Spontaneous Formation of Polymeric Nanoribbons in Water Driven by π-π Interactions

A simple method was developed to produce polymeric nanoribbons and other nanostructures in water. This approach incorporates a perylene diimide (PDI) functionalized by triethylene glycol (TEG) as a hydrophobic supramolecular structure directing unit (SSDU) into the core of hydrophilic poly(N,N-dimethylacrylamide) (PDMAc) chains using RAFT polymerization. All PDI-functional polymers dissolved spontaneously in water, forming different nanostructures depending on the degree of polymerization (DPn): nanoribbons and nanocylinders for DPn=14 and 22, and spheres for DPn>50 as determined by cryo-TEM and SAXS analyses. UV/Vis absorption spectroscopy was used to monitor the evolution of the PDI absorption signal upon dissolution. In solid form, all polymers show a H-aggregate absorption signature, but upon dissolution in water, the shortest DPn forming nanoribbons evolved to show HJ-aggregate absorption signals. Over time, the J-aggregate band increased in intensity, while cryo-TEM monitoring evidenced an increase in the nanoribbon's width. Heating the nanoribbons above 60 °C, triggered a morphological transition from nanoribbons to nanocylinders, due to the disappearance of J-aggregates, while H-aggregates were maintained. The study shows that the TEG-PDI is a powerful SSDU to promote 2D or 1D self-assembly of polymers depending on DPn through simple dissolution in water.

Hierarchical assembly of thermoresponsive helical dendronized poly(phenylacetylene)s through photo-crosslinking of the thermal aggregates

Supramolecular assembly of helical homopolymers to form stable chiral entities in water is highly valuable for creating chiral nanostructures and fabricating chiral biomaterials. Here we report on thermally induced supramolecular assembly of helical dendronized poly(phenylacetylene)s (PPAs) in aqueous solutions, and their in-situ photo-crosslinking at elevated temperatures to afford crosslinked nano-assemblies with hierarchical structures and stabilized helicities. These helical dendronized homopolymers carry cinnamate-cored dendritic oligoethylene glycol (OEG) pendants, which exhibit characteristic thermoresponsive behavior. Their thermal aggregation confers hexagonal packing of the polymer chains, and simultaneously resulting in enhancement of their chiralities. Assisted by radial amphiphilicity and worm-like molecular geometry, these dendronized PPAs form supramolecular twisted fibers, spheroid particles or toroids via thermal aggregation. Through UV photoirradiation above their cloud points (Tcps), cycloaddition of cinnamate moieties from the dendritic pendants promotes intermolecular crosslinking of dendronized PPA chains within the thermal aggregates, and simultaneously, the dynamic morphologies and supramolecular chirality from the dendronized PPAs through thermally induced aggregation can be fixed. In addition, photo-crosslinking can be occurred solely within individual aggregates due to the protection of densely packed dendritic OEGs. Therefore, various crosslinked assemblies from the dendronized homopolymers with tailorable morphologies and stabilized chirality are fabricated by tuning their thermally induced dynamic aggregations followed by in-situ photo-crosslinking. We believe that this work paves a convenient route to fabricate chiral assemblies with stabilized morphologies and fixed chiralities from dynamic helical homopolymers through intermolecular crosslinking, which can be promising for various chiral applications.

Self-assembly of amphiphilic homopolymers grafted onto spherical nanoparticles: complete embedded minimal surfaces and a machine learning algorithm for their recognition

By means of computer modelling, the self-assembly of amphiphilic A-graft-B macromolecules, grafted onto a spherical nanoparticle, is studied. In a solvent, that is poor for side pendants, the macromolecules self-assemble into thin membrane-like ABBA bilayers deviated from spherical nanoparticles. The bilayers form morphological structures that depend on the grafting density and macromolecular polymerization degree and can be referred to as the classical family of complete embedded minimal surfaces. The plane disk, catenoid, helicoid, Costa and Enneper surfaces as well as "double" helicoid and "complex minimal surface" were identified, and the fields of their stability were defined. The surfaces can be grouped according to the sequences of conformal transformations that transform them into each other. These surfaces arise in different experiments situationally. Results are summarized in a pie diagram constructed using a machine learning algorithm based on matching grafting points with a specially created planar graphic image.

