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Morphological Control of Poly(ethylene glycol)-block-poly(ε-caprolactone) Copolymer Aggregates in Aqueous Solution

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journal contribution
posted on 08.09.2008, 00:00 by Nichole Fairley, Bryan Hoang, Christine Allen
In aqueous solution, it was found that the amphiphilic copolymer poly(ethylene glycol)-b-poly(caprolactone) (PEG5000-b-PCL4100) formed different morphologies, including long rod-like, short rod-like, or spherical aggregates, when the copolymer concentration was increased. Nearly identical morphologies were observed with the addition of increasing amounts of PEG2000-distearoylphosphoethanolamine (PEG2000-DSPE) to the copolymer. The morphologies of the aggregates in solution were confirmed by negative stain transmission electron microscopy (TEM) and cryogenic-TEM (cryo-TEM). The critical micelle concentrations of the PEG5000-b-PCL4100 copolymer, PEG2000-DSPE and a mixture of the two materials (PEG5000-b-PCL4100/PEG2000-DSPE) were evaluated to determine the thermodynamic stability of the aggregates. Differential scanning calorimetry was performed to gain insight into the degree of mixing of PEG5000-b-PCL4100 and PEG2000-DSPE. Overall, combining PEG5000-b-PCL4100 and PEG2000-DSPE produced a single population of mixed micelles with rod-like or spherical morphologies depending on the material composition and concentration.