TY - JOUR ID - 10442/17213 A1 - Papagiannopoulos A. A1 - A1 - Zhao J. A1 - A1 - Zhang G. A1 - A1 - Pispas S. A1 - A1 - Radulescu A. Y1 - 2013/// T1 - Thermoresponsive transition of a PEO-b-PNIPAM copolymer: From hierarchical aggregates to well defined ellipsoidal vesicles JF - Polymer VL - 54 IS - 23 SN - 0032-3861 U3 - 10.1016/j.polymer.2013.09.016 PB - Elsevier Ltd SP - 6373–6380EP - UR - https://hdl.handle.net/10442/17213 N2 - We analyze in detail the morphology transition of poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-b-PNIPAM) diblock copolymer in water with small angle neutron scattering. A three-level hierarchical structure is found below the critical solution temperature (LCST) of PNIPAM. The small-scale structure corresponds to the unperturbed PEO-b-PNIPAM chains. These coils assemble into intermediate-size aggregates which have a constant number density in solution, independently of the solution concentration, under the assumptions of a simple model based on the concentration dependence of the fitting parameters. Large clusters are also observed, which comprise the large-size structure. Above the LCST the system transforms into a well-defined geometry of monodisperse elliptical vesicles which does not depend on the solution concentration. The vesicles become less asymmetric with a higher aggregation number at the highest temperature. ER -