A recent response on a publication from our team investigating solvent effects on propagation rate coefficients is commented. Among other issues, we point to the fact that the response interprets only a subset of the data provided in our original contribution.
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.
Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self‐assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.
This study presents a new method to produce fluorescent particles. Established methods are based on the incorporation of conjugated dye molecules into dielectric polymer matrices or preparation of colloids, which are composed of fluorescent conjugated polymer. By contrast, this study presents a method where dielectric polyacrylonitrile is exposed to microwave radiation leading to an intramolecular cyclization reaction producing π‐conjugated segments, which fluoresce blue. During this conversion, the particles shrink in diameter but as an ensemble they retain their monodispersity. This work investigates the optimal reaction conditions and characterizes the optical properties.
Simulated‐sunlight induced atom transfer radical polymerization is used for spatial control over polymer brush growth by in situ photo‐generation of the CuI/L activator complex from its higher oxidation state CuII/L deactivator complex using dye sensitized titanium dioxide nanoparticles. The polymerization is well controlled under sunlight irradiation. Another attractive feature of this method is the possibility of creating various patterned surfaces of brushes using photomasks. When a nanoporous alumina oxide membrane is used as the template for confinement diffusion of photogenerated CuI/L catalyst, patterns with sub‐50 nm resolution are obtained.
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.
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.
A series of fluorene‐based conjugated polymers containing the aggregation‐induced emissive (AIE)‐active tetraphenylethene and dicarboxylate pseudocrown as a receptor exhibits a unique dual‐mode sensing ability for selective detection of lead ion in water. Fluorescence turn‐off and turn‐on detections are realized in 80%–90% and 20% water in tetrahydrofuran (THF), respectively, for lead ion with a concentration as low as 10−8 m .
Conjugated polymers may be induced by intra‐ and/or intermolecular non‐covalent forces to fold into helical conformations. Helices formed by aromatic amide, hydrazide, and urea polymers possess a well‐organized cavity and depth, which is defined by their degree of polymerization. Driving forces may be intramolecular hydrogen bonding and/or solvophobicity, or guest induction. The resulting long helices represent a new class of unimacromolecular dynamic tubular architectures that exhibit unique properties or functions in, for example, molecular recognition, chirality transfer, and ion transporting. The recent advances are highlighted here.
Glycerol polymers are attracting increased attention due to the diversity of polymer compositions and architectures available. This article provides a brief chronological review on the current status of these polymers along with representative examples of their use for biomedical applications. First, the underlying chemistry of glycerol that provides access to a range of monomers for subsequent polymerizations is described. Then, the various synthetic methodologies to prepare glycerol‐based polymers including polyethers, polycarbonates, polyesters, and so forth are reviewed. Next, several biomedical applications where glycerol polymers are being investigated including carriers for drug delivery, sealants or coatings for tissue repair, and agents possessing antibacterial activity are described. Fourth, the growing market opportunity for the use of polymers in medicine is described. Finally, the findings are concluded and summarized, as well as the potential opportunities for continued research efforts are discussed.
In this Communication, novel water‐soluble hyperbranched polysiloxanes (WHPSs) simultaneously containing hydroxyl and primary amine groups are developed. The polymers are constructed via melt polycondensation, that is, transesterification reaction between ethoxyl groups of (3‐aminopropyl)triethoxysilane and hydroxyl groups of dihydric alcohols, using a one‐step process under catalyst‐free conditions. Surprisingly, the resultant WHPSs can emit bright blue fluorescence in the 100% solid state under the irradiation of UV light, and their photoluminescence intensities in aqueous solutions continuously go up along with increasing concentrations. Interestingly, their hydrolyzates display more intense luminescence compared to the unhydrolyzed. The efficient and easily controllable preparation strategy provides a remarkable and versatile platform for the fabrication of neoteric fluorescent materials for various potential applications.
