Biomedical Engineering Reference
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Fig. 16
Schematic illustration of vesicles made from PEG and malachite green and their disas-
sembly under UV illumination. (Reproduced from ref. Jiang et al.
2007b
)
PCL blocks. As PEG is liberated from the membrane by UV light, there is excess
hydrophobic material that must be stabilized by the remaining PEG shell. This
results in membrane thickening, decreasing overall size of the polymersome, and
flux of aqueous contents out of the polymersome (Fig.
17b, c
). Ultimately, there is
insufficient PEG surface-coverage to stabilize the PCL shell and the insoluble PCL
crashes out of solution and aggregates.
The above system is an example that light (a physical stimuli) induce irreversible
chemical structure changes in light-responsive polymers. The chemical structure
changes can also be produced by light in photo-inert polymers with the aid of pho-
tosensitizers as discussed below.
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