Physico-Chemical nanomaterials science

Micellar nanostructures of block copolymers with weakly and strongly interacting blocks  
Zheltonozhskaya T.B.1, Permyakova N.M.1, Kunitskaya L.R.1, Klepko V.V.1, Klimchuk D.O.2
1 Polymer Physics Department, Institute of Macromolecular Chemistry of the NAS of Ukraine. 48 Kharkivske Shosse, Kyiv-02160, Ukraine. 
E-mail: zheltonozhskaya@ukr.net 
2 Institute of Botany of the NAS of Ukraine, 2 Tereschenkovska St., 01601 Kyiv, Ukraine.

The micelles of block copolymers are advanced materials of modern nanotechnologies, therefore their structure, formation processes and functional properties depending on the chemical nature, relative length and interaction of individual blocks are widely studied. In this presentation, the various types of micelles formed from A-b-B diblock and A-b-B-b-A triblock copolymers with weakly and strongly interacting blocks are considered. The role of the relative length (degree of asymmetry) of A and B blocks and the strength of the interaction between them, which is determined by the nature of cooperative interactions (the salt or hydrogen bonds) and the nature of solvent, is shown.
In this context, considerable attention is paid to the micelle formation features of block copolymers with asymmetric chemically complementary blocks such as (methoxy)poly(ethylene oxide)/polyacrylamide, (methoxy)poly(ethylene oxide)/ poly(acrylic acid) and poly(acrylic acid)/polyacrylamide, which interact through hydrogen bonds. Thermodynamic parameters, specific micellar morphologies and sizes of micelles, as well as their functional capabilities in the delivery of poorly soluble drugs such as vitamins, prednisolon, doxorubicin and eumelanin, are discussed using the results of static and dynamic light scattering, UV-Vis and FTIR spectroscopy, and TEM.
In addition, two ways of self-assembly of these copolymers in dilute aqueous solutions resulting in the appearance either spherical or needle-like micellar structures are disclosed. The formation of intramolecular polycomplexes inside individual copolymer macromolecules, followed by segregation of hydrophobic sections of several polycomplexes is the first possible way of self-assembly, while the intermolecular complexation of blocks, belonging to different copolymer macromolecules, may be an alternative possible method. The key factor determining the way of self-assembly is the strength of the interaction of blocks.