A double hydrophilic block copolymer, poly(ethylene glycol)‐poly(3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate) (PEG‐SB), is synthesized by reversible addition‐fragmentation transfer (RAFT) polymerization using PEG methyl ether (4‐cyano‐4‐pentanoate dodecyl trithiocarbonate) as a chain transfer agent. PEG‐SB forms multi‐layered microspheres with dipole‐dipole interactions of the SB side chains as the driving force. The PEG‐SB polymers show an upper critical solution temperature (UCST) and the UCST is controllable by the polymerization degree. The PEG‐SB microspheres are dissociated above the UCST and then monodispersed microspheres (∼1 μm) are obtained when the solution temperature is decreased below the UCST again. The disassociation/association of the microspheres is also controllable using the concentration of NaCl. These multi‐responsive microspheres could be a powerful tool in the field of nano‐biotechnology.
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.
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.
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.
The chemical synthesis of a novel polyfuran, poly(2,3‐bis(hexylthio)‐[1,4]dithiino[2,3‐c]furan) ( PBDF ), substituted at the 2,3‐positions with an S‐alkylated dithiin unit, is reported. The new polymer has been characterized in terms of its electronic absorption, electrochemical, and thermal properties. Employment of the dithiin moiety provides intrinsic additional electroactivity, as well as a functional handle for substitution with alkyl groups, enhancing the processability of the polymer. The new polymer is compared with the closely related and well‐established literature compounds PEDOT and PEDTT as well‐studied, highly chalcogenated polythiophenes.
An efficient metal‐free homodifunctional bimolecular ring‐closure method is developed for the formation of cyclic polymers by combining reversible addition‐fragmentation chain transfer (RAFT) polymerization and self‐accelerating click reaction. In this approach, α,ω‐homodifunctional linear polymers with azide terminals are prepared by RAFT polymerization and postmodification of polymer chain end groups. By virtue of sym‐dibenzo‐1,5‐cyclooctadiene‐3,7‐diyne (DBA) as small linkers, well‐defined cyclic polymers are then prepared using the self‐accelerating double strain‐promoted azide–alkyne click (DSPAAC) reaction to ring‐close the azide end‐functionalized homodifunctional linear polymer precursors. Due to the self‐accelerating property of DSPAAC ring‐closing reaction, this novel method eliminates the requirement of equimolar amounts of telechelic polymers and small linkers in traditional bimolecular ring‐closure methods. It facilitates this method to efficiently and conveniently produce varied pure cyclic polymers by employing an excess molar amount of DBA small linkers.
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.
Detailed knowledge of the polymerization mechanisms and kinetics of academically and industrially relevant monomers is mandatory for the precision synthesis of tailor‐made polymers. The IUPAC‐recommended pulsed‐laser polymerization–size exclusion chromatography (PLP–SEC) approach is the method of choice for the determination of propagation rate coefficients and the associated Arrhenius parameters for free radical polymerization processes. With regard to specific monomer classes—such as acrylate‐type monomers, which are very important from a materials point of view—high laser frequencies of up to 500 Hz are mandatory to prevent the formation of mid‐chain radicals and the occurrence of chain‐breaking events by chain transfer, if industrially relevant temperatures are to be reached and wide temperature ranges are to be explored (up to 70 °C). Herein the progress and state‐of‐the‐art of high‐frequency PLP–SEC with pulse repetition rates of 500 Hz is reported, with a critical collection of to‐date investigated 500 Hz data as well as future perspectives for the field.
The attempts to mediate iterative RAFT polymerization of ionic monomers through visible light irradiation in water at 20 °C is reported, in which complete conversions are attained in several tens of minutes and the propagation suspends/restarts immediately for multiple times on cycling irradiation. This technique suits the one‐pot synthesis of NH2/imidazole‐based polymers with tuned structures from homo to random, block, random‐block, and block‐random‐block, thus is robust and promising to control the sequence of the ionized water‐soluble reactive copolymers.
The synthesis of tetracene‐ and pentacene‐annulated norbornadienes, formed through the Diels–Alder reaction of a dehydroacene with cyclopentadiene is reported. Ring‐opening metathesis polymerization (ROMP) leads to polymers that are investigated with respect to their physical, optical, and electronic properties by gel permeation chromatography (GPC), UV–vis spectroscopy, and cyclic voltammetry. The pentacene‐containing polymer P1 is successfully integrated into an organic field‐effect transistor (OFET); the tetracene‐containing polymer P2 is integrated into an organic light‐emitting diode (OLED).
