To
explore the mechanism of how the nanorod surface properties
regulate the compatibilization behavior and the morphology transition
in demixing polymer blends, we perform dissipative particle dynamics
simulations and study the impact of three typical nanorods on the
phase separation kinetics and structure as well as their location
and arrangement under both shear-free and shear conditions with the
variation of nanorod–polymer affinity parameters. Depending
on the dispersion and location of nanorods, blends in the quiescent
case either undergo full phase separation and generate bulky two-phase
morphology, or experience microphase separation and form BμE-like
structure, or proceed viscoelastic phase separation and take the kinetically
trapped cocontinuous network morphology, whereas shear flow can either
accelerate domain coarsening or strongly impact the phase behavior
through shear-induced bulk phase separation or shear-induced ordering
transition. Particularly, the shear-induced lamellar phase in Janus
nanorod-filled blends chooses parallel orientation and displays the
lateral ordering within layers.
In
the present work, we develop a coarse-grained (CG) model for polyimide
(PI) at 800 K and 1 atm by applying iterative Boltzmann inversion
(IBI) and the density correction method to derive the bonded and nonbonded
interaction potentials. Although the CG force field is built at a
single thermodynamic state point without any temperature correction,
the CG model possesses a rather favorable temperature transferability
in a wide temperature range of 300–800 K at P = 1 atm and a good pressure transferability to some extent in a
certain pressure range from 0.1 to 30 MPa. In addition to the local
conformation and local packing distribution functions, the thermodynamic
properties such as the glass transition temperature and the coefficient
of linear thermal expansion are predicted correctly by the CG model,
and the isothermal compressibility coefficients calculated from both
atomic and CG models are on the same order of magnitude. Additionally,
the stress–strain behavior under compression or tension of
the CG model shows a qualitative agreement with the atomistic results,
and the corresponding values of the elastic modulus of the CG model
at different temperatures roughly match with those of the atomistic
model.
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