A low-density polymorph of the well-known host compound p-tert-butylcalix[4]arene undergoes subtle structural changes when heated and cooled.
![Graphical abstract: Polymorphism of pure p-tert-butylcalix[4]arene: subtle thermally-induced modifications](http://hg.y866.cn/compound/lib/scimg/usr/1/B402452B.jpg)
