Supramolecular Star Polymers Research Articles

Gas-Controlled Self-Assembly of Metallacycle-Cored Supramolecular Star Polymer with Tunable Antibacterial Activity.

Herein, a three-armed amphiphilic metallacycle-cored star supramolecular polymer (Por-MOM-PDMAEMA) has been designed and synthesized via highly efficient post-assembly polymerization. This star polymer is further self-assembled into nanoparticles of different sizes depending upon the experimental conditions. The gas-controlled morphology transformation and tunable antibacterial activities of Por-MOM-PDMAEMAis systematically investigated and compared with metallacycle (MOM). The superior antibacterial activity of Por-MOM-PDMAEMA against multidrug-resistant P. aeruginosa implies that the presence of photodynamic photosensitizer (Por) and cationic polymer chain will significantly enhance antibactericidal activity, which is mainly attributed to the synergistic effect of photosensitizer and polymer chain linked in one metallacycle core. By leveraging the unique properties of metallacycle and their dynamic response to gaseous stimuli, the antibacterial properties of the Por-MOM-PDMAEMA can be finely tuned in response to gas triggers.

Supramolecular Synthesis of Star Polymers.

Supramolecular polymers, in which monomers are assembled via intermolecular interactions, have been extensively studied. The fusion of supramolecular polymers with conventional polymers has attracted the attention of many researchers. In this review article, the recent progress in the construction of supramolecular star polymers, including regular star polymers and miktoarm star polymers, is discussed. The initial sections briefly provide an overview of the conventional classification and synthesis methods for star polymers. Coordination-driven self-assembly was investigated for the supramolecular synthesis of star polymers. Star polymers with multiple polymer chains radiating from metal-organic polyhedra (MOPs) have also been described. Particular focus has been placed on the synthesis of star polymers featuring supramolecular cores formed through hydrogen-bonding-directed self-assembly. After describing the synthesis of star polymers based on host-guest complexes, the construction of miktoarm star polymers based on the molecular recognition of coordination capsules is detailed.

Polyoxometalate-cored supramolecular star polymers as a novel crosslinker for graphene oxide-based forward osmosis membranes: Anti-fouling, super hydrophilic and high water permeable

Forward osmosis (FO) process due to its potential in water desalination has attracted considerable attention. Although the FO process possesses numerous privileges like no requirement of external hydraulic pressure, it confronts some challenges. A major challenge is the development of high-performance FO membranes. In this study wa fabricated FO membranes with high water permeability and salt rejection utilizing a pressure-assisted self-assembly method. The supramolecular star polymers consisting of quaternary poly (2-(dimethylamino)ethyl methacrylate) and negatively charged blue lemon polyoxometalate (POM) (PDMAEMA@BL) was embedded into the graphene oxide (GO) active layer to construct physical crosslinking among GO nanosheets. The performance of membranes was analyzed by FO experiment to determination the water flux, reverse salt flux, and selectivity. Modified membranes showed significant augment in water flux in FO mode from 14.93 LMH in control polyamide TFC membrane to 37.26 in P@BL0.8 (0.8 ml of the 25%W/W PDMAEMA@BL). Likewise, the fouling properties of membranes were analyzed using sodium alginate (SA) organic foulant. As results showed, modified membranes performed better against fouling than conventional polyamide TFC membranes.

Supramolecular H-bonded three-arm star polymers by efficient combination of RAFT polymerization and thio-bromo “click” reaction

Efficient and versatile “click”-based post-polymerization tools for the straightforward modification of especially polymers with sophisticated architectures play a significant role in polymer chemistry. We here report on the synthesis of supramolecular three-arm star polymers by a combination of RAFT polymerization and the thio-bromo “click” reaction, consequently exploring the potential of this particular thiol-halogen “click” reactions as post-polymerization tool. Therefore, two new trivalent chain transfer agents (CTAs) bearing either trithiocarbonate or dithiobenzoate groups were designed and investigated for the RAFT polymerization of n-butyl acrylate (nBA) and styrene. Kinetic investigations of CTA/monomer combinations were performed to obtain star-shaped poly(n-butyl acrylate)s (PnBA) and poly(styrene)s (PS) with adjustable molecular weights and well controllable polydispersities in the range of 1.13–1.30. The capped thiol-groups were released by aminolysis and quantitatively converted into barbiturate or imidazolium end-groups, allowing to prepare functionalized supramolecular star polymers via this particular thio-bromo “click” reaction. Thereby, the best results for aminolysis were not obtained in a one-pot reaction as expected but in a two step process, while acetonitrile has been shown to be essential for the success of the reaction in contrast to the pKa-value of the investigated bases. As proven via NMR spectroscopy and mass spectrometry all desired supramolecular star polymers were obtained with an exceptional high extend of end-group functionality (>95%) underscoring the potential of this specific “click”-based post-polymerization modification tool in combination with RAFT polymerization.

