Interactions Between Multi-functional Spherical Polyelectrolyte Brushes And Heterogeneous Surfaces

Nano-materials and their applications in biological and industrial fields have been a hot area in today’s science for a long time. Functional nanoparticles have shown great potential in applications in biological field. Preparing multi-functional nanoparticles (pH-sensitive, temperature-sensitive, magnetic responsive type, etc.) and understanding the interaction between the particles and biological surfaces would help to lay the foundation of the applications of nanoparticles in protein and cell separation, targeted drug delivery and drug delivery and other areas.In this paper, three different types of spherical polyelectrolyte brushes have been synthesized:1) Poly (acrylic acid) (PAA) spherical polyelectrolyte brushes (SPB); 2) Magnetic spherical polyelectrolyte brushes (MSPB); 3) Spherical polyelectrolyte brushes loaded with silver nanoparticles (AgNPs-SPB). The adsorption behavior and the interaction between SPB and the heterogeneous surface, the magnetic responsiveness of MSPB under external magnetic field, and the synthesis routes of AgNPs-SPB prepared by different precursors have been studied. The selective adsorption of cells on the material surface could be simulated by studying the interaction between SPB and the heterogeneous surface, in the mean while, the interaction of MSPB under the external magnetic field would be help to apply SPB in the practical biological magnetic recycling and targeting application, and also, adjusting the precursor species would optimize the synthesis routs of AgNPs-SPB system and provide AgNPs-SPB with better performance for catalyst and so on. In this work, the details are as follows:1. Synthesis of PAA spherical polyelectrolyte brushes and poly-L-lysine multivalent heterogeneous surface. The effect of the deformation of particles and the change in the charge distribution on the particle-particle interaction and the initial rate of adsorption of particles from fluid on heterogeneous electrostatic surface were studied. It was proved that by changing the ionic strength and the density of the electrostatic attraction groups on the surface, the interaction between the surface and the particles could be adjusted from repulsion to attraction completely. It was found that the brush particles behave like a rigid sphere during the initial contact process of the particles with the adsorption group. It was proved that the numerical adsorption rate of the quasi steady state, dF/dt, could be calculated using the Leveque equation which was applied for rigid particles before:Within this formula, C is the initial concentration of the solution, L is the distance between the inlet of the flow chamber and the observation point, D is the diffusion coefficient of the free solution. At moderately low ionic strength, SPB particles would extend, compared to the harder silica particles, the adsorption of SPB would be more difficult, and the threshold of the PLL density would be higher. It is also found that the common calculated probability of particle adsorption PA(N)=Σn8n=ncrit PN(n) still could not explain the difference of SPB and silica particles adsorption behavior. The high threshold of SPB may be because of the deformation of the particles, or may be because that the decrease level of the attraction between SPB and the adsorbing group was higher than the increase level of the repulsion between SPB and the repulsion surface which was caused by the decrease of the density of the negative surface charge. The effect of the deformation of the particles has also been proved by the results that the deadsorption amount of SPB under high shear rate is higher than that of silica particles with the same size and zeta potential.Besides the initial adsorption rate and quasi steady state, the effect of the deformation, the change of the charge distribution and the change of the particle-particle interaction on the adsorption equilibrium state of particles were also studied in detail. By tuning the concentration of particles in the solution and the adsorption groups, the initial adsorption behavior of SPB particles could be regulated freely. On the surface with moderate adsorptive group density, the adsorption equilibrium state of SPB particles would not be affected by fluid power. We also studied the effect of ionic strength on the adsorption equilibrium, and found out that with the increase of ionic strength, the equilibrium adsorption capacity also increased, which was similar to the trend of the adsorption of rigid particles.2. The magnetic polyelectrolyte brushes with magnetic particles (MSPB) embedded in cores were successfully synthesized. The stability of MSPB system was very good, which could remain stable in a few months. At a certain shear rate, with the increase of magnetic field strength, the viscosity of magnetic polyelectrolyte brush system would increase, which was in correspondence with the general law of magnetic fluid. Under certain magnetic field strength, with the increasing shear rate, the viscosity of the system became smaller. By changing pH and the external magnetic field strength, the viscosity of the solution could be regulated freely. Due to the presence of the spherical polyelectrolyte brush polymer layer, Shliomis theory could not be applied as wished in MSPB system.3. In the synthetic process of AgNPs-SPB system, by changing the type of the precursor ([Ag(NH3)2]+and Ag+) and the content of the crosslinker N,N-methylene-bis-acrylamide (BIS), we successfully prepared several kinds of AgNPs-SPB system with different loading amount. The Mie theory was applied to predict the particle size prepared under different conditions and was in correspondence with the experiment results. It was found that the size and morphology of AgNPs could be adjusted by tuning the amount of BIS in SPB. In the mean while, it was also found that the catalytic efficiency of AgNPs from [Ag(NH3)2]+was higher than that from AgT,...