High‐porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil‐in‐water high internal phase emulsions (HIPEs) stabilized by gelatin‐graft‐poly(N‐isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell‐laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.
Emulsion‐templated highly porous polymers (polyHIPEs), containing distinct regions differing in composition, morphology, and/or properties, are prepared by the simultaneous polymerization of two high internal phase emulsions (HIPEs) contained within the same mould. The HIPEs are placed together in the mould and subjected to thiol‐acrylate photopolymerization. The resulting polyHIPE material is found to contain two distinct semicircular regions, reflecting the composition of each HIPE. The original interface between the two emulsions becomes a copolymerized band between 100 and 300 μm wide, which is found to be mechanically robust. The separate polyHIPE layers are distinguished from one another by their differing average void diameter, chemical composition, and extent of contraction upon drying.
A switch from carbanions to aza‐anions is performed by the addition of N‐tosylaziridine (TAz) to living poly(styryl) (PS) chains. This is the first example of carbanionic aziridine ring‐opening which was previously activated by amidation with a tosyl group to enable nucleophilic ring‐opening by the living chain end. Poly(styrene)‐tosylaziridines (PS‐TAz) with narrow molecular weight distributions and variable molecular weights are synthesized. The removal of the tosyl group and subsequent functionalization is shown, evidencing quantitative transfer to azaanionic species. All polymers are characterized in detail by 1H NMR spectroscopy, DOSY 1H NMR spectroscopy, and size exclusion chromatography (SEC). This strategy allows the introduction of amine groups via anionic polymerization in analogy to the well‐established epoxide termination.
Hierarchical semicrystalline block copolymer nanoparticles are produced in a segmented gas‐liquid microfluidic reactor with top‐down control of multiscale structural features, including nanoparticle morphologies, sizes, and internal crystallinities. Control of multiscale structure on disparate length scales by a single control variable (flow rate) enables tailoring of drug delivery nanoparticle function including release rates.
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.
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.
The directed self‐assembly of gold nanoparticles through the crystallization of surface‐grafted polyethylene oxide (PEO) in ethanol–water mixtures is described. This process is fully reversible and tunable through either the size of the core or the polymeric coating. Characterization by X‐ray scattering and electron microscopy of the self‐assembled structures reveals order at the nanoscale, typically not the case for thermoresponsive gold nanoparticles coated with lower or upper critical solution temperature polymers. A further novelty is the result of selective binding of calcium ions to the PEO in the fluid state: a reversible thermoresponsive transition become irreversible.
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.
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.
Swell! Superabsorbent, mechanically robust, high‐porosity hydrogels based on poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) have been successfully synthesized by templating within high internal phase emulsions (HIPEs). These hydrogel polyHIPEs (HG‐PHs) exhibit unusually high uptakes of water and of artificial urine through structure‐ and crosslinking‐dependent hydrogel‐swelling‐driven void expansion. An HG‐PH with 3.1 mmol g−1 of highly accessible sulfonic acid groups exhibits a 7 meq NaOH ion exchange capacity per gram polymer and rapid dye absorption. The highly swollen HG‐PHs do not fail at compressive strains of up to 60%, they retain water and recover their shapes upon the removal of stress. Unusually, the dry hydrogels have relatively high compressive moduli and achieve relatively high stresses at 70% strain.
Conjugated polymer nanoparticles based on poly[9,9‐bis(2‐ethylhexyl)fluorene] and poly[N‐(2,4,6‐trimethylphenyl)‐N,N‐diphenylamine)‐4,4′‐diyl] are fabricated using anionic surfactant sodium dodecylsulphate in water by miniemulsion technique. Average diameters of polyfluorene and polytriarylamine nanoparticles range from 70 to 100 and 100 to 140 nm, respectively. The surface of the nanoparticles is decorated with triplet emitting dye, tris(2,2′‐bipyridyl)ruthenium(II) chloride. Intriguing photophysics of aqueous dispersions of these hybrid nanoparticles is investigated. Nearly 50% quenching of fluorescence is observed in the case of dye‐coated polyfluorene nanoparticles; excitation energy transfer is found to be the dominant quenching mechanism. On the other hand, nearly complete quenching of emission is noticed in polytriarylamine nanoparticle‐dye hybrids. It is proposed that the excited state electron transfer from the electron‐rich polytriarylamine donor polymer to Ru complex leads to the complete quenching of emission of polytriarylamine nanoparticles. The current study offers promising avenues for developing aqueous solution processed‐electroluminescent devices involving a conjugated polymer nanoparticle host and Ru or Ir‐based triplet emitting dye as the guest.
Cross‐linked silicone elastomers constructed with dynamic‐covalent boronic esters are first synthesized by photoinitiated radical thiol−ene “click” chemistry. The resultant samples can be cut with a sharp knife into two pieces and then healed via the reversibility of the boronic ester cross‐linkages to restore the original silicone sample within 30 min. Regulation of luminescent properties is achieved by incorporating organic dye into the elastomers through a “one‐pot” thiol–ene reaction. The proposed synthesis procedure demonstrates a new strategy to produce boronic acid silicone materials capable of self‐healing without external forces.
