Electroactive hydrogel scaffolds are fabricated by the 3D‐printing technique using composites of 30% Pluronic F127 and aniline tetramer‐grafted‐polyethylenimine (AT‐PEI) copolymers with various contents from 2.5% to 10%. The synthesized AT‐PEI copolymers can self‐assemble into nanoparticles with the diameter of ≈50 nm and display excellent electroactivity due to AT conjugation. The copolymers are then homogeneously distributed into 30% Pluronic F127 solution by virtue of the thermosensitivity of F127, denoted as F/AT‐PEI composites. Macroscopic photographs of latticed scaffolds elucidate their excellent printability of F/AT‐PEI hydrogels for the 3D‐printing technique. The conductivities of the printed F/AT‐PEI scaffolds are all higher than 2.0 × 10−3 S cm−1, which are significantly improved compared with that of F127 scaffold with only 0.94 × 10−3 S cm−1. Thus, the F/AT‐PEI scaffolds can be considered as candidates for application in electrical stimulation of tissue regeneration such as repair of muscle and cardiac nerve tissue.
The synthesis of an ambipolar π‐conjugated copolymer consisting of alternating diketopyrrolopyrrole and tetrafluorobenzene via direct arylation polymerization (DAP) is reported. Two different combinations of monomers are investigated under various catalytic conditions for DAP. The target polymer obtained under an optimized catalytic condition shows minimal structural defects, a number‐average molecular weight of 33.2 kDa, and balanced electron and hole mobility of 1 × 10−2 cm2 V−1 S−1 in the organic field‐effect transistors fabricated and tested under ambient conditions.
Five three‐component chiral polymers incorporating (S )‐1,1′‐binaphthyl, tetraphenylethene (TPE) and fluorene moieties are designed and synthesized by Pd‐catalyzed Sonogashira reaction. All these polymers show obvious aggregation induced emission enhancement response behavior in the fluorescence emission region of 460–480 nm. Interestingly, three of them show aggregation‐induced circularly polarized luminescence (AICPL) signals in tetrahydrofuran–H2O mixtures. Most importantly, these AICPL signals can be tuned by changing the molar ratios of TPE and fluorene components through fluorescence resonance energy transfer and give the highest glum = ±4.0 × 10−3. This work provides a novel strategy for developing AICPL‐enhanced materials.
The performance of polymer field‐effect transistors (PFETs) based on short rigid rod semiconducting poly(2,5‐didodecyloxy‐p‐phenyleneethynylene) (D‐OPPE) is highlighted. The controlled heating and cooling of thin films of D‐OPPE allows for a recrystallization from the melt, boosting the performance of D‐OPPE‐based transistors. The improved film properties induced by controlled annealing lead to a hole field‐effect mobility around 0.014 cm2 V−1 s−1, an on/off ratio of 106, a sub‐threshold swing of 3 V dec−1 and a threshold voltage of −35 V, employing a poly(methyl methacrylate) (PMMA) gate dielectric. Thus, PFETs out of D‐OPPE compete now with spin‐coated, polycrystalline poly(3‐hexylthiophene)‐based PFETs.
Novel redox‐responsive polymeric nanogels that allow highly efficient enzyme encapsulation and reversible modulation of enzyme activity are developed. The nanogel synthesis and encapsulation of enzyme are performed simultaneously via in situ crosslinking of pyridyldisulfide‐functionalized water‐soluble reactive copolymers, which are synthesized via reversible addition–fragmentation chain transfer copolymerization. Obtained nanogels with loaded cellulase demonstrate very good colloidal stability in aqueous solutions. The enzymatic activity of cellulase is greatly reduced when encapsulated in the nanogels and rapidly recovered in 10 × 10−3 m dithiothreitol solution. Fluorescence resonance energy transfer (FRET)‐based experiments indicate that the recovered enzymatic activity is mainly ascribed to the release of the enzyme due to the degradation of the disulfide crosslinking network after addition of dithiothreitol (DTT), instead of the enhanced substrate transport rate. The developed enzyme immobilization method opens new possibilities for reversible activation/deactivation of enzymes and opens up new directions for targeted protein therapy and biotechnology applications.
Photoinitiated reversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of 2‐hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2‐(2‐methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (Mn = 475 g mol−1) as the macro‐RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible‐light irradiation (405 nm, 0.5 mW cm−2), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple “ON/OFF” switch of the light source. Finally, thermoresponsive diblock copolymer nano‐objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.
