The solubilisation behaviour of some dichloroalkanes in aqueous solutions of PEO-PPO-PEO triblock copolymers: a dynamic light scattering, fluorescence spectroscopy, and SANS study

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Abstract

The aggregation behaviour of PEO–PPO–PEO triblock copolymers in water and in water þchlorinated additive mixtures was studied by means of fluorescence spectroscopy, dynamic lightscattering (DLS), and small-angle neutron scattering (SANS). The copolymers were chosen suchas to investigate the effects of molecular architecture (L35 and 10R5) and molecular weight bykeeping constant the hydrophilic/hydrophobic balance (F88 and F108). 1,2-Dichloroethane wasused as a prototype of water basins contaminants. The hydrodynamic radius of the blockcopolymer aggregates (Rh,M) and the intensity ratio of pyrene of the first and the third vibrationalband (I1/I3) were determined as a function of temperature (10–45 1C) and concentration. Thecopolymer architecture essentially does not affect Rh,M in the entire range of temperature andconcentration investigated. At a given temperature, increasing macromolecular size leads to adecrease of Rh,M. With rising temperature Rh,M also decreases. According to the DLS results, theI1/I3 change with temperature clearly detects the aggregation only for F88 and F108. Thepresence of 1,2-dichloroethane, at concentrations close to its solubility in water, does not lead tochanges in the distribution of hydrodynamic radii for L35 and 10R5. Larger quantities of additiveinduce the formation of quite polydisperse mixed aggregates for L35 and of networks for 10R5.In the case of F88 and F108, low concentrations of additive lead to formation of mixedaggregates with smaller Rh,M. The SANS results corroborate the DLS and fluorescence findingsproving enhancement of the copolymer aggregation through the presence of 1,2-dichloroethane.The DLS findings combined with those from the fluorescence spectroscopy provide some insightinto the site of solubilisation of the additive in the aggregates.
Lingua originaleEnglish
pagine (da-a)2299-2312
Numero di pagine14
RivistaPhysical Chemistry Chemical Physics
Volume8
Stato di pubblicazionePublished - 2006

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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