Preparation And Properties Of Azo-based Polyurethanes

As a kind of block copolymer,polyurethane has presented a huge potential in applications for variety in segments.Thermal plastic polyurethane contains two phase:soft segment and hard segment which play different roles respectively,forming microstructure.Consequently,the chemical and physical properties could be adjusted through changing the formula or the ratio of soft segment to hard segment,enlarging the range of application to biological and medical fields.In this paper,a series of polyurethanes with azo group in the main and side chain were synthesized.In addition,their abilities of gas adsorption and shape memory as well as the effect of azo group position in the molecule chain were studied severally.Firstly,several methods of preparing porous materials from polymer and some course about gas adsorption on porous materials are introduced.Based on the way of solvent induced crystallization,dimethyl sulfoxide(DMSO)was chosen as the inducing solvent,because water-soluble DMSO had good solubility for many polymers and could crystallize below freezing point.Porous polymers were successfully obtained in this way.Besides,some of the practical operation conditions were investigated as effective factors for porosity and gas adsorption,such as the mass ratio of solvent to polymer,the time of inducing,inducing temperature,the temperature of washing with water and so on.The other aspect of this paper is concerned with the synthesis of azo based polyurethane(urea)which possesses shape memory properties and the effects of azo group structure and different strains on shape memory properties.On the basis of shape memory properties of polyurethanes,a plan of mixing shape memory polyurethanes and high molecular weight PCL for self healing was achieved.A few polymer films showing self healing property were prepared,after which scanning electron microscopy(SEM)and optical microscope(OM)were selected in order to determine the healing process of cracks on the films.