Two
hydrogen (H)-bond donors, phenol and l-threonine,
were added into the aqueous solutions containing crystalline micelles
of a poly(ε-caprolactone)-<i>b</i>-poly(ethylene oxide)
(PCL-<i>b</i>-PEO) block copolymer, respectively. Dynamic
light scattering (DLS) characterization showed that the micellar size
became smaller after addition of phenol. Transmission electron microscopy
(TEM) results revealed that the long crystalline cylindrical micelles
formed in the neat aqueous solution were fragmented into short cylinders
and even quasi-spherical micelles, as the phenol concentration increased.
By contrast, the spherical PCL-<i>b</i>-PEO crystalline
micelles could be transformed into short cylinders and then long cylinders
after addition of l-threonine. Reversible morphological transformation
was realized for the PCL-<i>b</i>-PEO crystalline micelles
by adding these two H-bond donors alternately. It is confirmed that
both phenol and l-threonine could form H-bonds with PEO.
We proposed that, the micellar corona was swollen by phenol, leading
to fragmentation of the micellar core, whereas the PEO blocks in the
micellar corona was dynamically cross-linked by l-threonine
beacuse of its multiple H-bond-donation groups, resulting in a smaller
reduced tethering density