Thiophene End-Functionalized Oligo-(D,L-Lactide) as a New Electroactive Macromonomer for the "Hairy-Rod" Type Conjugated Polymers Synthesis

The development of the modern society imposes a fast-growing demand for new advanced functional polymer materials. To this aim, one of the most plausible current methodologies is the end-group functionalization of existing conventional polymers. If the end functional group is able to polymerize, this method enables the synthesis of a molecularly complex, grafted architecture that opens the access to a wider range of material properties, as well as tailoring the special functions required for certain applications. In this context, the present paper reports on α-thienyl-ω-hydroxyl-end-groups functionalized oligo-(D,L-lactide) (Th-PDLLA), which was designed to combine the polymerizability and photophysical properties of thiophene with the biocompatibility and biodegradability of poly-(D,L-lactide). Th-PDLLA was synthesized using the path of "functional initiator" in the ring-opening polymerization (ROP) of (D,L)-lactide, assisted by stannous 2-ethyl hexanoate (Sn(oct)₂). The results of NMR and FT-IR spectroscopic methods confirmed the Th-PDLLA's expected structure, while the oligomeric nature of Th-PDLLA, as resulting from the calculations based on ¹H-NMR data, is supported by the findings from gel permeation chromatography (GPC) and by the results of the thermal analyses. The behavior of Th-PDLLA in different organic solvents, evaluated by UV-vis and fluorescence spectroscopy, but also by dynamic light scattering (DLS), suggested the presence of colloidal supramolecular structures, underlining the nature of the macromonomer Th-PDLLA as an "shape amphiphile". To test its functionality, the ability of Th-PDLLA to work as a building block for the synthesis of molecular composites was demonstrated by photoinduced oxidative homopolymerization in the presence of diphenyliodonium salt (DPI). The occurrence of a polymerization process, with the formation of a thiophene-conjugated oligomeric main chain grafted with oligomeric PDLLA, was proven, in addition to the visual changes, by the results of GPC, ¹H-NMR, FT-IR, UV-vis and fluorescence measurements.

Flexible Azo-Polyimide-Based Smart Surface with Photoregulatable Surface Micropatterns: Toward Rewritable Information Storage and Wrinkle-Free Device Fabrication

Stimulus-sensitive materials are of great fascination in surface and interface science owing to their dynamically tunable surface properties and/or morphologies. Herein, we have synthesized an azobenzene-containing polyimide (azo-PI) with enhanced chain flexibility for the fabrication of photosensitive surface patterns on a film/substrate wrinkle system or wrinkle-free devices. The phototriggered cis-trans isomerization kinetics of azobenzene groups in the novel azo-PI with various chain structures were systematically investigated. On the basis of the characteristics of stress relaxation that azobenzene reversible cis-trans isomerization induces in the wrinkled azo-PI film/substrate system, a variety of rewritable visual surface patterns with high resolution and a long legibility time (>30 days) could be easily constructed via visible-light irradiation, enabling the wrinkled azo-PI surfaces to be used as rewritable information storage media. Meanwhile, because of the visible-light irradiation strategy, these photoresponsive surfaces could find potential application in the fabrication of wrinkle-free flexible devices. This study not only sheds light on the influence of the azo-polymer chain structure on its photoresponsive behavior but also provides a versatile strategy for realizing tailor-made smart surface patterns on multilayer functional devices.

Hedgehog, Chamomile, and Multipetal Polymeric Structures on the Nanoparticle Surface: Computer Modelling

A single spherical nanoparticle coated with a densely grafted layer of an amphiphilic homopolymer with identical A-graft-B monomer units was studied by means of coarse-grained molecular dynamics. In solvent, selectively poor for mainchain and good for pendant groups; the grafted macromolecules self-assemble into different structures to form a complex pattern on the nanoparticle surface. We distinguish hedgehog, multipetalar, chamomile, and densely structured shells and outline the area of their stability using visual analysis and calculate aggregation numbers and specially introduced order parameters, including the branching coefficient and relative orientation of monomer units. For the first time, the branching effect of splitting aggregates along with the distance to the grafting surface and preferred orientation of the monomer units with rearrangements of the dense compacted shell was described. The results explain the experimental data, are consistent with the analytical theory, and are the basis for the design of stimulus-sensitive matrix-free composite materials.

