Nonspherical Nanoporous Structures

As already discussed, the segregation of PFMA induces parallel orientation of the nanosheets however, the vertical orientation of the PS cylinders implies orientation of the swollen bilayer nanosheets perpendicular to the surface. Although this structure may change to a horizontal orientation, which is the probable equilibrium structure, we did not observe such a morphological change in our experimental conditions. 

The appearance of nanosheet structures after the CO2 process is equivalent to the lamellar morphology in CO2, which is different from either the as-cast morphology or that expected from the block fraction. It is reasonable to conclude that the selective swelhng of the minority PFMA domains with CO2 increases the effective volume fraction of PFMA domains and induces order-to-order transition. 

AndruzzijL., Chiellini, E., Galli, G. etal. (2002) Engineering low surface energy polymers through molecular design Synthetic routes to fluorinated polystyrene-based block copolymers. Journal of Materials Chemistry, 

Arnold, M.E., Nagai, K., Spontak, RJ. etal. (2002) Microphase separated block copolymers comprising low surface energy fluorinated blocks and hydrophilic blocks synthesis and characterization. Macmmolecules, 35,3697-3707. Bates, F.S. and Fredrickson, G.H. (1990) Block copolymer thermodynamics - theory and experiment. Annual Review of 

Bertolucci, M., GaUi, G., Chiellini, E., and Wynne, K.J. (2004) Wetting behavior of films of new fluorinated styrene-siloxane block copolymers. Macromolecules, 37,3666-3672. 

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