Porous microspheres have been prepared by suspension free radical polymerization of acrylic acid (AA) in the presence of chitosan (CHI). The microspheres were characterized by FTIR and environmental SEM. The PAA content of the microspheres was estimated to be in the range 45–50 wt.‐%. The swelling degree of these particles is almost constant in the range 2 < pH < 5, but it increases considerably as the pH is raised from 5 to 10. The release profiles of microspheres loaded with meclofenamic acid (MF) were determined at pH 2, 7.4, and 10. The in vitro release of MF at different pHs was modulated by the solubility of the drug. These microcapsules are biodegradable and presented good biocompatibility and biodegradability during in vivo experiments.
ESEM microphotograph of the porous PAA/CHI microspheres. 相似文献
Gold nanoparticles‐coated polystyrene (AuNPs‐coated PS) composite particles with raspberry‐like morphology are successfully prepared with the aid of a unique thermodynamically driving effect. It is of considerable interest that the AuNPs generate and self‐assemble with raw, ordinary PS microspheres that preexist in the oxidation–reduction systems. The synthesized AuNPs‐coated PS composite particles have been extensively characterized using scanning electron microscope, transmission electron microscope, and UV–Vis‐NIR spectroscopy. The results indicate that the morphology of the resultant composite particles is governed by simply changing the amount and type of reductants and the concentration of PS microspheres. The AuNPs‐coated PS composite particles also exhibit the good surface‐enhanced Raman scattering and catalytic performances.
The synthesis of water soluble star‐block copolypeptides and their encapsulation properties are described. The star‐block copolypeptides, obtained by ring‐opening polymerization of amino acid N‐carboxyanhydrides, consist of a PEI core, a hydrophobic polyphenylalanine or polyleucine inner shell, and a negatively charged polyglutamate outer shell. The encapsulation study showed that these water soluble, amphiphilic star‐block copolypeptides could simultaneously encapsulate versatile compounds ranging from hydrophobic to anionic and cationic hydrophilic guest molecules.
Summary: A feasible method for the preparation of antimicrobial ultrafine fibers with silver nanoparticles was developed by direct electrospinning of a cellulose acetate (CA) solution with small amounts of silver nitrate followed by photoreduction. Silver nanoparticles in ultrafine CA fibers were stabilized by interactions with carbonyl oxygen atoms in CA. Ultrafine CA fibers with silver nanoparticles showed very strong antimicrobial activity.
TEM image of an ultrafine CA fiber electrospun from 10 wt.‐% CA solution with 0.5 wt.‐% AgNO3. 相似文献
DNA hydrogels which are composed of an entangled network without a crosslinker are synthesized and examined in regards to their sensitivity to salt and pH changes. The DNA hydrogel fibers only exhibited a marked response – that is a fast and large change in length – under biological conditions ([Na+] = 0.15 M at pH = 7) and are therefore suitable materials for bio‐inspired devices.
Intrinsically glucoside‐based microspheres are prepared in olive oil via a water in oil inverse suspension polymerization. The microspheres are characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) microscopy, and X‐ray photoelectron spectroscopy (XPS), evidencing the intrinsic glucose character of the spheres. A novel boronic acid fluorescent molecule was subsequently conjugated to the microspheres in an aqueous environment, exhibiting the spatial and uniform distribution of glucoside as well as the affinity of the microspheres to bind with boron, evidenced via fluorescence spectroscopy measurements.
Summary: The synthesis of a hyperbranched polymer containing a rhenium bipyridine complex is reported. The polymer was synthesized from a monomer that contains two chlorotricarbonyl rhenium(I ) bipyridine moieties and a stilbazole ligand, and the polymer was formed by the coordination reaction in one single step. Gel permeation chromatography results showed that the resulting polymer had a strong interaction with the column packing material, which was reduced when the eluent was added with an electrolyte. Both atomic force microscopy and laser light scattering showed that the size of the polymer molecules was in the range between 25–30 nm. A monolayer of polymer molecules could form on a pretreated substrate by the self‐assembly process, which can serve as the building block for multilayer ultrathin film devices.
