Abstract
Block copolymer (BCP) structure and dynamics were studied using small-angle neutron scattering (SANS), neutron spin echo (NSE) spectroscopy, and molecular dynamics (MD) simulations to obtain a fundamental understanding of the impact of an interfacial block on chain dynamics. A glassy block acted as the interface, and the dynamics of a rubbery block was studied. The rubbery block was protonated near the interface in one sample and near the chain end in another sample to observe the interfacial effect on the rubbery polymer. Analysis of the structure and dynamics revealed that the interfacial rubbery block was confined in layered morphologies and exhibited much slower dynamics than the chain-end rubbery block that was dispersed in the rubbery matrix. The interfacial rubbery block showed weaker dynamical relaxation than that at the chain end, and it also had critically important length scale dependence. Dynamical slowing was only observed at length scales significantly larger than the characteristic segmental length, and the disparity between interfacial and chain-end dynamics increased with increasing length.
| Original language | English |
|---|---|
| Pages (from-to) | 762-771 |
| Number of pages | 10 |
| Journal | Macromolecules |
| Volume | 56 |
| Issue number | 3 |
| DOIs | |
| State | Published - Feb 14 2023 |
Funding
The authors acknowledge support from NSF CAREER award number 1751450. The authors thank the FAMU-FSU College of Engineering Machine shop for fabrication of the metal presses used to process the samples into the appropriate shape for the niobium sample holder. The block copolymers were synthesized at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. Molecular dynamics simulations were carried out at the CNMS. This research also used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The MD simulations used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Scientific User Facility supported by the DOE Office of Science under Contract DE-AC02-05CH11231. Part of the MD simulation used resources at the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the US Department of Energy under Contract no. DE-AC05-00OR22725.