A master thesis from Aalborg University
Undersøgelse af vandbinding i vandige opløsninger af polyethylenglykol, polypropylenglykol og symmetriske treblok copolymerer af polyethylenglykol og polypropylenglykol
[Investigation of Water Binding in Aqueous Solutions of Poly(ethylene glycol), Poly(propylene glycol) and Symmetric Triblock Copolymers of Poly(ethylene glycol) and Poly(propylene glycol)]
Author(s)
Term
4. term
Education
Publication year
2009
Submitted on
2009-06-03
Pages
42 pages
Abstract
The aim of this thesis was to investigate the water binding in aqueous solutions of poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG) and amphiphilic symmetric triblock copolymers of PEG and PPG by water activity measurements as function of temperature and concentration. Furthermore, Differential Scanning Calorimetry (DSC) was used to determine the critical micelle temperature (cmt) of the triblock copolymers. Eight different PEG polymers, one PPG polymer and three different triblock copolymers were applied; however the PPG polymer was omitted as it could not be dissolved properly. The water activity measurements showed that the water activity increases with increasing temperature and decreasing concentration, i.e. water becomes a poorer solvent with increasing temperature because the polymer-water interactions are reduced. Excess enthalpies for the water binding were derived from the water activity measurements, but these are too large due to insufficient equilibrium time in the system. The DSC measurements showed that at a given concentration the cmt increases with increasing hydrophilicity of the copolymer.
Formålet med dette afgangsprojekt var at undersøge vandbindingen i vandige opløsninger af polyethylenglykol (PEG), polypropylenglykol (PPG) og amfifile symmetriske treblok copolymerer af PEG og PPG ved måling af vandaktivitet som funktion af temperatur og koncentration. Endvidere blev skanning kalorimetri (DSC) brugt til at bestemme den kritiske micelle temperatur (cmt) for treblok copolymererne. Otte forskellige PEG polymerer, en PPG polymer og tre forskellige treblok copolymerer blev anvendt; dog blev PPG polymeren undladt da den ikke kunne opløses ordentligt. Vandaktivitetsmålingerne viste at vandaktiviteten stiger med stigende temperatur og aftagende koncentration, dvs. at vand bliver et dårligere solvent med stigende temperatur fordi polymer-vand interaktionerne reduceres. Overskudsentalpier for vandbindingen blev udregnet fra vandaktivitetsmålingerne, men disse er for store pga. utilstrækkelig ligevægtstid i systemet. DSC målingerne viste at ved en given koncentration stiger cmt med stigende hydrofil karakter af copolymeren.
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