrite resistance even at a current density of 2 mA cm

Compared with linear homopolymer and block copolymer electrolytes, network-based solid polymer electrolytes (SPEs) demonstrated much improved lithium dendrite resistance and cell cyclability in lithium metal batteries (LMBs), suggesting that polymer chain architecture plays a pivotal role in SPE design. To further improve the state-of-the-art performance of SPEs, in this work, we report a novel interpenetrating network (IPN) SPE that is comprised of poly (ethylene oxide) and poly (propylene carbonate) (PPC) chains. The synthesis of the SPE is based on the crosslinking of octakis(3-glycidyloxypropyldimethylsiloxy)octasilsesquioxane and amine-terminated polyethylene glycol while incorporating linear PPC with a controlled concentration. The IPN SPEs showed improved ionic conductivity and a nearly threefold increase of lithium ion transference number. The optimized SPE could be stably cycled for over 300 ​h ​at a harsh current density of 1.5 ​mA ​cm−2 in the galvanostatic symmetrical cell plating/stripping experiment. Scanning electron microscopy (SEM) revealed that incorporation of PPC could effectively reduce the uneven lithium deposition while X-ray photoelectron spectroscopy (XPS) was used to confirm the active components that are associated with the stable solid electrolyte interface. Full LMBs fabricated using the IPN SPE, a lithium metal anode and a LiFePO4 cathode delivered high specific capacity of over 160 ​mAh g−1 at 0.1 C and over 95 ​mAh g−1 at 2 ​C with an excellent Coulombic efficiency and lifetime. This work demonstrated a new pathway of SPE molecular design towards high performance SPEs for LMB applications.

Replacing liquid electrolytes with solid-state electrolytes is a promising approach to achieving practical applications of lithium metal batteries (LMBs). In this work, ionic liquid N-methyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) was introduced into a hybrid network to obtain a series of gel polymer electrolytes (GPEs). Mechanical and electrochemical properties of the GPEs were tuned through controlling the network structure and ionic liquid contents, and ionic conductivity higher than 1 ​mS ​cm-1 at room temperature was achieved. The newly developed GPEs are flame-retardant and show excellent thermal and electrochemical stability as well as ultra-stability with lithium metal anode. Symmetrical lithium cells with the GPEs exhibit a stable cycling over 6800 ​h ​at a current density of 0.1 ​mA ​cm-2 and stable lithium stripping-plating at 1 ​mA ​cm-2, the highest current density reported for ionic liquid-based GPEs. Detailed correlation between mechanical properties, ionic conductivity and cell short-circuit time is discussed. Moreover, Li/LiFePO4 batteries with the obtained GPEs exhibit desirable cycling stability and rate performance over a wide temperature range from 0 ​°C to 90 ​°C, further suggesting that this new hybrid-network/ionic liquid GPE system has great potential for practical applications in next generation LMBs.

We report the formation and structure of poly(lactic acid) (PLA) nanofiber shish kebabs (NFSKs) containing stereocomplex crystal (SC) shish and SC/homocrystal (HC) kebabs. PLA-based NFSKs were obtained by combining electrospinning and controlled polymer crystallization in order to investigate the interplay between PLA SC and HC formation. Nanofibers were produced by electrospinning poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) blends and were used as the shish. A secondary polymer (either PDLA or PLLA/PDLA blends) was decorated on the nanofiber by an incubation method to form kebab lamellae. We show that both SC and HC kebab crystals can be formed using a SC shish following a soft epitaxy mechanism, while the subtle morphological differences in the resultant NFSKs reveal the propensity of SC nuclei in SC/HC crystallization.

