The homogeneous conversion of cellulose in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate with 2‐furoyl chloride, p‐toluenesulfonyl chloride, and triphenylmethyl chloride yields surprisingly pure cellulose acetate samples in any case. From NMR spectroscopic studies, it may be concluded that during the homogeneous functionalization reactive intermediates including furane‐2‐carboxylic acid/acetic acid anhydride and acetic acid triphenylmethyl ester are formed leading to the cellulose acetates with DS values in the range from 0.55 to 1.86.
A facile two‐step synthesis for branched poly(isoprene)s (PI) based on polyaddition of ABn‐type macromonomers is described. The synthesis of the macromonomers was achieved by anionic polymerization of isoprene and subsequent end‐capping of the polymers by addition of chlorodimethylsilane to the living carbanions. This led to PI‐based macromonomers with narrow polydispersity ( / < 1.15) and molecular weights in the range of 1 700 – 22 100 g · mol−1. Synthesis of the branched polymers was carried out by a hydrosilylation‐based polymerization of the macromonomers. Characterization via SEC, SEC‐MALLS, coupled SEC‐viscosimetry and 1H‐NMR‐spectroscopy supported the formation of branched structures. Interestingly, these branched polymers exhibited α‐values that were similar to those reported for hyperbranched polymers based on AB2‐monomers.
A series of π‐conjugated polymers linked by benzocarborane (1,2‐(buta‐1′,3′‐diene‐1′,4′‐diyl)‐1,2‐dicarbadodecaborane) were synthesized via Sonogashira–Hagihara polycondensation reaction. The opened molecular structure of diiodo monomer containing benzocarborane resulted in fast polymerization and high molecular weights. The obtained polymers were fully characterized by 1H, 13C, and 11B NMR spectroscopies. UV‐vis absorption and photoluminescence studies revealed the acceptor‐profile of benzocarborane. Unlike the polymers linked by o‐carborane, these polymers exhibited strong luminescence in the solution state, presumably because the inductive effect of carborane is dominant, rather than cage‐π interactions.
Summary: We study the impact of topological disorder on the mechanical response of hyperbranched macromolecules from a theoretical and numerical perspective. The polymer models are generated using a bond switching algorithm, and the emerging systems are described within the Zimm and Rouse pictures of macromolecular dynamics. The topological disorder is manifest in the frequency‐dependent dynamic moduli, . These are clearly distinct from that of regular hyperbranched fractals of the same size, and they do not obey simple scaling rules. The dynamic moduli reflect the short‐range order inherent in the model, and we thus suggest that the extent of disorder in branched tree‐like polymers may be well‐estimated experimentally using .
A poly(vinyl pyrrolidone) (PVP) seven-arms star polymer with lysozyme core was synthesized by conjugating linear N-succinimidyl ester terminated PVP polymer to lysozyme. Reactive PVP polymers were synthesized using a MADIX/RAFT agent functionalized with N-succinimidyl ester. The polymerization of N-vinyl pyrrolidone proceeded in a living fashion up to more than 90% conversion reaching molecular weight of up to 33 000 g · mol−1 with narrow molecular weight distributions. The PVP polymer was conjugated to lysozyme resulting in the attachment of seven PVP polymers to one lysozyme core. While the reaction was found to be complete when using low-molecular weight PVP, some by-products with less than seven arms were observed when using PVP with a molecular weight of 33 000 g · mol−1.
Poly(amidoamine)s with amino pendant groups were prepared by hydrogen‐transfer polyaddition of primary and secondary amines to bis‐acrylamines. Dansyl cadaverine (DC) doxorubicin (Dox) were bound to the polymers via a cis‐aconityl spacer to give conjugates containing 3 µg of DC per mg of polymer and 28 to 35 µg of Dox per mg of polymer. Release of DC and Dox at physiological and acidic pH varied from 0 to 35% over 48 h and was pH dependent. Although the ISA1Dox conjugate (IC50 = 6 µg Dox · mL?1) presented similar toxicity as the parent polymer without Dox, ISA23Dox showed increased toxicity (IC50 = 10 µg Dox · mL?1). These results suggest that ISA23Dox is able to release biologically active Dox in vitro and that this conjugate might be suitable for further development.
