A new approach to stabilize carbon nanotubes (CNTs) in aqueous solution with a reduction‐responsive water‐soluble polymer is reported. The novel polymer synthesized by a controlled radical polymerization is functionalized with pendant pyrene groups capable of adhering to the surface of CNTs through π–π noncovalent interactions, and labeled with disulfide linkages to exhibit reduction‐responsive cleavage. Upon the cleavage of junction disulfide linkages in a reducing environment, water‐soluble polymers are shed, retaining clean CNT surfaces for electrochemical catalytic reactions.
A new and easy method of stimuli‐triggered growth and removal of a bioreducible nanoshell on nanoparticles is reported. The results show that pH or temperature could induce the aggregation of disulfide‐contained branched polymers at the surface of nanoparticles; subsequently, the aggregated polymers could undergo intermolecular disulfide exchange to cross‐link the aggregated polymers, forming a bioreducible polymer shell around nanoparticles. When these nanoparticles with a polymer shell are treated with glutathione (GSH) or d,l ‐dithiothreitol (DTT), the polymer shell could be easily removed from the nanoparticles. The potential application of this method is demonstrated by easily growing and removing a bioreducible shell from liposomes, and improvement of in vivo gene transfection activity of liposomes with a bioreducible PEG shell.
Two soluble poly(phenyltriazolylcarboxylate)s (PPTCs) with high molecular weights (M w up to 26 800) are synthesized by the metal‐free 1,3‐dipolar polycycloadditions of 4,4′‐isopropylidenediphenyl diphenylpropiolate ( 1 ) and tetraphenylethene‐containing diazides ( 2 ) in dimethylformamide at 150 °C for 12 h in high yields (up to 93%). The resultant polymers are soluble in common organic solvents and are thermally stable with 5% weight loss temperatures higher than 375 °C. The PPTCs are nonemissive in solutions, but become highly luminescent upon aggregation, showing a phenomenon of aggregation‐induced emission. Their aggregates can be used as fluorescent chemosensors for high‐sensitivity detection of explosives.
Multivalent binding is a key for many critical biological processes and unique recognition and specificity in binding enables many of different glycans and proteins to work in a great harmony within the human body. In this study, the binding kinetics of synthetic glycopolypeptides to the dendritic cell lectin DC‐SIGN and their inhibition potential for DC‐SIGN interactions with the gp120 envelope glycoprotein of HIV‐1 (gp120) are investigated.
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.
Synthesis of a cyclodextrin (CD) polyrotaxane is achieved for the first time by simultaneous free radical polymerization of isoprene, threading by CD, and stoppering by copolymerization of styrene. This reaction is performed in an eco‐friendly manner in an aqueous medium similar to classical emulsion polymerization. Threaded CD rings of the polyrotaxane are cross‐linked by hexamethylene diisocyanate, leading to highly elastic slide‐ring gels.
Self‐initiated photografting polymerization is used to couple the polymerizable initiator monomer 2‐(2‐chloropropanoyloxy)ethyl acrylate to a range of polymeric substrates. The technique requires only UV light to couple the initiator to surfaces. The initiator surface density can be varied by inclusion of a diluent monomer or via selection of initiator and irradiation parameters. The functionality of the initiator surface is demonstrated by subsequent surface‐initiated atom transfer radical polymerization. Surfaces are characterized by x‐ray photoelectron spectroscopy (XPS), ellipsometry, and atomic force microscopy (AFM), and UV‐induced changes to the initiator are assessed by 1H NMR and gel permeation chromatography (GPC). This is the first time this one‐reactant one‐step technique has been demonstrated for creating an initiator surface of variable density.
A free‐standing polymer brush film with tailored thicknesses based on a colorless polydopamine (PDA) thin layer is prepared and characterized. The surface‐initiated atom transfer radical polymerization (ATRP) of 2‐hydroxyethyl methacrylate (HEMA) is performed on a PDA layer with thickness of ca. 6 nm, which generated an optically transparent and colorless free‐standing PHEMA brush film (1.5 cm × 1.5 cm). Because the cross‐linked PDA layer is used as the base for the polymer brushes, the reported method does not require cross‐linking the polymer brushes. The free‐standing film thicknesses of ≈16–75 nm are controlled by simply changing the ATRP reaction time. The results show that the free‐standing PHEMA brush film transferred onto a plate exhibits a relatively smooth surface and is stable in any solvent.
