Rheological properties of two‐dimensional model networks

We measured the tensio‐active properties of octamethylene dimethacrylate (1), octamethylene diisobutyrate (2) and octamethylene isobutyrate methacrylate (3) at the oil‐water interface. The results indicate that these molecules are strongly adsorbed at the boundary between oil and water. The amphiphatic compounds in the monolayer can be polymerized and cross‐linked by UV irradiation. The kinetics of surface gelation was studied by measuring the two‐dimensional shear modulus as a function of the time of irradiation. A two‐dimensional sol‐gel transition was observed which is in fairly good agreement with percolation theories. The kinetics of the two‐dimensional polymerization can be completely interpreted in terms of a simple reaction scheme. The elasticity of the two‐dimensional films depends strongly on the surface concentration of the cross‐linking agent. The rheological properties of the polymerized films exhibit typical features of rubber‐elastic systems and there exists an interesting analogy to corresponding structures of three‐dimensional networks.