A novel approach to the synthesis of miktoarm star-shaped poly(2-alkyl-2-oxazolines) with calix[8]arene core was developed using a combination of the “core first” (grafting from) and “grafting onto” methods. The star-shaped polymers of A8B8 type with grafted poly(2-ethyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline) arms were obtained using calix[8]arene based multifunctional branching center with sulfonyl chloride initiating moieties and as well as acyl hydrazide termination ones. The polymer structure has been confirmed by 1H NMR spectroscopy and UV spectroscopy. The molar mass characteristics of the samples were determined by size-exclusion chromatographic and light scattering. It was experimentally confirmed that all synthesized polymers had the target arm number, namely 8 or 16. The obtained miktoarm stars were characterized by narrow molar mass distributions, and the polymerization degree of the arms was 15. The synthesized stars had a high intramolecular density, which increased with the arm number. It is shown that the thermoresponsiveness of the studied stars depends on the number and structure of arms and on intramolecular density, while molecular mass is not a decisive factor determining their LCST behavior.For miktoarm stars, phase separation temperatures do not depend on the grafting configuration of poly(2-ethyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline) on the upper or lower rim of calix[8]arene.

A number of thermosensitive poly(2-alkyl-2-oxazoline)s, differing in macromolecule architecture and hydrophilic-hydrophobic balance, were synthesized and studied in order to determine the influence of their structure on the ability to extract oil from oil-contaminated sands. Aqueous 0.5

A novel method for the synthesis of star-shaped polyethylene glycols containing a calixarene branching center was proposed according to the “grafting onto” approach. Eight-armed star-shaped polyethylene glycol was synthesized starting from calix[8]arene octasulfonyl chloride and amino-functionalized linear polyethylene glycol. Molecular weight characteristics of this star-shaped polymer were estimated using gel permeation chromatography, sedimentation-diffusion analysis, and light scattering. The eight-armed structure of star-shaped polymer was confirmed by 1H NMR spectral data.

An original approach to the synthesis of a new promising class of thermo-sensitive polymers, polymer brushes with regularly alternating grafted poly(2-alkyl-2-oxazoline) chains (PAOx), is proposed based on the "grafting through" scheme. At first, poly(2-alkyl-2-oxazoline) macro-monomers were obtained with styrene and maleimide terminal functions by the cationic ring-opening polymerization of 2-ethyl- and 2-isopropyl-2-oxazolines. Then, polymer brushes (PAOx-PB) with alternating-side polyoxazoline chains were synthesized via radical polymerization in chlorobenzene solution initiated by azobisisobutyronitrile. Reactivity ratios of the macro-monomers were determined by the Fineman–Ross (r1 = 0.013; r2 = 0.107) and the Kelen–Tüdős (r1 = 0.012; r2 = 0.105) methods, indicating that their copolymerization results in the formation of a polymer brush with an alternating sequence of macro-monomer units in the backbone. Molecular weight characteristics of obtained PAOx-PB were determined by means of size-exclusion chromatography and static light-scattering. The resulting PAOx-PB have unimodal molecular weight distribution, a rather low degree of polymerization of the main chain and the number of side chains in the range of fSC = 10–20. The structure and monomer content of synthesized PAOx-PB were studied using 1HNMR spectroscopy. It was shown that they have equivalent contents of PEtOx and PIPrOx side chains. The high intramolecular density of PAOx-PB macromolecules and, accordingly, the strong folding of the side chains was indicated.

The binding of the biologically active natural dye curcumin by star-shaped poly-2-alkyl-2-oxazolines of various structures in an aqueous medium has been studied by spectrophotometry in the ultraviolet and visible regions. The objects of study were synthesized and previously described four- and eight-armed star-shaped poly-2-alkyl-2-oxazolines with calixarene central units. The Benesi–Hildebrand method was used to determine the binding constants of dye molecules by polymer micelles. The results obtained demonstrate highly efficient binding of curcumin by polymer macromolecules and micelles in aqueous solutions. It has been shown that the efficiency of curcumin binding by star polyoxazolines is determined to a greater extent by the structure of the hydrophobic calixarene central unit, rather than the nature of polyoxazoline arms.

A novel grafting-onto approach was applied to the synthesis of star-shaped poly(2-alkyl-2-oxazoline)s with macrocyclic calix[4]arene core. Cationic polymerizations of 2-ethyl-2-oxazoline and 2-isopropyl-2-oxazoline were terminated using calix[4]arene tetrahydrazide as a multifunctional termination agent. Molecular-weight and structural characteristics of obtained four-arm star poly(2-alkyl-2-oxazoline)s were determined by size exclusion chromatography and light scattering. The thermosensitivity of aqueous solutions of obtained star polymers was studied. Cloud points, determined for 1% wt. aqueous solutions were equal to tcp50% = 27.5 degrees C for CA4-PiPrOx and tcp50% = 73.1 degrees C for CA4-PEtOx. Critical micelle concentrations of aqueous solutions of star polymers were determined using UV-Vis absorption spectroscopy, they were equal to 2.20 x 10-4 g/mL for CA4-PEtOx and 1.68 x 10-4 g/mL for CA4-PiPrOx. It was shown that studied poly(2-alkyl-2-oxazoline)s form water-soluble complexes with hydrophobic curcumin. The composition of curcumin-polymer complexes and their stability in aqueous solutions were studied using UV-Vis absorption spectroscopy. Obtained Job's plots indicated the formation of bimolecular curcumin-polymer complexes. Binding constants of curcumin by studied calixarene-centered star polymers were equal to (5-7)x 104 L/mol.

