This communication describes the first application of cycloaddition between an in situ generated nitrile oxide with norbornene leading to a polymer crosslinking reaction for the preparation of poly(ethylene glycol) hydrogels under physiological conditions. Hydrogels with high water content and robust physical strength are readily formed within 2–5 min by a simple two‐solution mixing method which allows 3D encapsulation of neuronal cells. This bioorthogonal crosslinking reaction provides a simple yet highly effective method for preparation of hydrogels to be used in bioengineering.
Endowing unimolecular soft nanoobjects with biomimetic functions is attracting significant interest in the emerging field of single‐chain technology. Inspired by the compartmentalized structure and polymerase activity of metalloenzymes, copper‐containing compact nanoglobules have been designed, synthesized, and characterized endowed with metalloenzyme mimicking characteristics toward controlled synthesis of water‐soluble polymers and thermoresponsive hydrogels. When compared to metalloenzymes, artificial nanoobjects endowed with metalloenzyme mimicking characteristics offer increased stability against thermal changes and reduced degradability by hydrolytic enzymes.
The protection of primary amines available in proteins holds great potential to introduce a plethora of diverse functionalities along the protein backbone (e.g., via its carboxylic acid or alcohol moieties) while circumventing the crosslinking issue using conventional approaches. This paper reports on a straightforward and efficient proof‐of‐concept including the chemoselective N‐tert‐butyloxycarbonylation of the primary amines in the protein gelatin (gel‐NH‐BOC), followed by introducing crosslinkable methacrylamide moieties. The reaction is performed successfully under relatively mild conditions (50 °C). Following selective protein functionalization, the deprotection is realized by adding a catalytic amount of an aqueous hydrogen chloride solution. The present communication illustrates the occurrence of a straightforward and selective deprotection procedure, which is typically required to circumvent the occurrence of acidic hydrolysis of the protein backbone. The results hold promise for a large range of biomedical applications in which the presence of primary amines is essential for preserving the biological activity.
Improving thermal stability of TEMPO‐oxidized cellulose nanofibrils (TOCNs) is a major challenge for the development and preparation of new nanocomposites. However, thermal degradation of TOCNs occurs at 220 °C. The present study reports a simple way to improve thermal stability of TOCNs by the heat‐induced conversion of ionic bonds to amide bonds. Coupling amine‐terminated polyethylene glycol to the TOCNs is performed through ionic bond formation. Films are produced from the dispersions by the casting method. Infrared spectroscopy and thermogravimetric analysis confirm conversion of ionic bonds to amide bonds for the modified TOCN samples after heating. As a result, improvement of TOCNs' thermal stability by up to 90 °C is successfully achieved.
A new method for fabricating hydrogels with intricate control over hierarchical 3D porosity using microfiber porogens is presented. Melt electrospinning writing of poly(ε‐caprolactone) is used to create the sacrificial template leading to hierarchical structuring consisting of pores inside the denser poly(2‐oxazoline) hydrogel mesh. This versatile approach provides new opportunities to create well‐defined multilevel control over interconnected pores with diameters in the lower micrometer range inside hydrogels with potential applications as cell scaffolds with tunable diffusion and transport of, e.g., nutrients, growth factors or therapeutics.
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
Electrohydrodynamic cojetting has been employed to synthesize compartmentalized microfibers from thermally responsive hydrogels. The synthesis of the hydrogels as well as their transformation into compartmentalized microcylinders is discussed. After programmable shape‐shifting, snail‐like particles are obtained that undergo functional and structural reconfiguration in response to a change in temperature.
Graphene oxide–bacterial cellulose (GO/BC) nanocomposite hydrogels with well‐dispersed GO in the network of BC are successfully developed using a facile one‐step in situ biosynthesis by adding GO suspension into the culture medium of BC. During the biosynthesis process, the crystallinity index of BC decreases and GO is partially reduced. The experimental results indicate that GO nanosheets are uniformly dispersed and well‐bound to the BC matrix and that the 3D porous structure of BC is sustained. This is responsible for efficient load transfer between the GO reinforcement and BC matrix. Compared with the pure BC, the tensile strength and Young's modulus of the GO/BC nanocomposite hydrogel containing 0.48 wt% GO are significantly improved by about 38 and 120%, respectively. The GO/BC nanocomposite hydrogels are promising as a new material for tissue engineering scaffolds.
