A method for forming a piston seal of a hydraulic pump includes forming a reaction mixture that includes a prepolymer component, a polyol additive, a diol component, and a curative component, forming a sealing element with the reaction mixture and a mold, and curing the sealing element to form a piston seal of a hydraulic pump. The prepolymer component includes a polycarbonate-isocyanate prepolymer that is a reaction product of at least an isocyanate component and a polycarbonate polyol component.

In some aspects, the present disclosure provides systems for forming hydrogels that comprise (i) a reactive multi-arm polymer that comprises three or more polymer arms linked to a core region, each arm comprising a polyether segment and a reactive moiety comprising a cyclic imide carboxy-C.sub.1-C.sub.6-alkyl ester end group or each arm comprising a polyether segment and a reactive moiety comprising a C.sub.2-C.sub.6-isocyanoalkyl end group and (ii) a polyamino compound comprising at least two amino (NH.sub.2) groups, wherein the reactive multi-arm polymer and the polyamino compound react to form a crosslinked hydrogel that does not contain ester groups and has long-term stability in vivo. In some aspects, the present disclosure provides methods of treatment using such systems and hydrolysis-resistant crosslinked hydrogels formed from such systems.