Metal‐containing polymer hydrogels have attracted increasing interest in recent years due to their outstanding properties such as biocompatibility, recoverability, self‐healing, and/or redox activity. In this short review, methods for the preparation of metal‐containing polymer hydrogels are introduced and an overview of these hydrogels with various functionalities is given. It is hoped that this short update can stimulate innovative ideas to promote the research of metal‐containing hydrogels in the communities.
A series of fluorene‐based conjugated polymers containing the aggregation‐induced emissive (AIE)‐active tetraphenylethene and dicarboxylate pseudocrown as a receptor exhibits a unique dual‐mode sensing ability for selective detection of lead ion in water. Fluorescence turn‐off and turn‐on detections are realized in 80%–90% and 20% water in tetrahydrofuran (THF), respectively, for lead ion with a concentration as low as 10−8 m .
A simple polymerization of trichlorophosphoranimine (Cl3P = N−SiMe3) mediated by functionalized triphenylphosphines is presented. In situ initiator formation and the subsequent polymerization progress are investigated by 31P NMR spectroscopy, demonstrating a living cationic polymerization mechanism. The polymer chain lengths and molecular weights of the resulting substituted poly(organo)phosphazenes are further studied by 1H NMR spectroscopy and size exclusion chromatography. This strategy facilitates the preparation of polyphosphazenes with controlled molecular weights and specific functional groups at the α‐chain end. Such well‐defined, mono‐end‐functionalized polymers have great potential use in bioconjugation, surface modification, and as building blocks for complex macromolecular constructs.
In this work, a novel class of O2/N2 switchable polymers is reported, which is prepared by atom transfer radical copolymerization (ATRcoP) of commercially available 2,2,2‐trifluoroethyl methacrylate (FMA) and N,N‐dimethylaminoethyl methacrylate (DMA). The copolymer is random and contains 10 FMA units and 85 DMA units. Its aqueous solution becomes transparent with O2 bubbling and turns to turbid with N2 purging. This O2/N2‐responsive switchability between the transparent and turbid states is reversible. The FMA–DMA copolymer is thermosensitive and has a lower critical solution temperature (LCST) of 24.5 °C. O2 molecules interact with fluorinated groups of the copolymer and increase the LCST to 55 °C. Purging N2 removes O2 and returns the polymer thermosensitivity back to its initial state. The switchability occurs in the whole temperature range (24.5–55 °C).
Polydiacetylenes have received intense attention on account of their well‐established chromic alterations that are detectable often by the naked eye, making them ideal for a variety of applications such as biosensory materials. These polymers have been fabricated in a variety of materials platforms including 3D crystals, 2D monolayers, and 0D spherical vesicles; however, 1D morphologies that might be useful for directional energy migration are less common. This article describes the development and current research efforts of protein‐based 1D nanowire‐like supramolecular assemblies with embedded polydiacetylenes.
The present review focuses on the recent progress made in thin film orientation of semi‐conducting polymers with particular emphasis on methods using epitaxy and shear forces. The main results reported in this review deal with regioregular poly(3‐alkylthiophene)s and poly(dialkylfluorenes). Correlations existing between processing conditions, macromolecular parameters and the resulting structures formed in thin films are underlined. It is shown that epitaxial orientation of semi‐conducting polymers can generate a large palette of semi‐crystalline and nanostructured morphologies by a subtle choice of the orienting substrates and growth conditions.
The preparation of multifunctional polymers and block copolymers by a straightforward one‐pot reaction process that combines enzymatic transacylation with light‐controlled polymerization is described. Functional methacrylate monomers are synthesized by enzymatic transacylation and used in situ for light‐controlled polymerization, leading to multifunctional methacrylate‐based polymers with well‐defined microstructure.
The synthesis of highly efficient two‐photon uncaging groups and their potential use in functional conjugated polymers for post‐polymerization modification are reported. Careful structural design of the employed nitrophenethyl caging groups allows to efficiently induce bond scission by a two‐photon process through a combination of exceptionally high two‐photon absorption cross‐sections and high reaction quantum yields. Furthermore, π‐conjugated polyfluorenes are functionalized with these photocleavable side groups and it is possible to alter their emission properties and solubility behavior by simple light irradiation. Cleavage of side groups leads to a turn‐on of the fluorescence while solubility of the π‐conjugated materials is drastically reduced.
In this work, syndiotactic polypropylene (sPP) as well as isotactic polypropylene (iPP) are cross‐linked to gain a shape memory effect. Both prepared PP networks exhibit maximum strains of 700%, stored strains of up to 680%, and recoveries of nearly 100%. While x‐iPP is stable for many cycles, x‐sPP ruptures after the first shape‐memory cycle. It is shown by wide‐angle X‐ray scattering (WAXS) experiments that cross‐linked iPP exhibits homoepitaxy in the temporary, stretched shape but in contrast to previous reports it contains a higher amount of daughter than mother crystals.
Tuning the chain‐end functionality of a short‐chain cationic homopolymer, owing to the nature of the initiator used in the atom transfer radical polymerization (ATRP) polymerization step, can be used to mediate the formation of a gel of this poly(electrolyte) in water. While a neutral end group gives a solution of low viscosity, a highly homogeneous gel is obtained with a phosphonate anionic moiety, as characterized by rheometry and diffusion nuclear magnetic resonance (NMR). This novel type of supramolecular control over poly(electrolytic) gel formation could find potential use in a variety of applications in the field of electro‐active materials.
Diselenide‐containing polymers are facilely synthesized from polymers prepared by atom transfer radical polymerization (ATRP). Benefiting from the ATRP technology, this protocol provides a flexible route for controlling the polymer structure, which allows for a great variety of architectures of selenium‐containing polymer materials for applications in various fields. The oxidative and reductive responsive behavior of the obtained diselenide‐containing polymers is also investigated.
