Used for long-acting pegylation of biopharmaceuticals.
Linear structure, holds same functional groups in both ends, improve the pegylation efficiency on protein drugs. Including:

Mal-peg-mal -dimaleimidyl poly(ethylene glycol)]
Sc-peg-sc -disuccinimidyl poly(ethylene glycol)]
Ma-peg-ma -dimethacryloyl poly(ethylene glycol)]
Aa-peg-aa -diacryloyl poly(ethylene glycol)]
Eo-peg-eo -diglycidyl poly(ethylene glycol)]
Alkyne -peg- alkyne -diallyl poly(ethylene glycol)]
N3-peg-n [, -diazido poly(ethylene glycol)]
Ocn-peg-nco -diisocyanato poly(ethylene glycol)]
Ohc-peg-cho -diformyl poly(ethylene glycol)]
Hs-peg-sh -dimercapto poly(ethylene glycol)]
H2n-peg-nh2 -diamino poly(ethylene glycol)]
Hooc-peg-cooh --dicarboxyl poly(ethylene glycol)]
Ho-peg-oh [poly(ethylene glycol)]