Poly(2-acrylamidoglycolic acid) (PAGA): Controlled Polymerization Using RAFT and Chelation of Metal Cations

Double-hydrophilic block copolymer-metal ion associations: Structures, properties and applications

Hybrid polyionic complexes (HPICs), constructed from double-hydrophilic block copolymers and metal ions, have been largely developed with increasing interest in the past decade in the fields of catalysis, materials science and biological applications. The chemical natures of both blocks are very versatile, but one block should be able to interact with ions, and the second one should be neutral. Many metals have been used to form HPICs, which have, in their simplest architectural form, a core-shell structure of a few tens of nanometers in radius with an external shell made of the neutral block of the copolymer. In this review, we focus our discussion on the stability, shape, size and inner structure of these hybrid micelles. We then describe the most recent applications of HPICs, as reported in the literature, and point out the current challenges, missing structural information and future perspectives for this class of organized structures.

Cassava Starch-Based Thermo-Responsive Pb(II)-Imprinted Material: Preparation and Adsorption Performance on Pb(II)

Heavy metal pollution is currently an increasing threat to the ecological environment, and the development of novel absorbents with remarkable adsorption performance and cost-effectiveness are highly desired. In this study, a cassava starch-based Pb(II)-imprinted thermo-responsive hydrogel (CPIT) had been prepared by using cassava starch as the bio-substrate, N-isopropyl acrylamide (NIPAM) as the thermo-responsive monomer, and Pb(II) as the template ions. Later, a variety of modern techniques including FTIR, DSC, SEM, and TGA were employed to comprehensively analyze the characteristic functional groups, thermo-responsibility, morphology, and thermal stability of CPIT. The obtained material exhibited superior performance in adsorption of Pb(II) and its maximum adsorption capacity was high-up to 114.6 mg/g under optimized conditions. Notably, the subsequent desorption (regeneration) process was fairly convenient by simply rinsing with cold deionized water and the highest desorption efficiency could be achieved as 93.8%. More importantly, the adsorption capacity of regenerated CPIT still maintained 88.2% of the value of starting material even after 10 recyclings. In addition, the excellence of CPIT in selective adsorption of Pb(II) should also be highlighted as its superior adsorption ability (97.9 mg/g) over the other seven interfering metal ions.

Double hydrophilic copolymers - synthetic approaches, architectural variety, and current application fields

Solubility and functionality of polymeric materials are essential properties determining their role in any application. In that regard, double hydrophilic copolymers (DHC) are typically constructed from two chemically dissimilar but water-soluble building blocks. During the past decades, these materials have been intensely developed and utilised as, e.g., matrices for the design of multifunctional hybrid materials, in drug carriers and gene delivery, as nanoreactors, or as sensors. This is predominantly due to almost unlimited possibilities to precisely tune DHC composition and topology, their solution behavior, e.g., stimuli-response, and potential interactions with small molecules, ions and (nanoparticle) surfaces. In this contribution we want to highlight that this class of polymers has experienced tremendous progress regarding synthesis, architectural variety, and the possibility to combine response to different stimuli within one material. Especially the implementation of DHCs as versatile building blocks in hybrid materials expanded the range of water-based applications during the last two decades, which now includes also photocatalysis, sensing, and 3D inkjet printing of hydrogels, definitely going beyond already well-established utilisation in biomedicine or as templates.

A block copolymer templated approach for the preparation of nanoporous polymer structures and cellulose fiber hybrids by ozone treatment

Porous nanostructures were derived after self-assembly of amphiphilic block copolymers and subsequent ozone-mediated block segment degradation. Highly ordered pores were obtained for BCP films and for coatings at cellulose fibers’ surfaces.

Hybrid polymeric micelles stabilized by gallium ions: Structural investigation

The addition of gallium ions to a solution of a double-hydrophilic block copolymer, i.e. poly(ethylene oxide)-block-poly(acrylic acid), leads to the spontaneous formation of highly monodisperse micelles with a Hybrid PolyIon Complexes (HPICs) core. By combining several techniques, a precise description of the HPIC architecture was achieved. In particular and for the first time, NMR and anomalous small angle X-ray scattering (ASAXS) enable tracking of the inorganic ions in solution and highlighting the co-localization of the gallium and the poly(acrylic acid) blocks in a rigid structure at the core of the micelle. Such a core has a radius of ca 4.3 nm while the complete nano-object with its poly(ethylene oxide) shell has a total radius of ca 11 nm. The aggregation number was also estimated using the ASAXS results. This comprehensive structural characterization of the Ga HPICs corroborates the assumptions made for HPICs based on other inorganic ions and demonstrates the universality of the HPIC structure leading, for example, to new families of contrast agents in medical imaging.