Hedgehog, Chamomile and Multipetal Polymeric Structures on the Nanoparticle Surface: Theoretical Insights

An analytical theory describing the variety of different morphological structures that spontaneously self-assemble in layers of amphiphilic homopolymers tightly grafted to spherical nanoparticle is proposed. For this purpose, the following structures were identified and outlined: hedgehogs, in which macromolecules are combined into cylindrical aggregates; chamomile, when cylindrical aggregates are connected by their ends into loops; multipetal structure with macromolecules self-assembling into thin lamellae; and unstructured, swollen and uniformly compacted shells. The results are presented in the form of state diagrams and serve as a basis for the directional design of the surface pattern by varying system parameters (particle radius, grafting density and degree of polymerization) and solvent properties (quality and selectivity).

An Overview of the Supramolecular Systems for Gene and Drug Delivery in Tissue Regeneration

Tissue regeneration is a prominent area of research, developing biomaterials aimed to be tunable, mechanistic scaffolds that mimic the physiological environment of the tissue. These biomaterials are projected to effectively possess similar chemical and biological properties, while at the same time are required to be safely and quickly degradable in the body once the desired restoration is achieved. Supramolecular systems composed of reversible, non-covalently connected, self-assembly units that respond to biological stimuli and signal cells have efficiently been developed as preferred biomaterials. Their biocompatibility and the ability to engineer the functionality have led to promising results in regenerative therapy. This review was intended to illuminate those who wish to envisage the niche translational research in regenerative therapy by summarizing the various explored types, chemistry, mechanisms, stimuli receptivity, and other advancements of supramolecular systems.

Conductive Supramolecular Polymer Nanocomposites with Tunable Properties to Manipulate Cell Growth and Functions

Synthetic bioactive nanocomposites show great promise in biomedicine for use in tissue growth, wound healing and the potential for bioengineered skin substitutes. Hydrogen-bonded supramolecular polymers (3A-PCL) can be combined with graphite crystals to form graphite/3A-PCL composites with tunable physical properties. When used as a bioactive substrate for cell culture, graphite/3A-PCL composites have an extremely low cytotoxic activity on normal cells and a high structural stability in a medium with red blood cells. A series of in vitro studies demonstrated that the resulting composite substrates can efficiently interact with cell surfaces to promote the adhesion, migration, and proliferation of adherent cells, as well as rapid wound healing ability at the damaged cellular surface. Importantly, placing these substrates under an indirect current electric field at only 0.1 V leads to a marked acceleration in cell growth, a significant increase in total cell numbers, and a remarkable alteration in cell morphology. These results reveal a newly created system with great potential to provide an efficient route for the development of multifunctional bioactive substrates with unique electro-responsiveness to manipulate cell growth and functions.

Fibril Assembly and Gelation of Macromolecules with Amphiphilic Repeating Units

This paper reports the self-assembly of the fibrillar network in a concentrated solution of macromolecules with an amphiphilic structure of repeating units. The investigation of amphiphilic homopolymers and alternating copolymers with the linear and cyclic topologies, the solution with different polymer concentrations and solvent qualities, allows us to conclude that the ability to form a fibrillar gel with branched fibrils and regular subchain thickness is inherent for macromolecules with the solvophobic backbone and solvophilic pendants. The elements of the gel structure, such as the mesh size and fibrillar thickness, the number of cross-links, and their functionality, can be tuned and customized according to the requirements of their application. The results could be helpful for the directed design of the synthetic analogue of the relevant extracellular matrix, in tissue engineering, for fibrotic disease treatment and cell encapsulation.

Recent advances in the fabrication and bio-medical applications of self-assembled dipeptide nanostructures

Molecular self-assembly is a widespread natural phenomenon and has inspired several researchers to synthesize a compendium of nano/microstructures with widespread applications. Biomolecules like proteins, peptides and lipids are used as building blocks to fabricate various nanomaterials. Supramolecular peptide self-assembly continue to play a significant role in forming diverse nanostructures with numerous biomedical applications; however, dipeptides offer distinctive supremacy in their ability to self-assemble and produce a variety of nanostructures. Though several reviews have articulated the progress in the field of longer peptides or polymers and their self-assembling behavior, there is a paucity of reviews or literature covering the emerging field of dipeptide-based nanostructures. In this review, our goal is to present the recent advancements in dipeptide-based nanostructures with their potential applications.