The ruthenium benzimidazolylidene‐based N‐heterocyclic carbene (NHC) complex 4 catalyzes the direct dehydrogenative condensation of primary alcohols into esters and primary alcohols in the presence of amines to the corresponding amides in high yields. This efficient new catalytic system shows a high selectivity towards the conversion of diols to polyesters and of a mixture of diols and diamines to polyamides. The only side product formed in this reaction is molecular hydrogen. Remarkable is the conversion of hydroxytelechelic polytetrahydrofuran ( = 1000 g mol−1)—a polydispers starting material—into a hydrolytically degradable polyether with ester linkages ( = 32 600 g mol−1) and, in the presence of aliphatic diamines, into a polyether with amide linkages in the back bone ( = 16 000 g mol−1).
A new acceptor–donor–acceptor (A–D–A) small molecule based on benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) is synthesized via a Stille cross‐coupling reaction. A highly conjugated selenophene‐based side group is incorporated into each BDT unit to generate a 2D soluble small molecule (SeBDT‐DPP). SeBDT‐DPP thin films produce two distinct absorption peaks. The shorter wavelength absorption (400 nm) is attributed to the BDT units containing conjugated selenophene‐based side groups, and the longer wavelength band is due to the intramolecular charge transfer between the BDT donor and the DPP acceptor. SeBDT‐DPP thin films can harvest a broad solar spectrum covering the range 350–750 nm and have a low bandgap energy of 1.63 eV. Solution‐processed field‐effect transistors fabricated with this small molecule exhibit p‐type organic thin film transistor characteristics, and the field‐effect mobility of a SeBDT‐DPP device is measured to be 2.3 × 10−3 cm2 V−1 s−1. A small molecule solar cell device is prepared by using SeBDT‐DPP as the active layer is found to exhibit a power conversion efficiency of 5.04% under AM 1.5 G (100 mW cm−2) conditions.
The controlled folding of a single polymer chain is for the first time realized by metal‐ complexation. α,ω‐Bromine functional linear polymers are prepared via activators regenerated by electron transfer (ARGET) ATRP (,SEC = 5900 g mol−1, Đ = 1.07 and 12 000 g mol−1, Đ = 1.06) and the end groups of the polymers are subsequently converted to azide functionalities. A copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction is carried out in the presence of a novel triphenylphosphine ligand and the polymers to afford homotelechelic bis‐triphenylphosphine polymeric‐macroligands (MLs) (,SEC = 6600 g mol−1, Đ = 1.07, and 12 800 g mol−1, Đ = 1.06). Single‐chain metal complexes (SCMCs) are formed in the presence of Pd(II) ions in highly diluted solution at ambient temperature. The results derived via 1H and 31P{1H} NMR experiments, SEC, and DLS unambiguously evidence the efficient formation of SCMCs via metal ligand complexation.
Four novel conjugated polymers ( P1‐4 ) with 9,10‐disubstituted phenanthrene (PhA) as the donor unit and 5,6‐bis(octyloxy)benzothiadiazole as the acceptor unit are synthesized and characterized. These polymers are of medium bandgaps (2.0 eV), low‐lying HOMO energy levels (below −5.3 eV), and high hole mobilities (in the range of 3.6 × 10−3 to 0.02 cm2 V−1 s−1). Bulk heterojunction (BHJ) polymer solar cells (PSCs) with P1‐4 :PC71BM blends as the active layer and an alcohol‐soluble fullerene derivative (FN‐C60) as the interfacial layer between the active layer and cathode give the best power conversion efficiency (PCE) of 4.24%, indicating that 9,10‐disubstituted PhA are potential donor materials for high‐efficiency BHJ PSCs.
High‐molecular‐weight conjugated polymer HD‐PDFC‐DTBT with N‐(2‐hexyldecyl)‐3,6‐difluorocarbazole as the donor unit, 5,6‐bis(octyloxy)benzothiadiazole as the acceptor unit, and thiophene as the spacer is synthesized by Suzuki polycondensation. HD‐PDFC‐DTBT shows a large bandgap of 1.96 eV and a high hole mobility of 0.16 cm2 V−1 s−1. HD‐PDFC‐DTBT:PC71BM‐based inverted polymer solar cells (PSCs) give a power conversion efficiency (PCE) of 7.39% with a Voc of 0.93 V, a Jsc of 14.11 mA cm−2, and an FF of 0.56.
The fluorinated FI–Ti catalyst bis[N‐(3‐propylsalicylidene)‐pentafluoroanilinato] titanium(IV) dichloride (PFI) combined with dried methylaluminoxane (dMAO) is investigated for ethylene/1‐hexene copolymerization at 50 °C under atmospheric pressure. The reaction shows good livingness and has a high activity at high [H]/[E] molar ratios up to 14. Ultrahigh molecular weight (>1.4 × 106 g mol−1) copolymers with high 1‐hexene content (>25 mol%) are prepared. Kinetic parameters of the copolymerization with PFI are determined. The first‐order Markov statistics applies and the product of the reactivity ratios r1r2 is close to 1, giving random unit distributions.
