A new broad bandgap and 2D‐conjugated D‐A copolymer, PBDTBTz‐T , based on bithienyl‐benzodithiophene donor unit and bithiazole (BTz) acceptor unit, is designed and synthesized for the application as donor material in polymer solar cells (PSCs). The polymer possesses highly coplanar and crystalline structure with a higher hole mobility and lower HOMO energy level which is beneficial to achieve higher open circuit voltage (Voc) of the PSCs with the polymer as donor. The PSCs based on PBDTBTz‐T :PC71BM blend film with a lower PC71BM content of 40% demonstrate a power conversion efficiency (PCE) of 6.09% with a relatively higher Voc of 0.92 V. These results indicate that the lower HOMO energy level of the BTz‐based D–A copolymer is beneficial to a high Voc of the PSCs. The polymer, with highly coplanar and crystalline structure, can effectively reduce the content of fullerene acceptor in the active layer and can enhance the absorption and PCE of the PSCs.
Performance enhancement of polymer solar cells (PSCs) is achieved by expanding the absorption of the active layer of devices. To better match the spectrum of solar radiation, two polymers with different band gaps are used as the donor material to fabricate ternary polymer cells. Ternary blend PSCs exhibit an enhanced short‐circuit current density and open‐circuit voltage in comparison with the corresponding HD‐PDFC‐DTBT (HD)‐ and DT‐PDPPTPT (DPP)‐based binary polymer solar cells, respectively. Ternary PSCs show a power conversion efficiency (PCE) of 6.71%, surpassing the corresponding binary PSCs. This work demonstrates that the fabrication of ternary PSCs by using two polymers with complementary absorption is an effective way to improve the device performance.
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.
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.
Using the third‐generation Grubbs catalyst, the living ring‐opening metathesis polymerization of ferrocene/cobalticenium copolymers is conducted with theoretical numbers of 25 monomer units for each block, and their redox and electrochemical properties allow using the Bard–Anson electrochemical method to determine the number of metallocenyl units in each block.
CORM‐2, tricarbonyldichlororuthenium(II) dimer (Ru2Cl4(CO)6), is a common carbon monoxide releasing molecule (CORM) studied both in vitro and in vivo, but this compound possesses poor water solubility and a short half‐life, which hinders its clinical development. Herein, for the first time the conjugation of CORM‐2 is reported with a copolymer containing poly(4‐vinylpyridine) to yield water‐soluble CO‐releasing polymeric nanoparticles. CORM‐2 is rapidly conjugated to copolymers through pyridine groups as confirmed by inductively coupled plasma‐optical emission spectroscopy and infrared spectroscopy. In comparison with free CORM‐2, the copolymers functionalized with CORM‐2 display better water solubility and the CO release from the polymer‐based CORM is slow and sustained. This study paves the way for the potential use of a copolymer encapsulating CORM‐2 as a therapeutic agent.
Flow‐induced structure formation is investigated with in situ wide‐angle X‐ray diffraction with high acquisition rate (30 Hz) using isotactic polypropylene in a piston‐driven slit flow with high wall shear rates (up to ≈900 s−1). We focus on crystallization within the shear layers that form in the high shear rate regions near the walls. Remarkably, the kinetics of the crystallization process show no dependence on either flow rate or flow time; the crystallization progresses identically regardless. Stronger or longer flows only increase the thickness of the layers. A conceptual model is proposed to explain the phenomenon. Above a certain threshold, the number of shish‐kebabs formed affects the rheology such that further structure formation is halted. The critical amount is reached already within 0.1 s under the current flow conditions. The change in rheology is hypothesized to be a consequence of the “hairy” nature of shish. Our results have large implications for process modelling, since they suggest that for injection molding type flows, crystallization kinetics can be considered independent of deformation history.
