Multifarious Polymorphism of a Multiblock Amphiphilic Macrocycle Bearing Thermally Responsive Polyether Segment.

ABSTRACT: Formation of multiple crystalline phases of a multiblock amphiphilic macrocycle AT2B is demonstrated. AT2B forms a single crystal (Cr-?) by vapor diffusion and shows reversible single-crystal-to-single-crystal transition between two crystalline phases (Cr-? and Cr-?) by a temperature change, and crystalline AT2B (Cr-?) melts at 422 K, and the cooling rate from the melt influences the phase of the solid formed. By cooling at 1.0 K min^-1, AT2B forms crystalline phases (Cr-? and Cr-?), which are different from both Cr-? and Cr-?. On the other hand, cooling at 2.0 K min^-1 results in the formation of an amorphous phase, and a mechanical stress also triggers a crystal-to-amorphous solid transition. Interestingly, the amorphous solid crystallizes to give the fifth crystalline phase (Cr-?) upon heating before melting. It is suggested that these multiple phase transitions are driven by thermal conformational changes at the tetraethylene glycol chains of AT2B.

SUBMITTER: Muraoka T 

PROVIDER: S-EPMC6641220 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature