Optically active helical substituted (co)polyacetylenes containing pendent pyrene groups are prepared and then noncovalently immobilized on graphene via π–π interactions. The resulting graphene composite is characterized by XRD, FTIR, Raman, circular dichroism, UV‐vis absorption, TEM, TGA, and fluorescent spectroscopy techniques. The helical polyacetylene endows graphene with the desired optical activity. Also interestingly, the dispersibility of the functionalized graphene in tetrahydrofuran is remarkably improved due to the presence of the helical polymer chains. The present methodology opens new opportunities and serves as a versatile platform toward preparing novel graphene‐based materials.
A simplified one‐pot and less harmful method has been introduced for the synthesis of borinic acid monomer. The corresponding borinic acid polymer (PBA) has been prepared by reversible addition‐fragmentation chain transfer polymerization. Property investigations confirm the characteristics of PBA as a new type of “smart material” in the field of thermo‐responsive polymer. The potential application of PBA in the field of enzymatic biofuel cell has been illustrated with a wide open circuit potential of 0.92 V.
Radial symmetry is essential for the conventional view of the polymer spherulite microstructure. Typically it is assumed that, in the course of the spherulite morphogenesis, the lamellar crystals grow radially. Using submicron X‐ray diffraction, it is shown that in banded spherulites of poly(propylene adipate) the crystals have the shape of a helix with flat‐on crystals winding around a virtual cylinder of about 6 µm in diameter. The helix angle of 30° implies that the crystal growth direction is tilted away from the spherulite radius by this angle. The implications of the helical crystal shape contradict the paradigm of the spherulitic microstructure. The radial growth rate of such spherulites does not correspond to the crystal growth rate, but to the propagation rate of the virtual cylinder the ribbons wind around.
Recently, extensive investigations are carried out on design of highly controlled architecture and morphology by polymerizing the monomers doped in well‐defined liquid crystalline materials, followed by removal of the template liquid crystal molecules. In this communication, a photonic structure used as a new photonic bandgap (PBG) material is developed by imprinting helical structures on polymer matrices through multiple photocrosslinking processes in an induced chiral nematic mesophase using flexible polyethylene terephthalate (PET) films as substrates. The tuning properties of the reflection band of the imprinted cell are achieved using an uniaxial thermo‐stretching equipment. Furthermore, refilling of isotropic materials into the imprinted cells tune the reflection light wavelength leads to the change of color.
In this study, a material is designed which combines the properties of shape‐memory and electroactive polymers. This is achieved by covalent cross‐linking of polyvinylidene fluoride. The resulting polymer network exhibits excellent shape‐memory properties with a storable strain of 200%, and fixity as well as recovery values of 100%. Programming upon rolling induces the transformation from the nonelectroactive α‐phase to the piezoelectric β‐phase. The highest β‐phase content is found to be 83% for a programming strain of 200% affording a d33 value of −30 pm V−1. This is in good accordance with literature known values for piezoelectric properties. Thermal triggering this material does not only result in a shape change but also renders the material nonelectroactive.
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.
Cyclic polystyrene (PS) with a pendant coumarin group is prepared by the combination of atom transfer radical polymerization and “click” chemistry. Fluorescence resonance energy transfer process is observed in the fluorescence measurement of coumarin‐containing PS, and cyclic PS exhibits stronger emission than that of its linear precursor. When cyclic PS is irradiated under UV light at λ = 365 nm, 8‐shaped PS is achieved due to the dimerization of pendant coumarin group. Subsequently, 8‐shaped PS can be divided into single macrocycle under UV irradiation at λ = 254 nm via the photocleavage of coumarin dimer. The photoinduced coupling and dissociation are monitored by UV/vis spectra and gel permeation chromatography (GPC).
The entrapment of a protein in porous poly(d,l ‐lactide‐co‐glycolide) (PLGA) microspheres is demonstrated through the closure of their outer surface pores for sustained delivery of the protein. The porous PLGA microspheres with less than 10 μm in size are prepared by electrospraying. Aqueous solutions containing fluorescein isothiocyanate‐dextran or bovine serum albumin (BSA) are penetrated into the inner pores as a result of vacuum treatment, and the outer surface pores of the porous PLGA microspheres are then closed using a solvent (dimethyl sulfoxide) to ensure entrapment of the macromolecules. Confocal microscopy images confirm the presence of a large amount of the macromolecules inside the porous structure. Circular dichroism spectroscopy and release analysis reveal that BSA is entrapped without denaturation and released in a sustained manner for a period of over 2 months, respectively.
The combination of external potential dynamics and Brownian dynamics is introduced to study the kinetics of orientational ordering in block copolymer/superparamagnetic nanoparticle composites where the particles are smaller than the domain spacing and preferentially segregate into one block of the copolymer. This simulation method accounts for both excluded volume interactions and dipolar interactions between particles to quantify alignment kinetics. Two‐dimensional simulations reveal that higher dipolar interaction strengths lead to faster alignment of the block copolymer, where the orientation kinetics obeys an exponential rate law. The observed rate of alignment increases with increasing dipolar interaction strength and is dependent on the initial state of the block copolymer. The primary mechanism of orientational ordering is found to be the redistribution of monomer segments leading to bridging and growth of the block copolymer domains around the nanoparticles.
