ИСТИНА

Amphiphilic block copolymers are able to self-organization in water with a formation of various supramolecular structures such as spherical micelles, rod-like micelles, filomicelles (also called worm-like micelles), polymerosomes, etc. It is possible to control evolution of specific morphologies of the copolymers in water solutions by a variation of the polymer composition, architecture, molecular weight and monomer chemistry. Possibility to produce micelles based on amphiphilic block-copolymers with a defined morphology makes them attractive for applications as drug delivery systems. The objects of this study were non-toxic, biocompatible, biodegradable amphiphilic diblock (PLLAx-b-PEOy) and triblock (PLLAx/2-b-PEOy-PLLAx/2) copolymers with various hydrophobic/hydrophilic blocks lengths ratio. The aim of this study was to investigate influence of a composition of the initial block copolymers on the construction and properties of the micellar structures by small-angle x-ray scattering (SAXS). The research work was performed using synchrotron radiation at the P12 beamline at the Petra III storage ring (DESY, Hamburg). We have revealed that the investigated block copolymers in water solution formed complicated two-level systems consisting of individual micelles and ordered supramicellar structures, properties and parameters of which strongly depend on the architecture and composition of the initial block copolymers. In particular, considerable increasing of the length of the hydrophobic lactide block PLLA from 64 up to 418 units (the length of the hydrophilic block poly(ethylene oxide) was a constant) in the diblock copolymers resulted in a paradoxical decreasing of the periodicity of the ordered motifs, that can be explained by a formation of a folded structure of the long PLLA block. Increasing of the length of the hydrophobic lactide block PLLA from 30 up to 120 units in the triblock copolymers didn’t lead to a change of the system spacing. All block copolymers demonstrated a high degree of the polydispersity. For the investigated block copolymers based on PLLA and PEO micelles the main relatively narrow fraction was presented by micelles with diameter of about 20 nm, but there were also larger scattering objects with the sizes up to 150 nm in the solution. As a result, on the base of SAXS data, dynamic light scattering, atomic force and cryo-transmission microscopy data a theoretical model of the system was suggested. This work was supported in part by Russian Foundation for Basic Researches, project 16-03-00375.