High‐porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil‐in‐water high internal phase emulsions (HIPEs) stabilized by gelatin‐graft‐poly(N‐isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell‐laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.
Metal‐organic frameworks (MOFs) nanoparticles in combination with a nonionic surfactant (Pluronic L‐121) are used to stabilize dicyclopentadiene (DCPD)‐in‐water high internal phase emulsions (HIPEs). The resulting HIPEs containing the MIL‐100(Fe) nanoparticles (MIL: Materials of Institut Lavoisier) at the interface between the oil‐ and the water‐phases are then cured, and 100 μm thick, fully open, hierarchically porous hybrid membranes are obtained. The properties of the MIL‐100(Fe)@pDCPD polyHIPE membranes are characterized and it is found that up to 14 wt% of the MIL‐100(Fe) nanoparticles are incorporated in the hybrid material resulting in an increase of the microporosity up to 130 m2 g−1. Hybrid membranes show an appealing catalytic activity in Friedel–Crafts alkylation in a batch mode as well as in a flow‐through mode, thereby demonstrating the preserved accessibility of Lewis acidic sites in the MOF nanostructures.
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.
This study describes the development of a functional porous polymer for use as a scaffold to support 3D hepatocyte culture. A high internal phase emulsion (HIPE) is prepared containing the monomers styrene (STY), divinylbenzene (DVB), and 2‐ethylhexyl acrylate (EHA) in the external oil phase and the monomer acrylic acid (Aa) in the internal aqueous phase. Upon thermal polymerization with azobisisobutyronitrile (AIBN), the resulting porous polymer (polyHIPE) is found to have an open‐cell morphology and a porosity of 89%, both suitable characteristics for 3D cell scaffold applications. X‐ray photoelectron spectroscopy reveals that the polyHIPE surface contained 7.5% carboxylic acid functionality, providing a useful substrate for subsequent surface modifications and bio‐conjugations. Initial bio‐compatibility assessments with human hepatocytes show that the acid functionality does not have any detrimental effect on cell adhesion. It is therefore believed that this material can be a useful precursor scaffold towards 3D substrates that offer tailored surface functionality for enhanced cell adhesion.
This article summarizes recent progress in the post‐functionalization of conjugated polymers by electrochemical methods. These electrochemical polymer reactions typically proceed via electrochemical doping of a conjugated polymer film, followed by chemical transformation. Examples include the quantitative oxidative fluorination of polyfluorenes and oxidative halogenation of polythiophenes, as well as the reductive hydrogenation of polyfluorenones. The degree of functionalization, otherwise known as the reaction ratio, can be controlled by varying the charge passed through the polymer, allowing the optoelectronic properties of the conjugated polymers to be tailored. Wireless bipolar electrodes with an in‐plane potential distribution are also useful with regard to the electrochemical doping and reaction of conjugated polymers and allow the synthesis of films exhibiting composition gradients. Such bipolar electrochemistry can induce multiple reaction sites during electrochemical polymer reactions.
Hierarchical self‐assembly of transient composite hydrogels is demonstrated through a two‐step, orthogonal strategy using nanoparticle tectons interconnected through metal–ligand coordination complexes. The resulting materials are highly tunable with moduli and viscosities spanning many orders of magnitude, and show promising self‐healing properties, while maintaining complete optical transparency.
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.
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.
The sodium salt of the new bis(mesitoyl)phosphinic acid (BAPO‐OH) can be prepared in a very efficient one‐pot synthesis. It is well soluble in water and hydrolytically stable for at least several weeks. Remarkably, it acts as an initiating agent for the surfactant‐free emulsion polymerization (SFEP) of styrene to yield monodisperse, spherical nanoparticles. Time‐resolved electron paramagnetic resonance (TR‐EPR) and chemically induced electron polarisation (CIDEP) indicate preliminary mechanistic insights.
Swell! Superabsorbent, mechanically robust, high‐porosity hydrogels based on poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) have been successfully synthesized by templating within high internal phase emulsions (HIPEs). These hydrogel polyHIPEs (HG‐PHs) exhibit unusually high uptakes of water and of artificial urine through structure‐ and crosslinking‐dependent hydrogel‐swelling‐driven void expansion. An HG‐PH with 3.1 mmol g−1 of highly accessible sulfonic acid groups exhibits a 7 meq NaOH ion exchange capacity per gram polymer and rapid dye absorption. The highly swollen HG‐PHs do not fail at compressive strains of up to 60%, they retain water and recover their shapes upon the removal of stress. Unusually, the dry hydrogels have relatively high compressive moduli and achieve relatively high stresses at 70% strain.
