The structure–self-assembly relationship in PDMAEMA/polyester miktoarm stars

Abstract

Well-defined miktoarm star-shaped polymers based on a heterofunctional glucose derivative initiator, N,N′-dimethylaminoethyl methacrylate (DMAEMA) and various cyclic esters, such as ε-caprolactone (CL), lactide (LA), and glycolide (GA), were obtained by combining atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP) techniques and then the click reaction. In addition, linear block copolymers PDMAEMA-b-polyester have been obtained to estimate how the topology alters the physicochemical properties of macromolecules. The measurements of the cloud point temperatures (T_CP) and hydrodynamic diameters (D_h) have shown that the presence of salts in polymer solutions affects the phase transformation, resulting in an increase in T_CP values (48–55 °C in H₂O; 60–80 °C in PBS, pH 7.4) and aggregate sizes (D_h: 9–290 nm in H₂O; D_h: 8–337 nm in PBS, pH 7.4, at 25 °C). The critical aggregation concentration (CAC) of miktoarm stars decreased with decreasing DMAEMA unit content. TEM and AFM measurements in the solid state revealed that some miktostars created fractals. The microstructure studies provided by TEM analysis in the dark field mode indicated semicrystalline phase formation above the CAC, with a regular diffraction pattern in the case of a miktoarm star with a poly(lactide-co-glycolide-co-caprolactone) arm. AFM analysis showed the changes of the 3D topography of samples with different compositions of polyester arms.