Hydrophobic Association of Random Copolymers of Sodium 2-(Acrylamido)-2-methylpropanesulfonate and Dodecyl Methacrylate in Water As Studied by Fluorescence and Dynamic Light Scattering

• Published in: Macromolecules Vol. 32; no. 14; pp. 4631 - 4640
• Main Authors: Noda, Tetsuya, Morishima, Yotaro
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.07.1999
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; Alkyl methacrylate copolymer; Hydrodynamic radius; Property composition relationship; Hydrophobic interaction; Acrylamide derivative copolymer; Experimental study; Lateral group; Sulfonate copolymer; Polyelectrolyte; Random copolymer; Solution structure; Concentration effect; Molecular association; Hydrophobic group; Aqueous solution; Micellization
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma990202j

The association behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and dodecyl methacrylate (DMA) with its content (f DMA) varying from 1 to 15 mol % was investigated by fluorescence and quasielastic light scattering (QELS) techniques in 0.1 M NaCl aqueous solutions. The association behavior of the copolymers was found to depend strongly on f DMA. When f DMA < 3 mol %, some polymer chains exist as unimers with a hydrodynamic radius (R h) of about 5 nm while some polymers form multipolymer aggregates with R h ≈ 100 nm, arising from “hydrophobic cross-linking” by the interpolymer association of dodecyl groups. When f DMA is increased to 9 mol %, interpolymer hydrophobe associations lead to the formation of a multipolymer micelle with R h ≈ 10−13 nm. The aggregation number (N agg) of dodecyl groups in a micelle core was estimated to be about 195. When f DMA is further increased to 15 mol %, R h for the multipolymer micelle markedly increases to 70−180 nm, the size increasing with increasing polymer concentration, whereas N agg remains constant at about 158 independent of the polymer concentration. On the basis of the results from the fluorescence and QELS measurements, a unicore micelle model was proposed for the copolymer with f DMA = 9 mol %, and a bridged micelle model was proposed for the copolymer with f DMA = 15 mol %.