Controlling self‐assembly behaviors of liquid crystals is a fundamental issue for designing them as intelligent actuators. Here, anisotropic porous polyvinylidene fluoride film is utilized as a template to induce homogeneous alignment of liquid crystals. The mechanism of liquid crystal alignment induced by anisotropic porous polyvinylidene fluoride film is illustrated based on the relationship between the alignment behavior of liquid crystals and surface microstructure of anisotropic polyvinylidene fluoride film. Liquid crystal elastomer actuators with fast responsiveness, large strain change, and reversible actuation behaviors are achieved by the photopolymerization of liquid crystal monomer in liquid crystal cells coated with anisotropic porous films.
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.
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).
A facile approach is reported to process rod–coil block copolymers (BCPs) into highly ordered nanostructures in a rapid, low‐energy process. By introducing a selective plasticizer into the rod–coil BCPs during annealing, both the annealing temperature and time to achieve thermodynamic equilibrium and highly ordered structures can be decreased. This process improvement is attributed to enhanced chain mobility, reduced rod–rod interaction, and decreased rod–coil interaction from the additive. The novel method is based on kinetically facilitating thermodynamic equilibrium. The process requires no modification of polymer structure, indicating that a wide variety of desired polymer functionalities can be designed into BCPs for specific applications.
This review describes different synthetic strategies towards sequence‐defined, monodisperse macromolecules, which are built up by iterative approaches and lead to linear non‐natural polymer structures. The review is divided in three parts: solution phase‐, solid phase‐, and fluorous‐ and polymer‐tethered approaches. Moreover, synthesis procedures leading to conjugated and non‐conjugated macromolecules are considered and discussed in the respective sections. A major focus in the evaluation is the applicability of the different approaches in polymer chemistry. In this context, simple procedures for monomer and oligomer synthesis, overall yields, scalability, purity of the oligomers, and the achievable level of control (side‐chains, backbone, stereochemistry) are important benchmarks.
We present a method to produce anti‐fouling reverse osmosis (RO) membranes that maintains the process and scalability of current RO membrane manufacturing. Utilizing perfluorophenyl azide (PFPA) photochemistry, commercial reverse osmosis membranes were dipped into an aqueous solution containing PFPA‐terminated poly(ethyleneglycol) species and then exposed to ultraviolet light under ambient conditions, a process that can easily be adapted to a roll‐to‐roll process. Successful covalent modification of commercial reverse osmosis membranes was confirmed with attenuated total reflectance infrared spectroscopy and contact angle measurements. By employing X‐ray photoelectron spectroscopy, it was determined that PFPAs undergo UV‐generated nitrene addition and bind to the membrane through an aziridine linkage. After modification with the PFPA‐PEG derivatives, the reverse osmosis membranes exhibit high fouling‐resistance.
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.
The surface of polyacrylonitrile (PAN) film is treated with ethyleneamines (EDA) in a simple chemical vapor phase reaction. Successful introduction of amine functional groups on the cyano group of PAN backbone is verified by FT‐IR and NMR measurements. Further UV‐vis and photoluminescence analyses show a red shift of the emission peak after repeated EDA treatment, which might be attributed to the formation of imine conjugation from newly formed carbon‐nitrogen bonds on the PAN backbone. Further confocal laser scanning microscopy reveals that selective patterning of EDA on PAN films is possible via local polydimethylsiloxane masking. The results indicate that both chemical and optical patterning on PAN film can be realized via a single reaction and show the potential of this novel methodology in selective patterning.
The chemical control of cell division has attracted much attention in the areas of single cell‐based biology and high‐throughput screening platforms. A mussel‐inspired cytocompatible encapsulation method for achieving a “cell‐division control” with cross‐linked layer‐by‐layer (LbL) shells is developed. Catechol‐grafted polyethyleneimine and hyaluronic acid are chosen as polyelectrolytes for the LbL process, and the cross‐linking of polyelectrolytes is performed at pH 8.5. Cell division is controlled by the number of the LbL nanolayers and cross‐linking reaction. We also suggest a new measuring unit, , for quantifying “cell‐division timing” based on microbial growth kinetics.
Thin, phenylboronic acid‐containing polymer coatings are potentially attractive sensory layers for a range of glucose monitoring systems. This contribution presents the synthesis and properties of glucose‐sensitive polymer brushes obtained via surface RAFT polymerization of 3‐methacrylamido phenylboronic acid (MAPBA). This synthetic strategy is attractive since it allows the controlled growth of PMAPBA brushes with film thicknesses of up to 20 nm via direct polymerization of MAPBA without the need for additional post‐polymerization modification or deprotection steps. QCM‐D sensor chips modified with a PMAPBA layer respond with a linear change in the shift of the fundamental resonance frequency over a range of physiologically relevant glucose concentrations and are insensitive toward the presence of fructose, thus validating the potential of these polymer brush films as glucose sensory thin coatings.
