Polyacrylamides containing pendant aminobisphosphonate groups are synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization and a multicomponent postpolymerization functionalization reaction. A Moedritzer–Irani reaction installs the phosphonic acid groups on well‐defined, RAFT‐generated polymers bearing a pendant amine. An alternate route to the same materials is developed utilizing a three‐component Kabachnik–Fields reaction and subsequent dealkylation. Kinetics of the RAFT polymerization of the polymer precursor are studied. Successful functionalization is demonstrated by NMR and FTIR spectroscopy and elemental analysis of the final polymers.
A one‐pot procedure that straightforwardly combines reversible addition‐fragmentation chain transfer (RAFT) polymerization and end group transformation to remove the RAFT end groups is developed for the synthesis of well‐defined poly(meth)acrylates and polyacrylamides with inert end groups. This procedure only requires the addition of an amine at the end of the standard RAFT polymerization procedure, which avoids the separation and purification of the intermediate polymers and, hence, extremely reduces the working time and utilized amount of solvents. Upon addition of the amine, a thiol group is formed by aminolysis of the thiocarbonylthio group, which subsequently undergoes Michael addition with unreacted monomer leading to an inert thioether functionalized polymer.
This paper reports on the synthesis of well‐defined polyacrylamide‐based nanogels via reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization, highlighting a templateless route for the efficient synthesis of nanogels based on water‐soluble polymers. RAFT dispersion polymerization of acrylamide in co‐nonsolvents of water–tert‐butanol mixtures by chain extension from poly(dimethylacrylamide) shows well‐controlled polymerization process, uniform nanogel size, and excellent colloidal stability. The versatility of this approach is further demonstrated by introducing a hydrophobic co‐monomer (butyl acrylate) without disturbing the dispersion polymerization process.
Hierarchical self‐assembly of transient composite hydrogels is demonstrated through a two‐step, orthogonal strategy using nanoparticle tectons interconnected through metal–ligand coordination complexes. The resulting materials are highly tunable with moduli and viscosities spanning many orders of magnitude, and show promising self‐healing properties, while maintaining complete optical transparency.
Imitating the natural “energy cascade” architecture, we present a single‐molecular rod‐like nano‐light harvester (NLH) based on a cylindrical polymer brush. Block copolymer side chains carrying (9,9‐diethylfluoren‐2‐yl)methyl methacrylate units as light absorbing antennae (energy donors) are tethered to a linear polymer backbone containing 9‐anthracenemethyl methacrylate units as emitting groups (energy acceptors). These NLHs exhibit very efficient energy absorption and transfer. Moreover, we manipulate the energy transfer by tuning the donor–acceptor distance.
Though great attention has been paid in constructing well‐defined nano‐structures via the self‐assembly of amphiphilic macromolecules, the self‐assembly of non‐amphiphilic macromolecules in nanodroplet has drawn less attention up to now. Recently, we prepared a temperature‐responsive PEG‐based branched polymer with disulfide bonds in its backbone via reversible addition–fragmentation chain transfer (RAFT) polymerization of 2‐(2‐methoxyethoxy) ethyl methacrylate, oligo(ethylene glycol) methacrylate, and N,N′‐cystamine bisacrylamide. Subsequently, we loaded the branched polymer into nanodroplets, and have found that the self‐assembly behaviors of this branched polymer in the nanodroplet are different from those in common solution. Bioreducible nanocapsules with tunable size can easily formed in nanodroplet even at high concentration.
A novel polymer featuring oligoaniline pendants that exhibits reversible electroactivity and good electrochromic properties with high contrast value, acceptable switching times, and excellent coloration efficiency is presented. This polymer can undergo reversible changes in fluorescence in response to reductive and oxidative chemical stimulus, pH, and electrical potential. The fluorescence switching operation shows reasonable reversibility and reproducibility when subjected to multiple stimuli. In this elegant fluorescence switching system, the oligoaniline pendants are used as fluorophore and regulatory units simultaneously.
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.
Polymer beads have attracted considerable interest for use in catalysis, drug delivery, and photonics due to their particular shape and surface morphology. Electrospinning, typically used for producing nanofibers, can also be used to fabricate polymer beads if the solution has a sufficiently low concentration. In this work, a novel approach for producing more uniform, intact beads is presented by electrospinning self‐assembled block copolymer (BCP) solutions. This approach allows a relatively high polymer concentration to be used, yet with a low degree of entanglement between polymer chains due to microphase separation of the BCP in a selective solvent system. Herein, to demonstrate the technology, a well‐studied polystyrene‐poly(ethylene butylene)–polystyrene triblock copolymer is dissolved in a co‐solvent system. The effect of solvent composition on the characteristics of the fibers and beads is intensively studied, and the mechanism of this fiber‐to‐bead is found to be dependent on microphase separation of the BCP.
A unique method of fabricating PS/AuNPs composite particles in ex situ mode is proposed on the basis of thermodynamically driving mechanism. It is facile and versatile as it eliminates the need for surface functionalizations and modifications of both PS microspheres and AuNPs. The PS/AuNPs composite particles take on a raspberry‐like morphology with controllable coverage according to some thermodynamic factors, which have been extensively characterized by scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. More importantly, the PS/AuNPs composite particles hold higher catalytic efficiency and better repeatability than the previously reported results, which are confirmed in two oxidation–reduction reactions of 2‐nitroaniline/NaBH4 and rhodamine B/NaBH4.