Supramolecular star polymer films with tunable honeycomb structures templated by breath figures

Microporous films with tunable honeycomb structures were fabricated based on the self-assembly of a series of clusto-supramolecular star polymers (CSPs) guided by breath figure templates. The CSPs consist of a hydrophilic polyoxometalate cluster core and several hydrophobic polystyrene arms that are electrostatically connected to the core, in which three Keggin-type polyoxometalate clusters [CoW12O40]6-, [SiW12O40]4- and [PW12O40]3- were used as the cores. The dynamic bonding character endows CSPs a rearrangeable amphiphilic conformation that facilities them to accumulate at the oil/water interface to stabilize water droplets. By precisely adjusting the arm number and arm length of CSPs, we revealed the relationship between the structure and the film-forming behavior of CSPs. Regular pores with a small diameter as low as 260 nm were obtained by optimizing the structure of CSPs. Moreover, the CSPs could act as morphological modifiers to efficiently improve the microporous regularity of polystyrene films, even at a low CSP content of 0.8 wt%. To the best of our knowledge, this is the first work using supramolecular star polymers to fabricate microporous films by the breath figure method, which not only introduces a new film-formation material, but also provides a facile way to incorporate inorganic functional components into microporous polymer films.

Dual-Gated Supramolecular Star Polymers in Aqueous Solution

We introduce the formation of a dual responsive supramolecular star polymer system, displaying gated self-assembly behavior. The redox- and thermoresponsive star polymers are based on a 6-fold β-CD functionalized core molecule and RAFT-derived ferrocene end functionalized poly(N,N-dimethylacrylamide) (PDMA) and poly(N,N-diethylacrylamide) (PDEA) linear polymers. Complex formation is analyzed via various methods including dynamic light scattering (DLS). Chemical redox triggers, namely NaOCl and ascorbic acid, as well as electrochemical triggers can be utilized to shift the star polymers to the unbound state via CD/ferrocene complex dissociation. Moreover, heating above the lower critical solution temperature (approximately 34 °C) allows for a change from the coil to the globular state of the star polymers in the case of PDEA arms. For PDMA arms, heating to 70 °C allows shifting of the system to the unbound state. The response of the supramolecular star polymers is carefully studied via various methods including cyclic voltammetry (CV), DLS, and turbidimetry. Overall, the supramolecular star polymers can be transformed into predefined states via individually addressable temperature and/or redox stimuli, presenting a novel dual gated self-assembling supramolecular star polymer system in aqueous solution.

Controllable Nanostructure Formation through Enthalpy-Driven Assembly of Polyoxometalate Clusters and Block Copolymers

The coassembly of block copolymers (BCPs) with nanoscale inorganic objects is an important route to fabricate nanostructured polymer composites. However, the immiscibility of inorganic/polymeric interface is a recurring challenge to overcome, particularly for inorganic clusters, such as the polyoxometalates (POMs)/BCPs system. In this paper, we present a general method to incorporate POMs into BCP matrices, in which a POM cluster is embedded as a core in a supramolecular star polymer (SSP) whose arms possess the same chemical composition as a BCP segment. Because of the enthalpic interaction between SSP arms and BCP segments, the SSP can carry POM into BCP matrices to realize their coassembly. By this way, we successfully localize a Keggin-type POM cluster [CoW12O40]6– modified with polystyrene (PS) arms into the PS domain of poly(styrene-b-ethylene oxide) micelles, which induces the formation of a series of hybrid micelles with spherical, toroidal, and bicontinuous structures. The morphological transitio...

Self-Assembly of Polyoxometalate-Based Starlike Polymers in Solvents of Variable Quality: From Free-Standing Sheet to Vesicle

Polyoxometalate-based supramolecular star polymers, where an anionic polyoxometalate is closely encapsulated by a hydrophobic shell of cation terminated polystyrenes, are conceptually regarded as a model of star polymers to study their intra- and interstar interactions and self-assembled behaviors in solvents of variable quality. These model stars can self-assemble to form unilamellar free-standing sheets in the toluene/methanol mixture solvent with a methanol volume ratio of 50%. An increase in the methanol content to 75% or 80% results in a coexistence of free-standing sheets with vesicles, where several intermediates are captured for the morphological evolution from sheet to vesicle. With further increasing methanol content to 90%, pure vesicle phases form with unilamellar or oligolamellar features. All these aggregates are packed by the totally hydrophobic starlike polymers, where the core–shell structures are retained. This is distinctly different from the bilayered nanostructures formed by amphiphil...

