Synthesis and phase behaviour of poly(propylene imine) dendromesogens of lowest generations

ABSTRACT

Liquid crystal poly(propylene imine) dendrimers of the zero (D₀) and the first (D₁) generations were synthesised and structurally characterised by elemental analysis, FT-IR and nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MALDI-ToF). The phase behaviour of all the compounds was studied using polarisation microscopy and differential scanning calorimetry. Their structures were investigated by X-ray diffraction method by direct magnetic field influence. Analysis of diffraction patterns was carried out using the paracrystal model of Hosemann and the Fonk cluster model. Structural simulation and diffraction calculations on the models were used for determining the layer structure parameters of the dendrimers. Temperature behaviour of the structural parameters was considered in the interval from room temperature to isotropic melting temperature. It was determined that only the dendrimer of zero generation can be oriented by magnetic field. The schemes of phase transformations of the dendrimers look like: Cr→159^°С→Sm-C→274^°С→I for D₀ and G→55–66^°С→Sm-F→108^°С→Sm-C→274^°С→I for D₁.

Graphical Abstract

KEYWORDS:

• Liquid crystalline dendrimers
• X-ray diffraction
• phase transitions of the first and the second order
• smectic mesophases

Acknowledgments

Spectral and DSC researches have been conducted on the equipment of the Upper Volga Regional Center of physical and chemical researches; synthesis was performed under grant of the RFBR (No 18-03-00081_a).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Russian Foundation for Basic Research according to the research project No 18-03-00081_a.