Synthesis of tetraazacalix[2]arene[2]triazine-containing poly (dimethylsiloxane) with elastic property induced by pinning effect of the calixarene ring

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 (f(HS)) 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 (M-n) 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 M-n and f(HS) 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 f(HS) 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 degrees C to 105 degrees 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 ACATPDMSx 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 mu g/mL.

Automated summary

In this study, Tetraazacalix[2]arene[2]triazine dichloride was polymerized with PDMS via solution polycondensation to give azacalixarene-containing polymers, which were successfully fabricated into tough films. The ACAT-PDMS films exhibited high tensile strength, large elongation at break, and non-cytotoxicity to HeLa and IMR-90 cells.