Trimethoxysilylpropyl Ethylenediamine Research Articles

Fundamental studies of novel inorganic–organic charged zwitterionic hybrids: 2. Preparation and characterizations of hybrid charged zwitterionic membranes

A series of novel inorganic–organic hybrid charged zwitterionic membranes were successfully synthesized via sol–gel process of hybrid precursor. The hybrid precursor was obtained by a reaction of 3-glycidoxypropyltrimethoxysilane (GPTMS) with N-[3-(trimethoxysilyl) propyl] ethylene diamine (TMSPEDA), and then reacted with γ-butyrolactone (γ-BL) to create ion pairs in the polymer. The membrane properties were characterized through membrane potential, water content and piezodialysis measurements. The membrane potential against elapsed time revealed that both the amount of ionic charge sites and dip-coating times could highly impact the membrane characteristics. The membrane potential trends with pH values exhibited that the isoelectric point (IEP) was about pH 6.4 for membranes coated one time, while they also showed negative charge behaviors for membranes coated two times. The survey of water content indicated that water content was greatly affected by pH values. Piezodialysis measurements clearly showed that the conductivity of permeation solutions decreased with the elevating negative charge sites in membranes. The above results could be well explained based on a theoretical model derived by Tanioka et al. [Polymer 38 (1997) 4931–4934] for weak amphoteric membranes.

Sustained Enzyme Activity of Organophosphorus Hydrolase in Polymer Encased Multilayer Assemblies

Organophosphorus hydrolase (OPH), immobilized within polyelectrolyte multilayers deposited on glass beads (30−50 μm), showed sustained catalytic activity under ambient conditions for several months. OPH multilayers consist of two priming layers, branched poly(ethylene imine) (BPEI) and polystyrenesulfonate (PSS), followed by five alternating layers of BPEI and OPH. OPH multilayers coated on glass beads demonstrate catalytic activity similar to that of free enzyme, but over a much larger time scale (i.e., months vs hours). Stability of OPH multilayers coated on glass beads were also evaluated after depositing poly(acrylic acid) (PAA) as an outer priming layer for monomer assembly via electrostatic interactions. Three polymerizable monomers, 1,2-dihydroxypropyl methacrylate (DHPM), 1,2-dihydroxypropyl 4-vinylbenzyl ether (DHPVB), and N-[3-(trimethoxysilyl)propyl]ethylenediamine (TMSED), were anchored to the outer PAA layer and subsequently polymerized by UV irradiation or base-catalyzed hydrolysis. Polymerized DHPVB and TMSED rendered robust multilayer systems without affecting OPH activity. In aqueous sodium chloride (2 M for 2 h), OPH multilayers stabilized with an outer coating of TMSED remained 27% active as opposed to 0% activity for uncapped systems.