Summary: A novel kind of dendronized porphyrin polymers was synthesized by Sonogashira coupling of diethynyl‐functionalized porphyrin monomers and diiodo‐functionalized macromonomers bearing Fréchet‐type dendrons. The encapsulation of red‐light‐emitting porphyrin‐containing conjugated backbones into dendronized polymers can not only reduce the aggregation of polymer backbones and the self‐quenching of their fluorescence but also endow the porphyrin polymers with good solubility. We also report the optical and electrochemical properties of the porphyrin‐containing dendronized polymers.
Synthesis of a novel kind of dendronized porphyrin polymers by Sonogashira coupling of diethynyl‐functionalized porphyrin monomers and diiodo‐functionalized dendritic macromonomers. 相似文献
4‐Vinylbenzoyl azide was synthesized from p‐vinylbenzoic acid and polymerized by free radical polymerization. The obtained polymer contained acyl azide groups which were thermally transformed to the corresponding isocyanato groups. Reactions on these polymers with ethanol, hydroxyethyl methacrylate and 1‐pyrenebutanol proceeded quantitatively. Time‐resolved FT‐IR studies of the reactions with ethanol were carried out by varying the concentration and temperature. The effect of the solvent polarity on the Curtius rearrangement was investigated.
A nickel α‐diimine catalyst was used for Grignard metathesis (GRIM) polymerization of 2,5‐dibromo 3‐hexylthiophene and 2‐bromo‐5‐iodo‐3‐hexylthiophene monomers. GRIM polymerization of 2‐bromo‐5‐iodo‐3‐hexylthiophene generated regioregular polymers with molecular weights ranging from 3 000 to 12 000 g · mol−1. The nickel α‐diimine catalyst was also successfully used for the GRIM polymerization of a bulky benzodithiophene monomer.
Summary: A novel functionalised poly(1‐vinylpyrrolidin‐2‐one) (PVP) derivative, carrying a pre‐determined amount of 2‐(2‐pyridinyldithio)ethylamine moieties as side substituents, P(VP‐co‐VP‐SS‐Py), has been prepared from carboxylated VP copolymers, in turn obtained by copolymerising 1‐vinylpyrrolidin‐2‐one with 3,3‐di‐(ethoxycarbonyl)‐1‐vinylpyrrolidin‐2‐one in the presence of radical initiators. Using reaction solvents acting in the mean time as chain transfer agents could control its molecular weight. P(VP‐co‐VP‐SS‐Py) proved to be extremely reactive towards exchange reactions with molecules containing mercapto functions, including bioactive peptides. The exchange derivative with reduced glutathione, chosen as a model compound, was easily prepared.
Summary: We report the synthesis of well‐defined block copolymers by covalent coupling of hydroxy end‐functionalized polymers. Using the high volatility of the coupling agent phosgene as compared to the solvent, very high conversion (up to 96%) is obtained in a one‐pot reaction with as little as 10−5 moles of each of the reacting polymers, even without prior purification of the as‐received reagents. This has potential as an alternative to the currently practiced method of sequential living polymerization of constituent monomers, with the added advantage of direct knowledge and control over the length distribution of each block.
Coupling of end‐functionalized polymers using phosgene to form block copolymers of controlled composition. 相似文献
An organosilane with an alkyne group at the non‐condensable end, [(2‐propynylcarbamate)propyl]triethoxysilane, has been synthesized. Condensation of this organosilane with tetraethoxysilane can be achieved by a co‐condensation strategy to produce silica nanoparticles with surface alkyne functionality. The size and uniformity of size distribution of the silica nanoparticles are influenced by varying the concentration of the added organosilane. The alkyne‐functionalized silica nanoparticles are coupled directly with azide‐modified polymers by ‘click chemistry’ to yield organic–inorganic hybrid nanomaterials.