Joint biomechanical functions rely on the integrity of cartilage extracellular matrix. Understanding the molecular activities that govern cartilage matrix assembly is critical for developing effective cartilage regeneration strategies. This study elucidated the role of decorin, a small leucine-rich proteoglycan, in the structure and biomechanical functions of cartilage. In decorin-null cartilage, we discovered a substantial reduction of aggrecan content, the major proteoglycan of cartilage matrix, and mild changes in collagen fibril nanostructure. This loss of aggrecan resulted in significantly impaired biomechanical properties of cartilage, including decreased modulus, elevated hydraulic permeability, and reduced energy dissipation capabilities. At the cellular level, we found that decorin functions to increase the retention of aggrecan in the neo-matrix of chondrocytes, rather than to directly influence the biosynthesis of aggrecan. At the molecular level, we demonstrated that decorin significantly increases the adhesion between aggrecan and aggrecan molecules and between aggrecan molecules and collagen II fibrils. We hypothesize that decorin plays a crucial structural role in mediating the matrix integrity and biomechanical functions of cartilage by providing physical linkages to increase the adhesion and assembly of aggrecan molecules at the nanoscale.

We present here a systematic investigation on the glass transition temperature (Tg) for a series of highly purified cyclic polystyrene (c-PS) samples with molecular weight (MW) varying from 3300 to 13,400. Compared with their linear counterparts, c-PS samples show much higher Tg and exhibit weak Tg-MW dependence. By blending linear polystyrenes with c-PS, the linear polymer contamination effect on the Tg of c-PS was systematically investigated. It was found that the measured Tg of the mixtures increases with the decrease of linear polymer content and the relationship is consistent with Fox equation. These results are helpful to understand the origin of previously reported different Tg-MW relationship for c-PS.

Block copolymers (BCPs) are of growing interest because of their extensive utility in tissue engineering, particularly in biomimetic approaches where multifunctionality is critical. We synthesized polycaprolactone-polyacrylic acid (PCL-b-PAA) BCP and crystallized it onto PCL nanofibers, making BCP nanofiber shish kebab (BCP NFSK) structures. When mineralized in 2× simulated body fluid, BCP NFSK mimic the structure of mineralized collagen fibrils. We hypothesized that the addition of a calcium phosphate layer of graded roughness on the nano-structure of the nanofiber shish kebabs would enhance preosteoblast alkaline phosphatase (ALP) activity, which has been shown to be a critical component in bone matrix formation. The objectives in the study were to investigate the effect of mineralization on cell proliferation and ALP activity, and to also investigate the effect of BCP NFSK periodicity, a structural feature describing the distance between PCL-b-PAA crystals on the nanofiber core, on cell proliferation, and ALP activity. ALP activity of cells cultured on the mineralized BCP NFSK template was significantly higher than the nonmineralized BCP NFSK templates. Interestingly, no statistical difference was observed in ALP activity when the periodic varied, indicating that surface chemistry seemed to play a larger role than the surface roughness.

Solid polymer electrolytes (SPEs) are one of the most promising solutions to the safety issues of lithium batteries. Understanding the morphology and dynamic effects on the ion transport properties of SPEs would be essential for future SPE design. In this article, using poly(ethylene oxide) (PEO) as an example, we focus on morphology control in semicrystalline SPEs. We show that the effect of semicrystallinity can be quantitatively separated into volume, structure and dynamic effects. We further demonstrate that morphological control plays an important role in ion transport control in semicrystalline SPE systems.

Block copolymer brushes are of great interest due to their rich phase behavior and value-added properties compared to homopolymer brushes. Traditional synthesis involves grafting-to and grafting-from methods. In this work, a recently developed "polymer-single-crystal-assisted-grafting-to" method is applied for the preparation of block copolymer brushes on flat glass surfaces. Triblock copolymer poly(ethylene oxide)-b-poly(l-lactide)-b-poly(3-(triethoxysilyl)propyl methacrylate) (PEO-b-PLLA-b-PTESPMA) is synthesized with PLLA as the brush morphology-directing component and PTESPMA as the anchoring block. PEO-b-PLLA block copolymer brushes are obtained by chemical grafting of the triblock copolymer single crystals onto a glass surface. The tethering point and overall brush pattern are determined by the single crystal morphology. The grafting density is calculated to be ≈0.36 nm-2 from the atomic force microscopy results and is consistent with the theoretic calculation based on the PLLA crystalline lattice. This work provides a new strategy to synthesize well-defined block copolymer brushes.

