The　state　of　waterin　the　reversemicelles　of　C-12-S-C-12　center　dot　2Br　homologues　has　been　investigated　by　Fourier　transform　infrared　spectroscopy.　The　results　showed　that　the　solubilized　water　had　four　states:　the　quaternary　ammonium　head-group-bound,　the　Br-　-bound,　the　bulklike,　and　the　free　water.　With　increasing　W-0,　the　number　of　bulklike　water　per　surfactant　(nb)　rapidly　increased,　which　indicated　swelling　of　the　reverse　micelle.　The　number　of　the　head-bound　water　per　surfactant　(n(N+))　gradually　increased.　This　was　attributed　to　a　reduction　of　the　interfacial　curvature,　which　permitted　more　water　molecules　to　associate　with　the　ionic　heads　of　surfactants　and　also　led　to　a　part　of　n-hexanol　being　expelled　from　the　interface　and　thus　water　filled　up.　Owing　to　the　existence　of　n-hexanol　in　the　interface,　the　head-bound　water　of　the　present　system　was　smaller　than　that　of　AOT　system　at　the　same　W-0.　The　number　of　counterion-bound　water　per　surfactant　(n(Br-))　remained　unchanged　with　W-0.　This　was　due　to　much　smaller　dissociation　of　the　head　Of　C-12-2-C-12　center　dot　2Br　than　that　of　AOT.　With　increasing　s,　unchanged　n(N+)　is　attributed　to　the　comprehensive　effects　of　enlarged　head,　which　promotes　the　hydration,　increased　ionization　degree,　and　reduced　size　of　the　water　pool.　Owing　to　increased　ionization　degree,　n(Br-)　increases　with　s.　(C)　2007　Elsevier　Inc.　All　rights　reserved.