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.
Porous hollow silica particles (HSPs) are presented as new templates to control the product morphology in metallocene‐catalyzed olefin polymerization. By selectively immobilizing catalysts inside the micrometer‐sized porous hollow silica particles, the high hydraulic forces resulting from polymer growth within the confined geometries of the HSPs cause its supporting shell to break up from the inside. As the shape of the support is replicated during olefin polymerization, perfectly spherical product particles with very narrow size distribution can be achieved by using HSPs exhibiting a monomodal size distribution. Furthermore, the size of the obtained product particles can be controlled not only by the polymerization time but also by the size of the support material.
For the first time, polybutadiene is separated according to microstructure using solvent gradient interaction chromatography (SGIC). Superior separation of polybutadienes having different microstructures is obtained on a silica‐based reversed stationary phase and a mobile phase of acetone–hexane. This SGIC system enables the baseline separation of 1,2‐polybutadienes and 1,4‐polybutadienes even in cases where the samples have similar molar masses. 2D liquid chromatography is performed with the SGIC method separating according to microstructure in the first dimension coupled to size exclusion chromatography separating according to molar mass in the second dimension, thus providing comprehensive information on both microstructure and molar mass.
Heavy metal ion pollution has become a serious environmental problem. Herein, this study reports the synthesis of poly(ionic liquid) (PIL) membranes via in situ photo‐crosslinking of vinyl imidazole with both hydrophilic and hydrophobic ionic liquid monomers. The resultant amphiphilic polymer membranes are porous and exhibit high absorption capacity of metal ions (including Hg2+, Pb2+, Cu2+, Cd2+, and Zn2+) in both high (1000 mg L−1) and low (10 mg L−1) concentration metal ion solutions. These metal ionic absorption membranes are easily regenerated in acid solution and can be reused without significant decreases of absorption capacity after many cycles. These PIL membranes may have potential applications as eco‐friendly and safe heavy metal ion removal materials.
Janus particles with anisotropic biofunctionalities are perfect models to mimic anisotropic architectures and directional interactions that occur in nature. It is therefore highly desirable to develop reliable and efficient methods to synthesize biofunctional Janus particles. Herein, a facile method combining seeded‐emulsion polymerization and thiol‐click chemistry has been developed to synthesize Janus particles with glucose moieties on one side. These biofunctional Janus particles show region‐selective binding of protein, which represents a big step toward biomimicry, and demonstrates the potential of the bioJanus particles for targeted drug delivery and binding.
A thermally stable 2D array of spheres and their morphology control become important for the fabrication of novel nanostructures. Here, a simple method is presented for fabrication of large‐area and well‐ordered arrays of carbonized polystyrene (PS) hollow spheres with a controlled (close‐packed or non‐close‐packed hexagonal) morphology, prepared by combining the self‐assembly of PS‐grafted silica nanoparticles, etching, electron irradiation, and subsequent thermal annealing. Fine control in the 2D or 3D nanostructure of carbon materials can open up new opportunities for high‐performance nanoscale applications that require an efficient fabrication method for preparation of the porous carbon array.
Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real‐time image recording feature.
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
Poly‐(N‐isopropylacrylamide) (PNIPA) hydrogel films doped with uniaxially aligned liquid crystalline (LC) nanosheets adsorbed with a dye are synthesized and its anomalous photothermal deformation is demonstrated. The alignment of the nanosheet LC at the cm‐scale is easily achieved by the application of an in‐plane or out‐of‐plane AC electric field during photo‐polymerization. A photoresponsive pattern is printable onto the gel with μm‐scale resolution by adsorption of the dye through a pattern‐holed silicone rubber. When the gel is irradiated with light, only the colored part is photothermally deformed. Interestingly, the photo‐irradiated gel shows temporal expansion along one direction followed by anisotropic shrinkage, which is an anomalous behavior for a conventional PNIPA gel.
The fabrication of electrospun polymer fibers is demonstrated with anisotropic cross‐sections by applying a simple pressing method. Electrospun polystyrene or poly(methyl methacrylate) fibers are pressed by flat or patterned substrates while the samples are annealed at elevated temperatures. The shapes and morphologies of the pressed polymer fibers are controlled by the experimental conditions such as the pressing force, the pressing temperature, the pressing time, and the surface pattern of the substrate. At the same pressing force, the shape changes of the polymer fibers can be controlled by the pressing time. For shorter pressing times, the deformation process is dominated by the effect of pressing and fibers with barrel‐shaped cross‐sections can be generated. For longer pressing times, the effect of wetting becomes more important and fibers with dumbbell‐shaped cross‐sections can be obtained. Hierarchical polymer fibers with nanorods are fabricated by pressing the fibers with porous anodic aluminum oxide templates.
In this study, the group transfer polymerization (GTP) of the functional monomer 3‐(trimethoxysilyl)propyl methacrylate (TMSPMA) is reported to produce polymers of different architectures and topologies. TMSPMA is successfully polymerized and copolymerized with GTP to produce well‐defined (co)polymers that can be used to fabricate functional hybrid materials like hydrogels and films.
