Supramolecular self-assembly of novel thermo-responsive double-hydrophilic and hydrophobic Y-shaped [MPEO-b-PEtOx-b-(PCL)(2)] terpolymers

摘要

Nonlinear amphiphilic block copolymer architectures with precisely controlled structures bring new challenges to biomedical materials research. The paper describes the straightforward synthesis of new "snake tongue" Y-shaped terpolymers containing poly(ethylene oxide) (PEO), poly(2-ethyl-2-oxazoline) (PEtOx) and poly(3-caprolactone) (PCL) blocks into structure [AB(C)(2)] (herein referred to as [MPEO44-bPEtOx(252)-b-(PCL)(2x44)], [MPEO44-b-PEtOx(252)-b-(PCL)(2x87)], [MPEO44-b-PEtOx(252)-b-(PCL)(2x131)]). A series of well-defined Y-shaped terpolymers were successfully synthesised by a combination of living cationic and anionic ring-opening polymerization (ROP). The selected Y-shaped [MPEO44-b-PEtOx(252)-b-(PCL)(2x44)] terpolymer self-assembly was characterised in detail by static and dynamic light scattering, nanoparticle tracking analysis and cryo-transmission electron microscopy. The physico-chemical properties as well as the molecular architecture effect on the self-assembled structures and on the LCST were compared with the Y-shaped [MPEO44-b-PEtOx(252)-b-(PCL)(2x87)] and the [MPEO44-b-PEtOx(252)-b-(PCL)(2x131)] terpolymers. The results indicated a temperature-induced aggregation with an LCST between 60-63 degrees C for the [MPEO44-b-PEtOx(252)-b-(PCL)(2x44)], at 60 degrees C for the [MPEO44-b-PEtOx(252)-b-(PCL)(2x87)] and between 45-50 degrees C for the [MPEO44-b-PEtOx(252)-b-(PCL)(2x131)] with significant differences in the supramolecular self-assembly behaviour compared with the analogous linear structure, clearly indicating the crucial effect of the molecular architecture. Furthermore, the increase of the molecular weight fraction of the hydrophobic blockonthe Y-shaped triblock terpolymers likely induced a decrease of the LCST.