Unimer Structure and Micellization of Poly(ethyleneoxide)-Stereocontrolled Poly( N ‑isopropylacrylamide)Alternating Multiblock Copolymers in Aqueous Solution

Poly(ethylene oxide) (PEO)-poly(N-isopropylacrylamide) (PNiPAm) alternating multiblock (AMB) copolymers have been prepared by means of the stereospecific reversible-addition–fragmentation chain transfer polymerization of α,ω-dicarboxy PNiPAm, followed by the amide condensation with α,ω-diamino PEO. The meso diad (m) contents of PNiPAm blocks for the AMB copolymers (AMBm45, AMBm50, and AMBm58) are 45, 50, and 58%, respectively. Dynamic light scattering and small-angle X-ray scattering (SAXS) techniques have revealed that the unimer of AMBm45 in water behaves as an extended coil near room temperature, whereas those of AMBm50 and AMBm58 shrink slightly. As the temperature goes up, a uniform aggregate appears above a certain temperature. The fluorescent probe method has indicated that the hydrophobic core is formed as the temperature increases. According to SAXS and static light scattering measurements, the aggregate possesses a spherical core–shell structure with 10–15 nm radius and consists of 9–14 unimers....