Star-shaped six-arm poly-2-alkyl-2-oxazine and poly-2-alkyl-2-oxazoline with hexaaza [26]orthoparacyclophane derivative core were synthesized successfully using cationic ring-opening polymerization. Conformational behavior of prepared polymer stars were investigated by the methods of molecular hydrodynamics and optics in molecular dispersed solutions. It was shown that conformation characteristics of star-shaped polypeptoids depends on arm length, while the chemical structure weakly affects the behavior of the studied polymers in solutions. This behavior is caused by the close equilibrium rigidity of arms. The star-shaped polypeptoids have relatively high intramolecular density. All synthesized stars exhibit LCST behavior. Phase separation temperature depends on arm structure. It is lower for poly-2-alkyl-2-oxazines, monomer units of which contains one methylene group more than monomers of poly-2-alkyl-2-oxazoline.

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To cite this article: Alina I. Amirova, Olga V. Golub, Tatyana U. Kirila, Alla B. Razina, Andrey V. Tenkovtsev & Alexander P. Filippov (2015): The influence of arm length and number on starshaped poly(2-isopropyl-2-oxazoline) aggregation in aqueous solutions near cloud point, Soft Materials, Abstract: Four-arm star-shaped poly(2-isopropyl-2-oxazolines) (PiPrOx 4 ) are synthesized by cationic polymerization on t-butylcalix[4]arene macroinitiator. The obtained samples differ by polymerization degree of arms N PiPrOx = 9 and 25 and are characterized in chloroform. The behavior in aqueous solutions is studied by light scattering methods and compared with the results of investigation of eight-arm star with similar structure. Three types of particles are observed in solution of short-arm PiPrOx 4 at room temperature, whereas only two particle types are present in long-arm star solution. Arm shortening leads to widening of the phase transition interval. The arm number decreasing reduces the phase transition temperature by 1°C.

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Four-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx 4 -S) with short arms was studied by turbidimetry and light scattering in aqueous solutions at concentrations ranging from 0.00024 to 0.0326 g cm −3 . The molar mass M of the sample investigated was 5700 g mol −1 . In order to reveal the influence of arm length on solution properties, the results obtained for PiPrOx 4 -S were compared with the characteristics of four-arm star PiPrOx 4 -L with long arms and M = 13,000 g mol −1 . Arm shortening leads to appearance of the new type of particles and growth of the aggregation number. Stronger concentration dependences of phase transition temperatures and double widening of this interval are observed for PiPrOx 4 -S as compared to long-arm star. It is shown that arm lengthening causes more remarkable changes in solution behavior than the variation of arm number.