Interactions between brush-coated clay sheets in a polymer matrix

The interactions between clay sheets with lateral length L that are grafted by polymer chains of N monomers immersed in a chemically identical polymer melt of polymerization index P are calculated by using Edwards' self-consistent field theory. The calculation is carried out in two dimensions and shows that, as expected, for short grafted chains (aN(1/2)<<L, with a the segment size), the interactions and concentration profiles of the grafted layers are that of stretched brushes at flat interface; while for long grafted chains (aN(1/2)>>L), the interactions and concentration profiles are characteristic of star polymers. In the practically useful (but analytically untractable) case of intermediate grafted chain lengths, where aN(1/2)similar toL, we have found that the lateral length of the clay sheets is a new relevant length scale in determining the structure and interactions of the grafted layers. These results indicate that the structure and interactions of the brush-coated clay sheets can be tailored by varying the grafted chain length and/or the lateral length of the clay sheets to benefit the fabrication of polymer/clay nanocomposites. (C) 2003 American Institute of Physics.