Influence of Chemical Side Groups Containing Aromatic Rings: Flow-Induced Friction Enhancement or Reduction
Yiming Zhong, Shuang Liu, Longbo Luo, Qian Huang
Abstract
To explain the nonuniversality in extensional rheology of different polymer melts, contrary ideas, i.e., flow-induced friction reduction and flow-induced friction enhancement, have been proposed during the past decade. Here, we investigate this issue through an interesting case of poly(2-vinyl naphthalene) (P2VN). P2VN has very rigid naphthyl side groups, which may lead to flow-induced friction reduction. At the same time, the naphthyl groups also form strong π–π stacking, which may lead to flow-induced friction enhancement. By combining extensional rheology and wide-angle X-ray scattering, we show that P2VN exhibits flow-induced friction enhancement due to stronger π–π stacking along the flow direction. The result of P2VN is also compared with polystyrene (PS) and poly(4-vinyl biphenyl) (PVBP), which contain aromatic rings in their side groups as well. It is found that the configuration of the flow-induced π–π stacking in P2VN is different from that in PS and PVBP.