Plasticization of chitosan membrane for pervaporation of aqueous ethanol solution

The process of pervaporation in which two components diffuse through a nonporous polymer membrane was modelled when one of the penetrants can exert a plasticization action to the membrane material. Thereat a phenomenological model was employed for describing the plasticization effect on the diffusivities for penetrants in the membrane. The sorption equilibria and permeation fluxes for aqueous ethanol solutions in a chitosan membrane were measured, and the permeation fluxes for water were compared with those predicted by the proposed model. The concentration of sorbed water was linear with its weight fraction (x₄) in the feed solution, whereas the permeation flux of water was. affected by the plasticization action of sorbed water to the polymer. This plasticization effect on the diffusion process can be simulated in terms of the proposed phenomenological model.     

Synthesis of polyarylene homopolymers and copolymers via nickel(0)-catalyzed homocoupling of arylenebismesylates derived from bisphenols

A general and inexpensive procedure for the synthesis of poly(arylene)-type homopolymers and copolymers containing alternating oligophenylene and a functional group (X) (e.g. X = −O−, −CO−, −SO₂−, −C(CH₃)₂−, −CH₂−CH(Et)−, etc) is described. The synthetic method is based on the Ni(0)-catalyzed homocoupling of aryl bismesylates (MsOAr−X−ArOMs) derived from bisphenols. Symmetric X groups lead to regioregular crystalline and insoluble polymers whereas bulky, asymmetric X groups or the incorporation of comonomers yield regioirregular polymers and, respectively, copolymers with decreased crystallinity and increased solubility. This new synthetic method can be applied to the preparation of polymers with controlled rigidity which are amorphous, crystalline or liquid crystalline. Received: 22 January 1997/Accepted: 24 February 1997     

Biocompatibility of TiO2 nanotubes fabricated on Ti using different surfactant additives in electrolyte

This study examined the in vitro cell-material interactions on four different types of titanium surfaces: a polished Ti surface, TiO₂ nanotube surfaces fabricated in a fluorinated glycerol solution (TN), fluorinated glycerol solution with 1 wt% anionic surfactant sodium dodecyl sulphate (TN-SDS), and fluorinated glycerol solution with 1 wt% cationic surfactant cetyl trimethyl ammonium bromide (TN-CTAB), respectively. The surfaces exhibited distinct surface morphologies and geometrical features. Surface energy calculation shows that TN surface enhances the hydrophilic character by significantly increasing the surface energy. The osteoblast cell growth behavior on the four different surfaces was examined using the MC3T3-E1 cell line for 1 day. When the anodized surfaces were compared for the cell-materials interaction, each of the surfaces showed different properties that affected the cell–material interactions. Proliferation of the cells was noticed with distinctive cell-to-cell attachment on the TN surfaces. Good cellular adhesion with extracellular matrix extensions between the cells was noticed in the TN samples. The TiO₂ nanotubes grown in the surfactant-assisted fluorinated electrolyte did not show significant cell growth on the surface and some cell death was observed. The cell adhesion, differentiation and alkaline phosphatase activity were more pronounced on the TN surface. The MTT assays also revealed an increase in living cell density and proliferation on the TN surfaces. Overall, a rough surface morphology and surface energy are important factors for better cell material interactions.