Hyperbranched Polyelectrolytes Research Articles

Hierarchical Supramolecular Aggregation of Molecular Nanoparticles for Granular Materials with Ultra High-Speed Impact-Resistance.

The high-speed impact-resistanct materials are of great significance while their development is hindered by the intrinsic tradeoff between mechanical strength and energy dissipation capability. Herein, the new chemical system of molecular granular material (MGM) is developed for the design of impact-resistant materials from the supramolecular complexation of sub-nm molecular clusters (MCs) and hyper-branched polyelectrolytes. Their hierarchical aggregation provides the origin of the decoupling of mechanical strengths and structural relaxation dynamics. The MCs' intrinsic fast dynamics afford excellent high-speed impact-resistance, up to 5600 s-1 impact in a typical split-Hopkinson pressure bar test while only tiny boundary cracks can be observed even under 7200 s-1 impact. The high loadings of MCs and their hierarchical aggregates provide high-density sacrificial bonding for the effective dissipation of the impact energy, enabling the protection of fragile devices from the direct impact of over 200 ms-1 bullet. Moreover, the MGMs can be conveniently processed into protective coatings or films with promising recyclability due to the supramolecular interaction feature. The research not only reveals the unique relaxation dynamics and mechanical properties of MGMs in comparison with polymers and colloids, but also develops new chemical systems for the fabrication of high-speed impact-resistant materials.

Inside Back Cover: Heteroaromatic Hyperbranched Polyelectrolytes: Multicomponent Polyannulation and Photodynamic Biopatterning (Angew. Chem. Int. Ed. 35/2021)

A novel multicomponent polymerization has been developed for the facile synthesis of heteroaromatic hyperbranched polyelectrolytes. As Chunlei Zhu, Jacky W. Y. Lam, Ben Zhong Tang, and co-workers demonstrate in their Research Article on page 19222, the resulting hyperbranched polyelectrolytes show strong capability in facilitating the generation of reactive oxygen species, allowing their application in efficient bacterial killing and customizable photodynamic patterning of living organisms.

Heteroaromatic Hyperbranched Polyelectrolytes: Multicomponent Polyannulation and Photodynamic Biopatterning.

We reported an efficient multicomponent polyannulation for in situ generation of heteroaromatic hyperbranched polyelectrolytes by using readily accessible internal diynes and low-cost, commercially available arylnitriles, NaSbF6 , and H2 O/AcOH. The polymers were obtained in excellent yields (up to 99 %) with extraordinary high molecular weights (Mw up to 1.011×106 ) and low polydispersity indices. The resulting polymers showed good processibility and high quantum yields with tunable emission in the solid state, making them ideal materials for highly ordered fluorescent photopatterning. These hyperbranched polyelectrolytes also possessed strong ability to generate reactive oxygen species, which allowed their applications in efficient bacterial killing and customizable photodynamic patterning of living organisms in a simple and cost-effective way.

Heteroaromatic Hyperbranched Polyelectrolytes: Multicomponent Polyannulation and Photodynamic Biopatterning

AbstractWe reported an efficient multicomponent polyannulation for in situ generation of heteroaromatic hyperbranched polyelectrolytes by using readily accessible internal diynes and low‐cost, commercially available arylnitriles, NaSbF6, and H2O/AcOH. The polymers were obtained in excellent yields (up to 99 %) with extraordinary high molecular weights (Mw up to 1.011×106) and low polydispersity indices. The resulting polymers showed good processibility and high quantum yields with tunable emission in the solid state, making them ideal materials for highly ordered fluorescent photopatterning. These hyperbranched polyelectrolytes also possessed strong ability to generate reactive oxygen species, which allowed their applications in efficient bacterial killing and customizable photodynamic patterning of living organisms in a simple and cost‐effective way.

Water–Alcohol-Soluble Hyperbranched Polyelectrolytes and Their Application in Polymer Solar Cells and Photocatalysis

We report here a series of water–alcohol-soluble hyperbranched polyelectrolytes, which can be used as both cathode interfacial materials (CIMs) in polymer solar cells (PSCs) and organic photocataly...

