Theory 04/Soft Matter
Gels Form on an Attraction Range
The claim
Colloidal gelation occurs at a volume fraction set by the range of attraction rather than by the strength of attraction, so short-range attractions gel at much lower fractions.
01The mechanism
Gelation requires a spanning network; the range sets how many neighbours a particle must have, and thus the fraction at which a network exists.
02Predictions
- P1Critical fraction should fall as range narrows.
- P2Increasing strength at fixed range should not gel below the critical fraction.
03Refutation
Gelation tracking attraction strength would remove the range control.