Reversible addition‐fragmentation chain transfer polymerization yields reactive block copolymers bearing the pentafluorophenyl ester (PFPA) group, and subsequent Click amidation using 2,2,6,6‐tetramethylpiperidine‐N‐oxyl‐ and imidazolium‐functionalized primary amines produces the corresponding functional block copolymers, leading to installation of statistical radical‐ and ionic sites into the PFPA segment. The monolayered thin film devices fabricated using the obtained block copolymers exhibit repeatable switching of electric conductivity (on/off ratio > 103) under a bias voltage, which reveals that the coexistence of radicals and ions in the same spherical domain of the copolymer layer is a prerequisite for repeatable switching memory.
Messenger ribonucleic acids (mRNAs) are considered as promising alternatives for transient gene therapy, but to overcome their poor pharmacokinetic properties, smart carriers are required for cellular uptake and stimuli‐responsive release. In this work, a synthetic concept toward reductive decationizable cationic block copolymers for mRNA complexation is introduced. By combination of RAFT block copolymerization with postpolymerization modification, cationic block copolymers are generated with disulfide‐linked primary amines. They allow effective polyplex formation with negatively charged mRNA and subsequent release under reductive conditions of the cytoplasm. In first in vitro experiments with fibroblasts and macrophages, tailor‐made block copolymers mediate cell‐specific mRNA transfection, as quantified by polyplex uptake and mRNA‐encoding gene expression. Furthermore, RAFT polymerization provides access to heterotelechelic polymers with orthogonally addressable endgroup functionalities utilized to ligate targeting units onto the polyplex‐forming block copolymers. The results exemplify the broad versatility of this reductive decationizable mRNA carrier system, especially toward further advanced mRNA delivery applications.
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.
A series of optically active helical copolymers of phenylacetylenes are prepared by the rhodium‐catalyzed copolymerization of the imidazolidinone‐linked, catalytically active achiral phenylacetylenes and catalytically inactive chiral phenylacetylenes. The obtained chiral/achiral copolymers exhibit an induced circular dichroism in the UV–vis regions of the copolymer backbones resulting from a preferred‐handed helical conformation biased by the chiral imidazolidinone units incorporated in the copolymers. The copolymers are found to catalyze the asymmetric Diels–Alder reaction and produce the products with a moderate enantioselectivity in spite of the fact that the catalytically active units of the copolymers are achiral, indicating that the observed enantioselectivity totally originates from the helical chirality dynamically induced by the optically active, but catalytically inactive imidazolidinone units incorporated in the copolymers.
A rapid access to 2,2′‐bithiazole‐based copolymers has been developed on the basis of the sequential palladium‐catalyzed C H/C X and C H/C H coupling reactions. To assemble a “copolymer” through homopolymerization, a type of symmetric A‐B‐A‐type building block is designed as the monomer and prepared via the regioselective C5 H arylation of thiazole. A PdCl2/CuCl‐cocatalyzed oxidative C H/C H homopolymerization has been established to afford the 2,2′‐bithiazole‐based copolymers with high Mn (up to 69400). The current protocol features atom‐ and step‐economy and exhibits a potential in the highly efficient construction of conjugated copolymers.
Atom transfer radical polymerization (ATRP) is a versatile and robust tool to synthesize a wide spectrum of monomers with various designable structures. However, it usually needs large amounts of transition metal as the catalyst to mediate the equilibrium between the dormant and propagating species. Unfortunately, the catalyst residue may contaminate or color the resultant polymers, which limits its application, especially in biomedical and electronic materials. How to efficiently and economically remove or reduce the catalyst residue from its products is a challenging and encouraging task. Herein, recent advances in catalyst separation and recycling are highlighted with a focus on (1) highly active ppm level transition metal or metal free catalyzed ATRP; (2) post‐purification method; (3) various soluble, insoluble, immobilized/soluble, and reversible supported catalyst systems; and (4) liquid‐liquid biphasic catalyzed systems, especially thermo‐regulated catalysis systems.
