Influence of arm length on aqueous solution behavior of thermosensitive poly(2-isopropyl-2-oxazoline) stars

Four-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx4-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 PiPrOx4-S were compared with the characteristics of four-arm star PiPrOx4-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 PiPrOx4-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.