Structure-performance Relationship Of Extended Surfactants-Sodium Alkyl Propoxylated Sulfates

Extended surfactants are new anionic surfactants containing intermediate polarity groups（e.g. polypropylene group, PO group） between the hydrophilic head and the hydrophobic alkyl chain in a surfactant molecule. Intermediate polarity groups not only increases the hydrophobicity, but also smooths the intramolecular and interface polarity transition. The present research of extended surfactants has paid closed attention to their good solubilization in polar oils and ultra- low interfacial tension triggered by them, but less attention has been paid to their potential application in daily chemicals depending on the unique molecular structure of extended surfactants.Intermediates alkyl polypropylene ether（C_mP_nOH, 10, 12, 12-14, 13; m=8, n=3, 6, 9, 12） with different PO number（PON） were synthesized through isooctyl alcohol, isodecyl alcohol, dodecanol, dodecanol- myristyl alcohol and isotridecanol by propoxylation. Sixteen kinds of sodium alkyl polypropylene sulfate extended surfactants（C_mP_nS） were synthesized from C_mP_nOH by sulfation. C_mP_nS were obtained by post-purification, and the structures were identified by FT-IR, 1H-NMR and ESI-MS. Results showed that the target products were synthesized.The properties and performance of the C_mP_nS homologs, such as Krafft point, surface tension, foaming power, detergency, wetting power, emulsifying power, salt-tolerance, hard water-tolerance and lime soap dispersing power were measured and compared with those of sodium alkyl polyxyethlene sulfate（AES） and sodium dodecyl sulfate（SDS）, which respect to the influence of PO groups. Results were showed as followings:（1） it was notable that the introduction of PO groups produced two effects. First, it would smooth the transition of intramolecular polarity. Another benefit was that the critical micelle concentration（cmc） was decreased by increasing the equivalent carbon number of alkyl chain. It was indicated that the effect of each increase of three PO groups in molecular structure on cmc for C12 Pn S was approximately equivalent to increasing one-CH2- for SDS, such as Lgcmc=0.054-0.09×PON;（2） The foaming power, electrolyte-tolerance of C_mP_nS gradually decreased with the increase of PO number. With the increasing of carbon chain and PO number, the detergency of C_mP_nS to oil black carbon was better than that of AES. At the same time, the canvas-wetting power, the paraffin wax emulsifying power and lime soap dispersing power gradually increased with the growth of PO number.According to the performance determined above, extended surfactants were applied to replace of AES as the mian surfactants in three kinds of simulated formulation of liquid detergent（liquid laundry detergent, shower gel and dish washer）, and their performance were also determined. The results showed that the sensory and physicochemical properties of the detergents with extended surfactants met the industry standards.（1） The simulated laundry detergent formulas with C12P6 S, C12-14P3 S, C12-14P6 S, C13P6 S and C₁₃P₃ S as main sufactants had excellent solubolity at low temperature, relatively low viscosity and skin- irritation, better dirt removal ability than that with AES as main sufactant, which had the potentional hope to be applied in super-concentrated laundry detergent.（2） The simulated shower gel formulas with C12P3 S, C12-14P3 S, and C12P6 S had the characters of exquisite foaming power, quickly rinsing, and less skin- irritation than that with AES.（3） The simulative dish washer formulas with C12-14P3 S and C₁₃P₃ S had excellent washing power and hard water-tolerace.