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Near‐infrared (NIR)‐triggered shape memory hydrogels with promising mechanical strength hold immense potential in the field of biomedical applications and soft actuators. However, the optical and mechanical properties of currently reported hydrogels usually suffer from limited solubility and dispersion of commonly used photothermal additives in hydrogels, thus restricting their practical implementations. Here,, a set of NIR‐responsive shape memory hydrogels synthesized by polyaddition of diisocyanate‐terminated poly(ethylene glycol), imidazolidinyl urea (IU), and p‐benzoquinone dioxime (BQDO) is reported. The introduction of IU, a hydrogen bond reinforcing factor, significantly enhances the mechanical properties of the hydrogels, allowing for their tunable ranges of the ultimate tensile strength (0.4–2.5 MPa), elongation at break (210–450%), and Young's modulus (190–850 kPa). The unique hydrogels exhibit an intrinsic photothermal effect because of the covalently incorporated photothermal moiety (BQDO), and the photothermal supramolecular hydrogel shows controllable shape memory capabilities characterized by rapid recovery speed and high recovery ratio (>90%). This design provides new possibilities for applying shape memory hydrogels in the field of soft actuators. [ABSTRACT FROM AUTHOR]

N‐type conjugated polymers as the semiconducting component of organic electrochemical transistors (OECTs) are still undeveloped with respect to their p‐type counterparts. Herein, we report two rigid n‐type conjugated polymers bearing oligo(ethylene glycol) (OEG) side chains, PgNaN and PgNgN, which demonstrated an essentially torsion‐free π‐conjugated backbone. The planarity and electron‐deficient rigid structures enable the resulting polymers to achieve high electron mobility in an OECT device of up to the 10−3 cm2 V−1 s−1 range, with a deep‐lying LUMO energy level lower than −4.0 eV. Prominently, the polymers exhibited a high device performance with a maximum dimensionally normalized transconductance of 0.212 S cm−1 and the product of charge‐carrier mobility μ and volumetric capacitance C* of 0.662±0.113 F cm−1 V−1 s−1, which are among the highest in n‐type conjugated polymers reported to date. Moreover, the polymers are synthesized via a metal‐free aldol‐condensation polymerization, which is beneficial to their application in bioelectronics. [ABSTRACT FROM AUTHOR]

Conjugated polymers that support mixed (electronic and ionic) conduction are in demand for applications spanning from bioelectronics to energy harvesting and storage. To design polymer mixed conductors for high‐performance electrochemical devices, relationships between the chemical structure, charge transport, and morphology must be established. A polymer series bearing the same p‐type conjugated backbone with increasing percentage of hydrophilic, ethylene glycol side chains is synthesized, and their performance in aqueous electrolyte gated organic electrochemical transistors (OECTs) is studied. By using device physics principles and electrochemical analyses, a direct relationship is found between the OECT performance and the balanced mixed conduction. While hydrophilic side chains are required to facilitate ion transport—thus enabling OECT operation—swelling of the polymer is not de facto beneficial for balancing mixed conduction. It is shown that heterogeneous water uptake disrupts the electronic conductivity of the film, leading to OECTs with lower transconductance and slower response times. The combination of in situ electrochemical and structural techniques shown here contributes to the establishment of the structure–property relations necessary to improve the performance of polymer mixed conductors and subsequently of OECTs. [ABSTRACT FROM AUTHOR]

Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness. [ABSTRACT FROM AUTHOR]

The fabrication of block copolymer (BCP) vesicles with controlled membrane permeability and promising stability remains a considerable challenge. Herein, a new type of pH‐responsive and self‐crosslinked vesicle based on a hydrolytically hindered urea bond is reported. This kind of vesicle is formed by the self‐assembly of a pH‐responsive and hydrolytically self‐crosslinkable copolymer poly(ethylene glycol)‐block‐poly[2‐(3‐(tert‐butyl)‐3‐ethylureido)ethyl methacrylate‐co‐2‐(diethylamino)ethyl methacrylate] (PEG‐b‐P(TBEU‐co‐DEA)). The BCP can be easily synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization of 2‐(3‐(tert‐butyl)‐3‐ethylureido)ethyl methacrylate (TBEU) and 2‐(diethylamino)ethyl methacrylate (DEA) using PEG‐based macro‐chain transfer agent. The copolymer could self‐assemble into stable vesicles by the hydrophobic interaction and in situ cross‐linking between amines and isocyanates after the hydrolysis of the hindered urea bonds without any catalyst. Dynamic light scattering (DLS) studies show that the vesicles exhibit enhanced stability against the dilution of organic solvent, and the size can be adjusted through the change of pH values. Moreover, the alkaline phosphatase‐loaded vesicles can act as nano‐reactor and enable free diffusion of small molecules into the vesicles, followed by the significantly improved fluorescence intensity of phosphate‐caged fluorescein. This self‐crosslinking and pH‐sensitive vesicles may serve as a smart platform in controlled drug delivery and molecular reactor. [ABSTRACT FROM AUTHOR]

We synthesize and systematicallystudy a series of conjugated polymerswith oligo(ethylene glycol) (OEG) or alkyl chain as the side chainand poly[2,7-fluorene-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)]as the polymer backbone. Replacing alkyl chain with OEG chain candecrease the π–π stacking distance of polymer backbonein thin film from 0.44 to 0.41 nm because OEG chain is more flexiblethan alkyl chain. As the result, the conjugated polymer with OEG sidechain exhibits higher hole mobility, red-shifted absorption spectrumin thin film and smaller bandgap than those of the conjugated polymerwith alkyl side chain. With the increase of the length of OEG sidechain, the resulting conjugated polymers exhibit unchanged π–πstacking distance and decreased hole mobility. Moreover, owing tothe large polarity of OEG chain, OEG side chain makes the conjugatedpolymer suitable for polymer solar cell (PSC) devices processed withpolar nonhalogenated solvent, methoxybenzene. A power conversion efficiencyof 4.04% is demonstrated with the resulting PSC devices. This workprovides the new insight into the effect of OEG side chain on conjugatedpolymer, which can be used in the molecular design of novel conjugatedpolymer materials with excellent optoelectronic device performance. [ABSTRACT FROM AUTHOR]