A series of hydrogen-containing polysiloxanes(LPMHS)with different siloxane chain lengths(short for chain length,m+n)and ratios of siloxane links to hydrogen-containing siloxane links(short for chain link ratio,m/n)were prepared by polycondensation under acidic condition using octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane as monomers,and hexamethyldisiloxane as terminating agent.Subsequently,a series of butynediol ether(BEO)modified organosilicone surfactants(PSi-EO)were prepared from hydrogensilanization of LPMHS,characterized by FTIR and 1HNMR,analyzed for their properties,and evaluated for the structure-activity relationship.The results showed that when m/n=4,with the increase of m+n(5～30),PSi-EO exhibited a decrease in the antifoaming ability and the critical micelle concentration of its aqueous solution,a trend of increase first and then decrease in the foam-suppressing ability with the highest value reached when m+n=20(foam-suppressing time 16.53 min),and an increase in the minimum surface tension with the lowest surface tension determined by chain length.When m+n=20,with the decrease of m/n(18/2～14/6),PSi-EO displayed an increment in the antifoaming ability and reduction in the foam-suppressing ability,while the PSi-EO with m/n=17/3 showed an excellent antifoaming and foam-suppressing ability(antifoaming time 71.28 s,foam-suppressing time 19.34 min).With the increase of m+n and the decrease of m/n,the molecular chain of PSi-EO was extended and the amount of hydrophilic group grafting was increased,and its contact angle was also increased,and the wetting ability was reduced.The PSi-EO could form spherical micelles in aqueous solution,and the smaller aggregates could be self-assemble to form large and complex aggregates with an average particle size of 100～300 nm,and its aggregate morphology was independent of its chain length and chain link ratio.The PSi-EO molecules were more inclined to adsorb at the gas-liquid interface,and thus the surface tension of the bubble film in the vicinity of the molecules was rapidly reduced,which lead to the bubble bursting.
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