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.
This communication describes photoresponsive gels, prepared using ring‐opening metathesis polymerization (ROMP), that dissolve upon irradiation with ultraviolet light. Exposure of mixtures of norbornene‐type ROMP monomers and new photoreactive cross‐linkers comprising two norbornene units bound through a chain containing o‐nitrobenzyl esters (NBEs) to well‐known ruthenium carbene catalysts gave cross‐linked polymer networks that swelled in organic solvents or water depending on the structure of the monomer. These gels became homogeneous upon irradiation with UV light, consistent with breaking of the cross‐links through photolysis of the NBE groups. The irradiation time required for homogenization of the gels depended on the cross‐link density and the structure of the photoresponsive cross‐linker.
Bottlebrush polymers are synthesized using a tandem ring‐opening polymerization (ROP) and ring‐opening metathesis polymerization (ROMP) strategy. For the first time, ROP and ROMP are conducted sequentially in the same pot to yield well‐defined bottlebrush polymers with molecular weights in excess of 106 Da. The first step of this process involves the synthesis of a polylactide macromonomer (MM) via ROP of d ,l ‐lactide initiated by an alcohol‐functionalized norbornene. ROMP grafting‐through is then carried out in the same pot to produce the bottlebrush polymer. The applicability of this methodology is evaluated for different MM molecular weights and bottlebrush backbone degrees of polymerization. Size‐exclusion chromatographic and 1H NMR spectroscopic analyses confirm excellent control over both polymerization steps. In addition, bottlebrush polymers are imaged using atomic force microscopy and stain‐free transmission electron microscopy on graphene oxide.
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).
Hypoxia plays a critical role in the development and wound healing process, as well as a number of pathological conditions. Here, dextran‐based hypoxia‐inducible (Dex‐HI) hydrogels formed with in situ oxygen consumption via a laccase−medicated reaction are reported. Oxygen levels and gradients were accurately predicted by mathematical simulation. It is demonstrated that Dex‐HI hydrogels provide prolonged hypoxic conditions up to 12 h. The Dex‐HI hydrogel offers an innovative approach to delineate not only the mechanism by which hypoxia regulates cellular responses, but may facilitate the discovery of new pathways involved in the generation of hypoxic and oxygen gradient environments.
A thiofunctional thiazolidine is introduced as a new low‐molar‐mass building block for the introduction of cysteine residues via a thiol‐ene reaction. Allyl‐functional polyglycidol (PG) is used as a model polymer to demonstrate polymer‐analogue functionalization through reaction with the unsaturated side‐chains. A modified trinitrobenzenesulfonic acid (TNBSA) assay is used for the redox‐insensitive quantification and a precise final cysteine content can be predetermined at the polymerization stage. Native chemical ligation at cysteine‐functional PG is performed as a model reaction for a chemoselective peptide modification of this polymer. The three‐step synthesis of the thiofunctional thiazolidine reactant, together with the standard thiol‐ene coupling and the robust quantification assay, broadens the toolbox for thiol‐ene chemistry and offers a generic and straightforward approach to cysteine‐functional materials.
Poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA)‐based brush poly(phosphoamidate)s are successfully synthesized by a combination of ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) following either a commutative two‐step procedure or a straightforward one‐pot process using Grubbs ruthenium‐based catalysts for tandem catalysis. Compared with the traditional polymerization method, combining ROMP and ATRP in a one‐pot process allows the preparation of brush copolymers characterized by a relatively moderate molecular weight distribution and quantitative conversion of monomer. Moreover, the surface morphologies and aggregation behaviors of these polymers are studied by AFM and TEM measurements.
A simple process is developed to fabricate metallo‐supramolecular nanogels (MSNs) by the metallo‐supramolecular‐coordinated interaction between histidine and iron‐meso‐tetraphenylporphin. MSNs are composed of histidine‐modified dextran (DH) and iron‐meso‐tetraphenylporphin (Fe–Por) and exhibit excellent biocompatibility and stability. MSNs show pH responsiveness in the intracellular mildly acidic environment, which has great potential for acid‐triggered drug release delivery. In vitro drug release profiles demonstrate that the pH‐dependent disassembly of MSNs to histidine and Por results in a quicker release rate of loaded‐DOX at pH 5.3, while at pH 7.4 MSNs could hinder the release of loaded‐DOX due to the enhanced stability of MSNs.
Molecular bottle‐brush functionalized single‐walled carbon nanotubes (SWCNTs) with superior dispersibility in water are prepared by a one‐pot synthetic methodology. Elongating the main‐chain and side‐chain length of molecular bottle‐brushes can further increase SWCNT dispersibility. They show significant enhancement of SWCNT dispersibility up to four times higher than those of linear molecular functionalized SWCNTs.
In this work, activated ester chemistry is employed to synthesize biocompatible and readily functionalizable polymersomes. Via aminolysis of pentafluorophenyl methacrylate‐based precursor polymers, an N‐(2‐hydroxypropyl) methacrylamide (HPMA)‐analog hydrophilic block is obtained. The precursor polymers can be versatile functionalized by simple addition of suitable primary amines during aminolysis as demonstrated using a fluorescent dye. Vesicle formation is proven by cryoTEM and light scattering. High encapsulation efficiencies for hydrophilic cargo like siRNA are achieved using dual centrifugation and safe encapsulation is demonstrated by gel electrophoresis. In vitro studies reveal low cytotoxicity and no protein adsorption‐induced aggregation in human blood serum occurs, making the vesicles interesting candidates as nanosized drug carriers.
