Versatile Strategy for the Synthesis of Dendronlike Polypeptide/Linear Poly(ε-caprolactone) Block Copolymers via Click Chemistry

A new class of dendron-like polypeptide/linear poly(ε-caprolactone) block copolymers with asymmetrical topology (i.e., dendron-like poly(γ-benzyl-l-glutamate)/linear PCL copolymers having 2m PBLG branches, m = 0, 1, 2, and 3; denoted as PCL-Dm-PBLG) was for the first time synthesized via the combination of controlled ring-opening polymerization (ROP) of ε-caprolactone, click chemistry, and the ROP of γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA). The linear hydroxyl-terminated PCL (PCL-OH) was synthesized by controlled ROP of ε-caprolactone and then transformed into clickable azide-terminated PCL (PCL-N3). The PCL-N3 precursor was further click conjugated with propargyl focal point PAMAM-typed dendrons (i.e., Dm having 2m primary amine groups) to generate PCL-dendrons (PCL-Dm) using CuBr/PMDETA as catalyst in dimethylformamide solution at 35 °C. Finally, PCL-Dm was used as macroinitiator for the ROP of BLG-NCA monomer to produce the targeted PCL-Dm-PBLG block copolymers. Their molecular structures and physical properties were characterized in detail by FT-IR, NMR, matrix assisted laser desorption ionization time-of-flight mass spectrometry, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. To the best of our knowledge, this is the first report that describes the synthesis of dendron-like polypeptide/linear PCL block copolymers with asymmetrical topology via the combination of ROP and click chemistry. Consequently, this provides a versatile strategy for the synthesis of biodegradable and biomimetic dendron-like polypeptide-based biohybrids

Synthesis and Electronic Properties of Aldehyde End-Capped Thiophene Oligomers and Other α,ω-Substituted Sexithiophenes

A series of α,ω-aldehyde end-capped oligomers of thiophene with three, four, five, six, and eight thiophene units have been synthesized using the palladium-catalyzed Stille's coupling reactions. The UV−vis spectral data indicate that these aldehyde end-capped oligomers have longer conjugation lengths as evidenced by the higher λmax values than the corresponding unsubstituted oligothiophenes. The λmax value increases as the number of thiophene units is increased. The intrinsic conductivity of the solution-cast films of the aldehyde end-capped oligothiophenes is generally higher than that of their corresponding unsubstituted counterparts. Other α,ω-substituted sexithiophenes, such as n-dodecanoyl, tert-butyldimethylsilyl, hydroxymethyl, and [(n-butoxyethoxy)ethoxy]methyl sexithiophenes, have also been synthesized. α,ω-Bis([(n-butoxyethoxy)ethoxy]methyl)sexithiophene has a remarkably high solubility in chloroform (1.8 g/L) and a conductivity (1 × 10-6 S/cm) comparable to the unsubstituted sexithiophene

Facile Synthesis of High-Concentration, Stable Aqueous Dispersions of Uniform Silver Nanoparticles Using Aniline as a Reductant

A facile method was developed for preparing uniform silver nanoparticles with small particle sizes of less than 10 nm at high concentrations, in which aniline was used to reduce silver nitrate (AgNO3) to silver nanoparticles in the presence of dodecylbenzenesulfonic acid (DBSA) as a stabilizer. Upon the addition of excess NaOH to the DBSA−aniline−AgNO3 (DAA) system, the formation of silver nanoparticles was almost complete in just 2 min at 90 °C (in 94% yield). The average size of those resultant silver nanoparticles was 8.9 ± 1.1 nm, and the colloids were stable for more than 1 year at ambient temperature. A possible mechanism for the formation of silver nanoparticles was proposed to be related to two factors: one was the mesoscopic structures of the DAA system in which silver ions were restricted in the dispersed phases composed of DBSA and aniline; the other was Ag2O nanocrystallites generated in situ that could be readily reduced by aniline to small silver nanoparticles at high concentrations

Synthesis of Multiresponsive and Dynamic Chitosan-Based Hydrogels for Controlled Release of Bioactive Molecules

