A head-to-head comparison of poly(sarcosine) and poly(ethylene glycol) in peptidic, amphiphilic block copolymers

In this work we compare chemical and solution properties, like critical aggregate concentrations (CAC) and hydrodynamic radii of aggregates based on either poly(ethylene glycol) or poly(sarcosine) block copolymers in aqueous solution. The amine functionalized, hydrophilic polymers poly(sarcosine) (degree of polymerization, X-n = 100 and 200) and PEG (X-n = 121 and 242) of comparable hydrodynamic volume were used to initiate the ring opening polymerization of alpha-amino acid-N-carboxyanhydrides based on gamma-benzyl-L-glutamate (Glu(OBn)) or epsilon-carboxybenzyl-L-lysine (Lys(Z)). The second, hydrophobic block was kept at a degree of polymerization of 25 and 50 to enable a direct comparison of solution properties of block copolymers. In both cases block length could be precisely adjusted and all synthesized block copolymers have narrow molecular weight distributions and dispersities between 1.1 and 1.2. Both types of block copolymers display critical aggregate concentrations in the range of 6*10(-8)-3*10(-7) mol/L and aggregates possess hydrodynamic radii in a range of 40-100 nm. PEG based systems, however, have a slightly lower CAC and tend to form smaller micelles, while PSar based systems have commonly smaller mu(2) parameter indication more uniform aggregates. (C) 2015 Elsevier Ltd. All rights reserved.