Self-assembly behavior of oligo(ethylene glycol) substituted polycaprolactone homopolymers

In this work, non-ionic amphiphilic oligo(ethylene glycol)-substituted polycaprolactone homopolymers readily self-assembled to form micelles in a polar environment, which allowed the encapsulation of a hydrophobic molecule.

Perylene diimide-tagged N-heterocyclic carbene-stabilized gold nanoparticles: How much ligand desorbs from surface in presence of thiols?

N-Heterocyclic carbenes (NHCs) have recently emerged as viable alternatives to commonly used thiols to stabilize a variety of metal surfaces and nanoparticles. In this context, thanks to their biocompatibility and novel optical properties, NHC-stabilized gold nanoparticles (AuNPs) have been extensively studied. It has been shown that such materials exhibit improved stabilities in acidic and basic solutions, high temperatures, electrolyte solutions, cell culture media, and to some extent to nucleophilic thiols. Despite intense efforts, instability of NHC-functionalized AuNPs to thiols has been an ongoing challenge. In order to circumvent this problem, quantification of NHC desorption from nanoparticle surface by the invading thiols would constitute a necessary first step. To do this, we have first developed water-soluble azide decorated NHC-stabilized "clickable" AuNPs. Optically active perylene diimide (PDI)-tagged AuNP hybrids are then obtained by means of Cu-catalyzed alkyne-azide cycloaddition between these AuNPs and an alkyne-decorated PDI derivative. Investigation of photophysical properties of these AuNP/PDI hybrids revealed that the fluorescence of PDI molecules is effectively quenched by AuNPs in aqueous solution. The extent of NHC desorption from AuNP surface in presence of glutathione (4 mM), as a biologically relevant thiol, is then quantified by means of fluorescence emission restoration of PDI molecules upon detachment from AuNP surfaces. Our results demonstrate that while ∼20% of surface NHCs are displaced by glutathione within the first 24 h of their exposure to the thiol, ligand desorption reaches ∼45% after one week. We believe that these findings will provide more insight on true stability of NHC-stabilized materials.

Polyselenonium salts: synthesis through sequential selenium-epoxy 'click' chemistry and Se-alkylation

With the help of amphiphilic homopolymers, this work explores three new avenues in polymer chemistry: (i) the 'click' nature of the selenium-epoxy reaction, (ii) alkylation of the seleno-ethers as a means to prepare cationic polyelectrolytes, and (iii) the antibacterial activity of polyselenonium salts.

Dual Biochemically Breakable Drug Carriers from Programmed Telechelic Homopolymers

Well-defined hydrophilic telechelic dibromo poly(triethylene glycol monomethyl ether acrylate)s were prepared by single-electron transfer living radical polymerization employing a hydrophobic difunctional initiator containing acetal and disulfide linkages. Although the resulting homopolymers have low hydrophobic contents (<8.5 wt % of the entire structure), they are able to self-assemble in water into nanoscale micellelike particles via chain folding. Acetal and disulfide linkages were demonstrated to be "keystone" units for their dual stimuli-responsive behavior under biochemically relevant conditions. Their site-selective middle-chain cleavage under both acidic pH and reductive conditions splits the homopolymer into two equal-sized fragments and results in the breakdown of the nanoassemblies. The drug loading/delivery potential of these nanoparticles was investigated using curcumine combining in vitro drug release, cytotoxicity, and cellular uptake studies with human cancer cell lines (HT-29 and HeLa). Importantly, this strategy may be extended to prepare innovative nanoplatforms based on hydrophilic homopolymers or random copolymers for intelligent drug delivery.

Malleable Hydrogel Embedded with Micellar Cargo-Expellers as a Prompt Transdermal Patch

Although hydrogels are promising transdermal patches, they face spatiotemporal problems related to controlled drug release. From the "spatio" perspective, hydrogels are not malleable, therefore they do not fully contact curved skin, such as that found on the nose and fingers. From the "temporal" perspective, the internal network of a hydrogel retards cargo release. Herein, a malleable and rapid-cargo-releasing poly(vinyl alcohol)-borax hydrogel that embeds freely mobile poly(hydroxyethyl methacrylate) (PHEMA) micelles is prepared. The in situ polymerization of PHEMA within the matrix produces large compound micelle particles that are not bound by the matrix. The micelles act as expellers by sweeping out cargo upon exposure to wet conditions through a concentration gradient. The hydrogel embedded with the micellar cargo-expellers delivers a 25-fold larger 3-min release quantity of Nile Red (a model cargo) than the control hydrogel. The particles absorb mechanical shocks and the dynamic borate-diol bonds engender the hydrogel with self-healing properties, which results in a hydrogel that tightly contacts highly curved skin. Moreover, the hydrogel shows no toxicity in in vivo and skin irritation tests. This malleable hydrogel will inspire novel prompt skin-patch systems for pharmaceutical and cosmetics purposes.

