Fanzhu Li

High performance bio-based elastomers: energy efficient and sustainable materials for tires

Globally, we are faced with a massive growth in the number of urban vehicles. This growth comes at the cost of enormous fuel consumption, CO2 emissions and air pollution, commonly seen as a haze. With a strategy to fabricate low roll-resistance green tire elastomers from large-scale, bio-based chemicals, specifically itaconic acid, mono-alcohols and conjugated dienes, each of these problems can be reduced. By combining a molecular structural design with non-petroleum based silica and an in situ process to tune the viscoelastic properties of the elastomer composites, we have successfully manufactured silica/poly(di-n-butyl itaconate-co-butadiene) nanocomposite-based green tires that have very low roll-resistance, excellent wet skid resistance and good wear resistance, promote fuel efficiency and reduce our dependence on petrochemical resources. The results shown here open an important avenue for the synthetic rubber and automobile industry to ameliorate a major problem facing many cities worldwide, and also provide an effective route for resource sustainability.

Stress-strain behavior of block-copolymers and their nanocomposites filled with uniform or Janus nanoparticles under shear: a molecular dynamics simulation.

Although numerous research studies have been focused on studying the self-assembled morphologies of block-copolymers (BCPs) and their nanocomposites, little attention has been directed to explore the relation between their ordered structures and the resulting mechanical properties. We adopt coarse-grained molecular dynamics simulation to study the influence of the morphologies on the stress-strain behavior of pure block copolymers and block copolymers filled with uniform or Janus nanoparticles (NPs). At first, we examine the effect of the arrangement (di-block, tri-block, alternating-block) and the components of the pure block copolymers, and by varying the component ratio between A and B blocks, spherical, cylindrical and lamellar phases are all formed, showing that spherical domains bring the largest reinforcing effect. Then by studying BCPs filled with NPs, the Janus NPs induce stronger bond orientation of polymer chains and greater mechanical properties than the uniform NPs, when these two kinds of NPs are both located in the interface region. Meanwhile, some other anisotropic Janus NPs, such as Janus rods and Janus sheets, are incorporated to examine the effect on the morphology and the stress-strain behavior. These findings deepen our understanding of the morphology-mechanics relation of BCPs and their nanocomposites, opening up a vast number of approaches such as designing the arrangement and components of BCPs, positioning uniform or Janus NPs with different shapes and shear flow to tailor their stress-strain performance.

Tuning the structure and mechanical property of polymer nanocomposites by employing anisotropic nanoparticles as netpoints

Introducing carbon nanotubes or graphene sheets into polymer matrices has received lots of scientific and technological attention. For the first time, we report a new kind of polymer nanocomposite (PNC) by means of employing anisotropic nanoparticles (NPs) as netpoints (referred to as an end-linked system), namely with NPs acting as netpoints to chemically connect the dual end-groups of each polymer chain to form a network. By taking advantage of this strategy, the anisotropic NPs can be uniformly distributed in the polymer matrix, with the NPs being separated via the connected polymer chains. And the separation distance between NPs, the stress-strain behavior and the dynamic hysteresis loss (HL) can be manipulated by varying the temperature and the polymer chain flexibility. Meanwhile, the physically mixed system is investigated by changing the interaction strength between polymer and NPs, and the temperature. It is emphasized that compared to the physically mixed system, the end-linked system which employs carbon nanotubes or graphene as netpoints possesses good thermal stability because of its thermodynamically stable morphology, exhibiting both excellent static and dynamic mechanical properties. These results help us to design and fabricate high performance and multi-functional PNCs filled with carbon nanotubes or graphene, facilitating the potentially large industrial application of these nanomaterials.