title: Temperature and concentration effects on supramolecular aggregation and phase behavior for poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(propylene oxide) copolymers of different concentration in aqueous mixtures, 2.
abstract: The micro- and mesoscopic structure of reverse Pluronic 25R4 in aqueous mixtures has been studied by SANS, SAXS and shear rheology. These techniques have been able to give a deep insight into the complex structure of the system phase diagram, that includes an isotropic water-rich liquid phase L(1), and liquid crystalline phases with hexagonal, E, or lamellar order, D. Particular attention has been paid to the isotropic water-rich phase L(1), which has a large stability region in the temperature-composition phase diagram. This region is crossed by a large "cloudy zone". Below it, namely at low temperature and composition, SANS data show the presence of polymer unimers in a gaussian coil conformation. Above the "cloudy zone", at higher temperature and composition, the L(1) phase is structured as a network of interconnected multimeric micelles. Rheology adds information about the structuring of the L(1) phase showing its incipient hexagonal pre-structuring. This technique is also able to highlight the defective structure of the E phase itself. In the temperature and concentration ranges in which a lamellar phase D is present, SANS and SAXS results are in complete agreement, showing how interlamellar distance is influenced by both polymer composition and temperature according to an "ideal deswelling" or a "not ideal swelling" mechanism. In addition, in the D phase rheology suggests the presence of densely packed vesicles.
authors.affiliation: Università degli Studi di Napoli Federico II, Dipartimento di Chimica, Via Cinthia, 80126 Napoli (NA), Italy.
authors.forename: Gerardino
authors.initials: G
authors.lastname: D'Errico
authors.forename: Luigi
authors.initials: L
authors.lastname: Paduano
authors.forename: Ornella
authors.initials: O
authors.lastname: Ortona
authors.forename: Gaetano
authors.initials: G
authors.lastname: Mangiapia
authors.forename: Luigi
authors.initials: L
authors.lastname: Coppola
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Lo Celso
mesh_terms: D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D046911:Macromolecular Substances; D011409:Propylene Glycols; D014867:Water; D011092:Polyethylene Glycols