Springer Science and Business Media LLC

Estimation of the number of unit charges per primary particle in aged AgI sols or -suspensions shows that there is no reason to mistrust the applicability of “continuum condensor” double layer models.

Submicron hollow spheres are an interesting class of materials that receive significant attention nowadays. Closed and mechanically robust homogeneous hollow titania microspheres with as much shell thickness as 130 nm were fabricated by coating polystyrene beads with titania nanoparticles using sol–gel chemistry and subsequently removing the core either via heating or a chemical dissolution process. The thickness of the titania shell deposited on polystyrene core was finely tuned between 100 and 130 nm by varying the concentration of titania precursor, i.e., Ti(OEt)4 salt from 0.5 to 2 mM during the coating process. The obtained hybrid core–shell particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermo-gravimetric analysis. The approach employed is well suited to the preparation of titania-coated polystyrene hybrid particles and hollow titania spheres, which can find their applications as novel building blocks with unique optical properties for fabrication of advanced materials, catalyst, and drug delivery system.

Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of ε-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical structure and physical properties were investigated by GPC, NMR, DSC, TGAand XRD. The increase of CL/LA ratio in the diblock copolymer leads to lower T g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG–poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4% and the release behavior can be made well-controlled. MePEG–poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs.

Single-alkyl chain-containing amphiphilic oligomers with a terminal alkyl chain and several sugar side chains (i.e., C n -mGEMA, where n represents alkyl chain lengths of 12 or 16 and m represents the polymerization degree of glycosyloxyethyl methacrylate (GEMA) units of 3.0–7.1), and multi-alkyl chain-containing amphiphilic oligomers with several sugar side chains (i.e., xC12-mGEMA, where x represents the average number of alkyl chains and x–m is 0.2–6.6, 1.8–4.7, and 3.4–3.7), were synthesized via the radical oligomerization of one or two monomers in the presence of alkanethiol or 2-aminoethanethiol hydrochloride. Surface tension, pyrene fluorescence, and small-angle neutron scattering (SANS) measurements were used to characterize the solution properties of the oligomers and the nanostructures of their aggregates. Both amphiphilic oligomers are highly efficient in reducing the surface tension of water (42–48 mN m−1 for C n -mGEMA and 36–46 mN m−1 for xC12-mGEMA), despite the relatively large structures of the hydrophilic parts in sugar GEMA units. The critical micelle concentration (CMC) of C n -mGEMA and xC12-mGEMA increased with an increase in the degree of polymerization for hydrophilic GEMA units and a decrease in the alkyl chain length. The results of SANS determined that C n -mGEMA formed prolate ellipsoid micelles with a radius of 1.96 nm and an axial ratio of 1.58 for a low degree of polymerization (m = 3.0) in solution. However, the radius decreased to 1.33 nm and the axial ratio increased to 5.04 as the degree of polymerization of the amphiphilic oligomers increased to m = 7.1, indicating structural transformation to an asymmetric ellipsoid. On the other hand, the structure of the aggregates formed by xC12-mGEMA changed from ellipsoidal to an ellipsoidal cylinder shape with increasing number of alkyl chains, i.e., decreasing the number of GEMA units.