Stable nanoparticle vesicles were for the first time prepared from adamantyl‐ and cyclodextrin (CD)‐modified silica nanoparticles forming host–guest interactions in aqueous solution. Adamantyl‐functionalized nanoparticles were obtained from thiol‐isocyanate reaction of thiol‐modified nanoparticles with 1‐adamantyl isocyanate. The CD modified silica particles were isolated from a reaction of mono‐6‐para‐toluenesulfonyl‐β‐cyclodextrin with the thiol functionalized silica under microwave conditions in basic media. The obtained particles were characterized in respect of agglomeration and self‐assembly behavior in aqueous solution by dynamic light scattering and transmission electron microscopy. The found vesicle structures are exceptionally stable even after evaporation of water. Such inorganic hollow spheres formed through self‐assembly processes may be important for chemical storage and transport. The technique of chemically‐driven assembly is an attractive option to form useful complex structures by tunable agglomeration.
This study reports a continuous prepartion of spherical or hemispherical polymer particles simply utilizing the phase separation in polymer blend films during the coating process. We took an advantage of the strong phase separation between a water‐soluble crystalline polymer as a matrix and hydrophobic polymers as minor components. We demonstrated the prepartion of water‐soluble polystyrene (PS) particles, nitrilotriacetic acid (NTA)‐functionalized PS particles for protein separation, and semiconducting poly(3‐hexylthiophene) (P3HT) particles. The sizes of the particles could be controlled by adjusting the film thickness and weight fraction of the minor component polymers in the blend film. It provides a simple facile way to prepare polymer particles in a continous process.
A series of new conjugated copolymers incorporating the redox‐active pyrrolo‐TTF unit has been synthesised. The properties of the polymers have been investigated by cyclic voltammetry and electronic absorption spectroscopy, revealing that the pyrrolo‐TTF behaves very differently to its thieno‐TTF variant. In comparison to thieno analogues, the band gaps of the new polymers are wider than expected due to a decrease in the polarizability of the heteratom (nitrogen vs. sulfur) and steric interactions between repeat units. Whilst the pyrrolo‐TTF units are stronger electron donors than thieno‐TTFs in related structures, the two redox active elements of the new polymers (TTF and conjugated chain) function independently under oxidative conditions.
The lithium salt of 2,6‐difluoro‐2′‐sulfobenzophenone was conveniently synthesized in one‐pot by reacting 2,6‐difluorophenyllithium with 2‐sulfobenzoic acid cyclic anhydride in THF at −70 °C whereafter the product crystallized out of solution. A poly(arylene ether) and a poly(arylene sulfide) were prepared by polycondensation reactions to demonstrate the reactivity and efficacy of this new monomer to produce sulfonated high‐molecular weight aromatic polymers for fuel cell proton‐exchange membranes. This work demonstrated that organolithium chemistry may offer versatile and straightforward pathways to new functional monomers with fluorine atoms activated for nucleophilic aromatic substitution reactions.
Reversible addition fragmentation chain transfer (RAFT) polymerization is one of the most extensively studied reversible deactivation radical polymerization methods for the production of well‐defined polymers. After polymerization, the RAFT agent end‐group can easily be converted into a thiol, opening manifold opportunities for thiol modification reactions. This review is focused both on the introduction of functional end‐groups using well‐established methods, such as thiol‐ene chemistry, as well as on creating bio‐cleavable disulfide linkages via disulfide exchange reactions. We demonstrate that thiol modification is a highly attractive and efficient chemistry for modifying RAFT polymers.
Summary: A water‐soluble gold nanoparticle aggregate 2 was prepared by chloroauric acid and a polypseudorotaxane 1 of mono‐6‐thio‐β‐cyclodextrin with poly(propylene glycol) bis(2‐aminopropyl ether) ( ≈ 2 000) in the presence of sodium borohydride in N,N‐dimethylformamide (DMF) solution. The investigative results indicated that the gold nanoparticle aggregate 2 might act as an efficient DNA‐cleavage reagent.
A typical TEM image of gold nanoparticle aggregate 2 . 相似文献