We report herein a series of tetrablock-mimic azobenzene-containing [60]fullerene dyads that form supramolecular liquid crystals (LCs) from phase-segregated two-dimensional (2D) crystals. The unique double-, triple-, and quadruple-layer packing structure of fullerenes in the 2D crystals leads to different smectic supramolecular LC phases, and novel LC phase transitions were observed upon changes in the fullerene packing layer number in the 2D crystals. Interestingly, by combining the LC properties with 2D crystals, these materials show excellent electron mobility in the order of 10-3 cm2 V-1 s-1 , despite their relatively low fullerene content. Our results provide a novel method to manipulate 2D crystal layer thickness, with promising applications in optoelectronic devices.

In water, amphiphilic block copolymers (BCPs) can self-assemble into various micelle structures depicting curved liquid/liquid interface. Crystallization, which is incommensurate with this curved space, often leads to defect accumulation and renders the structures leaky, undermining their potential biomedical applications. Herein we report using an emulsion-solution crystallization method to control the crystallization of an amphiphilic BCP, poly (l-lactide acid)-b-poly (ethylene glycol) (PLLA-b-PEG), at curved liquid/liquid interface. The resultant BCP crystalsomes (BCCs) structurally mimic the classical polymersomes and liposomes yet mechanically are more robust thanks to the single crystal-like crystalline PLLA shell. In blood circulation and biodistribution experiments, fluorophore-loaded BCCs show a 24 h circulation half-life and a 8% particle retention in the blood even at 96 h post injection. We further demonstrate that this good performance can be attributed to controlled polymer crystallization and the unique BCC nanostructure., In block copolymer vesicles, crystallization often leads to defects and renders the structures leaky that undermines their potential biomedical application. Here the authors use an emulsion solution method to control the crystallization of an amphiphilic block copolymer at the curved liquid/liquid interface to improve the blood circulation time.

Even–even polyamides are known to grow as positive spherulites, which implies that the radial, fastest growth direction is parallel to the a-axis and hydrogen bond direction. However, after annealing/self-seeding close to Tm, crystallization in a limited Tc window (down to ≈20 °C below Tm) yields profuse negative spherulites and, frequently stemming from the latter, less frequent and ill-defined entities named “spherulitic aggregates”. The detailed structure and origin of these two entities, and especially of the negative spherulites, are still not clearly established although they were first observed some 70 years ago. The recent recognition that polymer spherulites (specifically, spherulites of PVDF in its γ phase) are made of scrolled, radiating lamellae and the observation and analysis of solution grown, scrolled nylon-66 single crystals provide useful guidelines for a renewed analysis of this structural puzzle. The present analysis relies heavily on the approach and on the detailed diffraction data o...

Synthetic scaffolds have emerged as a promising strategy in the field of tissue engineering and regenerative medicine due to their biocompatibility and resemblance of the extracellular matrix in tissues. Scaffolds can be tailored to specific architectures and have a controlled degradation based on their composition. However, one of the main drawbacks of synthetic scaffolds is that they are often limited due to their bioactivity. A novel technique that recently emerged for bone and mineralization applications has shown successful cellular bioactivity, which involves the polymer crystallization of nanofibers called nanofiber shish kebabs. These scaffolds allow for the formation of periodic kebab structure that is perpendicular to the nanofiber axis, which mimic mineralized collagen fibrils. They have attracted attention in bone tissue engineering because of their ability to direct biomimetic mineralization. Combined with block copolymer chemistry, the kebabs have the ability to attract Ca+2 and PO4−2 ions forming calcium phosphate minerals due to their negative charges. This review characterizes the nanofiber shish kebabs and similar systems in literature, investigates the biocompatibility and cellular response of these systems in vitro, and determines the ongoing and future research. Our purpose is to emphasize the potential and novelty of nanofiber shish kebabs as bone scaffolds, which closely mimic the hierarchical structure of bone. The current gold standard for bone tissue engineering is the use of autografts, the harvesting of the patient’s own healthy bone from a secondary location to replace the defect bone. This treatment is often painful and limited. This review discusses the potential of nanofiber shish kebabs as a bone scaffold for bone replacement. The purpose of this review is to summarize the research that have been done on nanofiber shish kebab scaffolds including material characterization and cellular behavior of different cell types on the scaffolds.

