Shaped Hairy Polymer Nanoobjects

Biomolecular condensates form spatially inhomogeneous network fluids

The functions of biomolecular condensates are thought to be influenced by their material properties, and these will be determined by the internal organization of molecules within condensates. However, structural characterizations of condensates are challenging, and rarely reported. Here, we deploy a combination of small angle neutron scattering, fluorescence recovery after photobleaching, and coarse-grained molecular dynamics simulations to provide structural descriptions of model condensates that are formed by macromolecules from nucleolar granular components (GCs). We show that these minimal facsimiles of GCs form condensates that are network fluids featuring spatial inhomogeneities across different length scales that reflect the contributions of distinct protein and peptide domains. The network-like inhomogeneous organization is characterized by a coexistence of liquid- and gas-like macromolecular densities that engenders bimodality of internal molecular dynamics. These insights suggest that condensates formed by multivalent proteins share features with network fluids formed by systems such as patchy or hairy colloids.

Molecular Bottlebrushes as Emerging Nanocarriers: Material Design and Biomedical Application

As a unique unimolecular nanoobject, molecular bottlebrushes (MBBs) have attracted great interest from researchers in nanocarriers attributed to their defined structure, size, and shape. MBBs with various architectures have been proposed and constructed with well-defined domains for loading "cargos", including core, shell, and periphery functional groups. Compared with nanomaterials based on self-assembly, MBBs have lots of advantages, including facile synthesis, flexible compositions, favorable stability, and tunable size and shape, that make them a promising nanoplatform for various applications. This paper summarizes the recent progress during the past decade, with a focus on developments within the last five years in the synthesis of MBBs with different architectures, and uses them as nanocarriers in drug delivery, biological imaging, and other emerging applications.

Biomolecular condensates form spatially inhomogeneous network fluids

The functions of biomolecular condensates are thought to be influenced by their material properties, and these will be determined by the internal organization of molecules within condensates. However, structural characterizations of condensates are challenging, and rarely reported. Here, we deploy a combination of small angle neutron scattering, fluorescence recovery after photobleaching, and coarse-grained molecular dynamics simulations to provide structural descriptions of model condensates that are formed by macromolecules from nucleolar granular components (GCs). We show that these minimal facsimiles of GCs form condensates that are network fluids featuring spatial inhomogeneities across different length scales that reflect the contributions of distinct protein and peptide domains. The network-like inhomogeneous organization is characterized by a coexistence of liquid- and gas-like macromolecular densities that engenders bimodality of internal molecular dynamics. These insights suggest that condensates formed by multivalent proteins share features with network fluids formed by systems such as patchy or hairy colloids.

Janus Composite Particles and Interfacial Catalysis Thereby

Janus composite particles (JPs) with distinct compartmentalization of varied components thus performances and anisotropic shape display a variety of properties and have demonstrated great potentials in diversify practical applications. Especially, the catalytic JPs are advantageous for multi-phase catalysis with much easier separation of products and recycling the catalysts. In the first section of this review, typical methods to synthesize the JPs with varied morphologies are briefly surveyed in the category of polymeric, inorganic and polymer/inorganic composite. In the main section, recent progresses of the JPs in emulsion interfacial catalysis are summarized covering organic synthesis, hydrogenation, dye degradation, and environmental chemistry. The review will end by calling more efforts toward precision synthesis of catalytic JPs at large scale to meet the stringent requirements in practical applications such as catalytic diagnosis and therapy by the functional JPs.

Non-spherical Polymeric Nanocarriers for Therapeutics: The Effect of Shape on Biological Systems and Drug Delivery Properties

This review aims to highlight the importance of particle shape in the design of polymeric nanocarriers for drug delivery systems, along with their size, surface chemistry, density, and rigidity. Current manufacturing methods used to obtain non-spherical polymeric nanocarriers such as filomicelles or nanoworms, nanorods and nanodisks, are firstly described. Then, their interactions with biological barriers are presented, including how shape affects nanoparticle clearance, their biodistribution and targeting. Finally, their drug delivery properties and their therapeutic efficacy, both in vitro and in vivo, are discussed and compared with the characteristics of their spherical counterparts.

Multi-tunable aggregation behaviors of thermo/pH-responsive toothbrush-like and jellyfish-like copolymers

Rational design of comb-like and linear conjugates comprising PNIPAM and PDMAEMA segments allows the construction of a multi-tunable hierarchical self-assembly platform and insight into the topology effect.