From green chemistry and nature-like technologies towards ecoadaptive chemistry and technology

Abstract Nature-like technologies can be considered as a logical development of green chemistry principles implemented to design novel materials and processes aimed at mimicking and reproducing natural life-sustaining mechanisms on molecular level. Humic substances which penetrate throughout the entire environment and represent from 50 to 90% of organic matter in soil and water ecosystems, play multiple life-sustaining functions on Earth. To name a few, HS regulate transport and availability of biogenic elements to plants, immobilize and mitigate toxicity of hazardous elements in the contaminated ecosystems, protect plants from non-specific abiotic stresses, play key role for fertility of soils determining water-retention and structure. Here we represent a novel platform for nature-inspired synthesis of soft and hybrid (nano)materials aimed at their use for soil and water clean up, carbon sequestration, soil fertility restoration. It is based on a smart use of natural hyperbranched polyelectrolytes – humic substances, which possess multiple functional groups including carboxyl, hydroxyl, amide, and others. Multiple functional groups of HS make them amenable both for classical chemical modification as well as for producing interpolyelectrolyte complexes. In this work, we present both approaches for manufacturing silicon-containing humic derivatives and supramolecular complexes with acquired new property – self-adhesion to both inorganic and bio-surfaces. The synthesis is conducted using humic materials from different sources and functional organosilanes. Self-assembly of the supramolecular silicon-humic systems occurs with formation of humic-silsesquioxane networks capable to adhere to mineral surfaces. This process is similar to immobilization of organic coatings to mineral surfaces. We have shown how this process can be realized in the ground waters for the purposes of the environmental clean up. We have also proposed to use the silicon-humic complexes for improving humus content of soils and for reconstructing soil restoration processes both in the lab and in the field. Another field of our research is synthesis of iron-containing humics-stabilized nanoparticles (NPs), which can be used as a source for plants nutrition instead of synthetic iron chelates. The idea is based on the natural phenomenon that in soils, water-stable sols of iron-containing NPs are formed due to complexing with HS, which can bind large amounts of poorly ordered iron (hydr)oxides providing for stabilization of colloidal iron in the form of NPs. It has been numerously shown that the presence of HS improves iron acquisition by plants in soils, but there was no systematic study so far with respect to a relationship between size and crystallinity of humics-stabilized iron-containing NPs and their availability to plants. We have conducted such a study and could establish conditions when humics-stabilized NPs could be taken up by plants with similar efficiency as FeEDTA. The presented data demonstrate good prospects for a use of green humics-based materials in nature-like technologies. We also hope that these studies will give rise to new branch of chemistry and technology which can be called ecoadaptive chemistry and technology.

Charge and hydration structure of dendritic polyelectrolytes: molecular simulations of polyglycerol sulphate.

Macromolecules based on dendritic or hyperbranched polyelectrolytes have been emerging as high potential candidates for biomedical applications. Here we study the charge and solvation structure of dendritic polyglycerol sulphate (dPGS) of generations 0 to 3 in aqueous sodium chloride solution by explicit-solvent molecular dynamics computer simulations. We characterize dPGS by calculating several important properties such as relevant dPGS radii, molecular distributions, the solvent accessible surface area, and the partial molecular volume. In particular, as the dPGS exhibits high charge renormalization effects, we address the challenges of how to obtain a well-defined effective charge and surface potential of dPGS for practical applications. We compare implicit- and explicit-solvent approaches in our all-atom simulations with the coarse-grained simulations from our previous work. We find consistent values for the effective electrostatic size (i.e., the location of the effective charge of a Debye-Hückel sphere) within all the approaches, deviating at most by the size of a water molecule. Finally, the excess chemical potential of water insertion into dPGS and its thermodynamic signature are presented and rationalized.

Protein Transport Properties of PAN Membranes Grafted with Hyperbranched Polyelectrolytes and Hyperbranched Zwitterions

A series of charge-modified polyacrylonitrile (PAN) membranes with different surface charge properties and densities have been obtained via first grafting with hyperbranched polyethylenimine (PEI) and then ring-opening with 1,4-butane sultone. The obtained PAN-gr-PEI membranes and PAN-gr-PEIS membranes have hyperbranched polycation and hyperbranched zwitterions tethered on the surface, respectively. They were characterized in detail by FT-IR, AFM, XPS, SEM, WCA, and zeta-potential measurements. Bovine serum albumin (BSA) and lysozyme (Lys) were chosen as model proteins in order to evaluate the separation performance of the modified membranes via dead-end ultrafiltration. The membranes grafted with PEI of different densities have different surface chemical compositions but very similar surface charge properties. PAN and PAN-gr-PEI membranes are highly negatively charged and moderately positively charged. PAN-gr-PEIS membranes show typical amphoteric characteristics. The UF performance is highly dependent o...

