Molecular Self-Assembly in Bicomponent Polymer Filaments
Dr. Melissa Pasquinelli and collaborators, funded by the Nonwovens Cooperative Research Center, have designed innovative new polymer filaments that exhibit thermally-responsive shape memory (patent pending) by exploiting both the elasticity afforded by supramolecular networks formed by thermoplastic elastomers and also the interfacial characteristics created during the processing of bicomponent filaments. As a key aspect of this technology development, dissipative particle dynamics (DPD) simulations were used to predict the polymer behavior in their melt phase and to provide details about the interfacial interactions and molecular network formation that occurs during the self-assembly (via microphase segregation) of the polymer molecules during filament processing. The results from these DPD simulations ascertain the strenth, dynamics and extent of intermixing in these systems as a result of processing conditions and chemical compositions. The predicted trends from the simulations have been pivotal in choosing polymers for scalable fabrication of thermally-responsive polymer filaments. Applications are heat-sensitive textiles and form-fitting materials.
Click to see a video of a DPD simulation of the interface in a bicomponent filament. The length scale is about 10 nm in each dimension with a duration of 0.5 micro sends. The video indicates that the homopolymer (green) intermixes with one part of the copolymer (yellow), whereas the other part of the copolymer (red) forms self-assembled aggregates due to microphase segregation. the intermixing between the polymers improves the strength at their interface, enhancing the thermal-responsive behavior and other properties of the filaments. This simulation consists of around 100,000 particles, observed for 500,000 'steps'. Over a hundred such simulations have been done. Each simulation was performed on 24 processors of the Henry2 cluster, running for about 100 hours.
Key collaborators include Syamal Tallury, PhD candidate in Fiber and Polymer Science and Materials Science and Engineering; Rich Spontak, Professor of CBE and MSE; and Behnam Pourdeyhimi, Professor of FPS and Director of the Nonwovens Institute. Other projects are highlighted on the Pasquinelli website, for example polymer-carbon nanotube interactions.