Rheo-kinetics On Photo-reversibly Viscoelastic Micellar System Of Polymerizable Surfactant

In this paper, a new photo-reversible micelle composed of polymerizable cationic surfactant n-cetyl dimethylallyl ammonium chloride (CDAAC) and trans-4-phenylazo benzoic acid (trans-ACA) was prepared. The optimum conditions for CDAAC/trans-ACA micellar system preparation and effects on viscosities were studied. This new kind photosensitive micellar system was confirmed to be reversible photorheogical micelle by 365nm UV light and 460nm visible light irradiation respectively. Photo-rheological, interfacial as well as micro-rheological properties of CDAAC/trans-ACA micellar systems before and after different light irradiations were investigated thoroughly. And for the first time a rheo-kinetics equation was established to well describe the dynamic changing of the rheological properties during UV irradiations. Main conclusions were drawn as follows:1) The new photosensitive micellar system of CDAAC/trans-ACA was obtained with an optimum molar concentration ratio of 1.4 and pH value of 8.22 at 45℃.2) Photo-reversibly rheological properties of CDAAC/trans-ACA micellar systems were investigated as follows:Before UV irradiation, micelle system exhibited well shear thinning properties, outstanding viscoelastic properties and thixotropy with stress overshoot. Upon exposure to UV light for 1 hour, the rheological properties of the systems showed the behavior of non-Newtonian fluids. The relative viscosity and steady shear viscosities of the systems decreased obviously. The dynamic rheological response converted to be weakly elastic and viscous. Thereafter, when the system was exposed to the visible light for 4 hour, a reverse photoisomerization of ACA occurred and in turn the rheological properties of the system back to its initial status, revealing that it is a new photo-reversible micellar system.3) Changes of interfacial tension and rheological properties of CDAAC/trans-ACA (14mM/10mM) solutions diluted by 20000 times after different light irradiations were studied for the first time. After UV irradiation, the tension of the solution increased by nearly 50.2% and interfacial modulus decreased by 20%. Upon exposure to visible light, the interfacial rheological properties convert to the initial, revealing the reversible interfacial rheological properties of this new photosensitive micellar system.4) For the first time the dynamic changing of the rheological properties, i.e., the decreasing of viscosity and viscoelasticity during the UV irradiation, has been studied and well described by a rheo-kinetics model. It was expected that the rheo-kinetics equation would be useful to describe the photo-induced processes for other photo-sensitive micelle fluids.5) The micro-rheological properties of CDAAC/trans-ACA viscoelastic micellar systems were studied with microrheometer based on diffusing wave spectroscopy. The macroscopic viscosity index (MVI), elasticity index (El), fluidity index (F1), and solid-liquid balance (SLB values of the systems that changing with different light irradiations showed the photosensitive reversible micro-rheological properties.This paper is expected to enrich the research field of photosensitive fluids and provide a certain basis for the research on rheo-kinetics during light irradiation.