Mega-supramolecules*

Guided by the statistical mechanics of ring-chain equilibrium, we designed polymers
that self-assemble into "mega-supramolecules'' (>5,000 kg/mol) at low concentration (<0.3%wt) in
hydrocarbon liquids. Experimental results accord with model predictions that end-functional
polymers can form a significant population of mega-supramolecules at low polymer concentration,
if and only if, the backbones are long (>400 kg/mol) and end-association is strong (16-18kT).
Hydrocarbon fuels are the world's dominant power source. Their heavy use in transportation
presents the risk of explosive post-impact fires. The events of 9/11/2001 inspired us to revisit
polymers for mist control to mitigate post-impact fuel explosions. Rheology, light and neutron
scattering of long end-functional polycyclooctadienes and acid or amine end groups verify
formation of mega-supramolecules. Post-impact flame propagation shows mega-supramolecules
control misting. Turbulent flow measurements show that mega-supramolecules also reduce drag
without chain scission: reversible linkages protect covalent bonds. Mega-supramolecules had no
adverse effect on diesel engines and, in fact, reduce diesel soot by 12%. Thus, long end-associative
polymers may open the way to fuel additives that reduce pollution and improve safety.