Interfacial tension behavior of double long-chain 1,3,5-triazine surfactants for enhanced oil recovery

► The nmin of double long-chain 1,3,5-triazine surfactants (A-DCTn-8) were studied. ► Interfacial tension behaviors of A-DCTn-8 under alkali-free system were studied. ► Influencing factors of producing ultra-low IFT were mainly investigated. ► A-DCT10-8 and A-DCT12-8 both could reduce IFT to ultra-low value. ► Homologues mixtures could improve oil-water interfacial tension property greatly.