Bio-inspired zwitterionic polymeric chelating assembly for treatment of copper-induced cytotoxicity and hemolysis

We developed a hemocompatible, bio-inspired, multivalent, polymeric-chelating assembly based on the poly(2-methacryloyloxyethyl phosphorylcholine)-b-poly(serinyl acrylate) (PMPC-b-PserA) zwitterionic diblock copolymer. Functional PMPC-b-PserA was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization to catch and encapsulate free copper ions (Cu²⁺) in a solution. PMPC with an identical polar group to phospholipids exhibits high hydrophilicity and fouling resistance against non-specific adsorption, and inertness to the metal ions. On the other hand, PserA with pendant groups of amino acids possesses a strong capability to react with Cu²⁺ by coordination interaction. Therefore, when PMPC-b-PserA was brought into contact with Cu²⁺, a hydrophobic core with multiple coordination "bridges" between polymers and Cu²⁺ was formed, leading to self-assembly of core-shell polymer-metal nanoparticles. As a result, free Cu²⁺ ions can be removed from the solution to prevent damage to cells and tissues. The synthesis and chemical structure of PMPC-b-PserA were characterized, and the formation of self-assembled polymer-Cu²⁺ nanoparticles and colloidal stability were analyzed. More importantly, the detoxification of PMPC-b-PserA in presence of Cu²⁺ with fibroblast cells was demonstrated by increased cell viability >80%. In addition, the hemolysis, which occurred due to disruption of RBC membranes by free Cu²⁺, was effectively suppressed by adding PMPC-b-PserA. The bio-inspired and biocompatible chelating agent of PMPC-b-PserA provides a new treatment approach to encapsulate and detoxify heavy metals in complex media for chelation therapy.

Polyether-Based Diblock Terpolymer Micelles with Pendant Anthracene Units-Light-Induced Crosslinking and Limitations Regarding Reversibility

The synthesis of 9-methylanthracenyl glycidyl ether (AnthGE) as a crosslinkable monomer that can be applied in anionic ring opening polymerization is reported. Diblock terpolymers of the composition methoxy-poly(ethylene oxide)-block-poly(2-ethylhexyl glycidyl ether-co-9-methylanthracenyl glycidyl ether) (mPEO-b-P(EHGE-co-AnthGE) with 10 to 24 wt% of AnthGE are synthesized and characterized. Their micellization behavior, as well as their light-induced core-crosslinking via irradiation with UV light (λ = 365 nm) is studied. The results are compared with studies on the dimerization, and the dimer cleavage via irradiation with UV-C light (λ = 254 nm), of the same diblock terpolymer in organic solution, and the small-molecule model compound 9-methoxymethylanthracene. Differences in ¹ H NMR spectra of the crosslinked or dimerized compounds and reaction kinetics of the dimerization reactions under different conditions suggest possible side reactions for the case of the core-crosslinking of micelles in aqueous solution. These side reactions limit the reversibility of the anthracene dimerization reaction in aqueous solutions, even if the anthracene molecule is encapsulated within the hydrophobic core of a polymeric micelle.

Polyelectrolyte Functionalisation of Track Etched Membranes: Towards Charge-Tuneable Adsorber Materials

Porous adsorber membranes are promising materials for the removal of charged pollutants, such as heavy metal ions or organic dyes as model substances for pharmaceuticals from water. Here, we present the surface grafting of polyethylene terephthalate (PET) track-etched membranes having well defined cylindrical pores of 0.2 or 1 µm diameter with two polyelectrolytes, poly(2-acrylamido glycolic acid) (PAGA) and poly(N-acetyl dehydroalanine) (PNADha). The polyelectrolyte functionalised membranes were characterised by changes in wettability and hydraulic permeability in response to the external stimuli pH and the presence of Cu²⁺ ions. The response of the membranes proved to be consistent with functionalisation inside the pores, and the change of grafted polyelectrolyte macro-conformation was due to the reversible protonation or binding of Cu²⁺ ions. Moreover, the adsorption of the model dye methylene blue was studied and quantified. PAGA-grafted membranes showed an adsorption behavior following the Langmuir model for methylene blue.

