Characteristics and advantages of surface-initiated graft-polymerization as a way of 'grafting from' method for graft-polymerization of functional monomers on solid particles

摘要

In our researches done in recent years, a late-model graft-polymerization way as a means of "grafting from" method was founded, and it is the surface-initiated graft-polymerization. By using this new means, various functional monomers were smoothly grafted on solid particles, getting a variety of functional grafted particles. The key of this way lied on constituting a redox surface-initiating system at the interface between the particle and the solution, so that a great deal of free radicals would be produced on the surfaces of solid particles, and smoothly initiated the monomer to be graft-polymerized on solid particles. In this work, based on a lot of experimental data, the characteristics and advantages of the surface-initiated graft-polymerization way were further summarized, and the relevant mechanisms were analyzed. The system of -NH2/S2O82- as a typical surface-initiating system was used, and the graft-polymerizations of three functional monomers, methacrylic acid (MAA), 2-hydroethyl methacrylate (HEMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA), on silica gel particles were carried out. For comparison, the graft-polymerizations of the above three monomers were also performed by using "grafting through" method. The experimental results show that the graft-polymerizations by using surface-initiated graft-polymerization way can be carried out under mild conditions. More importantly, two distinct characteristics of the surface-initiated graft-polymerization way are displayed as compared with the "grafting through" method, and they are high grafting degree and rapid graft-polymerization rate. For example, for the graft-polymerization of HEMA, as the surface-initiated graft-polymerization way is used, the grafted degree of PHEMA on PHEMA/SiO2 particles at 30 degrees C in 12 h reaches up to 41 g/100 g, whereas when the "grafting though" method is adopted, the grafted degree of PHEMA on PHEMA/SiO2 particles at 60 degrees C in 20 h only reaches 15 g/100 g.