importance of unimer exchange increases during the final stage of micellization.
Also, fusion/fission events appear to be virtually unaffected upon an increase in the
interaction energy although events involving small aggregates were found to be less
likely to occur. The effect of increasing corona length was, perhaps surprisingly,
found not to affect the relative contributions from the different mechanisms;
instead, the overall rate of events decreased. It should be mentioned that the range
of molecular weights studied by Li and Dormidontova corresponds to oligomers and
that there might be a significant difference for polymers. This is still to be studied
and compared to experimental results, providing a significant challenge for future
studies.
5.2 Morphological Transition Kinetics
Most of the works related to the kinetics of morphological transitions have been
performed in systems of regular (low molecular weight) surfactant micelles.
Examples include micelle-to-vesicle transitions [187–189] studied by TR-SANS
coupled with stopped-flow or with time resolved small-angle static and dynamic
light scattering [190, 191]. Such morphological transitions have also been observed
using TR-SAXS in other systems [192–194], where the processes can be resolved
on time scales of only a few milliseconds. Since morphological transition kinetics
of surfactant micelles have been extensively reviewed elsewhere [14, 15, 189, 195],
this will not be covered in more detail here because we are mainly dealing with
block copolymer systems in this review.
For block copolymer systems, most studies are related to ordering kinetics and
morphological transition in melts or concentrated solutions. Examples include
disorder-to-order [196], lamella-to-cylinder [197], cylinder-to-sphere [198], and
Fig. 39 Time evolution of
the aggregation number
distribution for A 2 B 3
oligomers undergoing
micellization. Note the
bimodal character of the
distribution function at
intermediate time stages.
Reprinted with permission
from [162]. Copyright (2010)
American Chemical Society
Kinetics of Block Copolymer Micelles Studied by Small-Angle Scattering Methods
149
Also, fusion/fission events appear to be virtually unaffected upon an increase in the
interaction energy although events involving small aggregates were found to be less
likely to occur. The effect of increasing corona length was, perhaps surprisingly,
found not to affect the relative contributions from the different mechanisms;
instead, the overall rate of events decreased. It should be mentioned that the range
of molecular weights studied by Li and Dormidontova corresponds to oligomers and
that there might be a significant difference for polymers. This is still to be studied
and compared to experimental results, providing a significant challenge for future
studies.
5.2 Morphological Transition Kinetics
Most of the works related to the kinetics of morphological transitions have been
performed in systems of regular (low molecular weight) surfactant micelles.
Examples include micelle-to-vesicle transitions [187–189] studied by TR-SANS
coupled with stopped-flow or with time resolved small-angle static and dynamic
light scattering [190, 191]. Such morphological transitions have also been observed
using TR-SAXS in other systems [192–194], where the processes can be resolved
on time scales of only a few milliseconds. Since morphological transition kinetics
of surfactant micelles have been extensively reviewed elsewhere [14, 15, 189, 195],
this will not be covered in more detail here because we are mainly dealing with
block copolymer systems in this review.
For block copolymer systems, most studies are related to ordering kinetics and
morphological transition in melts or concentrated solutions. Examples include
disorder-to-order [196], lamella-to-cylinder [197], cylinder-to-sphere [198], and
Fig. 39 Time evolution of
the aggregation number
distribution for A 2 B 3
oligomers undergoing
micellization. Note the
bimodal character of the
distribution function at
intermediate time stages.
Reprinted with permission
from [162]. Copyright (2010)
American Chemical Society
Kinetics of Block Copolymer Micelles Studied by Small-Angle Scattering Methods
149