We herein report the fabrication of a Velcro-mimicking surface based on polymer brushes. Using poly(ε-caprolactone) (PCL) as the model polymer, polymer loop brushes (PLBs) and singly tethered polymer brushes (STPBs) with nearly identical tethering point density and brush heights were synthesized using a polymer single crystal (PSC)-assisted grafting-to method. Atomic force microscopy-based single molecular force spectroscopy (AFM-SMFS) and macroscale lap-shear experiments both demonstrated that the PLBs led to strong adhesion that is up to ∼10 times greater than the STPBs, which is attributed to the enriched chain entanglement between the probing polymer and the brushes. We envisage that our results will pave the way towards a new materials design for strong adhesives and nanocomposites.

To date the scrolled morphology of γ-phase poly(vinylidene fluoride) (PVDF) has been witnessed via high temperature melt crystallization of crystalline thin films and through imaging of chemical etched PVDF bulk films. Here we show the first growth and characterization of free-standing γ-phase PVDF scrolls via solution crystallization. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy have been used to characterize and to further understand the fundamental preferred crystalline habit of the γ-phase of PVDF.

We present here the application of in situ cascade polycondensation-coupling ring-opening polymerization (PROP) method for the facile synthesis of a series of three-component poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock terpolymers (PBT-b-PEO-b-PPO-b-PEO-b-PBT)n, using cyclic oligo(butylene terephthalate)s (COBTs) as monomers and dihydroxyl end-functional PEO-b-PPO-b-PEO (EPE) as macroinitiator. The structure details of these copolymers were characterized by 1H-1H gCOSY and 1H-13C gHSQC NMR spectra. With the assignment of multiblock chain ends, block segmental ends and corresponding groups for each segment, the number-average molecular weights for multiblock terpolymers and each block segment were estimated by the quantitative 1H NMR spectra. Polymerization kinetics studies confirm the PROP mechanism. With crystalline PBT and PEO segments, the multiblock terpolymers are double-crystalline polymers, where the melting point and crystallinity of PBT and PEO segments increase with corresponding PBT and PEO content, respectively. The covalent linking of PBT segments with PEO segments leads to the confined crystallization environment for both blocks, where a strong depression on melting point of PEO crystals was observed, which becomes amorphous at an EPE triblock content of 50%. TEM and SAXS results show interesting lamella-like microphase separation morphologies in these multiblock terpolymers.

We presented here the synthesis of poly(butylene terephthalate) (PBT) and poly(ethylene oxide) (PEO) alternating multiblock copolymers (mBCPs), (PBT-b-PEO-b-PBT)n, via a novel cascade polycondensation-coupling ring-opening polymerization (PROP) method. The chemical structure of (PBT-b-PEO-b-PBT)n mBCPs was revealed by 1D and 2D NMR techniques. By blending with lithium bis(trifluoromethane)sulfonamide (up to r ≡ [Li+]/[EO] of 0.20), the mBCP-based solid polymer electrolytes (SPEs) show excellent performance in all-solid-state lithium batteries. Impedance spectroscopy showed that a maximum ionic conductivity, ∼8.2 × 10−4 S/cm at 90 °C, was achieved at r = 0.10 for the mBCP (76 wt.% PEO) SPEs. A high Cd (charge passed through the symmetric cell before short-circuit) of 441 C/cm2 was achieved at the current density of 0.3 mA/cm2 at 90 °C. Because of the facile synthesis, the rich molecular architecture of mBCP, and the high melting point of PBT, these new mBCP SPEs provide a new platform for SPE design.