Perfluoropolyether (PFPE)‐based thermoplastic fluoropolymers are synthesized by A2 + B2 step‐growth polymerization between PFPE‐diyne and fluorinated diazides. This versatile method allows synthesizing PFPE‐based materials with tunable physicochemical properties depending on the exact nature of the fluorinated segment of the diazide precursor. Semicrystalline or amorphous materials endowed with high thermostability (≈300 °C under air) and low glass transition temperature (≈−100 °C) are obtained, as confirmed by differential scanning calorimetry, thermogravimetry, and rheometry. Step‐growth polymerizations can be copper‐catalyzed but also thermally activated in some cases, thus avoiding the presence of copper residues in the final materials. This strategy opens up new opportunities to easily access PFPE‐based materials on an industrial scale. Furthermore, a plethora of developments can be envisioned (e.g., by adding a third trifunctional component to the formulations for the synthesis of PFPE‐based elastomers).
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.
This work deals with the in‐depth investigation of thiol‐yne based network formation and its effect on thermomechanical properties and impact strength. The results show that the bifunctional alkyne monomer di(but‐1‐yne‐4‐yl)carbonate ( DBC ) provides significantly lower cytotoxicity than the comparable acrylate, 1,4‐butanediol diacrylate ( BDA ). Real‐time near infrared photorheology measurements reveal that gel formation is shifted to higher conversions for DBC /thiol resins leading to lower shrinkage stress and higher overall monomer conversion than BDA . Glass transition temperature (Tg), shrinkage stress, as well as network density determined by double quantum solid state NMR, increase proportionally with the thiol functionality. Most importantly, highly cross‐linked DBC /dipentaerythritol hexa(3‐mercaptopropionate) networks (Tg ≈ 61 °C) provide a 5.3 times higher impact strength than BDA , which is explained by the unique network homogeneity of thiol‐yne photopolymers.
1,5,7‐Triazabicyclo[4.4.0]dec‐5‐ene (TBD)‐catalyzed polycondensation reactions of fatty acid derived dimethyl dicarbamates and diols are introduced as a versatile, non‐isocyanate route to renewable polyurethanes. The key step for the synthesis of dimethyl carbamate monomers from plant‐oil‐derived dicarboxylic acids is based on a sustainable base‐catalyzed Lossen rearrangement. The formed polyurethanes with molecular weights up to 25 kDa are characterized by SEC, DSC, and NMR analysis.
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.
A versatile one‐pot strategy for the preparation of reversibly cross‐linked polymer‐coated mesoporous silica nanoparticles (MSNs) via surface reversible addition–fragmentation chain transfer (RAFT) polymerization is presented for the first time in this paper. The less reactive monomer oligo(ethylene glycol) acrylate (OEGA) and the more reactive cross‐linker N,N′‐cystaminebismethacrylamide (CBMA) are chosen to be copolymerized on the external surfaces of RAFT agent‐functionalized MSNs to form the cross‐linked polymer shells. Owing to the reversible cleavage and restoration of disulfide bonds via reduction/oxidation reactions, the polymer shells can control the on/off switching of the nanopores and regulate the drug loading and release. The redox‐responsive release of doxorubicin (DOX) from this drug carrier is realized. The protein adsorption, in vitro cytotoxicity assays, and endocytosis studies demonstrate that this biocompatible vehicle is a potential candidate for delivering drugs. It is expected that this versatile grafting strategy may help fabricate satisfying MSN‐based drug delivery systems for clinical application.
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.
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.
The polymerization of ocimene has been first achieved by half‐sandwich rare‐earth metal dialkyl complexes in combination with activator and AliBu3. The regio‐ and stereoselectivity in the ocimene polymerization can be controlled by tuning the cyclopentadienyl ligand and the central metal of the complex. The chiral cyclopentadienyl‐ligated Sc complex 1 prepares syndiotactic cis‐1,4‐polyocimene (cis‐1,4‐selectivity up to 100%, rrrr = 100%), while the corresponding Lu, Y, and Dy complexes 2 – 4 and the achiral pentamethylcyclopentadienyl Sc, Lu, and Y complexes 5 – 7 afford isotactic trans‐1,2‐polyocimenes (trans‐1,2‐selectivity up to 100%, mm = 100%).
A direct and facile route toward semitelechelic polymers, end‐functionalized with palladated sulfur–carbon–sulfur pincer (PdII‐pincer) complexes is reported that avoids any post‐polymerization step. Key to our methodology is the combination of reversible addition‐fragmentation chain‐transfer (RAFT) polymerization with functionalized chain‐transfer agents. This strategy yields Pd end‐group‐functionalized materials with monomodal molar mass dispersities (Đ ) of 1.18–1.44. The RAFT polymerization is investigated using a PdII‐pincer chain‐transfer agent for three classes of monomers: styrene, tert‐butyl acrylate, and N‐isopropylacrylamide. The ensuing PdII‐pincer end‐functionalized polymers are analyzed using 1H NMR spectroscopy, gel‐permeation chromatography, and elemental analysis. The RAFT polymerization methodology provides a direct pathway for the fabrication of PdII‐pincer functionalized polymers with complete end‐group functionalization.
