Effect of block compositions of amphiphilic block copolymers on the physicochemical properties of polymeric micelles

Amphiphilic block copolymers with various chain lengths of poly(n-butyl methacrylate) blocks (PBMA) and poly(N-acryloylmorpholine) blocks (PAM) were prepared by RAFT polymerization. Packing parameter of block polymers in water (β < 0.2) indicated the formation of core-corona structures, which was further confirmed from a difference between core- and corona-forming chain surface areas. Hydrodynamic micellar size was related with the numbers of BMA (NBMA) and AM (NAM), and their ratios (NBMA/NAM). With increasing NBMA/NAM value, the polymer aggregation numbers and inner core sizes increased, while the critical micelle concentrations, the corona thickness, and the second virial coefficient of block copolymer micelles decreased. These properties changed with increasing NBMA/NAM value resulted in a linear increase in corona chain unit density (ρAM) that limited chain mobility. Thus, the interaction between the micelles and serum protein at low ρAM disappeared at a higher value. Consequently, both micellar properties and biocompatible effect can be regulated by tailoring the block compositions of amphiphilic polymers.