In recent decades, extensive studies have been devoted to assembling nanoparticles (NPs) into various ordered structures to achieve novel optical properties. However, it still remains a challenging task to assemble NPs into cyclic one-dimensional (1D) shapes, such as rings and frames. Herein, we report a directed assembly method to precisely assemble NPs into well-defined, free-standing frames using polymer single crystals (PSCs) as the template. Preformed poly(ethylene oxide) (PEO) single crystals were used as the template to direct the crystallization of block copolymer (BCP) poly(ethylene oxide)-b-poly(4-vinylpyridine) (PEO-b-P4VP), which directs the gold NPs (AuNPs) to form AuNP frames. By controlling the PSC growth, we were able to, for the first time, precisely tune both the size and width of the AuNP frame. These novel AuNP frames topologically resemble NP nanorings and cyclic polymer chains, and show unique surface plasmon resonance (SPR) behaviors.

Polymer structures with tunable symmetry and sizes are desired for applications such as lithography, filtration membranes, and separation. Here we report the self-assembled supramolecular hexagonal columnar (ΦH) structures with tunable lattice size varying from 5 to 7 nm by constructing hydrogen-bonded copolymers bearing poly(4-vinylpyridine) (P4VP) and two dendritic molecular additives, 1-[4′-(3″,4″,5″-tridecyloxybenzoyloxy)phenyleneoxycarbonyl]-3-[(4″-hydroxyphenyl)oxycarbonyl]benzene (12CBP) and 4-hydroxyphenyl (3,4,5-tridecyloxy)benzoate (12CTB). Despite the distinct molecular size difference between 12CBP and 12CTB, the resulting ternary supramolecular copolymers, P4VP(12CBP)x(12CTB)y, possess a homogeneous ΦH phase at x ≥ 0.1 and y ≥ 0.2. Each column is constructed with P4VP as the backbone tethered with mixed side chains. The column diameter is between the size of the corresponding P4VP(12CBP)x+y and P4VP(12CTB)x+y and could be easily tuned by varying x and y. The enhancement of ΦH in supramolecula...

Inspired by stimuli-triggered unraveling of the von Willebrand factor from a nonsticky globular to a stretched linear shape with exposure of functional groups in blood clotting, this article reports on the synthesis of thermosensitive binary heterografted linear molecular brushes that exhibit temperature-induced shape changing between extended wormlike and collapsed yet stable globular conformations in water. The molecular brushes are composed of two distinct side chain polymers: thermosensitive poly(ethoxydi(ethylene glycol) acrylate) (PDEGEA), which undergoes a lower critical solution temperature (LCST) transition at 9 °C in water, and poly(ethylene oxide) (PEO), which serves as a stabilizer for the collapsed state. A “grafting to” method was developed to construct molecular brushes by clicking alkyne end-functionalized side chain polymers onto an azide-bearing backbone polymer. While a 1.0 mg/g aqueous solution of PDEGEA homografted molecular brushes turned cloudy upon heating from 0 to 22 °C, at the s...

Janus nanoparticles could exhibit a higher interfacial activity and adsorb stronger to fluid interfaces than homogeneous nanoparticles of similar sizes. However, little is known about the interfacial diffusion of Janus nanoparticles and how it compares to that of homogeneous ones. Here, we employed fluorescence correlation spectroscopy to study the lateral diffusion of ligand-grafted Janus nanoparticles adsorbed at water/oil interfaces. We found that the diffusion was significantly slower than that of homogeneous nanoparticles. We carried out dissipative particle dynamic simulations to study the mechanism of interfacial slowdown. Good agreement between experimental and simulation results has been obtained only provided that the flexibility of ligands grafted on the nanoparticle surface was taken into account. The polymeric ligands were deformed and oriented at an interface so that the effective radius of Janus nanoparticles is larger than the nominal one obtained by measuring the diffusion in bulk solution. These findings highlight further the critical importance of the ligands grafted on Janus nanoparticles for applications involving nanoparticle adsorption at an interface, such as oil recovery or two-dimensional self-assembly.