Thioether-Bearing Hyperbranched Polyether Polyols with Methionine-Like Side-Chains: A Versatile Platform for Orthogonal Functionalization.

The synthesis of thioether-bearing hyperbranched polyether polyols based on an AB/AB2 type copolymerization (cyclic latent monomers) is introduced. The polymers are prepared by anionic ring-opening multibranching copolymerization of glycidol and 2-(methylthio)ethyl glycidyl ether (MTEGE), which is conveniently accessible in a single etherification step. Slow monomer addition provides control over molecular weights. Moderate dispersities (Đ = 1.48-1.85) are obtained, given the hyperbranched structure. In situ 1 H NMR copolymerization kinetics reveal reactivity ratios of rG = 3.7 and rMTEGE = 0.27. Using slow monomer addition, copolymer composition can be systematically varied, allowing for the adjustment of the hydroxyl/thioether ratio, the degree of branching (DB = 0.36-0.48), thermal properties, and cloud point temperatures in aqueous solution in the range of 29-75 °C. Thioether oxidation to sulfoxides enables to tailor the copolymers' solubility profile. Use of these copolymers as a versatile, multifunctional platform for orthogonal modification is highlighted. The methyl sulfide groups can be selectively alkoxylated, using propylene oxide, allyl glycidyl ether, or furfuryl glycidyl ether, resulting in functional hyperbranched polyelectrolytes. Reaction of the alcohol groups with benzyl isocyanate demonstrates successful orthogonal functionalization.

Intermolecular Forces Driving Encapsulation of Small Molecules by PAMAM Dendrimers in Water

The nature and relative strength of the intermolecular interactions responsible for the behavior of PAMAM dendrimers as encapsulating agents were investigated in neutral aqueous solution through optical spectroscopy methods. In order of relative importance, we found electrostatics, hydrogen bonding, and interactions mediated by aromatic moieties in the guest molecules to be the main drivers to complex formation in these systems. Insights were gained by studying the binding of small targeted organic anions to these dendrimers (G3–G6) by an indicator displacement method, monitoring spectral signals (absorbance, fluorescence emission, and anisotropy). This study contributes to a more complete understanding of the fundamental interactions involved when these hyperbranched polyelectrolytes function as supramolecular hosts, a role they commonly assume in many of their applications e.g. as drug delivery vectors.

Adsorption of Mixtures of Poly(amidoamine) Dendrimers and Sodium Dodecyl Sulfate at the Air–Water Interface

We relate the adsorption from mixtures of well-defined poly(amidoamine) (PAMAM) dendrimers of generations 4 and 8 with sodium dodecyl sulfate (SDS) at the air-water interface to the bulk solution properties. The anionic surfactant shows strong attractive interactions with the cationic dendrimers at pH 7, and electrophoretic mobility measurements indicate that the association is primarily driven by electrostatic interactions. Optical density measurements highlight the lack of colloidal stability of the formed bulk aggregates at compositions close to charge neutrality, the time scale of which is dependent on the dendrimer generation. Adsorption at the air-water interface was followed from samples immediately after mixing using a combination of surface tension, neutron reflectometry, and ellipsometry measurements. In the phase separation region for dendrimers of generation 4, we observed high surface tension corresponding to a depleted surfactant solution but only when the aggregates carried an excess of surfactant. Interestingly, these depleted adsorption layers contained spontaneously adsorbed macroscopic aggregates, and these embedded particles do not rearrange to spread monomeric material at the interface. These findings are discussed in relation to the interfacial properties of mixtures involving dendrimers of generation 8 as well as polydisperse linear and hyperbranched polyelectrolytes where there is polyelectrolyte bound to a surfactant monolayer. The results presented here demonstrate the capability of dendrimers to sequester anionic surfactants in a controllable manner, with potential applications as demulsification and antifoaming agents.

