Self-assembly Preparation Of Polymeric Gradient Structure Based On Non-equilibrium Phenomena

The non-equilibrium thermodynamics phenomenon was utilized to introduce a negative entropy flow which was large enough from the surroundings to cause the dissipation and derive substance movement spontaneously in the system polymer blending solution. The dissipation and substance movement was realized by regulating thermodynamic state in drying process and made the system order to form self-organizationally phase separated structure.According to the dissipative structure theory, the gradient evaporating dish was designed. The temperatures Tb and Ts were maintained to be constant by provide energy continually to its bottom and controlling the solvent evaporation rate on the surface of blend solution, respectively. So a negative entropy flow was introduced and the regulation of the open non-equilibrium thermodynamics device was realized.Based on thermodynamic non-equilibrium phenomenon, the blend films poly(lactic acid)(PLA)-poly(ethylene oxide)(PEO) with compositional gradient structure perpendicular to the free surface were successfully self-organized by setting the blend solution PLA/PEO-CHCl3 in the open system at non-equilibrium conditions to be dried, regulating and controlling non-equilibrium state. The compositional gradient structure in the films was characterized by polarized optic microscopy(POM) and Fourier transform infrared spectroscopy measurement. It was found that PLA concentrates at the air-side which the energy flows out from while PEO at the glass-side which the energy flows in, as the system is away from the equilibrium state. The composition of the resulted films distributes gradually along with energy movement direction and presents the tendency of increase with the system away from the equilibrium state. In addition, non-equilibrium state is the major factor that affects the formation of gradient structure.The island-sea type, gradient type and step type blend films polystyrene(PS)/ polyaniline(PANI) were prepared selectively by regulating thermodynamic state during the drying process of PS/ PANI/ N-methyl-2-pyrrolidone(NMP) blend solution. The POM and FTIR analysis results indicated that PS concentrates at the air-side while PANI at the glass-side and the gradient phase separated structure was formed along with energy movement direction during the drying process. The conductive Atomic Force Microscope and the surface conductivity measurement showed that air-side shows a high electrical conductivity with enrichment of PANI, and PANI and its high electrical conductivity continuously and gradually transits to another material(PS) and performance(high insulation) in the blending film. Inside the PANI/PS gradient structure, the micro fiber structure to the molecular chain form of PANI were formed and stretched to PS matrix enveloped by PS phase during PANI continuously and gradually reduces from air-side with enrichment of PANI to glass-side, showing the three-dimensional structure in nanoscale of PANI was formed in PS matrix. When the PANI content is within 0~30%, the conductivity of both sides of island-sea type blend films increased with the PANI content increasing, as well as that of air side of the gradient and step tupe blend films, while the conductivity of glass side kept high insulating performance of PS.