The hydrolysis of comb-like polymers with polythiirane main chains and PEO side chains linked with monothioacetal function of ester function was studied in various conditions. The monothioacetal link exhibited a rather good stability except in very acidic conditions. In a buffered medium, acidic as well as basic, the hydrolysis of the ester link was degenerated first order. In basic stoichiometric conditions the kinetics is second order and a ionic strength effect was evidenced. The energy of activation was also evaluated in these conditions.