Assembly of Short-Chain Amphiphilic Homopolymers into Well-Defined Particles

Linear homopolymers of norbornene (NBE) derivatives equipped with short-chain alcohol pendant groups were prepared by ring-opening metathesis polymerization (ROMP) and subsequently assembled into well-defined structures in alcohol solvents. The ratios of hydrophobic carbons and hydrophilic alcohol groups at the repeating monomeric unit in these short-chain amphiphilic polymers were found to play an important role in determining the size and distribution of the final globular structures. Unlike the assembly of other linear homo- and copolymers possessing long-chain amphiphilicity, NBE-based linear polymers were readily transformed into spherical particles with a layered conformation, whose sizes range from a few hundred nanometers to micrometers with narrow distributions, simply by controlling the concentration and molecular weights of the linear homopolymers without using any surfactants. In addition, the degree of the intermolecular forces with solvents (e.g., solvation) possessing different surface tensions and polarities highly affected the final diameter and distribution of the polymer particles, implying the importance of the selection of a proper solvent to regulate their structural features. As such, understanding the assembly of these types of short-chain homopolymers into uniform particles can allow for regulating the transformation of diverse linear amphiphilic polymers into precisely controlled structures for various applications.

Unusual Structures of Interpolyelectrolyte Complexes: Vesicles and Perforated Vesicles

By means of computer simulation and analytical theory, we first demonstrated that the interpolyelectrolyte complexes in dilute solution can spontaneously form hollow spherical particles with thin continuous shells (vesicles) or with porous shells (perforated vesicles) if the polyions forming the complex differ in their affinity for the solvent. The solvent was considered good for the nonionic groups of one macroion and its quality was varied for the nonionic groups of the other macroion. It was found that if the electrostatic interactions are weak compared to the attraction induced by the hydrophobicity of the monomer units, the complex in poor solvent tends to form "dense core-loose shell" structures of different shapes. The strong electrostatic interactions favor the formation of the layered, the hollow, and the filled structured morphologies with the strongly segregated macroions. Vesicles with perforated walls were distinguished as the intermediate between the vesicular and the structured solid morphologies. The order parameter based on the spherical harmonics expansion was introduced to calculate the pore distribution in the perforated vesicles depending on the solvent quality. The conditions of the core-shell and hollow vesicular-like morphologies formation were determined theoretically via the calculations of their free energy. The results of the simulation and theoretical approaches are in good agreement.

Thermoresponsive Poly(ß-hydroxyl amine)s: Synthesis of a New Stimuli Responsive Amphiphilic Homopolymer Family through Amine-Epoxy 'Click' Polymerization

A new synthesis of amphiphilic homopolymers is described. In this synthesis, commercially available and inexpensive primary amines and di-epoxide molecules are utilized as AA- and BB-types of monomers in an amine-epoxy ‘click’ polymerization process. This process can be carried out in water and at room temperature. It does not require a catalyst or inert conditions and forms no byproducts. Therefore, the polymer synthesis can be carried out in open-air and bench-top conditions and a post-synthesis purification step is not required. The modularity of the synthesis, on the other hand, allows for facile structural modulation and tuning of the thermally triggered aggregation process in the temperature range of 7 to 91 °C. Finally, the underlying principles can be translated from linear architectures to polymer networks (hydrogels).

