Conformational chirality of the biphenyl groups induced by the aggregation of poly{bis[4-(4’-(S)-2-methylbutoxy)-biphenoxy] phosphazene}

Abstract

Poly{bis[4-(4’-(S)-2-methylbutoxy)biphenyloxy]phosphazene}(PP-C) was designed and successfully synthesized, and then characterized by means of FT-IR spectroscopy, ¹H- and ³¹P-NMR, GPC spectroscopy, wide angle X-ray diffraction and differential scanning calorimetry. The results indicated that for PP-C, the M _w is 2.18×10⁵ and the PDI is 1.96. PP-C was a kind of crystallized polymer with a crystallizing point of -2.0 °C and a melting point of 28 °C. The conformational chirality of the PP-C molecules was studied using circular dichroism spectrum. It was found that in dilute THF solution, the biphenyl groups in the PP-C molecules twisted randomly. However, when the PP-C formed aggregates, the biphenyl groups tended to twist single-handedly, which was controlled by the adjacent chiral alkoxy groups.

Keywords

polyphosphazene / biphenyl / chirality / aggregates

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