We demonstrate by molecular simulations that the Ostwald ripening of crystalline polymer nuclei within the fast-evaporation-induced 2D skin layer is retarded at suitable temperatures and evaporation rates. Such an anomalous ripening can be attributed to the interplay between the thermodynamically driven diffusion of noncrystalline fragments toward the growing nuclei and the diffusive current away from the free surface caused by the densification in the nonequilibrium skin layer. The growth orientation of the nuclei inside the skin plane can be adjusted during this anomalous ripening process, which is beneficial for fabricating 2D polymer crystals.

One of the fundamental laws in crystallization is translational symmetry, which accounts for the profound shapes observed in natural mineral crystals and snowflakes. Herein, we report on the spontaneous formation of spherical hollow crystals with broken translational symmetry in crystalline molecular bottlebrush (mBB) polymers. The unique structure is named as mBB crystalsome (mBBC), highlighting its similarity to the classical molecular vesicles. Fluorescence resonance energy transfer (FRET) experiments show that the mBBC formation is driven by local chain overcrowding-induced asymmetric lamella bending, which is further confirmed by correlating crystalsome size with crystallization temperature and mBBʼs side chain grafting density. Our study unravels a new principle of spontaneous translational symmetry breaking, providing a general route towards designing versatile nanostructures., One of the fundamental laws in crystallization is translational symmetry but breaking translational symmetry can be used as a general route towards the design of nanostructures. Here the authors show that overcrowding in molecular bottlebrush polymers allows for spontaneous formation of spherical hollow crystals with broken translational symmetry.

Nanoparticles can be assembled into complex structures and architectures by using a variety of methods. In this review, we discuss recent progress of using polymer crystallization (particularly polymer single crystals, PSCs) to direct nanoparticle assembly. PSCs have been extensively studied since 1957. Mainly appearing as quasi-two-dimensional (2D) lamellae, PSCs are typically used as model systems to determine polymer crystalline structures, or as markers to investigate the crystallization process. Recent research has demonstrated that they can also be used as nanoscale functional materials. Herein, we show that nanoparticles can be directed to assemble into complex shapes by using in situ or ex situ polymer crystal growth. End-functionalized polymers can crystallize into 2D nanosheet PSCs, which are used to conjugate with complementary nanoparticles, leading to a nanosandwich structure. These nanosandwiches can find interesting applications for catalysis, surface-enhanced Raman spectroscopy, and nanomotors. Dissolution of the nanosandwich leads to the formation of Janus nanoparticles, providing a unique method for asymmetric nanoparticle synthesis.

This article reports on the light-triggered unfolding of single stimuli-responsive linear molecular bottlebrushes, composed of either homografted poly(methoxydi(ethylene glycol) acrylate-co-o-nitrobenzyl acrylate) (P(DEGMA-co-NBA)) or heterografted poly(ethylene oxide) (PEO) and poly(o-nitrobenzyl acrylate) (PNBA) side chains, from compact globular to wormlike shapes in an effort to mimic the triggered unravelling of proteins such as the von Willebrand factor and talin. PDEGMA is a thermosensitive polymer with a lower critical solution temperature (LCST) of 38 °C in water. The hydrophobic o-nitrobenzyl group can be cleaved by UV irradiation, yielding a hydrophilic carboxylic acid group. This increased the LCST or solubility of the corresponding side chains in water, triggering the shape transitions of brush molecules from globular to wormlike. The brushes were synthesized by a “grafting to” method using the copper-catalyzed cycloaddition of alkyne end-functionalized side chain polymers and an azide-bearing backbone polymer. For 0.2 mg g−1 P(DEGMA-co-NBA) molecular brushes in water, a dynamic light scattering study showed that the apparent hydrodynamic size decreased with increasing temperature, with the LCST occurring at 23 °C. Atomic force microscopy revealed that the brush molecules changed from an extended wormlike morphology at 4 °C to compact globular nano-objects upon heating to 30 °C. UV irradiation of the solution at 30 °C for 70 min unfolded the brushes to an extended wormlike conformation. For heterografted PEO/PNBA molecular brushes, the collapsed compact nano-objects in water, stabilized by PEO side chains, were prepared by gradually adding a DMF solution of brushes into water, followed by dialysis to remove DMF. Similarly, upon UV irradiation, the brush molecules changed to wormlike conformations.

