(121b) A Coarse-Grained Molecular Dynamics Study On the Effect of Nanoparticles On Cylindrical Confined Assembly of Symmetric and Asymmetric Block Copolymers

Our recent experimental study of electrospinning the block copolymer (BCP)/nanoparticle (NP) nanocomposites has revealed that various self-assembling structures can be formed in submicron scale fibers. [1,2] In an attempt to understand and control the self-assembly of BCP/NP nanocomposites in nanofibers, model symmetrical and asymmetrical BCPs with and without NPs under cylindrical confinement were studied using a coarse-grained molecular dynamics simulation. First, the effect of important parameters such as the ratio of the confinement radius to the length of BCP domain, d/l, polymer chain lengths, and the polymer-wall interactions on the confined assembly was thoroughly investigated. By examining both cross-section and assembled structures in the core along the cylinder axis, we have constructed a phase diagram for both symmetrical and asymmetrical BCP systems where structures were categorized by three features: the number of layers of domains, the number of axially connected domains, and the number of radially connected domains. Secondly, various concentrations (10% - 30%) of NPs with three different interactions with BCP, i) A domain selective, ii) B domain selective and iii) non-selective (neutral), were incorporated into BCPs. It is predicted that the swelling of either domain caused by the inclusion of selective NPs gives rise to different morphologies when they are compared with the corresponding BCP systems with the same domain ratio. Finally, the predicted BCP/NP structures will thoroughly be validated by those observed in electrospun BCP/NP nanofibers. The current study demonstrates that coarse-grained MD simulation can offer a useful guidance in the formation of self assembled structures in electrospun BCP/NP nanofibers.

 

[1] V. Kalra, J. H. Lee, J. H. Park, M. Marquez and Y. L. Joo, Small, 2009, 5, 2323-2332.

[2] V. Kalra, J. H. Lee, S. G. Lee, M. Marquez, U. Wiesner, and Y. L. Joo, Small, 2008, 4, 2067-2073.