A series of polyhydroxyether-polydimethylsiloxane (PDMS) graft copolymers were analysed and tested to determine the effects of factors such as the number-average molecular weight (M(n)BAR) of the PDMS segments, overall PDMS content and nature of the graft linkage on thermal characteristics, hydrolytic stability, tensile properties and morphology. D.s.c. measurements showed that the copolymers exhibit two-phase morphology even at very low PDMS M(n)BAR (< 1000 g mol-1). Despite the presence of the silyl ether linkage, such copolymers display quite good hydrolytic stability. When the PDMS M(n)BAR is in the region of 5000 g mol-1, changes in the overall composition have only a marginal effect on thermal stability.