Polyamides are very important polymers that find applications from commodities up to the automotive and biomedical sectors, and their impact is continuously growing. The synthesis of structurally significant, chiral, and sustainable polyamides is described via a new, convenient, and solvent‐free anionic polymerization of a biobased ε‐lactam, which is obtained from the renewable terpenoid ketone l ‐menthone in a one‐step synthesis. These polyamides are shown to have outstanding structural and thermal properties, which are thus introduced via the structure and chirality of the natural lactam monomer and which are discussed and compared with those of petroleum‐based, established, and commercial polyamide Nylon‐6. X‐ray data reveal a remarkable degree of crystallinity in these green polymers and emphasize the impact of their structural features on the resulting properties.
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.
A novel water‐soluble fluorescent glycodendrimer based on perylene bisimides is synthesized, which exhibits high fluorescence quantum yield of 54%. While the binding interactions of PBI‐Man with Concanavalin A (Con A) are studied by fluorescence spectra and CD spectra, which show strong binding affinity for Con A with the binding constant of 3.8 × 107m −1 for monomeric mannose, nearly four orders of magnitude higher affinity than the monovalent mannose ligand. Furthermore, the fluorescence imaging of macrophage cell with PBI‐Man is investigated, and shows selectively binding interaction with the mannose receptor‐medicated cell entry. Moreover, the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) activities of PBI‐Man show that PBI‐Man as a biocompatible agent is noncytotoxic to living cells.
Functionalized polyfluorene receives more and more attention due to its wide applications. Here, the syntheses of three novel polyfluorene‐based methacrylate macromonomers exhibiting a vast flexibility for further applications are reported. Their emissions strongly depend on the end groups and thus the macromonomers provide blue, green, and red emissions simultaneously with the same excitation light of 365 nm. Their well‐defined copolymers with 2‐(dimethylamino) ethyl methacrylate via reversible addition‐fragmentation chain transfer polymerization are investigated in detail. These copolymers exhibit high quantum yields in solid film (up to 0.8), and self‐assemble into photoluminescent nanoparticles in aqueous solutions with pure blue, green, and red emissions. By simply mixing them, perfect white light emission with high quality is obtained. These aqueous nanoparticles solutions are ready for ink‐jet printing to produce exquisite bright and colorful fluorescent pictures.
Supramolecular microgel capsules based on polyethylene glycol (PEG) are a promising class of soft particulate scaffolds with tailored properties. An approach to fabricate such particles with exquisite control by droplet‐based microfluidics is presented. Linear PEG precursor polymers that carry bipyridine moieties on both chain termini are gelled by complexation to iron(II) ions. To investigate the biocompatibility of the microgels, living mammalian cells are encapsulated within them. The microgel elasticity is controlled by using PEG precursors of different molecular weights at different concentrations and the influence of these parameters on the cell viabilities, which can be optimized to exceed 90% is studied. Reversion of the supramolecular polymer cross‐linking allows the microcapsules to be degraded at mild conditions with no effect on the viability of the encapsulated and released cells.
The creation of hierarchical nanostructures in polymeric materials has been intensively studied due to the great potential to tailor their physicochemical properties. Although much success has been achieved over the past decades in block copolymers, hierarchical structure engineering in polymer blends remains a great challenge. Here, the formation of hierarchical lamellae‐in‐lamella nanostructures from polymer blends via controlled nonequilibrium freezing is reported. Polymer blends are first dissolved in molten hexamethylbenzene (HMB) to form a homogeneous melt. When cooled to below its melting temperature, the HMB is crystallized and depleted, and the polymers are directionally solidified. This process is rapid enough that phase separation of the polymer blends is kinetically trapped at the nanoscale level. Then, the polymer blend epitaxially crystallizes onto the HMB inside the nanophase, resulting in the hierarchical lamellae‐in‐lamella structure. This structure is stable under ambient conditions and tunable depending on the annealing temperature and blending ratio.
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.
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.
Dynamic covalent hydrogels are facilely prepared from biocompatible polysaccharides in physiological conditions by the formation of phenylboronate ester cross‐links. This is based on the simple mixing of carboxylate‐containing polysaccharides (i.e., hyaluronic acid or carboxymethylcellulose) modified with phenylboronic acid and maltose moieties according to mild coupling reactions performed in aqueous solution. The formation of dynamic networks based on reversible boronic‐ester cross‐links is demonstrated by analyzing their rheological behavior. This study shows that these gels can adapt their structure in response to chemical stimuli such as variations in pH or addition of glucose and self‐heal.