Precision Wormlike Nanoadjuvant Governs Potency of Vaccination

It remains unclear how the precise length of one-dimensional nanovehicles influences the characters of vaccination. Here, a unimolecular nanovehicle with tailored size and aspect ratio (AR) is applied to deliver CpG oligodeoxynucleotide, a Toll-like receptor (TLR) 9 agonist, as an adjuvant of recombinant hepatitis B virus surface antigen (rHBsAg), for treating chronic hepatitis B (CHB). Cationic nanovehicles with fixed width (ca. 45 nm) but varied length (46 nm-180 nm), AR from 1 to 4, are prepared through controlled polymerization and are loaded with CpG by electrostatic interaction. We reveal that the nanoadjuvant with AR = 2 shows the highest retention in proximal lymph nodes. Importantly, it is more easily internalized into antigen-presenting cells and accumulates in the late endosome, where TLR9 is located. Such a nanoadjuvant exhibits the strongest immune response with rHBsAg to clear the hepatitis B virus in the CHB mouse model, showing that the AR of nanovehicles governs the efficiency of vaccination.

Hierarchical self-assembly of miktoarm star copolymers with pathway complexity

The self-assembly of amphiphilic miktoarm star copolymers shows hierarchical pathway complexity from molecular building blocks to miktoarm stars to micellar nano-objects to complex hierarchical assemblies.

Synthesis and properties of pH-cleavable toothbrush-like copolymers comprising multi-reactive Y junctions and a linear or cyclic backbone

Y-junction-bearing toothbrush-like copolymers can exhibit unique physical properties and hierarchical (co)assembly behaviors dependent on topology, external stimuli and hydrolysis.

Synthesis, thermoresponsivity and multi-tunable hierarchical self-assembly of multi-responsive (AB)mC miktobrush-coil terpolymers

Stimuli-responsive miktobrush-coil terpolymers can exhibit unique physical properties and hierarchical self-assembly behaviors dependent on composition, concentration and external stimuli.

Guided Assembly of Well-Defined Hierarchical Nanoporous Polymers by Lewis Acid-Base Interactions

Three-dimensional hierarchical nanoporous polymers and carbon nanomaterials with well-defined superstructures are of great interest for various intelligent applications, whereas a facile and versatile approach to access those materials with a high surface area, stable well-defined morphology, and ordered pores still remains a significant challenge. Herein, we report a self-regulated Lewis acid-base interaction-mediated assembly strategy for the in situ synthesis of morphology-engineered hyper-cross-linked porous polymers and carbon materials. A series of functionalized aromatic compounds (FAC) is subjected to self-cross-linking via classic Friedel-Crafts chemistry to achieve stable porous polymers with a high surface area. Varying the monomer/catalyst combination had a dramatic effect on the acid-base interaction, facilitating the tailoring of the self-assembled morphologies from nanotubes to hollow nanospheres, and even nanosheets. A mechanistic study showed that the byproducts generated during cross-linking orchestrate the interactions between the catalyst (acid) and FAC (base) and simultaneously drive the self-assembly to yield specific morphologies. Based on the rigid hollow polymer framework and intrinsic hydroxyl functionality, the hyper-cross-linked hollow nanospheres were easily transformed to an acid-functionalized catalyst for efficient biodiesel production. Moreover, high-quality porous carbonaceous nanocounterparts such as carbon nanotubes, hollow carbon nanospheres, and carbon nanosheets could also be produced by direct pyrolysis of the corresponding polymer precursors. These findings may provide guidance for the facile design of morphology-controlled functionalized polymers and carbon nanomaterials for various applications.

Length effects of cylindrical polymer brushes on their in vitro and in vivo properties

Understanding the relationship between the morphology and biological performance of nanomaterials is very important for their biomedical applications. However, most of the published research focused on spherical systems. The biological properties of the anisotropic nanomaterials have not been studied enough. In this study, we synthesized three sets of cylindrical polymer brushes (CPBs) with different lengths (∼34, 60 and 119 nm) by taking advantage of controlled radical polymerization and Cu(i)-catalyzed alkyne-azide click chemistry. These CPBs had one-dimensional wormlike morphology, the same chemical structure and diameter, desirable water solubility, abundant amino groups and narrowly distributed lengths. These characteristics encouraged us to study length effects on their in vitro and in vivo properties. We demonstrated that longer CPBs had higher cellular uptake, lower tissue permeability, shorter blood circulation time, lower tumor accumulation and rapider body clearance than their shorter counterparts. This work might provide important guidance for the design of biomedical nanomaterials.

