Synthesis of tetraazacalixarenetriazine-containing poly(dimethylsiloxane) with elastic property induced by pinning effect of the calix arene ring

Abstract Tetraazacalix [2] arene [2] triazine dichloride was polymerized with telechelic poly(dimethylsiloxane)s having NH2 terminals (PDMSx; degree of polymerization x = 8, 18, 38) via solution polycondensation to give the corresponding azacalixarene-containing polymers (ACAT-PDMSx) in good yield. The fraction of the hard ACAT moiety (fHS) of the ACAT-PDMS polymers was calculated to be 33.0%, 20.4%, and 11.6% for x of 8, 18, and 38, respectively. The number-average molecular weight (Mn) of the polymers ranged from 20 to 32 kDa, and freestanding tough films were successfully fabricated via solvent cast method. As a control sample, a polymer not containing azacalixarene (AnDCT-PDMS) with Mn and fHS values of 21 kDa and 19.8%, respectively, was prepared via the solution polymerization of 2-anilino-4,6-dichloro-1,3,5-triazine (AnDCT) with PDMS8. Although the fHS values of AnDCT-PDMS8 and ACAT-PDMS18 were similar, the film obtained from the former polymer was much softer and sticky at room temperature than that from the latter. Interestingly, the ACAT-PDMS18 film exhibited a tensile strength of 2.7 MPa, a modulus of 2.0 MPa, and an elongation at break of 200%. The glass transition temperature of the ACAT-PDMSx films ranged from 77°C to 105°C according to thermomechanical and dynamic mechanical analyses. Wide-angle X-ray diffraction and polarized optical microscopy studies indicated that the azacalixarene units were first locally aggregated via multiple hydrogen bonds within the ACAT-PDMSx films and then were well dispersed in the film on heating. The ACAT-PDMS polymer showed no cytotoxicity to HeLa and IMR-90 cells in the experimental concentration of below 100 μg/mL.