The formation of a poly(2,6‐carbazole) derivative during an electrochemical polymerization process is shown. Comparison of 3,5‐bis(9‐octyl‐9H‐carbazol‐2‐yl)pyridine and 3,5‐bis(9‐octyl‐9H‐carbazol‐3‐yl)pyridine by electrochemical and UV–Vis‐NIR spectroelectrochemical measurements and DFT (density functional theory) calculation prove the formation of a poly(2,6‐carbazole) derivative. Both of the compounds form stable and electroactive conjugated polymers.
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.
Moisture or water has the advantages of being green, inexpensive, and moderate. However, it is challenging to endow water‐induced shape memory property and self‐healing capability to one single polymer because of the conflicting structural requirement of the two types of materials. In this study, this problem is solved through introducing two kinds of supramolecular interactions into semi‐interpenetrating polymer networks (semi‐IPNs). The hydrogen bonds function as water‐sensitive switches, making the materials show moisture‐induced shape memory effect. The host–guest interactions (β‐cyclodextrin‐adamantane) serve as both permanent phases and self‐healing motifs, enabling further increased chain mobility at the cracks and self‐healing function. In addition, these polyvinylpyrrolidone/poly(hydroxyethyl methacrylate‐co‐butyl acrylate) semi‐IPNs also show thermosensitive triple‐shape memory effect.
A novel diblock copolymer consisting of poly(vinylferrocene) (PVFc) and poly(N,N‐diethylacrylamide) (PDEA) is synthesized via a combination of anionic and RAFT polymerization. The use of a novel route to hydroxyl‐end‐functionalized metallopolymers in anionic polymerization and subsequent esterification with a RAFT agent leads to a PVFc macro‐CTA ( = 3800 g mol−1; Đ = 1.17). RAFT polymerization with DEA affords block copolymers as evidenced by 1H NMR spectroscopy as well as size exclusion chromatography (6400 ≤ ≤ 33700 g mol−1; 1.31 ≤ Đ 1.28). Self‐assembly of the amphiphilic block copolymers in aqueous solution leads to micelles as shown via TEM. Importantly, the distinct thermo‐responsive and redox‐responsive character of the blocks is probed via dynamic light scattering and found to be individually and repeatedly addressable.
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.
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 novel photo‐induced homogeneous atom transfer radical polymerization (ATRP) system is constructed using an organic copper salt (Cu(SC(S)N(C2H5)2)2) as a photo‐induced catalyst at 30 °C. Herein, N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) is used as a ligand, ethyl 2‐bromophenylacetate (EBPA) as an ATRP initiator, and (2,4,6‐trimethylbenzoyl) diphenylphosphine oxide (TPO) as a photo‐induced radical initiator to establish an ICAR (initiators for continuous activator regeneration) ATRP using methyl methacrylate (MMA) as a modal monomer. The effect of the concentration of the organic copper on the polymerization is investigated in detail. It is found that well‐controlled polymerization can be obtained even with the amount of (Cu(SC(S)N(C2H5)2)2 decreasing to a 1.56 ppm level, with the molecular weight of the resultant polymers increasing linearly with monomer conversion while maintaining a narrow molecular weight distribution (/ < 1.3).
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.
Recently, polymer drug conjugates (PDCs) have attracted considerable attention in the treatment of cancer. In this work, a simple strategy has been developed to make PDCs of an antitumor alkylating agent, chlorambucil, using a biocompatible disulphide linker. Chlorambucil‐based chain transfer agent was used to prepare various homopolymers and block copolymers in a controlled fashion via reversible addition–fragmentation chain transfer polymerization. Chlorambucil conjugated block copolymer, poly(polyethylene glycol monomethyl ether methacrylate)‐b‐poly(methyl methacrylate), formed nanoaggregates in aqueous solutions, which are characterized by dynamic light scattering and field emission‐scanning electron microscopy. Finally, the simplicity of the design is exemplified by performing a release study of chlorambucil under reducing condition by using D,L‐dithiothreitol.
Pure quaternary tetraalkylammonium chlorides with one long alkyl chain dissolved in various organic solvents constitute a new class of cellulose solvents. The electrolytes are prepared in high yields and purity by Menshutkin quaternization, an inexpensive and easy synthesis route. The pure molten tetraalkylammonium chlorides dissolve up to 15 wt% of cellulose. Cosolvents, including N,N‐dimethylacetamide (DMA), may be added in large excess, leading to a system of decreased viscosity. Contrary to the well‐established solvent DMA/LiCl, cellulose dissolves in DMA/quaternary ammonium chlorides without any pretreatment. Thus, the use of the new solvent avoids some disadvantages of DMA/LiCl and ionic liquids, the most extensively employed solvents for homogeneous cellulose chemistry.