We present here that in two-dimensional (2D) fullerene supramolecular liquid crystals (SLCs), the phase diagram and lamella thickness of SLCs and 2D crystals can be tuned by the flexible alkyl tail and spacer length, due to their different effects on enthalpy and entropy changes during SLC formation.

MXenes represent a new family of 2D transition metal carbides and/or carbides that has attracted a great deal of attention in various applications because of their unique electrical, thermal, and mechanical properties. In this work, we report on the structure and crystallization behavior of poly(ethylene oxide)(PEO)/MXene nanocomposites. MXene Ti 3 C 2 T x (where T is a surface termination) was synthesized and used as the nanofiller to form polymer nanocomposites using a solution blending method. Their morphologies, structures and crystallization behaviors were investigated using transmission electron microscopy, atomic force microscopy, polarized light microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Both non-isothermal and isothermal crystallization behaviors were studied. We show that the presence of 2D Ti 3 C 2 T x accelerates PEO crystallization at very low MXene contents, while it inhibits PEO crystallization as the loading increases. The fastest crystallization rate was observed at 0.5 wt% MXene content. This was attributed to the competition of nucleation and confinement effect of the 2D filler.

A polymerized ionic liquid diblock copolymer (PILBCP-TFSI), poly(MMA-b-MUBIm-TFSI), consisting of an ionic liquid monomer, (1-[(2-methacryloyloxy)undecyl]-3-butylimidazolium bis(trifluoromethane)sulfonamide) (MUBIm-TFSI), and a non-ionic monomer, methyl methacrylate (MMA), was synthesized via reverse addition fragmentation chain transfer polymerization followed by anion exchange metathesis. Free standing, mechanically stable transparent solid polymer films were produced with PILBCP-TFSI containing 1 M lithium bis(trifluoromethane)sulfonamide in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (Li-TFSI/EMIm-TFSI). The resulting PILBCP-TFSI + Li-TFSI/EMIm-TFSI films possessed ion conductivities from 1 to 10 mS cm−1 from 25 °C to 105 °C. Solid-state lithium-ion coin cell batteries were assembled and tested at room temperature with PILBCP-TFSI + Li-TFSI/EMIm-TFSI films as the solid-state electrolyte and separator and resulted in a maximum discharge capacity of 112 mAh g−1 at 0.1 C with a Coulombic efficiency greater than 94% over 100 cycles. For the first time, these results demonstrate the feasibility of PIL block copolymers as solid-state electrolytes and separators in lithium-ion batteries.

We report herein the effects of solvent, concentration, and molecular weight of α-alkynyl-ω-azido polystyrenes (l-PS-N3) on the synthesis of monocyclic polystyrenes (c-PS) by intra-chain coupling of l-PS-N3 via Cu-catalyzed azide/alkyne cycloaddition method. By using fully end-functionalized l-PS-N3 as precursors, the optimum cyclization conditions to synthesize high purity c-PS (>99% by SEC) are revealed, at concentrations around 7.9 μmol/L in DMF. The c-PS products are fully characterized by SEC, LCCC, 1H NMR, and MALDI-TOF Mass spectrometry. The yield of c-PS decreases with increment of concentration of l-PS-N3 as predicted by Jacobson and Stockmayer's equation. Interestingly, among the three studied PS samples with different molecular weight (∼4k, 9k, 14k Da), the medium one (PS9k) provides the best c-PS yield, while in the three studied solvent (toluene, DMF, cyclohexane), DMF gives the best yied. The results reveal that the PS chain conformation in the solution, which is affected by the solvent and molecular weights, plays an important role in the intra-chain cyclization reaction.