Self-Association of a Thermosensitive Amphiphilic Block Copolymer Poly(N‑isopropylacrylamide)‑b‑poly(N‑vinyl-2-pyrrolidone) in Aqueous Solution upon Heating

• Published in: Macromolecules Vol. 46; no. 1; pp. 226 - 235
• Main Authors: Sato, Takahiro, Tanaka, Kohei, Toyokura, Akiko, Mori, Rika, Takahashi, Rintaro, Terao, Ken, Yusa, Shin-ichi
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08-01-2013
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; Temperature effect; Composition effect; Radius of gyration; Acrylamide derivative copolymer; Experimental study; Monodispersed polymer; Phase separation; Diblock copolymer; Pyrrolidone(vinyl) copolymer; Molecular aggregation; Aqueous solution; Micellization; Amphiphilic polymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma3020992

The self-association behavior of a thermosensitive amphiphilic block copolymer, poly(N-isopropylacrylamide)-b-poly(N-vinyl-2-pyrrolidone) (PNIPAM-b-PNVP) in water upon heating was investigated by static and dynamic light scattering (SLS and DLS), small-angle X-ray scattering (SAXS), and pulsed field gradient NMR (PFG-NMR). Combining SLS and DLS with SAXS and PFG-NMR, we conclude that above 40 °C, the unimer or a few arms star micelle of the copolymer coexists with large spherical particles of uniform density, which should be regarded as concentrated-phase droplets produced by a liquid–liquid phase separation. The spherical particles of PNIPAM-b-PNVP samples with the PNIPAM content less than 0.32 became smaller with increasing temperature. This temperature dependence was explained in terms of the packing parameter for amphiphiles.