Cylindrically confined assembly of asymmetrical block copolymers with and without nanoparticles

Abstract

Our recent experimental study on electrospinning of block copolymer (BCP)-nanoparticle (NP) nanocomposites has revealed the formation of unique self-assembling structures in submicron scale fibers. In this paper, we use coarse-grained molecular dynamics (MD) simulations to investigate the effect of cylindrical confinement on self-assembly of model asymmetrical BCPs with and without NPs with the aim to understand and control our experimentally found structures. First, the effects of the ratio of the cylindrical confinement diameter to the BCP domain spacing, D/L 0 , the total polymer chain length, and the polymer-wall interactions on the confined assembly were thoroughly investigated. We examined the core assembled structures along the cylinder axis and constructed a phase diagram for asymmetrical BCP. The structures are categorized by three features: the number of layers of domains, radially interconnected domains, and the number of axially perforated domains. Secondly, NPs with selective attraction towards the (i) minor domain (A) and (ii) major domain (B) were incorporated into asymmetric BCPs. We found that swelling of either domain caused by the inclusion of selective NPs yields different morphologies when compared with a pure BCP with the same effective volume ratio. Interestingly, the effect of confinement on nanoparticle placement was prominently seen if nanoparticles were selectively placed into the minor domain that preferentially wets the confining wall. Finally, the predicted BCP-NP structures are validated by those observed in electrospun BCP-NP nanofibers. The current study demonstrates that coarse-grained MD simulation can offer a useful tool to elucidate, predict and tailor self-assembled structures in electrospun BCP-NP nanofibers.

Tailoring nanorod alignment in a polymer matrix by elongational flow under confinement: simulation, experiments, and surface enhanced Raman scattering application

“…Our previous comparisons of block copolymer-nanoparticle nanostructure between polymer melt simulation and solution-electrospinning experiments have indeed shown good agreement. 42 Overall, the good agreement between experiments and simulation validates our simulation as a predictive tool for probing nanorod-polymer composite structures under extensional ow. Finally, we have constructed a series of contour plots to provide an overview of how exactly elongational ow strength (_ 3), nanorod aspect ratio (N), and polymer-nanorod interaction can affect nanorod orientation and dispersion (Fig.…”

Diversifying Nanoparticle Assemblies in Supramolecule Nanocomposites Via Cylindrical Confinement

“…The system morphological degeneracy is evident. The morphological degeneracy between unconfined and cylindrically confined states has been theoretically predicted for both BCP and BCP/NP blends [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] . The degeneracy occurs when different states are similar in energy.…”

Morphology of diblock copolymers in porous media

“…The theoretical/numerical approaches that have been used to study copolymers in cylindrical confinement include SCFT [40][41][42][43][44][45], DFT [46], MC [47][48][49][50][51][52][53], SA [30,[54][55][56][57], dissipative particle dynamics [58], coarse-grained molecular dynamics [59] and TDGL theory [60]. These studies have yielded detailed phase diagrams associated with the new morphologies and how these vary with pore diameter, chemical incompatibility and the block asymmetry [1].…”