Kinetically Controlling the Polymerization of Microgels for Synthesis of Silver Nanoparticles in a Confined Space

Controllable synthesis of materials is a dream of scientists, which is closing to the reality after the advancement of fundamental studies. It is generally believed that the structure of materials is controlled by thermodynamics and kinetics. When the materials are formed in a condition far away from equilibrium, the kinetic factors play an important role in shaping materials. The aim of this paper is to evaluate whether the diffusion and reaction also influence the structure of organic materials. We take the preparation of poly(N-isopropylamide) microgels as an example. The diffusion of chemicals is regulated by changing the viscosity of solvents while the reaction is regulated by changing the amount of initiators. It is found that slow diffusion and reaction are in favor of propagation reaction, which leads to the formation of long polymer chains. The microgels composed of these long chains have high swelling ratio. On the other hand, the microgels formed in the high diffusion and reaction consists of shorts chains and demonstrates low swelling ratio. In the followings, we used the microgels as reactor to synthesize silver particles. It is found that the size and the density of silver particles are dependent on the swelling ratio of microgels. This study indicates that controlling chemical diffusion and reaction is a general approach to regulate the structure of materials.