Novel macrocyclic amine‐linked oligocarbazole hollow microspheres are synthesized via a one‐step oxidative method in aqueous solution. Upon altering the oxidants and acidic media, the average diameters of the obtained hollow microspheres are tunable from 0.23 to 2.0 μm. With attractive amine and carbazole functionalities, exposed surface area, thermostability, and photoluminescent properties, the amine‐linked oligocarbazole hollow microspheres are directly assembled to yield heavy metal sorbents with excellent selectivity and recyclability, shown to efficiently remove lead from contaminated water.
A novel type of emulsion gel based on star‐polymer‐stabilized emulsions is highlighted, which contains discrete hydrophobic oil and hydrophilic aqueous solution domains. Well‐defined phenol‐functionalized core‐crosslinked star polymers are synthesized via reversible addition‐fragmentation chain transfer (RAFT)‐mediated dispersion polymerization and are used as stabilizers for oil‐in‐water emulsions. Horseradish‐peroxidase‐catalyzed polymerization of the phenol moieties in the presence of H2O2 enables rapid formation of crosslinked emulsion gels under mild conditions. The crosslinked emulsion gels exhibit enhanced mechanical strength, as well as widely tunable composition.
The electrical memory characteristics of the n‐channel organic field‐effect transistors (OFETs) employing diverse polyimide (PI) electrets are reported. The synthesized PIs comprise identical electron donor and three different building blocks with gradually increasing electron‐accepting ability. The distinct charge‐transfer capabilities of these PIs result in varied type of memory behaviors from the write‐one‐read‐many (WORM) to flash type. Finally, a prominent flexible WORM‐type transistor memory is demonstrated and shows not only promising write‐many‐read‐many (WMRM) multilevel data storage but also excellent mechanical and retention stability.
Well‐defined ABC triblock copolymers based on two hydrophilic blocks, A and C, and a hydrophobic block B are synthesized and their self‐assembly behavior is investigated. Interestingly, at the same solvent, concentration, pH, and temperature, different shape micelles are observed, spherical and worm‐like micelles, depending on the preparation method. Specifically, spherical micelles are observed with bulk rehydration while both spherical and worm‐like micelles are observed with film rehydration.
Dynamic covalent hydrogels are facilely prepared from biocompatible polysaccharides in physiological conditions by the formation of phenylboronate ester cross‐links. This is based on the simple mixing of carboxylate‐containing polysaccharides (i.e., hyaluronic acid or carboxymethylcellulose) modified with phenylboronic acid and maltose moieties according to mild coupling reactions performed in aqueous solution. The formation of dynamic networks based on reversible boronic‐ester cross‐links is demonstrated by analyzing their rheological behavior. This study shows that these gels can adapt their structure in response to chemical stimuli such as variations in pH or addition of glucose and self‐heal.
Synthesis of hydroxy‐functionalized cyclic olefin copolymer (COC) is achieved with remarkably high activity (up to 5.96 × 107 g‐polymer mol‐Ti−1 h−1) and controlled hydroxy group in a wide range (≈17.1 mol%) by using ansa‐dimethylsilylene (fluorenyl)(amido)titanium complex. The catalyst also promotes living/controlled copolymerization to afford novel diblock copolymers consisting of hydroxy‐functionalized COC and semicrystalline polyolefin sequence such as polyethylene and syndiotactic polypropylene, where the glass transition temperature of the norbornene/10‐undecen‐1‐ol segment and each block length are controlled by comonomer composition and copolymerization time, respectively.
Imitating the natural “energy cascade” architecture, we present a single‐molecular rod‐like nano‐light harvester (NLH) based on a cylindrical polymer brush. Block copolymer side chains carrying (9,9‐diethylfluoren‐2‐yl)methyl methacrylate units as light absorbing antennae (energy donors) are tethered to a linear polymer backbone containing 9‐anthracenemethyl methacrylate units as emitting groups (energy acceptors). These NLHs exhibit very efficient energy absorption and transfer. Moreover, we manipulate the energy transfer by tuning the donor–acceptor distance.
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 authors study adjustable bandgap properties of the novel triple chalcogenophene‐based polymer poly‐(3‐hexyl‐2(3‐(4‐hexylthiophene‐2‐yl)‐4,5‐butylselenophene‐1‐yl)‐5‐(4,5‐butyltellurophene‐1‐yl)thiophene) through a combination of morphological, spectroscopic, and computational techniques. The bandgap can be tuned after polymerization by means of mild temperature annealing, which will allow for a partnership with a broader range of donor/acceptor molecules, a property that makes it potentially suitable for organic photovoltaic implementation. The bandgap is modified by selection of the annealing temperatures, and the process is arguably related to the aggregation of tellurophene units, as similar effects are observed in polytellurophenes. Moreover, adequate chemistry engineering ensures easy solution processability and attainment of homogeneous films, which is also essential for applications.
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).
