Self-organization in aqueous solutions of thermosensitive star-shaped and linear gradient copolymers of 2-ethyl-2-oxazoline and 2-isopropyl-2-oxazoline

Kirila, Tatyana; Smirnova, A. V.; Kurlykin, M. P.; Теньковцев, А. В.; Филиппов, А. П.

doi:10.1007/s00396-020-04638-z

Cited by 15 publications

(10 citation statements)

References 57 publications

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“…This fact indicates indirectly the close densities of polymer molecules and aggregates built from them. Qualitatively similar phenomena were previously observed for solutions of graft copolymers APE-g-PAlOx [8,9,11] and star-shaped PAlOx [76][77][78]. However, in the latter case, a difference in the compaction degree was found not for molecules and aggregates, but for different supramolecular structures, namely, for micelle-like aggregates and large loose aggregates.…”

Section: Dependence Of the Characteristics Of Pdms-g-piprox Aqueous Ssupporting

confidence: 85%

Amphiphilic Molecular Brushes with Regular Polydimethylsiloxane Backbone and Poly-2-isopropyl-2-oxazoline Side Chains. 2. Self-Organization in Aqueous Solutions on Heating

et al. 2020

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The behavior of amphiphilic molecular brushes in aqueous solutions on heating was studied by light scattering and turbidimetry. The main chain of the graft copolymers was polydimethylsiloxane, and the side chains were thermosensitive poly-2-isopropyl-2-oxazoline. The studied samples differed in the length of the grafted chains (polymerization degrees were 14 and 30) and, accordingly, in the molar fraction of the hydrophobic backbone. The grafting density of both samples was 0.6. At low temperatures, macromolecules and aggregates, which formed due to the interaction of main chains, were observed in solutions. At moderate temperatures, heating solutions of the sample with short side chains led to aggregation due to dehydration of poly-2-isopropyl-2-oxazoline and the formation of intermolecular hydrogen bonds. In the case of the brush with long grafted chains, dehydration caused the formation of intramolecular hydrogen bonds and the compaction of molecules and aggregates. The lower critical solution temperature for solutions of the sample with long side chains was higher than LCST for the sample with short side chains. It was shown that the molar fraction of the hydrophobic component and the intramolecular density are the important factors determining the LCST behavior of amphiphilic molecular brushes in aqueous solutions.

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Section: Dependence Of the Characteristics Of Pdms-g-piprox Aqueous Ssupporting

confidence: 85%

Amphiphilic Molecular Brushes with Regular Polydimethylsiloxane Backbone and Poly-2-isopropyl-2-oxazoline Side Chains. 2. Self-Organization in Aqueous Solutions on Heating

et al. 2020

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“…Therefore, the species under discussion are supramolecular structures. Similar aggregates, which are usually called micelle-like structures, have been repeatedly observed for stimulus-sensitive polymers [ 6 , 35 , 38 , 39 , 40 , 41 , 42 ], including the star-shaped PAlOx and PAlOz [ 43 , 44 , 45 , 46 ]. The formation of these supramolecular structures in solutions of the studied CPh6-PAlOx is mainly caused by interaction of hydrophobic CPh6 core.…”

Section: Resultsmentioning

confidence: 55%

Self-Organization in Dilute Aqueous Solutions of Thermoresponsive Star-Shaped Six-Arm Poly-2-Alkyl-2-Oxazines and Poly-2-Alkyl-2-Oxazolines

et al. 2021

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The behavior of star-shaped six-arm poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines in aqueous solutions on heating was studied by light scattering, turbidimetry and microcalorimetry. The core of stars was hexaaza [26] orthoparacyclophane and the arms were poly-2-ethyl-2-oxazine, poly-2-isopropyl-2-oxazine, poly-2-ethyl-2-oxazoline, and poly-2-isopropyl-2-oxazoline. The arm structure affects the properties of polymers already at low temperatures. Molecules and aggregates were present in solutions of poly-2-alkyl-2-oxazines, while aggregates of two types were observed in the case of poly-2-alkyl-2-oxazolines. On heating below the phase separation temperature, the characteristics of the investigated solutions did not depend practically on temperature. An increase in the dehydration degree of poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines led to the formation of intermolecular hydrogen bonds, and aggregation was the dominant process near the phase separation temperature. It was shown that the characteristics of the phase transition in solutions of the studied polymer stars are determined primarily by the arm structure, while the influence of the molar mass is not so significant. In comparison with literature data, the role of the hydrophobic core structure in the formation of the properties of star-shaped polymers was analyzed.

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“…Consequently, just as in pure water in water-salt solutions of CPh6-PAlOx, the species with radius R m are small aggregates, the reason for the formation of which is the interaction of hydrophobic CPh6 cores. These so-called micelle-like structures [ 75 , 76 , 77 , 78 ] were often observed in solutions of star-shaped PAlOx [ 79 , 80 ]. Taking into account that the form of star-shaped macromolecules with short arms and micelle-like structures [ 81 ] is close to spherical, the aggregation degree m agg can be estimated by comparing the volumes of macromolecules and aggregates using the formula: m agg ≈ ( R m / R h–D ) 3 …”

Section: Resultsmentioning

confidence: 99%

Influence of Salt on the Self-Organization in Solutions of Star-Shaped Poly-2-alkyl-2-oxazoline and Poly-2-alkyl-2-oxazine on Heating

et al. 2021

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The water–salt solutions of star-shaped six-arm poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines were studied by light scattering and turbidimetry. The core was hexaaza[26]orthoparacyclophane and the arms were poly-2-ethyl-2-oxazine, poly-2-isopropyl-2-oxazine, poly-2-ethyl-2-oxazoline, and poly-2-isopropyl-2-oxazoline. NaCl and N-methylpyridinium p-toluenesulfonate were used as salts. Their concentration varied from 0–0.154 M. On heating, a phase transition was observed in all studied solutions. It was found that the effect of salt on the thermosensitivity of the investigated stars depends on the structure of the salt and polymer and on the salt content in the solution. The phase separation temperature decreased with an increase in the hydrophobicity of the polymers, which is caused by both a growth of the side radical size and an elongation of the monomer unit. For NaCl solutions, the phase separation temperature monotonically decreased with growth of salt concentration. In solutions with methylpyridinium p-toluenesulfonate, the dependence of the phase separation temperature on the salt concentration was non-monotonic with minimum at salt concentration corresponding to one salt molecule per one arm of a polymer star. Poly-2-alkyl-2-oxazine and poly-2-alkyl-2-oxazoline stars with a hexaaza[26]orthoparacyclophane core are more sensitive to the presence of salt in solution than the similar stars with a calix[n]arene branching center.

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Self-organization in aqueous solutions of thermosensitive star-shaped and linear gradient copolymers of 2-ethyl-2-oxazoline and 2-isopropyl-2-oxazoline

Cited by 15 publications

References 57 publications

Amphiphilic Molecular Brushes with Regular Polydimethylsiloxane Backbone and Poly-2-isopropyl-2-oxazoline Side Chains. 2. Self-Organization in Aqueous Solutions on Heating

Amphiphilic Molecular Brushes with Regular Polydimethylsiloxane Backbone and Poly-2-isopropyl-2-oxazoline Side Chains. 2. Self-Organization in Aqueous Solutions on Heating

Self-Organization in Dilute Aqueous Solutions of Thermoresponsive Star-Shaped Six-Arm Poly-2-Alkyl-2-Oxazines and Poly-2-Alkyl-2-Oxazolines

Influence of Salt on the Self-Organization in Solutions of Star-Shaped Poly-2-alkyl-2-oxazoline and Poly-2-alkyl-2-oxazine on Heating

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