In the present paper, we investigate the structure and the stability of colloidal complex made from poly(N-isopropylacrylamide)-b-poly(acrylic acid) (PNIPAM-b-PAA) as thermosensitive neutral-anionic block copolymer and dodecyltrimethyl-ammonium bromide (DTAB) as cationic surfactant under various conditions, specifically the effects of the DTAB concentration (surfactant-to-polymer charge ratio) and temperature. By DLS and SANS, for Z < ZC, single surfactant micelle decorated by diblock copolymers and single diblock copolymers coexist. Above ZC, the colloidal complex reveals the core-shell microstructure. The core is constituted of densely packed DTAB micelles, most likely connected between them by the PAA blocks. The corona is made from PNIPAM, and at higher temperatures PNIPAM corona collapse to form larger aggregates. A semi-quantitative interpretation of the SANS data allows to determine the core and corona dimensions, as well as the average aggregation numbers of micelles.