Features of Solution Behavior of Polymer Stars with Arms of Poly-2-alkyl-2-oxazolines Copolymers Grafted to the Upper Rim of Calix[8]arene

Star-shaped polymers with arms of block and gradient copolymers of 2-ethyl- and 2-isopropyl-2-oxazolines grafted to the upper rim of calix[8]arene were synthesized by the “grafting from” method. The ratio of 2-ethyl- and 2-isopropyl-2-oxazoline units was 1:1. Molar masses and hydrodynamic characteristics were measured using molecular hydrodynamics and optics methods in 2-nitropropane. The arms of the synthesized stars were short and the star-shaped macromolecules were characterized by compact dimensions and heightened intramolecular density. The influence of the arm structure on the conformation of star molecules was not observed. At low temperatures, the aqueous solutions of the studied stars were not molecular dispersed but individual molecules prevailed. One phase transition was detected for all solutions. The phase separation temperatures decreased with a growth of the content of more hydrophobic 2-isopropyl-2-oxazoline units. It was shown that the way of arms grafting to the calix[8]arene core affects the behavior of aqueous solutions of star-shaped poly-2-alkyl-2-oxazoline copolymers. In the case of upper rim functionalization, the shape of calix[8]arene resembles a plate. Accordingly, the core is less shielded from the solvent and the phase separation temperatures are lower than those for star-shaped poly-2-alkyl-2-oxazolines with lower rim functionalization of the calix[8]arene.

Poly(2-oxazoline)-Based Amphiphilic Gradient Copolymers as Nanocarriers for Losartan: Insights into Drug–Polymer Interactions

The current study is focused on the development of highly stable drug nanocarriers by encapsulating losartan potassium (LSR) into an amphiphilic biocompatible poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (PMeOxz72-grad-PPhOxz28) gradient copolymer (GC). Based on dynamic light scattering (DLS), the PMeOxz72-grad-PPhOxz28 (where the subscripts denote %wt composition of the components) GC formed micelles and aggregates of 13 nm and 96 nm in aqueous milieu. The presence of hydrophobic LSR molecules altered the structural characteristics of the GC, modulating the organization of the polymeric components and revealing the formation of hyper micellar nanostructures in addition to micelles. The 2D-NOESY experiments evidenced intermolecular interactions between the phenyl ring of LSR with the phenyl group of PPhOxz and eminent correlations between the butyl chain of LSR with the phenyl group of PPhOxz and methylene group of PMeOxz, respectively. Additionally, NMR studies as a function of temperature demonstrated that the presence of hydrophilic PMeOxz segments in the gradient core of PMeOxz72-grad-PPhOxz28 nanoassemblies induced an increased fluidity of the core matrix, especially upon heating, thus causing water penetration, resulting in increased proton mobility. Lastly, the ultrasound release profile of LSR signified that a great amount of the encapsulated LSR is tightly bound to the PMeOxz72-grad-PPhOxz28 nanoassemblies.

One-pot synthesis for gradient copolymers via concurrent tandem living radical polymerization: mild and selective transesterification of methyl acrylate through Al(acac)3 with common alcohols

The acrylate based gradient copolymers were successfully synthesized by concurrent tandem living radical polymerization using Al(acac)3 as cocatalyst with common alcohols.