The monolayer behaviors at the air/water interface of a series of bolaamphiphiles, poly(methylenebis(benzimidazoles)) with the number of methylene groups running from 0 to 8, are investigated. It has been found that the monolayer formation can be induced by the presence of Ag(I) ion in the subphases, while no monolayer could form on plain water surface. It has been further shown that when the number of the methylene groups between the benzimidazole moieties is equal to or larger than 6, reverse U-shape monolayers can be formed. The six-methylene group is the shortest length so far reported for bolaamphiphiles to bend to form the reverse U-shape monolayer at the air/water interface.