A pH‐responsive core cross‐linked star (CCS) polymer containing poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) arms was used as an interfacial stabilizer for emulsions containing toluene (80 v%) and water (20 v%). In the pH range of 12.1‐9.3, ordinary water‐in‐oil emulsions were formed. Intermediate multiple emulsions of oil‐in‐water‐in‐oil and water‐in‐oil‐in‐water were formed at pH 8.6 and 7.5, respectively. Further lowering the pH resulted in the formation of gelled high internal phase emulsions of oil‐in‐water type in the pH range of 6.4‐0.6. The emulsion behavior was correlated with interfacial tension, conductivity and configuration of the CCS polymer at different pH.
In this study, the group transfer polymerization (GTP) of the functional monomer 3‐(trimethoxysilyl)propyl methacrylate (TMSPMA) is reported to produce polymers of different architectures and topologies. TMSPMA is successfully polymerized and copolymerized with GTP to produce well‐defined (co)polymers that can be used to fabricate functional hybrid materials like hydrogels and films.
Supramolecular polyfluorenol enable assembly into conjugated polymer nanoparticles (CPNs). Poly{9‐[4‐(octyloxy)phenyl]fluoren‐9‐ol‐2,7‐diyl} (PPFOH)‐based supramolecular nanoparticles are prepared via reprecipitation. PPFOH nanoparticles with diameters ranging from 40 to 200 nm are obtained by adding different amounts of water into DMF solution. Size‐dependent luminescence is observed in PPFOH‐based hydrogen‐bonded nanoparticles that is different from that of poly(9,9‐dioctylfluorenes). Finally, white light‐emitting devices using CPNs with a size of 80 nm exhibit white emission with the CIE coordinates (0.31, 0.34). Amphiphilic conjugated polymer nanoparticles are potential organic nano‐inks for the fabrication of organic devices in printed electronics.
Poly (N‐isopropylacrylamide) (pNIPAm)‐based hydrogels and hydrogel particles (microgels) have been extensively studied since their discovery and “popularization” a few decades ago. While their uses seem to have no bounds, this Feature Article is focused on their development and application for sensing small molecules, macromolecules, and biomolecules. Hydrogel/microgel‐based photonic materials with order in one, two, or three dimensions are highlighted, which exhibit optical properties that depend on the presence and concentration of various analytes.
To enhance the limited degradability of poly(ethylene glycol) (PEG), a straightforward method of synthesizing poly[(ethylene glycol)‐co‐(glycolic acid)] (P(EG‐co‐GA)) via a ruthenium‐catalyzed, post‐polymerization oxyfunctionalization of various PEGs is developed. Using this method, a set of copolymers with GA compositions of up to 8 mol% are prepared with minimal reduction in molecular weight (<10%) when compared to their commercially available starting materials. The P(EG‐co‐GA) copolymers are shown to undergo hydrolysis under mild conditions.
The synthesis of tetracene‐ and pentacene‐annulated norbornadienes, formed through the Diels–Alder reaction of a dehydroacene with cyclopentadiene is reported. Ring‐opening metathesis polymerization (ROMP) leads to polymers that are investigated with respect to their physical, optical, and electronic properties by gel permeation chromatography (GPC), UV–vis spectroscopy, and cyclic voltammetry. The pentacene‐containing polymer P1 is successfully integrated into an organic field‐effect transistor (OFET); the tetracene‐containing polymer P2 is integrated into an organic light‐emitting diode (OLED).
Metallocenes are organometallic compounds with reversible redox profiles and tunable oxidation and reduction potentials, depending on the metal and substituents at the cyclopentadienyl rings. Metallocenes have been introduced in macromolecules to combine the redox‐activity with polymer properties. There are many examples of such hydrophobic polymer materials, but much fewer water‐soluble examples are found scattered across the polymer literature. However, in terms of drug delivery and other biological applications, water solubility is essential. For this very reason, all the synthetic routes to water‐soluble metallocene containing polymers are collected and discussed here. The focus is on neutral ferrocene‐ and ruthenocene‐containing and charged cobaltocenium‐containing macromolecules (i.e., symmetrical sandwich complexes). The synthetic protocols, self‐assembly behavior, and other benefits of the obtained materials are discussed.
The synthesis and electrochemical characterization of novel polymers bearing phenoxyl‐radicals as redox‐active side chains is described. The monomers are synthesized from the corresponding phenols and quinones, respectively. These compounds are subsequently polymerized via ring‐opening metathesis polymerization. The electrochemical properties of the phenoxyl‐radical polymers are characterized using cyclic voltammetry and the most promising polymer is investigated as active material in a lithium coin‐cell, creating the first phenoxyl‐lithium battery. These phenoxyl‐containing polymers represent interesting anode materials for organic radical and lithium batteries due to their suitable redox‐potentials and possibility to create batteries with higher potentials as well as straightforward synthesis procedures.
A commercially available palladium N‐heterocyclic carbene (Pd‐NHC) precatalyst is used to initiate chain‐growth polymerization of 2‐bromo‐3‐hexyl‐5‐trimethylstannylthiophene. The molecular weight of the resultant poly(3‐hexylthiophene) can be modulated (7 to 73 kDa, Đ = 1.14 to 1.53) by varying the catalyst concentration. Mass spectrometry data confirm control over the polymer end groups and 1H NMR spectroscopy reveals that the palladium catalyst is capable of “ring‐walking”. A linear relationship between Mn and monomer conversion is observed. Atomic force microscopy and X‐ray scattering verify the regioregular nature of the resultant polythiophene.
