The effect of arm number and solution concentration on phase separation of thermosensitive poly(2-isopropyl-2-oxazoline) stars in aqueous solutions

• Published in: Colloid and polymer science 2016-06, Vol.294 (6), p.947-956
• Main Authors: Amirova, Alina I., Golub, Olga V., Kirila, Tatyana U., Razina, Alla B., Tenkovtsev, Andrey V., Filippov, Alexander P.
• Format: Article
• Language: English
• Subjects: Aggregates; Aqueous solutions; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Complex Fluids and Microfluidics; Density; Dilution; Food Science; Nanotechnology and Microengineering; Original Contribution; Phase separation; Physical Chemistry; Polymer Sciences; Soft and Granular Matter; Stars; Thermosensitive; Turbidimetry
• ISSN: 0303-402X; 1435-1536
• DOI: 10.1007/s00396-016-3853-3

Four-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx 4 ) with calix[4]arene core was studied by methods of turbidimetry and light scattering in aqueous solutions at concentrations ranging from 0.0002 to 0.0364 g cm −3 . The role of arm number in thermosensitive behavior was determined by comparing the experimental data with the results for eight-arm PiPrOx 8 star. First of all, it is concerned with the growth of large aggregate fraction in PiPrOx 4 solution and the formation of middle mode particles even at low temperature which causes the decrease phase separation temperatures. At relatively high concentrations ( c >0.01 g cm −3 ), the dilution of PiPrOx 4 solutions is accompanied by slow growth of phase transition temperatures, and the width Δ T  = (1–2) °C of this interval does not depend on the concentration. In the dilute regime, Δ T rises and reaches 9 °C. It is shown that the changes of thermosensitive stars’ behavior with arm number reduction are caused by lower intramolecular density of PiPrOx 4 in comparison with that of PiPrOx 8 .