A　homologue　of　dissymmetric　quaternary　ammonium　Gemini　surfactants,　hexanediyl-α-(butylazobenzene　dimethylammonium)-ω-(alkyldimethylammonium)　dibromides　(referred　to　as　a4-6-m,　m　=　12,　14,　16),　and　a　symmetric　quaternary　ammonium　Gemini　surfactant,　hexanediyl-α,ω-bis(butylazobenzene　dimethylammonium　bromide)　(referred　to　as　a4-6-4a),　have　been　synthesized.　The　Krafft　temperature　at　1　wt%　concentration　was　determined　to　be　17-32　°C　for　dissymmetric　a4-6-m　homologues　depending　on　the　length　of　aliphatic　tail　and　42.5　°C　for　symmetric　a4-6-4a.　After　UV　light　irradiation,　the　content　of　their　cis-azobenzene　isomers　reaching　photostationary　state　was　estimated　to　be　ca.　67-71%　for　the　dilution.　The　critical　micelle　concentration　(cmc)　of　a4-6-m　is　close　to　that　of　12-6-m,　indicating　that　the　both　are　equivalent　from　the　self-assembly　point　of　view.　But　the　cmc　of　a4-6-4a　is　higher　than　that　of　a4-6-12　or　12-6-12,　showing　the　effect　of　the　steric　inhibition　on　aggregation　owing　to　the　two　rigid　terminal　azobenzene　groups　per　molecule.　After　UV　light　irradiation,　the　twisted　cis-azobenzene　groups　in　both　a4-6-m　and　a4-6-4a　molecules　shows　more　obvious　steric　inhibition,　resulting　in　a　larger　cmc　than　that　of　the　trans-surfactants.　©　2009　Elsevier　B.V.　All　rights　reserved.