The purpose of this thesis is to investigate the PEO-PPO-PEO triblock copolymer Pluronic P85, with special emphasis on the influence of PEO-PPO diblock impurities on the lattice structure of the gel phase in aqueous solutions. The commercial P85 from BASF (P85AR) contain about 13 wt% PPO-PEO diblock impurities and 87 wt% PEO-PPO-PEO triblock copolymers. NMR , DSC, rheology , HPLC and SAXS, in one and two dimensions, are utilized to characterize 30wt % commercial P85 samples as well as samples where the impurities are removed (P85Main) and where PEG is added (P85AR+PEG), as it is assumed that PEG behave similar to the PEO-PPO impurities. The experiments show that this 30wt % P85 gelates around 29oC and that the gel dissolves around 55oC. With the addition of PEG, these temperatures decrease. The one dimensional SAXS measurements only record a part of the spectrum, which makes structure determination from these data impossible. Two dimensional SAXS measurements on P85AR indicate that the sample assumes a FCC lattice structure during heating, but a BCC lattice structure during cooling. This rearrangement is not visible on a longer measurement on P85AR. The addition of PEG leads to clear changes in the scattering pattern, but indicate neither BCC nor FCC lattice structures. The two dimensional SAXS measurements on the purified P85 failed, which means that none of the data accurately describes the absence of impurities in P85 gels. Under the assumption that PEG behaves similar to the impurities, there are however clear indications that the presence of additional impurities alters the lattice structure of the gel phase substantially.
|Uddannelser||Fysik, (Bachelor/kandidatuddannelse) KandidatKemi, (Bachelor/kandidatuddannelse) Kandidat|
|Udgivelsesdato||5 jan. 2015|
|Vejledere||Dorthe Posselt & Søren Hvidt|