γ‐(D,L)‐Polyglutamic acid [γ‐(D,L)‐PGA, or γ‐PGA] produced by Bacillus subtilis (natto) both on laboratory and pilot scale fermenter systems has been characterized. γ‐PGA in its free acid form (H+) is insoluble in water. The salt forms of K+, Na+, NH4+, Ca2+, and Mg2+ of γ‐polyglutamates are fully soluble in water. The structural characteristics of the salts of γ‐Polyglutamates (Na+, K+, NH4+, Ca2+, and Mg2+) were determined with 1H‐ and 13C‐NMR spectroscopy and FT‐IR spectroscopy. The thermal properties were determined with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The typical physical and chemical properties including pH‐titration curve, concentration‐dependent viscosity temperature‐dependent viscosity, and heavy metal binding properties with Pb2+, Cd2+, and Cu2+ were also determined. The biological functionalities were partially characterized with in vivo feeding studies with broilers and egg‐layers, and activation of GTF (Glucose tolerance factor) activity with rat 3T3‐L1 cell culture studies. γ‐(D,L)‐Polyglutamic acid [γ‐(D,L)‐PGA] appears to have five different conformations depending on the environmental conditions. They are the α‐helix, β‐sheet, helix‐to‐random coil transition, random‐coil and enveloped aggregate. The conformational states, hydrogen bonding and polyanionic nature make γ‐PGA a versatile multi‐functional biopolymer possessing many useful biological functionalities.

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SUMMARYThe interpenetrating polymer networks (IPNs) prepared from polyurethane (PU) and a glycidyl ether of phenol formaldehyde (GEPF) were synthesized by using a simultaneous polymerization method. The effects of PU molecular weight and amount on the mechanical property are discussed. For the PU/GEPF IPNs based on polyester-type PU, as the PU content was increased, the tensile strength and fracture energy decreased, but the impact strength increased significantly. However, for the PU/GEPF IPNs based on polyether-type PU, the extent of heterogeneity was decreased with decreasing molecular weight of polyether polyol in PU and the tensile strength and fracture energy were enhanced. The impact strength increased to a maximum value and then decreased when the PU content was further increased. ZUSAMMENFASSUNG:Interpenetrierende Netzwerke (IPN) aus Polyurethanen (PU) und dem Glycidylether eines Phenol-Formaldehyd-Kondensates (GEPF) wurden durch gleichzeitige Polymerisation (,,Cokondensation") hergestellt. Der EinfluB des PU-Molekulargewichts und -Gehalts auf die mechanischen Eigenschaften wird diskutiert. Bei PU/GEPF IPN aus Polyester-Typ-PU nahmen mit steigendem PU-Gehalt sowohl die Zugfestigkeit als auch die Bruchenergie ab, wahrend die Schlagfestigkeit signifikant anstieg. Demgegenuber zeigten PU/GEPF IPN aus Polyether-np-PU eine sinkende Heterogenittit mit abnehmendem Molekulargewicht der Polyetherpolyol-Komponente im PU und dementsprechend eine Zunahme sowohl der Zugfestigkeit als auch der Bruchenergie. Die Schlagfestigkeit zeigte dagegen mit steigendem PU-Gehalt zunachst einen Anstieg zu einem Maximalwert, um dann wieder abzufallen.

ABSTRACT:Interpenetrating polymer networks (IPNs) were prepared from polyurethane (PU)-modified epoxy with different molecular weight of polyol and polyurethanes based on the mixture of polydiol and polytriol by a one-shot method. Two types of PU-modified epoxy: PU-crosslinked epoxy and PU-dangled epoxy were synthesized, and the effects of the different molecular weights of polyol in the PU-modified epoxy/PU IPNs on the dynamic mechanical properties, morphology, and damping behavior were investigated. The results show that the damping ability is enhanced through the introduction of PU-modified epoxy into the PU matrix to form the IPN structure. As the molecular weight of polyol in PU-modified epoxy increases, the loss area (LA) of the two types of the IPNs increases. PU-dangled epoxy/PU IPNs exhibit much higher damping property than that of the PU-crosslinked epoxy/PU IPNs with 20 wt % of PUcrosslinked epoxy.