We report a new class of molecules, linactants, that partition at phase boundaries and reduce the line tension between coexisting two-dimensional phases in molecular monolayers. The line tension between hydrocarbon-rich and fluorocarbon-rich phases was determined by monitoring the relaxation kinetics of deformed domains. Two partially fluorinated linactant molecules (with one and two tails, respectively) were synthesized and tested; the more efficient single-tail variant reduced the line tension by more than 20% at a mole fraction of only $8\times {10}^{-4}$.

• Received 28 September 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.037802