Interphase structures and dynamics near nanofiller surfaces in polymer solutions

We report the structures and dynamics of hydrogenated polybutadiene (PB) chains bound to carbon black nanoparticle surfaces in polymer solutions composed of deuterated PB and deuterated toluene using small-angle neutron scattering and neutron spin echo techniques together with molecular dynamics (MD) simulations. The experimental results showed that the swollen bound chains exhibit the so-called breathing dynamics at polymer concentrations (c) below and above the overlap polymer concentrations. Interestingly, the collective dynamics slowed down by a factor of 2 compared to that in pure d-toluene when the chain lengths of the bound and matrix polymer are equal. However, when the free polymer chains were longer than the bound chains, the decrease in collective dynamics was not as significant. MD simulations showed that the matrix chains, whose length is equal to that of the bound chains, can be accommodated in the bound layer effectively and are “strangulated” by the bound chains, while the longer matrix chains only partly penetrate into the bound chains and the diffusion behavior was hardly affected compared to that in bulk.