(376m) Multiscale Modeling of the UV-Sensitive Spiropyran/Merocyanine Micelles

Multiscale Modeling of the UV- Sensitive Spiropyran/Merocyanine Micelles

Mackenzie Mallard, Seung
Min Lee, Connor Callaway, and Seung Soon Jang*

Computational NanoBio
Technology Laboratory, School of Materials Science and Engineering, Georgia
Institute of Technology, 771 Ferst Drive, Atlanta, GA
30332

Reaction design optimization is an innovative field that drastically
improves facets of polymer manufacturing, pharmaceutical production, and
related industries. More specifically, the potential that multicompartment
micelles (MCM) have to be efficient nanoreactors has
caused MCM research to gain popularity. Not only can micelles be used as
immobilized molecular catalysts, but they also possess high reactivity and
selectivity. Due to the complexity of the multicompartment micelle structure,
dissipative particle dynamics (DPD) simulations have been used to model the
behavior of spiropyran and reactants in micelles. Spiropyran is a photochromic organic compound used in
medical applications. The introduction of UV to this photochromic material causes
a change of hydrophobicity which consequently drives a change in the micelle
morphology. In our present work, we apply miscibility analyses in order to
prepare a coarse-grained model of a tri-polymer micelle with spiropyran. The micelle will consist of a hydrophilic
block, a spiropyran block, and a hydrophobic block.
The strength of the interaction between a pair of polymer blocks can be
measured by the χ-parameter whose value is also dependant on
process conditions such as temperature and composition of a solution. In order
to run DPD simulations, χ-parameter calculations must be obtained to ensure an accurate
representation of the conversion of spiropyran to merocyanine within the micelle. The change in
hydrophobicity that results from the conversion of spiropyran
to merocyanine causes the change of micelle structure. Using
coarse-grained modeling, we investigate the self-aggregation of a spiropyran micelle and the changes in morphology due to the
photochromic nature of spiropyran/merocyanine.
Because these micelles possess the potential for multi-step catalysis, the
effects of the introduction of reactants to the spiropyran
micelle are studied, as well as how reactants behave when spiropyran
is converted to merocyanine.