The
effect of the number of layers, various defects and functional
groups on solubility parameter of graphene was studied through molecular
dynamics (MD) simulation. We predigested three-component Hansen solubility
parameters (δD, δP, δH) to two-component solubility parameters (δvdW, δele), and the two-component solubility parameters
of graphene functionalized by different groups, such as hydroxyl,
carboxyl, amino, methyl and epoxy with different grafting ratios were
obtained. Further, the graphene/styrene butadiene rubber (SBR) composites
were constructed to investigate the effect of functional groups and
grafting ratios on components compatibility. It was found that the
defects and functional groups had strong impact on solubility parameter
of graphene, whereas the number of layers had a negligible effect.
Two-component solubility parameters were proven to be able to predict
compatibility of graphene and SBR. Additionally, the common effect
of multifunctional groups on solubility parameter was also investigated.
The combination of multifunctional groups with a proper content can
obtain lower solubility parameter than a single group. The present
study is expected to provide significant insight into the relationship
between solubility parameter of graphene and compatibility of graphene/SBR
composites.
Due
to the exchangeability of dynamic covalent bonds in the covalent adaptable
networks (CANs) at elevated temperature, they possess recyclability
while still maintaining many of the superior properties of thermosets.
The exploration of dynamic covalent chemistry is of great significance
to the expansion of CANs library and hence the sustainable development
of thermosets. In this work, we discovered that, in absence of catalyst,
the direct metathesis of the cyclic acetals proceeds while the acyclic
acetals cannot. The metathesis kinetics of the cyclic acetals were
fully revealed with model compounds. For the CANs demonstration, a
series of cross-linked spirocyclic acetal polymers with excellent
reprocessability, high thermal stability, and high refractivity were
prepared via thiol–ene click polymerization. We envisage that
the uncovering of the catalyst-free metathesis of cyclic acetals will
enrich the dynamic chemistry of acetals and greatly promote the development
of acetal-based CANs and their potential applications in optical devices.
The dynamic properties, filler–rubber interactions, and filler dispersion in silica/SSBR composites with various chemical structures of SSBR were studied using MD. Competing effects led to the existence of an optimum modifier content of 14.2 wt%.
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