A new strategy for synthesis of “umbrella‐like” poly(ethylene glycol) with monofunctional end group for bioconjugation

A novel strategy was used to synthesize poly(ethylene glycol) (PEG) with “umbrella‐like” structure containing a single reactive group at the “handle” of the “umbrella”. 1‐(Bis(2‐hydroxyethyl)amino)‐3‐(1‐ethoxyethoxy)propan‐2‐ol was used to initiate the ring‐opening polymerization (ROP) of ethylene oxide (EO) in the presence of diphenylmethylpotassium (DPMK) to obtain three‐arm PEG (PEG3), then terminated by benzyl bromide or ethyl bromide. The resultant PEG3 was hydrolyzed to generate hydroxyl group at the conjunction point, and the second step ROP of EO was carried out using PEG3‐OH as macroinitiator in the presence of DPMK. The obtained four‐arm PEG (PEG4) contained a functional hydroxyl group at the end of the fourth arm, which could be easily modified to bioactive groups such as carboxyl, active ester, amino, etc. The well‐defined structure of “umbrella‐like” PEG was characterized by GPC, ¹H NMR, and MALDI‐TOF MS in detail. Propionic acid succinimidyl ester of PEG4 (10 kDa) was utilized for protein conjugation with interferon α‐2b. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010