title: Micellisation of triblock copolymers of ethylene oxide and 1,2-butylene oxide: effect of B-block length.
abstract: We have used pyrene fluorescence spectroscopy and isothermal titration calorimetry (ITC) to investigate the effect of hydrophobic-block length on values of the critical micelle concentration (cmc) for aqueous solutions of triblock poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers (B(n)E(m)B(n), where m and n denote the respective block lengths) with hydrophobic block lengths in the range n=12-21. Combined with results from previous work on B(n)E(m)B(n) copolymers with shorter B blocks, plots of log(10)(cmc) (cmc in molar units and reduced to a common E-block length) against total number of B units (n(t)=n for diblock or n(t)=2n for triblock copolymers) display transitions in the slopes of the two plots, which indicate changes in the micellisation equilibrium. These occur at values of n(t)which can be assigned to the onset and completion of collapse of the hydrophobic B blocks, an effect not previously observed for reverse triblock copolymers. The results are compared with related data for diblock E(m)B(n) copolymers.
authors.affiliation: Departamento de Física de la Materia Condensada, Facultad de Física, Universidad de Santiago de Compostela, Spain.
authors.forename: Adriana
authors.initials: A
authors.lastname: Cambón
authors.forename: Manuel
authors.initials: M
authors.lastname: Alatorre-Meda
authors.forename: Josué
authors.initials: J
authors.lastname: Juárez
authors.forename: Antonio
authors.initials: A
authors.lastname: Topete
authors.forename: Dharmista
authors.initials: D
authors.lastname: Mistry
authors.forename: David
authors.initials: D
authors.lastname: Attwood
authors.forename: Silvia
authors.initials: S
authors.lastname: Barbosa
authors.forename: Pablo
authors.initials: P
authors.lastname: Taboada
authors.forename: Víctor
authors.initials: V
authors.lastname: Mosquera
mesh_terms: D002151:Calorimetry; D004852:Epoxy Compounds / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D011092:Polyethylene Glycols / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D004852:Epoxy Compounds; D008823:Micelles; C087757:poly(ethylene oxide)-poly(butylene oxide) copolymer; D011092:Polyethylene Glycols