Structurally dependent self-assembly and luminescence of polyoxometalate-cored supramolecular star polymers

A series of hybrid supramolecular star polymers (SSPs) consisting of a polyoxometalate EuW10O369− (EuW10) core and different length of polystyrene arms have been fabricated by a “core-first” method, in which the anionic EuW10 clusters were firstly encapsulated by cationic molecules with trithioester terminal groups and subsequently polystyrene arms were grafted by reversible addition–fragmentation chain-transfer (RAFT) polymerization. The SSPs exhibit structurally dependent self-assembly behaviours in solution, at the air–water interface and solid state. It was found that the SSPs with short arms form large assemblies with a diameter over 100 nm in chloroform, while those with long arms tend to be mono-dispersed. Meanwhile, the distance between the EuW10 cores of adjacent SSPs in Langmuir monolayers and casting films can be precisely adjusted by PS arms, which leads to a tunable colour purity of EuW10 luminescence. This tight structure–property relationship enables the polyoxometalate-cored SSPs to act as potential building blocks for the construction of hybrid polymer materials with controllable functions.

A Facile Route to Viologen Functional Macromolecules through Azide-Alkyne [3+2] Cycloaddition

Viologen end and side-chain functional macromolecules are synthesized through a high-yielding, copper-mediated azide-alkyne [3+2] cycloaddition reaction. Specifically, poly(ethylene glycol) (PEG) and the C-terminus of a model oligopeptide are quantitatively end-coupled to a viologen moiety as confirmed by (1) H NMR, gel permeation chromatography (GPC), and mass spectrometry (MS). Side-chain functionalization of a styrene backbone is also readily achieved forming a polyelectrolyte species and demonstrating the applicability of this method across a range of macromolecular species. It is found that viologen itself slows the reaction and that careful choice of counter ions, the specific chelating ligand for the copper-mediated reaction, solvent, as well as the amount of copper also play major roles in the time to completion of the reaction and hence the yield. Macromolecules formed through this route bind effectively with supramolecular host molecule cucurbit[8]uril allowing for controlled solution-phase self-assembly, for example of a supramolecular star polymer.

Tunable Interactions of Polyoxometalate-Based Brushlike Hybrids in Solvents of Variable Quality: From Self-Recognition to Supramolecular Recognition

The controllable interactions of a spherical polymer brush modeled by a poly(styrene-b-4-vinylpyridinium methyl iodide)-polyoxometalate composite micelle, SVP-6, with a polyoxometalate-based supramolecular star polymer, PSP-4, in solvents of variable quality allow us to tune their self-assembly behaviors from self-recognition to supramolecular recognition. In the former case, isolated, contractive spheres together with a few vesicles formed by PSP-4 coexist with multimicelle aggregates formed by SVP-6, whereas SVP-6 is hosted inside the vesicle of PSP-4 in the latter case. This work represents an important step toward the development and understanding of programmable self-assembly of brushlike polymers into complex materials.

Supramolecular star polymers with compositional heterogeneity

AbstractWe present the synthesis of supramolecular star polymers with heterogeneous chemical compositions through potassium cation‐templated assembly of guanosine end‐functionalized random, diblock, and Y‐shaped copolymers. The assembly and disassembly processes of the synthesized star polymers have been systematically examined on changing the concentration, the temperature, the solvent, and the amount of cation using 1H NMR, UV/vis, and CD spectroscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Effect of precursor chemical composition on the formation and stability of G-quadruplex core supramolecular star polymers

A homologous series of guanosine end-functional poly(butadiene)s has been prepared. The potassium cation-templated assembly of these guanosine functionalised precursors then furnished supramolecular star polymers with a G-quadruplex core. Comparison with the previously reported poly(ethylene glycol)-based supramolecular star polymers revealed that in designing supramolecular star polymers, chemically non-polar assembly precursors – that do not interfere with the supramolecular interactions of the core – are essential for the preparation of high stability and high molecular weight supramolecular branched architectures. In addition, in comparison to star polymers composed of chemically polar polymer chains, the non-polar supramolecular ensembles show chain-length independent properties.