PU nanocomposites from bifunctional nanoparticles: impact of liquid interphase on mechanical properties

The Fe₃O₄@Poly(1,4-butanediol)/polyurethane nanocomposite is a highly interphase-dependable material with unique characteristics. Firstly, the nanoparticle's organic shell allows simple fabrication of very well dispersed nanocomposites and the incorporation of extremely high amounts of nanoparticles (NP) into the polymer matrix. Secondly, both chemical and physical aspects of the nanoparticles determine the material's mechanical behavior. The chemical functionality of the organic layer - free hydroxyl groups at the end of the tethered chains - ensures the material's stiffening through covalent bonds with the matrix, while being at molten state provides high flexibility and deformability yet maintaining mechanical resistance. As a result, nanocomposites at the low concentration region show increased elastic modulus and tensile strength and slight increase in total strain, while highly concentrated nanocomposites show reduction of elastic modulus and tensile strength and roughly double the total strain. The combination of the chemical and physical functionalities ensures high compatibility between nanoparticles and matrix and allows the production of highly concentrated - above 90% in weight - nanocomposites as a cohesive and flexible material, instead of a brittle wafer. This bifunctionality effect is unprecedented and the results open a wide range of new possibilities in the tailoring of functional nanomaterials for all sorts of applications in materials science.

Facile Fabrication of Size-Tunable Core/Shell Ferroelectric/Polymeric Nanoparticles with Tailorable Dielectric Properties via Organocatalyzed Atom Transfer Radical Polymerization Driven by Visible Light

An unconventional but facile approach to prepare size-tunable core/shell ferroelectric/polymeric nanoparticles with uniform distribution is achieved by metal-free atom transfer radical polymerization (ATRP) driven by visible light under ambient temperature based on novel hyperbranched aromatic polyamides (HBPA) as a functional matrix. Cubic BaTiO3/HBPA nanocomposites can be prepared by in-situ polycondensation process with precursors (barium hydroxide (Ba(OH)2) and titanium(IV) tetraisopropoxide (TTIP)) of ferroelectric BaTiO3 nanocrystals, because precursors can be selectively loaded into the domain containing the benzimidazole rings. At 1200 °C, the aromatic polyamide coating of cubic BaTiO3 nanoparticles are carbonized to form carbon layer in the inert environment, which prevents regular nanoparticles from gathering. In addition, cubic BaTiO3 nanoparticles are simultaneously transformed into tetragonal BaTiO3 nanocrystals after high temperature calcination (1200 °C). The outer carbon shell of tetragonal BaTiO3 nanoparticles is removed via 500 °C calcination in air. Bi-functional ligand can modify the surface of tetragonal BaTiO3 nanoparticles. PMMA polymeric chains are growing from the initiating sites of ferroelectric BaTiO3 nanocrystal surface via the metal-free ATRP technique to obtain core/shell ferroelectric BaTiO3/PMMA hybrid nanoparticles. Changing the molar ratio between benzimidazole ring units and precursors can tune the size of ferroelectric BaTiO3 nanoparticles in the process of polycondensation, and the thickness of polymeric shell can be tailored by changing the white LED irradiation time in the organocatalyzed ATRP process. The dielectric properties of core/shell BaTiO3/PMMA hybrid nanoparticles can be also tuned by adjusting the dimension of BaTiO3 core and the molecular weight of PMMA shell.

Temperature and solvent isotope dependent hierarchical self-assembly of a heterografted block copolymer

A heterografted block copolymer with doubly thermoresponsive grafts is designed to address the challenge in hierarchical self-assembly. Upon heating, solvent isotope dependent morphology transitions from spheres to nanobowls, vesicles, disks, nanosheets, nanoribbons and hyperbranched micelles can be achieved. The strategy provides a general platform to prepare diverse thermoreversible nano-objects.

Microfluidically mediated atom-transfer radical polymerization

Microfluidically mediated atom-transfer radical polymerization can be used to fabricate polymer brushes with a controlled gradient.

Bioinspired hierarchically hairy particles for robust superhydrophobic coatings via a droplet dynamic template method

Bioinspired hierarchically hairy particles are prepared by using initiator droplets as dynamic templates to achieve a robust superhydrophobic coating.

