Synthesis and thermophysical properties of nanocrystalline polycalix[4]amides and polycalix[4]arene containing mesogenic triazole units and their heavy metal sorption

Abstract

A series of novel polycalix[4]arenes bearing triazole units, polytriazolecalixamides (PTCAs) and polytriazolecalixarenes (PTCs) were prepared by direct polycondensation of a new bistriazole-substituted dicarboxylic acid of calix[4]arene with commercial diamines and by click reaction of bisethenylcalixarene with diazides, respectively. These polycalixarenes were obtained in high yields and possessed inherent viscosities in range 0.42–0.59 dl/g. These polymers were readily soluble in polar aprotic solvents such as N,N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone at room temperature. Nanocrystalline structures of PTCAs and amorphous PTCs were determined by XRD patterns and confirmed by differential scanning calorimetry as well as transmission electron microscopy and atomic force microscopy imaging techniques. Glass transition temperatures were between 134 and 165°C. Thermogravimetric analysis showed that the polycalixarenes displayed high thermal stability ranged from 273 to 360°C at a point of 10% weight loss, and char yields were about 43.2–61.6% at 600°C in nitrogen. All of these polymers showed promising sorption properties towards risky transition metal ions such as Cu²⁺, Cr²⁺, Co²⁺, Cd²⁺ and especially Pb²⁺ in solid–liquid extraction, which fulfill our needs in synthesizing novel high-performance polymers.

Keywords:

• calix[4]arene
• nanocrystalline polyamide
• triazoles
• heavy metal removal
• click reaction

Acknowledgements

The financial supports by the research council of the University of Mazandaran are gratefully acknowledged.