A highly living polymer with over 100 kg mol−1 molecular weight is very difficult to achieve by controlled radical polymerization since the unavoidable side reactions of irreversible radical termination and radical chain transfer to monomer reaction become significant. It is reported that over 500 kg mol−1 polystyrene with high livingness and low dispersity could be synthesized by a facile two‐stage reversible addition–fragmentation transfer emulsion polymerization. The monomer conversion reaches 90% within 10 h. High livingness of the product is ascribed to the extremely low initiator concentration and the chain transfer constant for monomer unexpectedly much lower than the well‐accepted values in the conventional radical polymerization. The two‐stage monomer feeding policy much decreases the dispersity of the product.
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 fused ladder indacenodithiophene (IDT)‐based donor–acceptor (D–A)‐type alternating conjugated polymer, PIDTHT‐BT, presenting n‐hexylthiophene conjugated side chains is prepared. By extending the degree of intramolecular repulsion through the conjugated side chain moieties, an energy level for the highest occupied molecular orbital (HOMO) of –5.46 eV – a value approximately 0.27 eV lower than that of its counterpart PIDTDT‐BT – is obtained, subsequently providing a fabricated solar cell with a high open‐circuit voltage of approximately 0.947 V. The hole mobility (determined using the space charge‐limited current model) in a blend film containing 20 wt% PIDTHT‐BT) and 80 wt% [6,6]‐phenyl‐C71 butyric acid methyl ester (PC71BM) is 2.2 × 10–9 m2 V–1 s–1, which is within the range of reasonable values for applications in organic photovoltaics. The power conversion efficiency is 4.5% under simulated solar illumination (AM 1.5G, 100 mW cm–2).
Conjugated pillar[5]arene‐diketopyrrolopyrrole copolymer ( P1 ) is synthesized by the copolymerization of a difunctionalized pillar[5]arene and a diketopyrrolopyrrole‐based monomer, which shows large extinction coefficients (1.1 × 104m –1 cm–1) at 519 nm and strong emission at 587 nm. P1 exhibits very strong host–guest binding affinity towards adiponitrile but low binding affinity towards 1,4‐dihalobutane and 1,4‐bis(imidazol‐1‐yl)butane. Such an enhanced selectivity is first found in the polypseudorotaxane between pillararene and neutral guests in organic solution and is successfully used for the recognition and adsorption of adiponitrile by the formation of a P1 ‐adiponitrile polypseudorotaxane.
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.
A one‐pot method is introduced for the successful synthesis of narrow‐distributed (Đ = 1.22) vinyl polymer with both ultrahigh molecular weight (UHMW) (Mw = 1.31 × 106 g mol−1) and micro‐/nanomorphology under mild conditions. The method involves the following four stages: homogeneous polymerization, polymerization‐induced self‐assembly (PISA), PISA and reorganization, and PISA and multiple reorganizations. The key points to the production of UHMW polystyrene are to minimize radical termination by segregating radicals in different nanoreactors and to ensure sufficient chain propagation by promoting further reorganizations of these reactors in situ. This method therefore endows polymeric materials with the outstanding properties of both UHMW and tunable micro‐/nanoparticles under mild conditions in one pot.
Highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as transparent electrodes for organic light‐emitting diodes (OLEDs) are doped with a new solvent 1,3‐dimethyl‐2‐imidazolidinone (DMI) and are optimized using solvent post‐treatment. The DMI doped PEDOT:PSS films show significantly enhanced conductivities up to 812.1 S cm−1. The sheet resistance of the PEDOT:PSS films doped with DMI is further reduced by various solvent post‐treatment. The effect of solvent post‐treatment on DMI doped PEDOT:PSS films is investigated and is shown to reduce insulating PSS in the conductive films. The solvent posttreated PEDOT:PSS films are successfully employed as transparent electrodes in white OLEDs. It is shown that the efficiency of OLEDs with the optimized DMI doped PEDOT:PSS films is higher than that of reference OLEDs doped with a conventional solvent (ethylene glycol). The results present that the optimized PEDOT:PSS films with the new solvent of DMI can be a promising transparent electrode for low‐cost, efficient ITO‐free white OLEDs.
Layer‐by‐layer (LbL) assembly has emerged as the leading non‐vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide‐based barrier films. This Feature Article is a mini‐review of LbL‐based multilayer thin films with a ‘nanobrick wall’ microstructure comprising polymeric mortar and nanoplatelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water‐based thin films exhibit oxygen transmission rates below 5 × 10‐3 cm3 m‐2 day‐1 atm‐1 and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake‐filled polymers are briefly reviewed.
