Abstract
In aqueous solutions hydrophobically modified polyethylene glycol (HM-PEG) forms a transient polymer network held together by intermolecular hydrophobic associations. In the present investigation we have used NMR-diffusometry to study how the addition of methylated alpha-cyclodextrin (M-alpha-CD) influences the polymer network. The addit
on of M-alpha-CD resulted in an increased mean self-diffusion of HM-PEG,
DHM-PEG, which is referred to a degradation of the polymer network when
hydrophobic associations are disrupted due to complex formation between
the hydrophobic groups of HM-PEG and M-alpha-CD. Addition of small
amounts of M-alpha-CD results in a dramatic increase in DHM-PEG. Upon
further addition of M-a-CD the increase in DHM-PEG is less dramatic and
at excess M-alpha-CD, DHM-PEG levels off and equals the mean
self-diffusion coefficient for unmodified PEG with the same molecular
weight. The suggested interpretation is that the addition of the first
molecules of M-alpha-CD mainly reduces the probability for hydrophobic
associations inter-connecting different clusters of polymer micelles
whereas at higher M-alpha-CD concentrations a disengagement of the
individual clusters into separate HM-PEG molecules becomes
important. (C) 2003 Elsevier B.V. All rights reserved.
on of M-alpha-CD resulted in an increased mean self-diffusion of HM-PEG,
DHM-PEG, which is referred to a degradation of the polymer network when
hydrophobic associations are disrupted due to complex formation between
the hydrophobic groups of HM-PEG and M-alpha-CD. Addition of small
amounts of M-alpha-CD results in a dramatic increase in DHM-PEG. Upon
further addition of M-a-CD the increase in DHM-PEG is less dramatic and
at excess M-alpha-CD, DHM-PEG levels off and equals the mean
self-diffusion coefficient for unmodified PEG with the same molecular
weight. The suggested interpretation is that the addition of the first
molecules of M-alpha-CD mainly reduces the probability for hydrophobic
associations inter-connecting different clusters of polymer micelles
whereas at higher M-alpha-CD concentrations a disengagement of the
individual clusters into separate HM-PEG molecules becomes
important. (C) 2003 Elsevier B.V. All rights reserved.
| Original language | English |
|---|---|
| Pages (from-to) | 171-179 |
| Journal | Colloids and Surfaces A: Physicochemical and Engineering Aspects |
| Volume | 228 |
| Issue number | 1-3 |
| DOIs | |
| Publication status | Published - 2003 |
Subject classification (UKÄ)
- Physical Chemistry (including Surface- and Colloid Chemistry)
Free keywords
- Hydrophobically modified polyethylene glycol
- Methylated α-cyclodextrin
- NMR diffusometry