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 and self‐assembly of novel semiconducting rod–coil type graft block copolymers based on poly(para‐phenylene vinylene) (PPV) copolymers is presented, focusing on the ordering effect of linear versus hyperbranched side chains. Using an additional reactive ester block, highly polar, linear poly(ethylene glycol), and hyperbranched polyglycerol side chains are attached in a grafting‐to approach. Remarkably, the resulting novel semiconducting graft copolymers with polyether side chains show different solubility and side‐chain directed self‐assembly behavior in various solvents, e.g., cylindrical or spherical superstructures in the size range of 10 to 120 nm, as shown by TEM. By adjusting the molecular weight and the topology of the polyether segments, self‐assembly into defined superstructures can be achieved, which is important for the efficient charge transport in potential electronic applications.
Polydopamine‐based coatings are fabricated via an electric field‐accelerating and ‐directing codeposition process of polydopamine with charged polymers such as polycations, polyanions, and polyzwitterions. The coatings are uniform and smooth on various substrates, especially on those adhesion‐resistant materials including poly(vinylidene fluoride) and poly(tetrafluoroethylene) membranes. Moreover, this electric field‐directed deposition method can be applied to facilely prepare Janus membranes with asymmetric chemistry and wettability.
A novel and non‐cytotoxic self‐healing supramolecular elastomer (SE) is synthesized with small‐molecular biological acids by hydrogen‐bonding interactions. The synthesized SEs behave as rubber at room temperature without additional plasticizers or crosslinkers, which is attributed to the phase‐separated structure. The SE material exhibits outstanding self‐healing capability at room temperature and essential non‐cytotoxicity, which makes it a potential candidate for biomedical applications.
A triblock copolymer containing the complementary hydrogen bonding recognition pair ureidoguanosine–diaminonaphthyridine (UG–DAN) as pendant functional groups is synthesized using ring‐opening metathesis polymerization (ROMP). The norbornene‐based DAN monomer is shown to allow for a controlled polymerization when polymerized in the presence of a modified‐UG molecule that serves as a protecting group, subsequently allowing for the fabrication of functionalized triblock copolymers. The self‐assembly of the copolymers was characterized using dynamic light scattering and 1H NMR spectroscopy. It is demonstrated that the polymers self‐assemble via complementary hydrogen bonding motifs even at low dilutions, indicating intramolecular interactions.
Bridgehead imine‐substituted cyclopentadithiophene structural units, in combination with highly electronegative acceptors that exhibit progressively delocalized π‐systems, afford donor–acceptor (DA) conjugated polymers with broad absorption profiles that span technologically relevant wavelength (λ) ranges from 0.7 < λ < 3.2 μm. A joint theoretical and experimental study demonstrates that the presence of the cross‐conjugated substituent at the donor bridgehead position results in the capability to fine‐tune structural and electronic properties so as to achieve very narrow optical bandgaps (Egopt < 0.5 eV). This strategy affords modular DA copolymers with broad‐ and long‐wavelength light absorption in the infrared and materials with some of the narrowest bandgaps reported to date.
The combination of dendritic and linear polymeric structures in the same macromolecule opens up new possibilities for the design of block copolymers and for applications of functional polymers that have self‐assembly properties. There are three main strategies for the synthesis of linear‐dendritic block copolymers (LDBCs) and, in particular, the emergence of click chemistry has made the coupling of preformed blocks one of the most efficient ways of obtaining libraries of LDBCs. In these materials, the periphery of the dendron can be precisely functionalised to obtain functional LDBCs with self‐assembly properties of interest in different technological areas. The incorporation of stimuli‐responsive moieties gives rise to smart materials that are generally processed as self‐assemblies of amphiphilic LDBCs with a morphology that can be controlled by an external stimulus. Particular emphasis is placed on light‐responsive LDBCs. Furthermore, a brief review of the biomedical or materials science applications of LDBCs is presented.