Star-like supramolecular polymers fabricated by a Keplerate cluster with cationic terminated polymers and their self-assembly into vesicles

The electrostatic combination of a Keplerate cluster, [Mo(132)O(372)(CH(3)COO)(30)(H(2)O)(72)](42-) with cationic terminated poly(styrene) yields polyoxometalate-based supramolecular star polymers, which can further self-assemble into vesicular aggregates in CHCl(3)-MeOH mixed solvent.

Construction of Polymer–Protein Bioconjugates with Varying Chain Topologies: Polymer Molecular Weight and Steric Hindrance Effects

We report on the fabrication of well-defined polymer-protein bioconjugates with varying chain architectures, including star polymers, star block copolymers, and heteroarm star copolymers through the specific noncovalent interaction between avidin and biotinylated synthetic polymer precursors. Homopolymer and diblock precursors site-specifically labeled with a single biotin moiety at the chain terminal, chain middle, or diblock junction point were synthesized by a combination of atom-transfer radical polymerization (ATRP) and click reactions. By taking advantage of molecular recognition between avidin and biotin moieties, supramolecular star polymers, star block copolymers, and heteroarm star copolymers were successfully fabricated. This specific binding process was also assessed by using the diffraction optic technology (DOT) technique. We further investigated the effects of polymer molecular weights, location of biotin functionality within the polymer chain, and polymer chain conformations, that is, steric hindrance effects, on the binding numbers of biotinylated polymer chains per avidin within the polymer-protein bioconjugates, which were determined by the standard avidin/2-(4-hydroxyazobenzene)benzoic acid (HABA) assay. The binding numbers vary in the range of 1.9-3.3, depending on the molecular weights, locations of biotin functionality within synthetic polymer precursors, and polymer chain conformations.

Design of Heterocomplementary H‐Bonding RAFT Agents – Towards the Generation of Supramolecular Star Polymers

Supramolecular poly(vinyl acetate) PVAc 3-arms stars were successfully generated by Reversible Addition-Fragmentation chain Transfer (RAFT)-polymerized chains bearing hydrogen-bonding heterocomplementary associating units. Chain Transfer Agents (CTA) bearing thymine- and diaminopyridine-based units were first synthesized and proved to mediate efficiently the polymerization of VAc. The binding ability of the chains in solution was then demonstrated by (1) H NMR and GPC measurements, proving the formation of the supramolecular stars.

Controlled polymerization and self-assembly of a supramolecular star polymer with a guanosine quadruplex core

A novel supramolecular star polymer is reported, which can be prepared either from atom-transfer radical polymerization (ATRP) of a self-assembled initiator or from self-assembly of a guanosine-capped linear polymer.

A Strategy for Synthesis of Ion‐Bonded Supramolecular Star Polymers by Reversible Addition‐Fragmentation Chain Transfer (RAFT) Polymerization

AbstractWe have developed a novel strategy for the preparation of ion‐bonded supramolecular star polymers by RAFT polymerization. An ion‐bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert‐butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by 1H NMR and GPC. The results show that the polymerization possesses the character of living free‐radical polymerization and the ion‐bonded supramolecular star polymers PSt, PtBA, and PSt‐b‐PtBA, with six well‐defined arms, were successfully synthesized.magnified image

Supramolecular Star Polymers. Increased Molecular Weight with Decreased Polydispersity through Self-Assembly

A ditopic structure containing two heterocyclic DeAP units and programmed to self-assemble is used as an initiation unit for the synthesis of polylactide and polystyrene. The resultant polymers self-assemble into higher molecular weight structures with a lower molecular weight distribution. The largest discrete nanoscale polymeric assembly is proposed to be a hexameric star with a molecular weight of ca. 92.7 kDa. All polymeric assemblies generally exhibit PDI values of 1.3 to 1.5, which are lower than the PDI value of the corresponding polymeric arms. A hexameric assembly is stabilized by 30 hydrogen bonds, including six AADD.DDAA contacts. The hexameric star is formed under conditions that are at least partially controlled by kinetics.

A Supramolecular Triarm Star Polymer from a Homotritopic Tris(Crown Ether) Host and a Complementary Monotopic Paraquat-Terminated Polystyrene Guest by a Supramolecular Coupling Method

The first supramolecular star polymer based on pseudorotaxane host-guest complexation was prepared from statistical complexation of a homotritopic tris(crown ether) host and monotopic paraquat-terminated polystyrene guest in solution. The formation of this supramolecular star polymer was confirmed by proton NMR characterization and viscosity studies.