Orthogonal functionalization of alternating polyesters: selective patterning of (AB) n sequences

Precision functionalized polyesters, with defined monomer sequences, are prepared using an orthogonal post-polymerization strategy. These polyesters can be synthesized from bio-derived monomers and are targeted to degrade, by hydrolysis processes, to biocompatible diols and diacids; the new structures enabled by this methodology would be very difficult to synthesize by alternative strategies. A series of 9 well-defined highly alternating AB-type copolyesters, containing terminal and internal alkene functionalities, are synthesized in high conversions by the ring-opening copolymerization of epoxides and cyclic anhydrides. Firstly, the polyesters are functionalized by a selective hydroboration-oxidation reaction to exclusively and quantitatively hydroxylate the terminal alkenes, leaving the alternating internal alkenes unreacted. Subsequently, the internal alkenes are quantitatively transformed into carboxylic acid, amine, alkyl and oligo-ether groups, by thiol-ene reactions, to afford AB polyesters with alternating functional substituents. Three polyesters showing alternating hydrophilic/hydrophobic side-chain sequences self-assemble in solution to form nanostructures that are characterized using transmission electron microscopy and dynamic light scattering methods (R h = 100-300 nm). The selective patterning methodology provides facile, efficient and orthogonal functionalization of alternating polyesters with near-quantitative (AB) n repeat sequences. The method is expected to be generalizable to other polymers and provides access to completely new AB alternating structures with the potential to exploit ligand multi-valency and adjacency to enhance properties.

Lamellae and parking garage structures in amphiphilic homopolymer brushes with different grafting densities

This article is devoted to the study of polymer layers of amphiphilic homopolymers tightly grafted to a flat surface at the nodes of a square lattice. It was shown that, due to the amphiphilicity of monomer units containing groups with different affinities, in a selective solvent, such layers form lamellae perpendicular to the grafting surface. The period of the lamellae depends on the grafting density and the quality of the solvent. The results are presented in the form of a state diagram in variables "the energy of attraction of the side groups" (effective solvent quality) and "the distance between the grafting points" (inversely proportional to the square root of the grafting density). The diagram contains the regions of stability of lamellae with significantly different periods, and a transitional area with a parking garage structure. The diagram is constructed by calculating the layer-by-layer structure factor and the angle of inclination of the lamellae in the slice. The calculations were performed for different sizes of the simulation box, and the most commensurate size was determined by a special procedure for each grafting density. The results may be interesting not only to specialists in polymer science but also to all those who investigate the processes of self-organization and rearrangement in dense systems.

pH-Responsive Micellar Nanoassemblies from Water-Soluble Telechelic Homopolymers Endcoding Acid-Labile Middle-Chain Groups in Their Hydrophobic Sequence-Defined Initiator Residue

A middle-chain cleavable telechelic poly(oligoethylene glycol) methyl ether acrylate) (MCCT-POEGA-Br) was synthesized by single-electron transfer living radical polymerization (SET-LRP) initiated from an acetal-containing hydrophobic sequence-defined difunctional initiator. In aqueous medium, above a certain concentration, this hydrophilic homopolymer self-assembled into nanogel-like large micelles that exhibit an encapsulating capacity for both hydrophobic and hydrophilic cargo. The sequence-defined cleavage pattern encoded in the initiator residue allowed precise middle-chain cleavage, leading to quantitative disassembly of the corresponding nanoobjects. Dye release studies performed in an acidic environment demonstrated the potential of this new design concept in the preparation of pH-responsive nanocarriers. In addition, fluorescently tagged nanoassemblies could also be obtained via the thio-bromo "click" modification of MCCT-POEGA-Br prior to self-assembly. This strategy may provide facile access to a diversity of multistimuli-responsive nanocarriers based on commercially available hydrophilic monomers and sequence-defined difunctional initiators synthesized by this simple design strategy.

Nanobowls with controlled openings and interior holes driven by the synergy of hydrogen bonding and π-π interaction

Asymmetric nanoparticles such as nanobowls have promising potential in many fields due to their interior asymmetric cavities and specific concave structure. However, the fabrication of nanobowls and control over their openings and interior holes are still challenging. Herein we demonstrate a versatile strategy for preparing nanobowls with precisely controlled openings and interior holes based on the synergy of hydrogen bonding and π-π interaction of homopolymers. We designed and synthesized a series of amphiphilic homopolymers with an amino alcohol moiety and azobenzene pendant (poly(2-hydroxy-3-((4-(phenyldiazenyl)phenyl)amino)propyl methacrylate) (PHAzoMA)). The homopolymers can self-assemble into nanobowls due to the heterogeneous shrinkage of the preformed spheres. Upon increasing the molecular weight of the homopolymers from 10.1 to 76.9 kg mol-1, the sizes of the openings of nanobowls can be precisely controlled from 242 to 423 nm with a linear relationship as a result of the enhancement of the hydrogen bonding and π-π interaction between homopolymer chains. Overall, we have prepared finely controlled nanobowls by the synergy of non-covalent interactions such as hydrogen bonding and π-π interaction of polymers, which opens a new avenue for the preparation of asymmetric nanoparticles.

