Ziyong Zhang

Polysaccharides-based nanoparticles as drug delivery systems.

Natural polysaccharides, due to their outstanding merits, have received more and more attention in the field of drug delivery systems. In particular, polysaccharides seem to be the most promising materials in the preparation of nanometeric carriers. This review relates to the newest developments in the preparation of polysaccharides-based nanoparticles. In this review, four mechanisms are introduced to prepare polysaccharides-based nanoparticles, that is, covalent crosslinking, ionic crosslinking, polyelectrolyte complex, and the self-assembly of hydrophobically modified polysaccharides.

Oxygen/nitrogen transport in ionomer composite membranes containing a cobalt Schiff base complex

Different amounts of (N,N′-disalicylideneethylenediamin)cobalt (CoS) were blended to a cobalt (II)-neutralized sulfonated EPDM (Co(II)-S-EPDM) ionomer membrane to enhance its oxygen-enriching ability. Various influence factors on permeabilities and selectivities of the composite membranes, such as the gas pressure difference, the CoS content, and the testing temperature have been investigated. Oxygen permeability coefficients (P) and oxygen/nitrogen separation factors (α) increased simultaneously by decreasing the gas pressure difference or by increasing the CoS content. In comparison with the EPDM matrix, P and α of Co(II)-S-EPDM–CoS (85/15) composite membrane increased from 11.0 Barrer and 4.38 to 37.0 Barrer and 9.60. Obvious enhancement in the oxygen-enriching property shows that the dual actions of cobaltous ion crosslinking and addition of an abundant cobalt complex may be an effective way to improve a rubbery polymer membrane. As high as 15 wt % of the CoS could be blended.

Enhanced mechanical properties and blood compatibility of PDMS/liquid crystal cross-linked membrane materials.

A novel polydimethylsiloxane/liquid crystal cross-linked membrane (PDMS/LC) was prepared by using PDMS containing vinyl groups and LCs containing unsaturated linkages as matrix materials. Mechanical properties, liquid crystalline performance and blood compatibility of the PDMS/LC cross-linked membrane containing different LC contents and LC groups were investigated, respectively. The results showed that mechanical properties of the membrane increased more significantly than those of pure PDMS membranes. The PDMS/LC cross-linked membrane also possessed better membrane-forming ability, lower hemolysis rate, less platelets adhesion and more favorable anti-coagulant properties. Additionally, mechanical properties and blood compatibility of the membrane can be enhanced simultaneously and obviously due to the introduction of the cholesteric liquid crystals and the application of the preferred cross-linked reaction without byproducts.

A graphene oxide polymer brush based cross-linked nanocomposite proton exchange membrane for direct methanol fuel cells

Functional polymer brush modified graphene oxide (FPGO) with functional linear polysiloxane brushes was synthesized via surface precipitation polymerization (sol–gel) and chemical modification. Then, FPGO was covalently cross-linked to the sulfonated polysulfone (SPSU) matrix to obtain novel SPSU/FPGO cross-linked nanocomposite membranes. Meanwhile, SPSU/GO composite membranes and a pristine SPSU membrane were fabricated as control groups. Reduced agglomeration of the inorganic filler and better interfacial interaction, which are benefit to increase diffusion resistance of methanol and to generate continuous channels for fast proton transportation at elevated temperature, were observed in SPSU/FPGO cross-linked membranes. Moreover, the enhanced membrane stability (thermal, oxidative and dimensional stability) and good mechanical performance also guaranteed their proton conducting durability. It is noteworthy that the SPSU/FPGO-1 cross-linked membrane possesses the best comprehensive properties among all the prepared membranes and Nafion®117, it acquires the highest proton conductivity of 0.462 S cm−1 at 90 °C under hydrated conditions together with a low methanol permeability of 1.71 × 10−6 cm2 s−1 at 30 °C. The resulting high membrane selectivity displays the great potential of the SPSU/FPGO cross-linked membrane for DMFCs application.