| abstract |
Multi-armed, monofunctional, and hydrolytically stable polymers are described having the structure n n n wherein Z is a moiety that can be activated for attachment to biologically active molecules such as proteins and wherein P and Q represent linkage fragments that join polymer arms poly a and poly b , respectively, to central carbon atom, C, by hydrolytically stable linkages in the absence of aromatic rings in the linkage fragments. R typically is hydrogen or methyl, but can be a linkage fragment that includes another polymer arm. A specific example is an mPEG disubstituted lysine having the structure n n n where mPEG a and mPEG b have the structure CH 3 O—(CH 2 CH 2 O) n CH 2 CH 2 — wherein n may be the same or different for poly a - and poly b - and can be from 1 to about 1,150 to provide molecular weights of from about 100 to 100,000. |