Abstract To avoid side effects in alkali-surfactant-polymer (ASP) flooding due to use of caustic alkalis, surfactant-polymer (SP) flooding free of alkali has been paid more attention in recently years. This calls surfactants more hydrophobic than those used in ASP flooding. A carboxyl betaine with double long alkyls, didodecylmethylcarboxyl betaine (diC 12 B), is such a candidate which behaves very well in reducing crude oil/water interfacial tension (IFT) but suffers from poor aqueous solubility and large adsorption loss by negatively charged sandstone. In this paper a new type of carboxyl betaines derived from renewable materials were synthesized by inserting EO groups between the long alkyl chains and head groups, and both homogenous compounds (diC 12 E n B, n = 2, 3, 4) and a mixture of homologues diC 12–14 E n B ( n = 2.2) derived from commercially available coconut alcohol polyoxyethylene ether were obtained and their properties as surfactants for SP flooding free of alkali were evaluated. The results show that with increasing EO number the solubility of the surfactants increases whereas the adsorption loss decreases, and accordingly the hydrophilicity of the surfactants increases, leading to a decrease of their preferred alkane carbon number ( N min ). Using these surfactants solely ultra low IFT ( 12 E 2 B, diC 12 E 4 B, and diC 12–14 E 2.2 B against C 13–15 , C 7–9 , and C 8–9 n -alkanes, respectively, and an order of 10 −2 mN/m IFT between Daqing crude oil and connate water can be achieved. However, ultra low IFT between Daqing crude oil and connate water can be achieved by using these surfactants via formulations. In comparison with diC 12 B the new surfactants with EO groups have both improved aqueous solubility and lower adsorption loss when employed in SP flooding free of alkali.