Synthesis of hydroxy‐functionalized cyclic olefin copolymer (COC) is achieved with remarkably high activity (up to 5.96 × 107 g‐polymer mol‐Ti−1 h−1) and controlled hydroxy group in a wide range (≈17.1 mol%) by using ansa‐dimethylsilylene (fluorenyl)(amido)titanium complex. The catalyst also promotes living/controlled copolymerization to afford novel diblock copolymers consisting of hydroxy‐functionalized COC and semicrystalline polyolefin sequence such as polyethylene and syndiotactic polypropylene, where the glass transition temperature of the norbornene/10‐undecen‐1‐ol segment and each block length are controlled by comonomer composition and copolymerization time, respectively.
Cationic polyelectrolytes showing an upper critical solution temperature (UCST) are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization in water at a temperature well above the UCST. The polymerization is well controlled by the RAFT process, with excellent pseudo‐first‐order kinetics. The cloud point is highly dependent on the polyelectrolyte concentration, molecular weight, and presence of added electrolyte. Alkylation of a neutral polymer is also conducted to obtain polyelectrolytes with different hydrophobic groups, which are shown to increase the cloud point.
Enzymatic catalysis and control over macromolecular architectures from reversible addition‐fragmentation chain transfer polymerization (RAFT) are combined to give a new method of making polymers. Horseradish peroxidase (HRP) is used to catalytically generate radicals using hydrogen peroxide and acetylacetone as a mediator. RAFT is used to control the polymer structure. HRP catalyzed RAFT polymerization gives acrylate and acrylamide polymers with relatively narrow molecular weight distributions. The polymerization is rapid, typically exceeding 90% monomer conversion in 30 min. Complex macromolecular architectures including a block copolymer and a protein‐polymer conjugate are synthesized using HRP to catalytically initiate RAFT polymerization.
Anion recognition between the triurea receptor and phosphate anion is demonstrated as the cross‐linkage to build supramolecular polymer gels for the first time. A novel multi‐block copolymer ( 3) is designed to have functional triurea groups as cross‐linking units along the polymer main chain. By virtue of anion coordination between the triurea receptor and phosphate anion with a binding mode of 2:1, supramolecular polymer gels are then prepared based on anion recognition using 3 as the building block.
Diselenide‐containing polymers are facilely synthesized from polymers prepared by atom transfer radical polymerization (ATRP). Benefiting from the ATRP technology, this protocol provides a flexible route for controlling the polymer structure, which allows for a great variety of architectures of selenium‐containing polymer materials for applications in various fields. The oxidative and reductive responsive behavior of the obtained diselenide‐containing polymers is also investigated.
Photodegradable physically cross‐linked polymer networks are prepared from self‐assembly of photolabile triblock copolymers. Linear triblock copolymers composed of poly (o‐nitrobenzyl methacrylate) and poly(ethylene glycol) (PEG) segments of variable molecular weights were synthesized using atom transfer radical polymerization. Triblock polymers with low‐molecular‐weight PEG segments form solid films upon hydration with robust mechanical properties including a Young's modulus of 76 ± 12 MPa and a toughness of 108 ± 31 kJ m−3. Triblock polymers with high‐molecular‐weight PEG segments form physically cross‐linked hydrogels at room temperature with a dynamic storage modulus of 13 ± 0.6 kPa and long‐term stability in hydrated environments. Both networks undergo photodegradation upon irradiation with long wave UV light.
Spontaneous formation of polymer nanoparticles of well‐defined, <100 nm sizes with controlled solid/hollow morphology and fluorescent properties is reported. The nanoparticle formation is assisted by temperature‐triggered nucleation of an amphiphilic polymer—poly(N‐isopropylacrylamide) (PNIPAM)—and mediated by hydrogen bonding of the emerged nuclei with tannic acid (TA). The pH of solution and TA/PNIPAM ratios are explored as parameters that define TA/PNIPAM assembly. Well‐defined nanoparticles are formed in a wide range of neutral pH when the TA/PNIPAM ratio exceeds its critical, pH‐dependent value. Dynamic light scattering and zeta potential measurements as well as atomic force microscopy and electron energy loss spectroscopy indicate that solid nanoparticles or nanocapsules are formed depending on the solution pH and that enhanced ionization of TA favors hollow morphology. Nanocapsules exhibit label‐free fluorescence at neutral pH values and therefore can be useful in imaging applications.
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.
Here, the preparation of a novel block copolymer consisting of a statistical copolymer N‐(2‐hydroxypropyl) methacrylamide‐s‐N‐(3‐aminopropyl) methacrylamide and a short terminal 3‐guanidinopropyl methacrylamide block is reported. This polymer structure forms neutral but water‐soluble nanosized complexes with siRNA. The siRNA block copolymer complexes are first analyzed using agarose gel electrophoresis and their size is determined with fluorescence correlation spectroscopy. The protective properties of the polymer against RNA degradation are investigated by treating the siRNA block copolymer complexes with RNase V1. Heparin competition assays confirm the efficient release of the cargo in vitro. In addition, the utilization of microscale thermophoresis is demonstrated for the determination of the binding strength between a fluorescently labeled polyanion and a polymer molecule.
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.
