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

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-bPEtOx252-b-(PCL)2 44], [MPEO44-b-PEtOx252-b-(PCL)2 87], [MPEO44-b-PEtOx252-b-(PCL)2 131]). 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-PEtOx252-b(PCL)2 44] 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-PEtOx252-b-(PCL)2 87] and the [MPEO44-b-PEtOx252-b(PCL)2 131] terpolymers. The results indicated a temperature-induced aggregation with an LCST between 60–63 C for the [MPEO44-b-PEtOx252-b-(PCL)2 44], at 60 C for the [MPEO44-b-PEtOx252-b-(PCL)2 87] and between 45–50 C for the [MPEO44-b-PEtOx252-b-(PCL)2 131] 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 fractionof thehydrophobicblockon theY-shaped triblock terpolymers likely inducedadecreaseof theLCST.