An inexpensive, facile, and environmentally benign method has been developed for the preparation of multiresponsive, dynamic, and self-healing chitosan-based hydrogels. A dibenzaldehyde-terminated telechelic poly(ethylene glycol) (PEG) was synthesized and was allowed to form Schiff base linkages between the aldehyde groups and the amino groups in chitosan. Upon mixing the telechelic PEG with chitosan at 20 °C, hydrogels with solid content of 4–8% by mass were generated rapidly in <60 s. Because of the dynamic equilibrium between the Schiff base linkage and the aldehyde and amine reactants, the hydrogels were found to be self-healable and sensitive to many biochemical-stimuli, such as pH, amino acids, and vitamin B6 derivatives. In addition, chitosan could be digested by enzymes such as papain, leading to the decomposition of the hydrogels. Encapsulation and controlled release of small molecules such as rhodamine B and proteins such as lysozyme have been successfully carried out, demonstrating the potential biomedical applications of these chitosan-based dynamic hydrogels

Polystyrene Bead-Assisted Self-Assembly of Microstructured Silica Hollow Spheres in Highly Alkaline Media

Polystyrene Bead-Assisted Self-Assembly of Microstructured Silica Hollow Spheres in Highly Alkaline Medi

Synthesis of Multiresponsive and Dynamic Chitosan-Based Hydrogels for Controlled Release of Bioactive Molecules

An inexpensive, facile, and environmentally benign method has been developed for the preparation of multiresponsive, dynamic, and self-healing chitosan-based hydrogels. A dibenzaldehyde-terminated telechelic poly(ethylene glycol) (PEG) was synthesized and was allowed to form Schiff base linkages between the aldehyde groups and the amino groups in chitosan. Upon mixing the telechelic PEG with chitosan at 20 °C, hydrogels with solid content of 4–8% by mass were generated rapidly in <60 s. Because of the dynamic equilibrium between the Schiff base linkage and the aldehyde and amine reactants, the hydrogels were found to be self-healable and sensitive to many biochemical-stimuli, such as pH, amino acids, and vitamin B6 derivatives. In addition, chitosan could be digested by enzymes such as papain, leading to the decomposition of the hydrogels. Encapsulation and controlled release of small molecules such as rhodamine B and proteins such as lysozyme have been successfully carried out, demonstrating the potential biomedical applications of these chitosan-based dynamic hydrogels

Recyclable Monolithic Vitrimer Foam for High-Efficiency Solar-Driven Interfacial Evaporation

With the exponentially rapid development of solar-driven interfacial evaporation, evaporators with both high evaporation efficiency and recyclability are highly desirable to alleviate resource waste and environmental problems but remain challenging. Here, a monolithic evaporator was developed based on a dynamic disulfide vitrimer (a covalently cross-linked polymer network with associative exchangeable covalent bonds). Two types of solar absorbers, carbon nanotubes and oligoanilines, were simultaneously introduced to enhance the optical absorption. A high evaporation efficiency of 89.2% was achieved at 1 sun (1 kW m–2). When the evaporator was applied to solar desalination, it shows self-cleaning performance with long-term stability. Drinkable water with low ion concentrations satisfying the drinkable water levels of the World Health Organization and a high output (8.66 kg m–2, 8 h per day) was obtained, revealing great potential for practical seawater desalination. Moreover, a high-performance film material was obtained from the used evaporator via simple hot-pressing, indicating excellent fully closed-loop recyclability of the evaporator. This work provides a promising platform for high-efficiency and recyclable solar-driven interfacial evaporators

First Example of Free Radical Ring-Opening Polymerization with Some Characteristics of a Living Polymerization

First Example of Free Radical Ring-Opening Polymerization with Some Characteristics of a Living Polymerizatio

First Example of Free Radical Ring-Opening Polymerization with Some Characteristics of a Living Polymerization

First Example of Free Radical Ring-Opening Polymerization with Some Characteristics of a Living Polymerizatio

In Situ Encapsulation of Horseradish Peroxidase in Electrospun Porous Silica Fibers for Potential Biosensor Applications

Nanoporous silica nanofibers have been employed as a matrix to encapsulate horseradish peroxide enzymes via a simple electrospinning method. A viscous solution of prehydrolyzed tetramethyl orthosilicate, β-d-glucose, poly(vinyl alcohol), and enzymes were employed as spinning solution to generate porous fibers in the form of nonwoven mats. The silica fiber mats thus produced have a high surface area because of the small diameter (100 to 200 nm) of the fibers as well as the extreme porosity (2 to 4 nm) of individual fibers caused by the glucose template present in them. The high surface area, mechanical flexibility, thermal stability, reusability, and freedom of encapsulating various enzymes make porous silica nanofibers excellent biosensors