Методом спектрофотометрии в ультрафиолетовой и видимой областях исследовано связывание биологически активного природного красителя куркумина звездообразными поли-2-алкил-2-оксазолинами различной структуры в водной среде. Объектами исследования были синтезированные и описанные ранее четырех- и восьмилучевые звездообразные поли-2-алкил-2-оксазолины с каликсареновыми центрами ветвления. Методом Бенеши‒Гильдебранда определены константы связывания молекул красителя мицеллами полимера. Полученные результаты демонстрируют высокоэффективное связывание куркумина макромолекулами и мицеллами полимеров в водных растворах. Показано, что эффективность связывания куркумина звездообразными полиоксазолинами определяется в большей степени не природой полиоксазолиновых лучей, а структурой гидрофобного каликсаренового центра ветвления.

New four-arm star poly(2-alkyl-2-oxazolines) and poly(2-alkyl-2-oxazines) were synthesized using sulfochlorinated calix[4]arene derivative as a multifunctional initiator. Their characteristics were investigated by gel permeation chromato graphy, light scattering and viscometry. The polymer stars obtained were shown to have well-defined architecture and high intramolecular density.

Features of ionic ring-opening polymerization for preparing star-shaped polymers are considered. The possibilities of controlled synthesis of star-shaped structures using cyclic monomers of various classes are demonstrated. Data on the preparation of star polymers using the approaches of "grafting from" a multifunctional initiator, "grafting through" a macromonomer, and "grafting to" a multifunctional coupling agent are systematized and summarized.

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.

Linear and star-shaped poly(2-ethyl-2-oxazine)s have been synthesized. The star core was a calix[4]arene. The linear polymers and star arms were prepared by the cationic ring-opening polymerization of 2-ethyl-2-oxazine. The grafting-onto approach was used to synthesize the polymer stars. Molar masses were in the range from 2500 to 38,000 g center dot mol- 1 for linear samples and from 5100 to 23,000 g center dot mol- 1 for stars. Hydrodynamic and conformational behavior of synthesized polymers were investigated by molecular hydrodynamics and optics methods in dilute solutions in 2-nitropropane. It was shown that linear poly(2-ethyl-2-oxazine) is a flexible-chain polymer with length of statistical Kuhn segment 1.5 nm and macromolecular diameter 0.5 nm. The molecules of starshaped poly(2-ethyl-2-oxazine) are characterized by compact structure and high intramolecular density. The arms are coiled to shield the calix[4]arene core from the solvent. The arm lengthening leads to a decrease in the intramolecular density and shape symmetry of the star-shaped molecules.

A new approach to the synthesis of sulfonyl chloride initiators with the calixarene core for the cationic polymerization of 2-oxazolines is developed. The kinetics of 2-ethyl-2-oxazoline polymerization with the synthesized octafunctional initiator at 100°С in sulfolane is studied. It is shown that the decelerated initiation of polymerization is observed in the system and the rate constant of chain propagation is kp = 1.20 × 10–3 L/(mol s). Using the cationic ring-opening polymerization of 2-alkyl-2-oxazolines initiated by calix[8]arene functionalized by sulfonyl chloride groups in the lower rim, star-shaped thermosensitive polymers are synthesized, and the molecular weight characteristics of the polymers are investigated. The critical micelle concentration of star-shaped poly(2-isopropyl-2-oxazoline) is determined (СCMC = 6.25 × 10–5 g/mL), and the solubilizability of the synthesized polymers is investigated using hydrophobic dye curcumin as an example.

Novel amphiphlic four-arm star-shaped poly (2-alkyl-2-oxazoline) s with calix [4] arene core were synthesized using the “grafting from” approach. The chlorosulfonated calix [4] arene derivative was synthesized and successfully applied as a multifunctional initiator for the cationic ring-opening polymerization of 2-alkyl-2-oxazolines. Obtained star-shaped poly (2-alkyl-2-oxazoline) s were characterized by means of NMR, UV-Vis spectroscopy and gel-permeation chromatography. It was shown that star-shaped poly (2-isopropyl-2-oxazoline) perform thermosensitivity in aqueous solutions.

Novel amphiphilic graft copolymers with various polyester backbone and poly(2-alkyl-2-oxazoline) side chains were synthesized using polyester-type macroinitiators with sulfonyl chloride initiating groups. The obtained graft copolymers exhibit thermoresponsive properties in aqueous solutions in a broad temperature interval.

Both hydrophilic N-methylpyridinium p-toluenesulfonate and hydrophobic 5,10,15,20-tetraphenylporphyrin additives decrease the phase transition temperature of thermoresponsive poly-2-isopropyl-2-oxazoline star-shaped polymer in aqueous solutions.

In aqueous and saline solutions, one or more chloride ions per monomer unit are necessary for evident changes in the self-organization of poly-2-isopropyl-2-oxazoline and solution behavior on heating.

Star-shaped eight-arm poly(2-isopropyl-2-oxazoline)s with basic and acidic groups were synthesized using a "grafting from" approach. Molar masses were 13,700 and 14,900 g mol(-1) for polybase and polyacid, respectively. The aqueous solutions of synthesized polymers and their mixture were investigated by the light scattering and turbidimetry methods within wide range of temperatures and pH values. It was shown that the studied polymers separately do not exhibit pH-sensitivity due to the low content of ionogenic groups. For the solutions of mixture, one phase transition was detected, the onset temperature T-1 of which lies between the phase separation temperatures for polymers. The value of T-1 for mixture decreases with increasing acidity of the medium.

Starlike thermosensitive polymers were synthesized by cationic polymerization of 2-alkyl-2-oxazolines using a new type of sulfonyl chloride macroinitiator. It was confirmed that the polymerization on the multisulfonyl chloride initiator proceeds in the absence of irreversible chain termination and makes it possible to obtain polymers with a narrow molecular weight distribution. The polymers demonstrate a lower critical solution temperature and an ability to form complexes with hydrophobic low-molecular-weight compounds.