This study places a focus on flow-induced demixing of polyisoprene (PI) and poly(4-tert butyl styrene) (PtBS) polymer blends with high dynamic contrast. The rheological response is governed by the more immobilized PtBS chains. In contrast, the dielectric response at low frequency reflects exclusively the normal mode of PI chains having type-A dipole parallel along the chain backbone. These features enable selective detection of the component dynamics of PtBS or PI chains under either the small amplitude oscillatory shear or the nonlinear steady shear through a combination of rheological and dielectric techniques. We find the Cox–Merz rule fails significantly for the PtBS/PI blends, which is attributed to flow-induced demixing when the shear rate is higher than the relaxation rate of PtBS chains and lower than that of PI chains. The flow-induced demixing is further supported by varying the molecular parameters of PtBS, copolymerizing PtBS with polystyrene, as well as by the rheo-dielectric measurements that show a broadening of the PI relaxation mode distribution. This demixing could be partly driven by the increased conformational entropy of the PI chains after segregation from the surrounding restrictive PtBS chains. Graphical abstract
Dual-band electrochromic device (Db-ECD) can tune visible and near-infrared (NIR) radiation independently. The Db-ECDs have inspired considerable interest for their potential applications in smart windows and camouflage. Organic small molecules and polymers were examined carefully though, exploring organics with dual-band electrochromism is still challenging. Herein, the triazine-centered viologen analogues, 2,4,6-tri(pyridyl-4-propyl)-1,3,5-triazine bromide (TPPT) and 2,4,6-tri(pyridyl-4-benzyl)-1,3,5-triazine bromide (TPBT) show excellent dual-band electrochromic behaviors with high dynamic contrasts (66.63% at 887 nm and 50.71% at 600 nm for TPPT, and 59.79% at 900 nm and 66.90% at 600 nm for TPBT, respectively). The Db-ECDs fabricated via gel electrolyte mixed with TPPT or TPBT can work at a low driving voltage down to ∼0.6 V, rendering a high coloration efficiency (up to 230.94 cm 2 C -1 ) in the NIR region , the absorbance difference at 1037 nm reaching up to 2.58 for TPPT. This work sets the stage for novel organic materials of dual-band electrochromic gadgets.
危险品化学品经营许可证（带存储）