The controlled synthesis of poly(oligo(2‐ethyl‐2‐oxazoline)methacrylate) (P(OEtOxMA)) polymers by Cu(0)‐mediated polymerization in water/methanol mixtures is reported. Utilizing an acetal protected aldehyde initiator for the polymerization, well‐defined polymers are synthesized (>99% conversion, Ð < 1.25) with subsequent postpolymerization deprotection resulting in α‐aldehyde end group containing comb polymers. These P(OEtOxMA) are subsequently site‐specifically conjugated, via reductive amination, to a dipeptide (NH2‐Gly‐Tyr‐COOH) as a model peptide, prior to conjugation to the functional peptide oxytocin. The resulting oxytocin conjugates are evaluated in comparison to poly(oligo(ethylene glycol) methyl ether methacrylate) combs synthesized in the same manner for potential effects on thermal stability in comparison to the native peptide.
Network polymers of cobaltporphyrin derivatives are prepared by a facile click reaction via the Michael addition of acetoacetate‐substituted tetraphenyl cobaltporphyrin and tri‐ or tetra‐acrylates. The conversion is saturated for 1 h in the presence of a catalyst, which almost reaches the same gelation point of the formed network polymers. Deeply and homogeneously red‐colored membranes with a sub‐micrometer thickness are yielded on a porous supporting membrane. They are still tough even with a very high content of the rigid porphyrin residue. The oxygen permeability is high, at 10–100 Barrer, and the oxygen/nitrogen permselectivity (PO2/PN2) is significantly enhanced with the porphyrin content reaching 30, for the membranes with ca. 70 wt% porphyrin content.
Continuous conductive gold nanofibers are prepared via the “tubes by fiber templates” process. First, poly(l‐lactide) (PLLA)‐stabilized gold nanoparticles (AuNP) with over 60 wt% gold are synthesized and characterized, including gel permeation chromatography coupled with a diode array detector. Subsequent electrospinning of these AuNP with template PLLA results in composite nanofibers featuring a high gold content of 57 wt%. Highly homogeneous gold nanowires are obtained after chemical vapor deposition of 345 nm of poly(p‐xylylene) (PPX) onto the composite fibers followed by pyrolysis of the polymers at 1050 °C. The corresponding heat‐induced transition from continuous gold‐loaded polymer tubes to smooth gold nanofibers is studied by transmission electron microscopy and helium ion microscopy using both secondary electrons and Rutherford backscattered ions.
Supramolecular polyfluorenol enable assembly into conjugated polymer nanoparticles (CPNs). Poly{9‐[4‐(octyloxy)phenyl]fluoren‐9‐ol‐2,7‐diyl} (PPFOH)‐based supramolecular nanoparticles are prepared via reprecipitation. PPFOH nanoparticles with diameters ranging from 40 to 200 nm are obtained by adding different amounts of water into DMF solution. Size‐dependent luminescence is observed in PPFOH‐based hydrogen‐bonded nanoparticles that is different from that of poly(9,9‐dioctylfluorenes). Finally, white light‐emitting devices using CPNs with a size of 80 nm exhibit white emission with the CIE coordinates (0.31, 0.34). Amphiphilic conjugated polymer nanoparticles are potential organic nano‐inks for the fabrication of organic devices in printed electronics.
The functionalization of zinc oxide (ZnO) nanoparticles by poly(3‐hexylthiophene) (P3HT) brush is completed by the combination of a mussel inspired biomimetic anchoring group and Huisgen cyclo‐addition “click chemistry.” Herein, the direct coupling of an azide modified catechol derivative with an alkyne end‐functionalized P3HT is described. This macromolecular binding agent is used to access core@corona ZnO@P3HT with a stable and homogeneous conjugated organic corona. Preliminary photoluminescence measurement proves an efficient electron transfer from the donor P3HT to the acceptor ZnO nanoparticles upon grafting, thus demonstrating the potential of such a combination in organic electronics.
Porous polymer membranes made via electrostatic complexation are fabricated from a water‐soluble poly(ionic liquid) (PIL) for the first time. The porous structure is formed as a consequence of simultaneous phase separation of the PIL and ionic complexation with an acid, which occurred in a basic solution of a nonsolvent for the PIL. These membranes have a stimuli‐responsive porosity, with open and closed pores in isopropanol and in water, respectively. This property is quantitatively demonstrated in filtration experiments, where water is passing much slower through the membranes than isopropanol.
The present review focuses on the recent progress made in thin film orientation of semi‐conducting polymers with particular emphasis on methods using epitaxy and shear forces. The main results reported in this review deal with regioregular poly(3‐alkylthiophene)s and poly(dialkylfluorenes). Correlations existing between processing conditions, macromolecular parameters and the resulting structures formed in thin films are underlined. It is shown that epitaxial orientation of semi‐conducting polymers can generate a large palette of semi‐crystalline and nanostructured morphologies by a subtle choice of the orienting substrates and growth conditions.
Temperature‐triggered phase separation of recombinant proteins has offered substantial opportunities in the design of nanoparticles for a variety of applications. Herein, the temperature‐triggered phase separation behavior of a recombinant hydrophilic resilin‐like polypeptide (RLP) is described. The transition temperature and sizes of RLP‐based nanoparticles can be modulated based on variations in polypeptide concentration, salt identity, ionic strength, pH, and denaturing agents, as indicated via UV–Vis spectroscopy and dynamic light scattering (DLS). The irreversible particle formation is coupled with secondary conformational changes from a random coil conformation to a more ordered β‐sheet structure. These RLP‐based nanoparticles could find potential use as mechanically‐responsive components in drug delivery, nanospring, nanotransducer, and biosensor applications.