Sequential Nucleophilic "Click" Reactions for Functional Amphiphilic Homopolymers

Amphiphilic homopolymers with high densities of functional groups are synthetically challenging. Thiol-yne nucleophilic click reactions have been investigated to introduce multiple functional groups in polymers with high density. An electron deficient alkyne group bearing methacrylate monomer was polymerized using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Subsequently, the electron deficient alkyne group on polymer side chain was readily reacted with a thiol reagent using triethylamine (TEA) as the organocatalyst. This reaction was found to be very efficient under mild conditions. The resultant homopolymer bearing thiol vinyl ether functional groups could perform a second thiol addition with a stronger base, such as triazabicyclodecene (TBD), to prepare multifunctional homopolymers. This stepwise addition process was monitored by 1H NMR as well as gel permeation chromatography. The fidelity of this method was demonstrated by attaching four different functionalities, including both hydrophobic and hydrophilic moieties. Furthermore, these dual functionalized polymers bearing dithio-acetal groups are sensitive to reactive oxygen species (ROS), which compromises the host-guest properties of the assembly in response to this stimulus. The ROS responsive polymers reported here may have potential use in therapeutic delivery.

An amphiphilic metallaclip with enhanced fluorescence emission in water: synthesis and controllable self-assembly into multi-dimensional micro-structures

A new amphiphilic organoplatinum(ii) metallaclip with enhanced fluorescence emission in water and multi-dimensional well-defined micro-structures in CH₃OH–H₂O mixture was designed and fabricated successfully.

Synthesis of Multifunctional Homopolymers through Using Thiazolidine Chemistry and Post-Polymerization Modification

Multifunctional homopolymers, defined here as polymers that contain multiple reactive functional groups per repeat unit, are versatile scaffolds for preparing complex macromolecules via post-polymerization modification. However, there are limited methods for preparing multifunctional homopolymers that contain more than one nucleophilic site per repeat unit. Herein, a strategy to synthesize a multifunctional homopolymer using thiazolidine chemistry is demonstrated. Controlled radical polymerization of a thiazolidine-containing acrylamido monomer allows for the synthesis of a polymer with pendent latent nucleophiles. Ring-opening of the thiazolidine affords a homopolymer with two side-chain reactive sites, an amine and a thiol. One-pot functionalization via disulfide formation and acyl substitution is performed to introduce two distinct groups in each repeat unit.

Synthesis of multifunctional homopolymers via sequential post-polymerization reactions

This mini-review highlights recent developments in the synthesis of multifunctional homopolymers, i.e., homopolymers with multiple pendent functionalities.

Precise surface structure of nanofibres with nearly atomic-level precision

The solenoidal wrapping of a DNA chain around a nanofibre transcribes the precise sequence structure of the DNA onto the nanofibre surface.

Self-assembly of random co-polymers for selective binding and detection of peptides

Amphiphilic random co-polymers, which form stable reverse micelle-type assemblies, have been designed and synthesized. We demonstrate that the reverse micelles, formed by these co-polymers are capable of selectively binding peptides through electrostatic interactions, indicating that these random polymers can self-organize into functionally selective materials. Moreover, these random co-polymers also enable the ordered co-crystallization of matrix and extracted guest molecules, giving rise to substantial signal enhancements during MALDI-MS detection. Together, these observations represent an excellent example of how random polymers can self-assemble into ordered, functional materials.

Programmable Nanoassemblies from Non-Assembling Homopolymers Using Ad Hoc Electrostatic Interactions

Robust nanostructures were obtained from polymers that otherwise do not assemble by using a novel approach based on electrostatic self-assembly. The essence of this strategy involves the use of divalent counterions to temporarily perturb the packing features of the ionic groups in a homopolymer, which results in a vesicle-like structure that is captured in situ through a simple crosslinking reaction. The fidelity of the assembly has been tested for molecular transport across the nanomembrane, both for the molecules encapsulated in the lumen and for those trapped in the membrane itself. The membranes are addressable for robust multifunctionalization of their surfaces and for tunable transmembrane molecular transport.