Block copolymers containing dimethyl siloxane and carboxylic acid sequences were synthesized by group transfer polymerization (GTP) of various methacrylates and acrylates using silyl ketene acetal terminated poly(dimethylsiloxane) (PDMS) as initiator, followed by hydrolysis of the ester sequences to the free acid. The block copolymers were obtained with controlled molecular weight and narrow molecular weight distribution. The tert-butyl methacrylate (tBMA) and trimethyl silyl methacrylate (TMSMA) polymerized more slowly than corresponding acrylates. tert-Butyl and trimethyl silyl ester groups in the poly(meth)acrylate block could be quantitatively hydrolyzed. Most copolymers were contaminated by unincorporated homo-PDMS, which was efficiently removed by hexane or supercritical CO2 extraction. The solubility and thermal properties (DSC, TGA) were investigated for the hydrolyzed amphiphilic polymers.