Synthesis and Properties of Novel Double-Tail Trisiloxane Surfactants with High Spreading Ability

摘要

A new type of double-tail trisiloxane surfactants of the general formula R1NR2CH2CH(OH)CH2O(CH2CH2O)xCH3 (x = 8.4, 12.9, 17.5, 22; R 1 = Me3SiOSiMe(CH2)3OSiMe3, R 2 = CH2CH(OH)CH2OR3, R 3 = CH2CH(C2H5)CH2(CH2)2CH3) has been synthesized by reacting single-tail trisiloxane surfactants with 2-ethylhexyl glycidyl ether. Their structures were characterized with 1H-NMR and 13C-NMR spectroscopy. These double-tail trisiloxane surfactants reduce the surface tension of water to less than 24 mN/m at a level of 10−5 mol/L. The spreading ability (SA) of the double-tail trisiloxane surfactant solution on Parafilm (or Ficus microcarpa leaf) surfaces is better than that on polyethylene terephthalate surface. The SA of the solution of the double-tail trisiloxane surfactants 1J with average ethoxy units of 8.4 is far better than the others, and its solution (5.0 × 10−3 mol/L) possesses an SA value of over 15 within 10 min on Parafilm and Ficus microcarpa leaf surfaces. The surface tension values of aqueous solutions (1.0 × 10−3 mol/L) of the double-tail trisiloxane surfactants 1J are still less than 25 mN/m over 21 days in an acidic environment (pH 4.0) and 139 days in an alkaline environment (pH 10.0), respectively. It is suggested that the SA and hydrolysis resistance of double-tail trisiloxane surfactants are able to be improved by changing the structure of the hydrophobic group, such as increasing the molar ratio of methyl to methylene.