The first polymer bearing exTTF units intended for the use in electrical charge storage is presented. The polymer undergoes a redox reaction involving two electrons at −0.20 V vs Fc/Fc+ and is applied as active cathode material in a Li‐organic battery. The received coin cells feature a theoretical capacity of 132 mAh g−1, a cell potential of 3.5 V, and a lifetime exceeding more than 250 cycles.
A unique fabrication process of low molar mass, crystalline polypeptoid fibers is described. Thermoresponsive fiber mats are prepared by electrospinning a homogeneous blend of semicrystalline poly(N‐(n‐propyl) glycine) (PPGly; 4.1 kDa) with high molar mass poly(ethylene oxide) (PEO). Annealing of these fibers at ≈100 °C selectively removes the PEO and produces stable crystalline fiber mats of pure PPGly, which are insoluble in aqueous solution but can be redissolved in methanol or ethanol. The formation of water‐stable polypeptoid fiber mats is an important step toward their utilization in biomedical applications such as tissue engineering or wound dressing.
A facile and versatile method for the synthesis of Janus graphene oxide (GO) nanosheets with different structures is reported. Based on electrostatic assembly, Janus GO nanosheets can be easily functionalized with a template polymer or be defunctionalized by altering the ionic strength. By using this approach, Janus GO nanosheets are prepared successfully with hydrophobic polystyrene chains on one side and hydrophilic poly(2‐(dimethylamino)ethyl methacrylate) chains on the other side.
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.
A facile and versatile approach to constructing colorless surface coatings based on green tea polyphenols is reported, which can further act as a photoinitiating layer to initiate radical polymerization. These colorless green tea polyphenol coatings are capable of successfully photografting polymer brushes, and the resulting polymer brush patterns show spatial shape adjustability by masked UV irradiation. Both surface modifications and photografted polymer brushes do not alter the original color of the substrates. This method could be promising for the development of surface modifications.
A key feature of any living system is the ability to sense and react to the environmental stimuli. The biochemical characterization of the underlying biological sensors combined with advances in polymer chemistry has enabled the development of stimulus‐sensitive biohybrid materials that translate most diverse chemical and biological input into a precise change in material properties. In this review article, we first describe synthesis strategies of how biological and chemical polymers can functionally be interconnected. We then provide a comprehensive overview of how the different properties of biological sensor molecules such as competitive target binding and allosteric modulation can be harnessed to develop responsive materials with applications in tissue engineering and drug delivery.
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.
A new approach is reported for the preparation of a graphene–epoxy flexible transparent capacitor obtained by graphene–polymer transfer and UV‐induced bonding. SU8 resin is employed for realizing a well‐adherent, transparent, and flexible supporting layer. The achieved transparent graphene/SU8 membrane presents two distinct surfaces: one homogeneous conductive surface containing a graphene layer and one dielectric surface typical of the epoxy polymer. Two graphene/SU8 layers are bonded together by using an epoxy photocurable formulation based on epoxy resin. The obtained material showed a stable and clear capacitive behavior.
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.
Metal‐containing polymer hydrogels have attracted increasing interest in recent years due to their outstanding properties such as biocompatibility, recoverability, self‐healing, and/or redox activity. In this short review, methods for the preparation of metal‐containing polymer hydrogels are introduced and an overview of these hydrogels with various functionalities is given. It is hoped that this short update can stimulate innovative ideas to promote the research of metal‐containing hydrogels in the communities.
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.
Surface‐initiated photo‐induced copper‐mediated radical polymerization is employed to graft a wide range of polyacrylate brushes from silicon substrates at extremely low catalyst concentrations. This is the first time that the controlled nature of the reported process is demonstrated via block copolymer formation and re‐initiation experiments. In addition to unmatched copper catalyst concentrations in the range of few ppb, film thicknesses up to almost 1 μm are achieved within only 1 h.