Switchable Oligo(glycidyl ether) Acrylate Bottlebrushes "Grafted-from" Polystyrene Surfaces: A Versatile Strategy toward Functional Cell Culture Substrates

Thermoresponsive brushes based on linear poly(glycidyl ether)s (PGEs) have already shown to be functional coatings for cell sheet fabrication. In here, we introduce a method to functionalize polystyrene (PS) tissue culture substrates with thermoresponsive coatings comprising glycidyl ether-based bottlebrush architectures. Utilizing the UV-induced "grafting-from" approach, thermoresponsive oligo(glycidyl ether) acrylate (OGEA) macromonomers were polymerized from PS substrates under bulk conditions. Applying ellipsometry, water contact angle (CA), and atomic force microscopy (AFM) measurements, we found that OGEA coatings exhibit a complex, gel-like structure comprising nanosized roughness and exhibit a temperature-dependent phase transition in water through the reversible hydration of OGEA bottlebrush side chains. To assess the utility of the coatings as functional substrates for cell sheet fabrication, human dermal fibroblast (HDF) adhesion and detachment were investigated. By adjusting the bottlebrush properties via the grafting procedure and coating structure, we were able to harvest confluent HDF sheets from functionalized PS substrates in a temperature-triggered, controlled manner. As the first report on surface-grafted bottlebrushes comprising thermoresponsive side chains with molecular weight of up to 1 kDa, this study demonstrates the potential of OGEA-based coatings for cell sheet fabrication.

Synthesis, self-assembly and drug release behaviors of reduction-labile multi-responsive block miktobrush quaterpolymers with linear and V-shaped grafts

Stimuli-tunable topological/morphological transitions and drug release properties based on novel disulfide-functionalized coil–comb–coil quaterpolymers were revealed.

Stepwise self-assembly of a block copolymer-platinum(ii) complex hybrid in solvents of variable quality: from worm-like micelles to free-standing sheets to vesicle-like nanostructures

The self-assembly process of formation of worm-like micelles of a block copolymer-platinum(ii) complex hybrid is investigated with respect to the influence of solvent quality. When the solvent quality is moderately weakened, unilamellar free-standing sheets are achieved, in which the worm-like micelles snap off to form star micelles together with a few short worms. Extremely worsened solvent quality leads to unilamellar vesicle-like nanostructures, onto which only star micelles emerged. With the intermediate solvent quality, the sheets coexist with the vesicle-like nanostructures. This is well correlated with mechanistic insights regarding the morphological transition from sheet- to vesicle-like nanoassemblies. In these aggregates, short worms and star micelles still hold their core-shell structures. Furthermore, these unconventional superstructures are well interrelated with their luminescence properties. This result challenges the conventional paradigm of the amphiphilic self-assembly of surfactants and block copolymers in selective solvents, where they form bilayered nanostructures and are required universally to be rearranged during the morphological transition from micelles to vesicles.

Multi-POSS cluster-wrapped polymers and their block copolymers with a PEO bottlebrush polymer: synthesis and aggregation

In this paper, we report an approach for synthesizing multicluster-wrapped polymers and their block copolymers with a bottlebrush polymer with controlled chain length and composition via living ring-opening metathesis polymerization.

C1 polymerization: a unique tool towards polyethylene-based complex macromolecular architectures

The recent developments in organoborane initiated C1 polymerization of ylides open unique horizons towards perfectly linear polymethylenes (equivalent to PE) and PE-based complex structures. This review summarizes research on conventional and newly discovered initiators/ylides, as well as initial efforts on C3 polymerization.

A design principle of polymers processable into 2D homeotropic order

How to orient polymers homeotropically in thin films has been a long-standing issue in polymer science because polymers intrinsically prefer to lie down. Here we provide a design principle for polymers that are processable into a 2D homeotropic order. The key to this achievement was a recognition that cylindrical polymers can be designed to possess oppositely directed local dipoles in their cross-section, which possibly force polymers to tightly connect bilaterally, affording a 2D rectangular assembly. With a physical assistance of the surface grooves on Teflon sheets that sandwich polymer samples, homeotropic ordering is likely nucleated and gradually propagates upon hot-pressing towards the interior of the film. Consequently, the 2D rectangular lattice is constructed such that its b axis (side chains) aligns along the surface grooves, while its c axis (polymer backbone) aligns homeotropically on a Teflon sheet. This finding paves the way to molecularly engineered 2D polymers with anomalous functions.

Going beyond the classical amphiphilicity paradigm: the self-assembly of completely hydrophobic polymers into free-standing sheets and hollow nanostructures in solvents of variable quality

Self-assembly is well-known to occur in amphiphiles, and the totally hydrophobic ones are never reported to self-assemble. In this work we report for the first time that the latter can self-assemble into free-standing sheets and hollow spheres in toluene/methanol mixed solvents by modulating the solvent quality. The homopolymers studied in this work are polystyrene (PS), polyphenylacetylene (PPA), and poly(3-hexyl thiophene) (P3HT), representing polymers with different rigidity. All the three form a homogenous solution in toluene, but self-assembly occurs in the toluene/methanol mixed solvents. Micrometer sized free-standing sheets were formed for PS, PPA, and P3HT at methanol volume fractions being 43%, 50%, and 67%, respectively, and hollow spheres were observed for PPA at higher methanol fractions of 75 and 90%. Under the latter solvent conditions, PS forms solid spheres, yet ill-defined aggregates and free-standing sheets coexist in the case of P3HT. This non-solvent induced self-assembly was explained by a delicate balance of two "opposing forces": van der Waals attractive and entropic repulsive forces generated between the segments of these homopolymers within a single chain, between two chains, and among more chains in the solvents of worsened quality.

