A　series　of　bimodal　mesoporous　silicas　(BMMs)　have　been　synthesized　under　different　aqueous　alkaline　conditions,　including　sodium　hydroxide　(NaOH),　ethylenediamine　(EDA)　as　well　as　dipotassium　phosphate　(DKP).　Their　morphologies　and　textural　properties　were　fully　characterized　by　X-ray　diffraction　(XRD),　scanning　and　transmission　electron　microscope　(SEM/TEM),　N-2　adsorption/desorption　isotherms,　and　Fourier　transform　infrared　(FT-IR)　spectroscopy.　The　results　showed　that　a　weak　alkaline　system　was　beneficial　to　obtain　a　low　order　degree　of　the　mesopore　structure　with　uniform　spherical　morphology,　whereas　a　strong　alkaline　medium　was　favorable　to　achieve　a　high　order　degree　of　the　mesopore　structure　with　relatively　larger　but　irregular　nanoparticles.　During　the　sol-gel　process　with　combination　of　the　template　synthesis　technique,　the　use　of　a　strong　base　may　accelerate　the　silicate　condensation　with　irregular　morphologies　as　a　result.　Also,　it　may　accelerate　the　growth　of　the　micellar　(cetyltrimethyl　ammonium　bromide)　phase　with　ordered　arrangement.　Therefore,　the　effects　of　different　alkaline　media　on　the　mesopores　and　morphologies　of　these　BMMs　were　remarkable.　To　account　for　the　observation,　a　possible　mechanism　was　proposed.　(C)　2014　Elsevier　B.V.　All　rights　reserved.