A superhydrophobic polythiophene film (SSPTH) is prepared by double‐layer electrodeposition on an indium tin oxide (ITO) glass electrode. This film shows not only electroresponsive superhydrophobic features, but also high transparency compared with the usual polythiophene film. The water‐droplet adhesion on the SSPTH film can be switched between sliding and pinned states under the applied potential. More intresetingly, the change in water‐droplet adhesion results in a change in cell adsorption on the SSPTH film. The low‐adhesion (dedoped) SSPTH films can prevent Hela cell adhesion, whereas high‐adhesion (doped) SSPTH films can promote Hela cell adsorption. This controllable cell adhesion on a SSPTH film may be developed as a smart biointerface material.
Cyclic multiblock polymers with high‐order blocks are synthesized via the combination of single‐electron transfer living radical polymerization (SET‐LRP) and copper‐catalyzed azide‐alkyne cycloaddition (CuAAC). The linear α,ω‐telechelic multiblock copolymer is prepared via SET‐LRP by sequential addition of different monomers. The SET‐LRP approach allows well control of the block length and sequence as A‐B‐C‐D‐E, etc. The CuAAC is then performed to intramolecularly couple the azide and alkyne end groups of the linear copolymer and produce the corresponding cyclic copolymer. The block sequence and the cyclic topology of the resultant cyclic copolymer are confirmed by the characterization of 1H nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared spectroscopy, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry.
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.
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.
Enzymes are attractive, “green” alternatives to chemical catalysts within the industrial sector, but their robustness to environmental conditions needs optimizing. Here, an enzyme is tagged chemically and recombinantly with a self‐assembling peptide that allows the conjugate to spontaneously assemble with pure peptide to form β‐sheet‐rich nanofibers decorated with tethered enzyme. Above a critical concentration, these fibers entangle and form a 3D hydrogel. The immobilized enzyme catalyzes chemical transformations and critically its stability is increased significantly where it retains activity after exposure to high temperatures (90 °C) and long storage times (up to 12 months).
The different mechanisms contributing to adhesion between two polymer surfaces are summarized and described in individual examples, which represent either seminal works in the field of adhesion science or novel approaches to achieve polymer–polymer adhesion. A further objective of this article is the development of new methodologies to achieve strong adhesion between low surface energy polymers.
Surface‐active polymers that display nonfouling properties and carry binding groups that can adsorb onto different substrates are highly desirable. We present a postmodification protocol of an active‐ester‐containing polymer that allows the creation of such a versatile platform. Poly(pentafluorophenyl acrylate) has been postmodified with a fixed grafting ratio of a nonfouling function (mPEG) and various combinations of functional groups, such as amine, silane and catechol, which can provide strong affinity to two model substrates: SiO2 and TiO2. Adsorption, stability and resistance to nonspecific protein adsorption of the polymer films were studied. A polymer was obtained that maintained its surface functionality under a variety of harsh conditions. EG surface‐density calculations show that this strategy generates a denser packing when both negatively and positively charged groups are present within the backbone, and readily allows the fabrication of a broad combinatorial matrix.
By simply blending two diblock copolymers with the same chemistry but with different compositions one is able to create well‐defined larger soft nanoparticles as well as bimodal soft nanoparticles. Specifically, blending two diblock copolymers in a solvent good for both blocks followed by a gradual introduction of a non‐solvent results in a mixed micelle, larger than their pure block‐copolymer‐forming micelles. The formation of well‐defined larger micelle is due to the balance between the ability of the mixed micelles to assemble or merge in comparison to their pure diblock copolymer micelles. Evidently, the blending ratio, the mixing protocol, and non‐solvent addition rate are crucial to achieving well‐defined larger or bimodal micelles.
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.
Two‐dimensional (2D) palladium nanocube array is achieved on plasma‐etched block copolymer templates, while the well‐aligned nanocubes remain active. Anisotropic nanocubes are site‐selectively assembled on various nanopatterns by capillary force. The nanocube array is proved to be easily tunable, and the dimensional commensurability plays a key role in the configurations of the nanocube assemblies. Not only catalytic nanocube array under confinement but also template for the growth of nanoscale zinc oxide (ZnO) nanorods is exemplified as the potential application of the nanoarray.
A novel strategy for the incorporation of carbon dioxide into polymers is introduced. For this purpose, the Ugi five‐component condensation (Ugi‐5CC) of an alcohol, CO2, an amine, an aldehyde, and an isocyanide is used to obtain step‐growth monomers. Polymerization via thiol‐ene reaction or polycondensation with diphenyl carbonate gives diversely substituted polyurethanes or alternating polyurethane‐polycarbonates, respectively. Furthermore, the application of 1,12‐diaminododecane and 1,6‐diisocyanohexane as bifunctional components in the Ugi‐5CC directly results in the corresponding polyamide bearing methyl carbamate side chains ( = 19 850 g mol−1). The latter polymer is further converted into the corresponding polyhydantoin in a highly straightforward fashion.
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.