Highly grafted polystyrene/polyvinylpyridine polymer gold nanoparticles in a good solvent: effects of chain length and composition

In this work, the structural features of spherical gold nanoparticles (NPs) decorated with highly grafted poly(styrene) (PS), poly(vinylpyridine) (PVP) and PS-PVP diblock copolymer brushes immersed in a good solvent are investigated by means of Dissipative Particle Dynamics (DPD) simulations as a function of grafted chain length and of homopolymer and copolymer chain composition. For NPs grafted either by PS or PVP homopolymer brushes (selected as a proof of concept), good agreement between the Daoud-Cotton theory, experimental evidence, and our DPD simulations is observed in the scaling behavior of single chain properties, especially for longer grafted chains, and in brush thickness prediction. On the other hand, for grafted chain lengths comparable to NP dimensions parabolic-like profiles of the end-monomer distributions are obtained. Furthermore, a region of high concentration of polymer segments is observed in the monomer density distribution for long homopolymers. In the case of copolymer-decorated NPs, the repulsion between PS and PVP blocks is found to substantially influence the radius of gyration and the shape of the end-monomer distribution of the relevant polymer shell. Moreover, for diblock chains, the un-swollen region is observed to be thinner (and, correspondingly, the swollen layer thicker) than that of a NP modified with a homopolymer of the same length. Finally, the lateral segregation of PS and PVP blocks is evidenced by our calculations and a detailed analysis of the corona behavior is reported, thus revealing the key parameters in controlling the surface properties and the response of diblock copolymer modified nanoparticles.

Structural properties of polymer-brush-grafted gold nanoparticles at the oil-water interface: insights from coarse-grained simulations

In this work, the structural properties of amphiphilic polymer-brush-grafted gold nanoparticles (AuNPs) at the oil-water interface were investigated by coarse-grained simulations. The effects of grafting architecture (diblock, mixed and Janus brush-grafted AuNPs) and hydrophilicity of polymer brushes are discussed. Simulation results indicate that functionalized AuNPs present abundant morphologies including typical core-shell, Janus-type, jellyfish-like, etc., in a water or oil-water solvent environment. It is found that hydrophobic/weak hydrophilic polymer-brush-grafted AuNPs have better phase transfer performance, especially for AuNPs modified with hydrophobic chains as outer blocks and weak hydrophilic chains as inner blocks. This kind of AuNP can cross the interface region and move into the oil phase completely. For hydrophobic/strong hydrophilic polymer-brush-grafted AuNPs, they are trapped in the interface region instead of moving into any phase. The mechanism of phase transfer is ascribed to the flexibility and mobility of outer blocks. Besides, we study the desorption energy by PMF analysis. The results demonstrate that Janus brush-grafted AuNPs show the highest interfacial stability and activity, which can be further strengthened by increasing the hydrophilicity of grafted polymer brushes. This work will promote the industrial applications of polymer-brush-grafted NPs such as phase transfer catalysis and Pickering emulsion catalysis.

The use of azide-alkyne click chemistry in recent syntheses and applications of polytriazole-based nanostructured polymers

The rapid development of efficient organic click coupling reactions has significantly facilitated the construction of synthetic polymers with sophisticated branched nanostructures. This Feature Article summarizes the recent progress in the application of efficient copper-catalyzed and copper-free azide-alkyne cycloaddition (CuAAC and CuFAAC) reactions in the syntheses of dendrimers, hyperbranched polymers, star polymers, graft polymers, molecular brushes, and cyclic graft polymers. Literature reports on the interesting properties and functions of these polytriazole-based nanostructured polymers are also discussed to illustrate their potential applications as self-healing polymers, adhesives, polymer catalysts, opto-electronic polymer materials and polymer carriers for drug and imaging molecules.

Controlling the Nanoscale Rotational Behaviors of Nanoparticles on the Cell Membranes: A Computational Model

Nanoparticles prefer to bind to a membrane with a surface coated by short or rigid ligands, as shown by computer simulations. To realize such a preferred configuration, the nanoparticle can spontaneously spin itself on the membrane surface, no matter what its initial orientation is.