Water‐soluble hyperbranched polyelectrolytes with high fluorescence quantum yield: Facile synthesis and selective chemosensor for Hg2+ and Cu2+ ions

AbstractNew water‐soluble hyperbranched polyfluorenes bearing carboxylate side chains have been synthesized by the simple “A2 + B2 + C3” protocol based on Suzuki coupling polymerization. The linear polyfluorene analogue LPFA was also synthesized for comparative investigation. The optical properties of the neutral precursory polymers in CHCl3 and final carboxylic‐anionic conjugated polyelectrolytes in buffer solution were investigated. The obtained hyperbranched polyelectrolyte HPFA2 with lower content of branch unit (2%) showed excellent solubility and high fluorescence quantum yield (ϕF = 89%) in aqueous solution. Fluorescence quenching of HPFA2 by different metal ions was also investigated, the polyelectrolyte showed high selectivity for Hg2+ and Cu2+ ions relative to other various metal ions in buffer solution. The Stern‐Volmer constant Ksv was determined to be 0.80 × 106 M−1 for Hg2+ and 3.11 × 106 M−1 for Cu2+, respectively, indicating the potential application of HPFA2 as a highly selective and sensitive chemosensor for Hg2+ and Cu2+ ions in aqueous solution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3431–3439, 2010

Hyperbranched Poly[bis(alkylene)pyridinium

Abstract3,5‐Bis(bromomethyl)pyridine hydrobromide and 3,5‐bis(bromobutyl)pyridine hydrobromide were synthesized from commercially available 3,5‐lutidine. The poly(N‐alkylation) of these monomers readily yielded new hyperbranched polyelectrolytes. The progress of reaction was followed by 1H NMR. A second‐order kinetic scheme fits the experimental data. Rate constants and activation parameters were determined, showing the higher reactivity of 3,5‐bis(bromomethyl)pyridine hydrobromide. This was explained by the electron‐attractive effect of pyridinium groups on the CH2Br end groups. The structures of the hyperbranched poly[3,5‐bis(alkylene)pyridinium]s were investigated by 1H and 13C NMR spectroscopy and a preliminary study of their properties is reported.magnified image

Fluorescence observations on complex formation between linear and hyperbranched polyelectrolytes in dilute aqueous solutions

The complexation between poly(ethylene imine) (PEI) and poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) or AMPS copolymers was investigated with the relative excimer emission intensity I E/ I M of a cationic probe 1-pyrenemethylamine hydrochloride (PyMeA · HCl), fluorescence nonradiative energy transfer (NRET) I Py/ I Np of naphthalene to pyrene labels, the fluorescence anisotropy r and I E/ I M of pyrene labels. PEI was a hyperbranched weak polycation in acid solution, which formed complex with anionic polyelectrolytes due to the electrostatic attraction. The I E/ I M of PyMeA · HCl probe decreased to zero, the intra-, intermolecular NRET I Py/ I Np and I E/ I M of pyrene labels on the AMPS copolymers reached their maxima when χ was increased from 0 to 2.4, which was defined as the mole ratio of the amino group in PEI to the AMPS group in the polyanion. These facts indicated the formation of nonstoichiometric complex of the oppositely charged polyelectrolytes when χ = 2.4 at the concentration much lower than their overlap concentrations. The intermolecular aggregate appeared as indicated by an increase in the intermolecular I Py/ I Np and r with χ up to 2.4 due to neutralizing and hydrophobizing the polyelectrolytes and the bridging effect of the PEI chain bound on different polyanion chains. At high pH, PEI became a neutral polymer and did not bind with the AMPS anion to form the complex as illustrated by the constant value of r for the pyrene labels attached to the AMPS polyanion as that without addition of PEI. The amino group in PEI quenched pyrene and naphthalene emission, resulting a decrease in both I Np and I Py.

Amphiphilic hyperbranched polyelectrolytes: a new type of polysoap

Hyperbranched hydrophobized polyelectrolytes of the ionene type are prepared. They are investigated as a new type of polysoap, with respect to viscosifying behaviour, surface activity and solubilization power. Compared to linear analogues, the visoasifying effect is reduced. Compared to classical polysoap architectures, such as analogous "tail-end-type" and "head-type" polysoaps, the hyperbranched polysoaps behave rather similarly to the "head-type" ones: they exhibit notable surface activity, whereas the solubilization capacity is moderate only.