The metal‐containing hyperbranched polymer synthesized here. 相似文献
Detection of the adduct radical by ESR spectroscopy and after‐effect ESR measurements of the adduct radical concentrations in the photosensitized polymerization of styrene (St) in the presence of dimers of α‐methylstyrene (MSD) and methyl methacrylate have revealed that the dominant mechanism of adduct radical loss changes from bimolecular termination to fragmentation as the temperature is increased beyond 90 °C for St/MSD.
The aim of this study is to investigate the feasibility and efficacy of PEC nanoparticles as delivery system for cancer chemotherapy. Assembly of paclitaxel‐loaded nanoparticles with high loading efficiency and narrow‐size distribution is successful. For non‐invasive in vivo tracing, nanoparticle blends of chelator bearing poly(lactide) with PEC and PLGA are successfully prepared. Pharmacokinetic studies in mice reveal a twofold higher circulation time of PEC as compared to PLGA. A tumor model shows an accumulation of PEC NPs in cancerous tissue and a higher anti‐tumor efficiency compared to the standard Taxol?, which is reflected in a significantly slower tumor growth compared to the NaCl control group.
An ultra‐fast fabrication of large‐scale colloidal PCs via spray coating was demonstrated. The latex spheres with hydrophobic core and hydrophilic shell were designed, and the latex shell with abundant COOH groups resulted in strong hydrogen bonding interaction among latex spheres, which boosted latex arrangement during the spray procedure. The resultant samples with area of 7 × 12 cm2 were easily fabricated within 1 min on different substrates. This ultra‐fast fabrication procedure would be of great importance for the practical application of PCs for optic devices and functional coatings.
The carbon nitride poly(triazine imide) with intercalated bromide ions is a layered, graphitic material of 2D covalently bonded molecular sheets with an exceptionally large gallery height of 3.52 Å due to the intercalated bromide anions. The material can be cleaved both mechanically and chemically into thin sheets and scrolls analogous to the carbon‐only systems graphite and graphene.
Summary: Dissipative particle dynamics simulation was performed to study the formation of multicompartment micelles from ABC star triblock copolymers in water. The study revealed some new morphologies that had not been observed before and also provided a direct visualization of the evolution of wormlike multicompartment micelles that follows the fusion process. Thus, this work provides molecular understanding of multicompartment micelles which will be useful for the future rational synthesis of novel micelles.
Multicompartment micelles formed from ABC star triblock copolymers in water by DPD simulations. 相似文献
A novel α,ω‐heterofunctional poly(ethylene oxide) (PEO) macromonomer possessing methacryloyl and thienyl end groups was prepared by ring‐opening polymerization of ethylene oxide initiated by potassium thienylethoxide and termination of the living PEO ends with methacryloyl chloride. Incorporation of methacryloyl and thienyl groups was confirmed by free‐radical and oxidative polymerization processes, respectively, and by means of 1H NMR analysis.
This paper highlights the powerful combination of reversible addition–fragmentation chain transfer (RAFT) radical polymerization and various click/coupling chemistries. This is not an exhaustive review but rather an overview demonstrating the impressive possibilities that the “marriage” of these two synthetic approaches offers in modern macromolecular design and synthesis.
In this study, the hydrophobic liquid template method was firstly used to prepare temperature sensitive, porous poly(N‐isopropylacrylamide) (PNIPAAm) hydrogel. During the radical polymerization, hydrophobic polydimethylsiloxane (PDMS) and surfactant sodium dodecyl sulfate (SDS) were used as liquid templates and stabilizer, respectively. After removal of the liquid templates, porous PNIPAAm hydrogel was obtained. This gel exhibited superfast shrinking properties when being transferred from below to above the lower critical solution temperature (LCST), which was ascribed to the interconnected porous structures.
We report here a facile synthesis of high performance electro‐active polymer actuator based on a sulfonated polyimide with well‐defined silver electrodes via self‐metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer‐metal composite actuators. Also, the self‐metallized silver electrodes exhibit outstanding metal‐polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion‐based actuators.
