Studies On Self-assembly Behavior Of Biomembrane Model System Based On Amphoteric Polyurethane

In this thesis, two kinds of biomembrane model system were establishedbased on amphoteric polyurethane(APU, prepared in our lab), which wereSodium dodecyl sulphate (SDS)/APU and liposome/APU complex system. Theassembly behavior of the complex system were studied by dynamic lightscattering, ultraviolet spectrophotometer(UV), fluorescent spectrophotometer andtransmission electron microscopy(TEM) methods, etc. The interaction between the SDS and APU micelles was studies by addingSDS into APU solutions. The self-assembly model between SDS and APUmicelle was established. The effects on the self-assembly behavior were studied,including the content of the ionic groups on APU chains, the concentration ofpolymers, the value of pH, salts and small amount ethanol. The studying results indicated that, when SDS was added into APU solutions,electrostatic interaction and hydrophobic assembly between SDS and APUmicelles with positive charge on the surfaces and order-assembly of SDS on APUmicellar surfaces occurred. As a result, the complex system of SDS/APU changedfrom the initial clear to precipitation, and then the precipitation was redisperedand the system was clear again. The results also indicated that the criticalaggregate concentration(cac) of SDS on APU micelles was lower than its criticalmicellar concentration(CMC). When the concentration of SDS was large enough,the complex system of SDS and APU could form complex micelles with APUmicelle encapsulated by SDS double molecule layer. In addition, the self-assembly behavior of the liposome/APU complexsystem was also studied. The studying results indicated that the electrostaticinteraction and the hydrophobic interaction played an important role in theadsorption or fusion between the APU micelles and local negative chargedliposomes, which led to "complex micelles" forming. The structure of liposomeswas destroyed, when APU micelles absorded and fused with liposomes. This wasreflected by a red shift in UV spectrogram of the complex system. The assemblybehavior of the complex system largely depended on APU concentration and wasvery different from phosphatidylchdine (PC) /APU complex system.