Plasticizers assisted, shear-induced domino-assembly of nanofibrous polyaniline in PP matrix

• Polyaniline/polypropylene polyblend prepared by melt-mixing.
• Shear induced domino-like morphology.
• n-Dodecylbenzene sulfonic acid and zinc stearate plasticizers.

A nanofibrous polyaniline (PANFDBZnSt) was easily prepared when aniline monomers are polymerized in the presence of both n-dodecylbenzenesulfonic acid (DBSA) and zinc stearate (Zn(St)2). The obtained PANFDBZnSt can be melt-mixed with PP matrix plasticized by both DBSA and Zn(St)2 (PPDBZnSt) at 150 °C with shear rate as low as 40 rpm. During melt-mixing, the hairy-rod PANFDBZnSt blended with some of PPDBZnSt are able to self-assemble into rectangular layers that line up into erected domino-like structure in the PPDBZnSt matrix at higher shear rates. The intermolecular conjugation length of PANFDBZnSt molecules inside of the dominos is increased due to the shear-induced self-assembly and additional λmax was found in the Near-IR range when shear rates were higher than 40 rpm. SEM and AFM micrographs show that pieces of dominos grow from the polyblend with shear rate higher than 40 rpm but some of the plasticizers (DBSA & Zn(St)2) and PANFDBZnSt are spun out of the domino-structure at shear rate higher than 100 rpm. DSC thermograms demonstrate additional melting point contributed from the domino morphology. The IR-spectra reveal the formation of dominos come from the alkyl affinity between DBSA, Zn(St)2 that belonged to both PANFDBZnSt and PPDBZnSt. X-ray diffraction patterns indicate the (1 1 1) plane of PP in the polybelnds was depressed at high shear rates. The rectangular layers of PANFDBZnSt inside of dominos contribute to new diffraction peak at lower angle which shifts to higher angle when some PANFDBZnSt molecules slip out with the lubrication of DBSA or Zn(St)2 plasticizers at shear rates higher than 100 rpm.

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