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Thermo‐ and pH‐Responsive Micelles of Poly(acrylic acid)‐ block ‐Poly( N , N ‐diethylacrylamide)

2005; Wiley; Volume: 26; Issue: 7 Linguagem: Inglês

10.1002/marc.200400510

1521-3927

Xavier André, Mingfu Zhang, Axel H. E. Müller,

Hydrogels: synthesis, properties, applications

Abstract Summary: The bis‐hydrophilic block copolymer, poly(acrylic acid) 45 ‐ block ‐poly( N , N ‐diethylacrylamide) 360 , was obtained after hydrolysis of poly( tert ‐butyl acrylate) 45 ‐ block ‐poly( N , N ‐diethylacrylamide) 360 , synthesized by sequential anionic polymerization of tert ‐butyl acrylate ( t BA) and N , N ‐diethylacrylamide (DEAAm) in the presence of Et 3 Al. The polymer is stimuli‐sensitive with respect to both pH and temperature in aqueous solution, reversibly forming spherical crew‐cut micelles with PDEAAm‐core (〈 R h 〉 z = 21.5 nm) under alkaline conditions for T > 35 °C as well as inverse star‐like micelles with an expanded PAA‐core (〈 R h 〉 z = 43.8 nm) under acidic conditions for T < 35 °C, as indicated by dynamic light scattering. Modes of micelle formation for poly(acrylic acid) 45 ‐ block ‐poly( N , N ‐diethylacrylamide) 360 in aqueous solution depending on the pH and temperature. image Modes of micelle formation for poly(acrylic acid) 45 ‐ block ‐poly( N , N ‐diethylacrylamide) 360 in aqueous solution depending on the pH and temperature.