Via electron paramagnetic resonance (EPR) spectroscopy, the type of radicals occurring during acrylamide (AAm) homopolymerization in aqueous solution is investigated between −5 and +100 °C. The radicals are produced photochemically under stationary conditions. Midchain AAm radicals (MCRs) are clearly identified by EPR which demonstrates that secondary propagating AAm radicals (SPRs) undergo backbiting reactions. Above 50 °C, the fraction of MCRs even exceeds the one of SPRs. The extent of backbiting is however well below the one in butyl acrylate polymerization at identical temperature.
Here, a novel method is demonstrated for the preparation of three‐arm branched microporous organic nanotube networks (TAB‐MONNs) based on molecular templating of three‐arm branched core–shell bottlebrush copolymers and Friedel–Crafts alkylation reaction. The unique three‐arm branched bottlebrush copolymers are synthesized by a combination of atom transfer radical polymerization, reversible addition‐fragmentation chain transfer polymerization, and ring‐opening polymerization techniques. In this approach, the length and diameter of branched tube units can be well‐controlled by rational molecular design. Moreover, the as‐prepared TAB‐MONNs possess a high surface area and exhibit a superior adsorption capacity for Rhodamine 6G (R6G) and p‐cresol.
Described herein is a new printing method—direct writing of conducting polymers (CPs)—based on pipette‐tip localized continuous electrochemical growth. A single barrel micropipette containing a metal wire (Pt) is filled with a mixture of monomer, supporting electrolyte, and an appropriate solvent. A droplet at the tip of the pipette contacts the substrate, which becomes the working electrode of a micro‐electrochemical cell confined to the tip droplet and the pipette. The metallic wire in the pipette acts as both counter and reference electrode. Electropolymerization forms the CP on the working electrode in a pattern controlled by the movement of the pipette. In this study, various width poly(pyrrole) 2D and 3D structures are extruded and characterized in terms of microcyclic voltammetry, Raman spectroscopy, and scanning electron microscopy.
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.
Cross‐linked azobenzene liquid‐crystalline polymer films with a poly(oxyethylene) backbone are synthesized by photoinitiated cationic copolymerization. Azobenzene moieties in the film surface toward the light source are simultaneously photoaligned during photopolymerization with unpolarized 436 nm light and thus form a splayed alignment in the whole film. The prepared films show reversible photoinduced bending behavior with opposite bending directions when different surfaces of one film face to ultraviolet light irradiation.
The coordination polymerization of silyl‐protected ω‐alkenols such as ω‐alken‐α‐oxytriisopropylsilanes 1 provides poly(ω‐alkenyl‐α‐oxytriisopropylsilalne)s with a highly isospecific microstructure ([mmmm] > 95%) when a combination of [OSSO]‐type bis(phenolato) dichloro zirconium(IV) complex 2 and dried methylaluminoxane is used as the precatalyst and activator, respectively. The resulting siloxy‐substituted polymers could be efficiently transformed into the corresponding functionalized polyolefins, which contained up to 90% acetyl groups and ≈7% hydroxy groups in the terminal side chains.
Cationic polyelectrolytes showing an upper critical solution temperature (UCST) are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization in water at a temperature well above the UCST. The polymerization is well controlled by the RAFT process, with excellent pseudo‐first‐order kinetics. The cloud point is highly dependent on the polyelectrolyte concentration, molecular weight, and presence of added electrolyte. Alkylation of a neutral polymer is also conducted to obtain polyelectrolytes with different hydrophobic groups, which are shown to increase the cloud point.
This study proposes a method to coat thin films of non‐volatile solvents on substrates. A small amount of crystalline polymer dissolved in solvents forms a network of crystalline fibrils during the coating process. The network suppresses dewetting of the solvent liquid and helps the liquid film sustaining on the substrate. This strategy can be used in soft lithography to generate micropatterns of diverse materials without having a residual layer. This process does not request etching for achieving residual layer‐free micropatterns, which has been a long challenge in soft lithography. As examples, we demonstrate micropatterns of polymer hydrogels and metal oxides (ZnO, In2O3
The superior capabilities of structured microreactors over batch reactors are demonstrated for reversible addition–fragmentation chain transfer (RAFT) solution polymerization of n‐butyl acrylate with the aid of simulations, explicitly accounting for the chain length distribution of all macrospecies types. Since perfect isothermicity can be established in a microreactor, less side products due to backbiting and β‐scission are formed compared to the batch operation in which ineffective heat removal leads to an undesirable temperature spike. For a given RAFT chain transfer agent (CTA), additional microstructural control results under microflow conditions by optimizing the reaction temperature, lowering the dilution degree, or decreasing the initial molar ratio of monomer to RAFT CTA.
Liver cancer remains a significant medical problem and one promising therapeutic approach is to embolize the tumor. One emerging embolization strategy is to use thermoresponsive materials that can be injected but gel at the tumor site. It is now reported on thermoresponsive nanocomposites generated by grafting poly(N‐isopropylacrylamide) chains on bacterial cellulose nanowhiskers. Chemical and physical evidences are provided for grafting and demonstrated a sol–gel transition when the temperature is increased above 34.3 °C. Cytotoxicity test in human umbilical vein endothelial cells indicates the excellent biocompatibility of these nanocomposites for use as embolic materials. These results suggest that the nanocomposites offer appropriate properties for embolization of hepatocellular carcinoma.
