Coassembly of Poly(ethylene oxide)-block-poly(methacrylic acid) and N-Dodecylpyridinium Chloride in Aqueous Solutions Leading to Ordered Micellar Assemblies within Copolymer Aggregates

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• 作者：Mariusz Uchman ; Miroslav 艩t臎p谩nek ; Sylvain Pr茅vost ; Borislav Angelov ; Jan Bedn谩r ; Marie-Sousai Appavou ; Michael Gradzielski ; Karel Proch谩zka
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：August 28, 2012
• 年：2012
• 卷：45
• 期：16
• 页码：6471-6480
• 全文大小：504K
• 年卷期：v.45,no.16(August 28, 2012)
• ISSN：1520-5835

文摘

Formation of polyelectrolyte鈥搒urfactant (PE鈥揝) complexes of poly(ethylene oxide)-block-poly(methacrylic acid) (PEO₇₀₅鈥揚MAA₄₇₆) and N-dodecylpyridinium chloride (DPCl) in aqueous solution was studied by static and dynamic light scattering (SLS, DLS), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM). While it was found previously [Macromolecules1997, 30, 3519] by microcalorimetric titration that in a similar system (PEO₁₇₆鈥揚MAA₁₈₆) crystallization of aliphatic tails of N-dodecylpyridinium bromide did not occur, in our system it was evidenced by SAXS that upon addition of DPCl to fully ionized PEO₇₀₅鈥揚MAA₄₇₆ the ordered arrangement of the surfactant occurs in a certain range of PEO₇₀₅鈥揚MAA₄₇₆ concentrations and surfactant-to-polyelectrolyte charge molar ratio (Z). Our data suggest a four-step process in the behavior of the PEO₇₀₅鈥揚MAA₄₇₆/DPCl system: (i) coexistence of loose aggregates of electrostatically bound surfactants to PMAA block with free and almost unperturbed copolymer coils at Z 1, (ii) formation of aggregates containing ill-defined cores formed by DPCl micelles attached to coiled PMAA chains (beads-on-a-string nanoparticles) in the range around Z = 0.5, (iii) formation of compact core鈥搒hell nanoparticles with a core formed by densely packed ordered (crystalline) DPCl micelles and PEO shell starting slightly before charge equimolarity (Z = 1), and (iv) the region of coexistence of the core鈥搒hell nanoparticles with free DPCl micelles in excess above equimolarity (Z 1). In the region around Z = 0.5, the nanoparticles with nonordered cores coexist in a mixture either with a fraction free chains and large swollen nanoparticles decorated by surfactant micelles (at lower Z) or with the core鈥搒hell nanoparticles (at higher Z). PE鈥揝 complexes were characterized in detail in terms of molar mass, size, shape, and internal structure.