Cholesterol-Functionalized Linear/Brush Block Copolymers for Metal-Incorporated Nanostructures with Modulated Core Density and Enhanced Self-Assembly Efficiency

Metal-mediated self-assembly of chelating double-hydrophilic block copolymer has become a facile preparation strategy of great importance for the metal-chelated hybrid nanostructures. Herein, we present a delicate control over the morphology regulation of metal-chelated nanostructures by a terminal modification of polymer building blocks with mesogenic cholesterol. Such a molecular design motif at an end of chelating linear/brush-type block copolymer imparts not only additional hydrophobicity for enhanced cohesive force to facilitate the metal-mediated self-assembly, but also significant morphological alteration of a metal-chelated core that otherwise generally forms a spherical interior with cholesterol-free block copolymers. The presence of cholesterol entities localized at the central core further allows for the density modulation of the final Pt^II-chelated nanostructures while maintaining the colloidal stability, comparable to that of the cholesterol-free nanoparticles in physiological conditions. This metal-mediated assembly strategy with modified polymer building blocks can provide a potential platform for the delivery of inorganic agents.

Triple-Responsive Polyampholytic Graft Copolymers as Smart Sensors with Varying Output

Three triggers result in two measurable outputs from polymeric sensors: multiresponsive polyampholytic graft copolymers respond to pH-value and temperature, as well as the type and concentration of metal cations and therefore, allow the transformation of external triggers into simply measurable outputs (cloud point temperature (T_CP ) and surface plasmon resonance (SPR) of encapsulated silver nanoparticles). The synthesis relies on poly(dehydroalanine) (PDha) as the reactive backbone and gives straightforward access to materials with tunable composition and output. In particular, a rather high sensitivity toward the presence of Cu²⁺ , Co²⁺ , and Pb²⁺ metal cations is found.

Synthesis of biscarboxylic acid functionalised EDTA mimicking polymers and their ability to form Zr(iv) chelation mediated nanostructures

We present a new biscarboxylic acid acrylate, which is used for the synthesis of double hydrophilic EDTA-mimicking block copolymers capable of self-assembly upon zirconium complexation.

Construction of Paramagnetic Manganese-Chelated Polymeric Nanoparticles Using Pyrene-End-Modified Double-Hydrophilic Block Copolymers for Enhanced Magnetic Resonance Relaxivity: A Comparative Study with Cisplatin Pharmacophore

Cationic metal-mediated self-assembly of double-hydrophilic block copolymers (DHBCs) has been of great interest for the preparation of hybrid nanoparticles for versatile applications. Among many functional transition-metal ions, manganese (Mn^II) is a highly attractive element due to its paramagnetic property with a high coordination number. However, Mn^II does not lead to the efficient self-assembly of DHBCs because of the relatively high aqueous solubility of coordinated Mn^II. This article reports a facile method for direct conjugation of Mn^II ions inside sterically stabilized polymer assemblies, composed of pyrene-end-modified DHBCs. Nitroxide-mediated radical polymerization was used to prepare the poly(ethylene glycol)- b-poly(acrylate) DHBC precursor, followed by the end-modification with pyrene maleimide via the radical-exchange reaction. Employing the self-associated DHBC as the nanoscale template, the simple addition of Mn^II enables a large number of polyvalent Mn^II ions to be immobilized at the chelating blocks of DHBCs, which can be readily monitored by the excimeric fluorescence emission change of the terminal pyrene fluorophore. The resulting Mn^II-loaded polymeric nanoparticles (Mn^II-PNPs) possess nanogel-like scaffolds, which allow for efficient water permeation at the Mn^II-incorporated interior for enhanced magnetic resonance contrasting effect. Additionally, by comparing the coordination properties of Mn^II and cisplatin, we endeavor to understand the internal structures and the relevant physicochemical features of metal-chelated nanoparticles.