Investigation Of Two Types Liquid-to-Solid Transition And Dynamical Heterogeneity Of Complex Fluids

Complex fluids respond as soft solid under certain conditions and can be altered to liquid by some actions,the mechanism of keep the origin state and the liquid-solid transition(LST)is unclear.It is noted that the linear viscoelastic spectrum of LST of complex fluids can be divided into two types,which were named Type I and Type II respectively in this present work.LAPONITE^?suspension and Hyaluronic sodium-Di(ethylene glycol)methyl ether methacrylate(DEGMA)-2-(3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)-ureido)ethyl methacrylate(UPy MA)aqueous solution(HDU)were selected as the experiment model of colloidal suspension and polymer solution,we studied LST of complex fluids by macro-rotational rheology and probe micro-rheology,investigated the preshear effect of the LST viscoelastic spectrum of LAPONITE^?suspension,the gelation of the polymer solution and the scaling law of dynamical heterogeneity of the system in the gelation process.The main content of this work can be divided as following four parts:1.The oscillation multi-wave test was applied to characterize the LST of LAPONITE^?suspensions with different concentration of particle and added salt which stood for 24 hours and sheared with rate of 1000 s^-1 for 300 s.Samples showed two types viscoelastic spectrum.The(8(8_L-(8(8_s phase diagram has been established according to the LST type of samples.Compared with the result of preshear rate of 500 s^-1,a conclusion can be deduced that the behavior of LST of LAPONITE^?suspension depends on the shear rate,the higher the shear rate,the more samples tend to show the initial LST behavior of samples which is as-prepared.2.By simulation and calculation of the interaction between colloidal particles,we obtained the potential energy of equivalent model of samples with different component.The repulsive barrier of samples decreases with the increase of concentration of particles,the viscoelastic spectrum of LST changed from type II to type I,which is dependent the peak value of repulsive barrier.Preshear rebuilt the structure and size distribution of clusters in the suspension and changed the mechanism of cluster aggregation,which depend on the preshear rate.Obtaining smaller and denser cluster,the higher shear rate is needed,the size distribution of clusters is narrower.The LST type of samples depends on the size distribution and aggregation mechanism of clusters in the suspensions.3.The uncertainty of result of probe micro-rheological experiment from the components of instrument and algorithm of data processing was studied systematically via the theorical?simulation and experimental method.The result indicated that the error from the instrument is the statistic and dynamic error of camera which is used to record the trajectories of probe particles and the algorithm error is mainly noise which is amplified by the numerical unilateral Fourier transition of data processing,which is highly related to the discrete and cut-off degree of data.the instrument error can be measured by experiment and algorithm error can be modified via optimization.4.The probe micro-rheology was applied to investigate the temperature dependent gelation process of HDU aqueous solution,such a polymer solution with a lower critical solution temperature(LCST).The result showed that there is critical behavior in the gelation process and the gel point can be determined definitely by Winter-Chambon criteria.The dynamical heterogeneity of system was indicated by the non-Gaussianity of motion of probe particles,we also analyzed the dynamical heterogeneity and the scaling law based on self-proposed theorical framework.The result revealed that the heterogeneous size decrease with the gelation process,while the scale of the heterogeneous size exhibited critical behavior and reached the maximum value in the vicinity of gel point with power law changing.