Excellent performance of aromatic polyguanamines induced by multiple hydrogen bondable tetraazacalix[2]arene[2]-triazine ring in their main chain

摘要

A series of poly(guanamine) ( c -PG)s containing tetraazacalix[2]arene[2]-triazine ( m PDA _(2) CyC _(2) ) were successfully prepared by solution polycondensation of m PDA _(2) CyC _(2) with various aromatic diamines in an aprotic organic solvent with a lithium chloride additive (5 wt%) at 150 °C for 6 hours. The number-average molecular weights ( M _(n) )s of these c -PG polymers reached up to 31?500, with a relatively broad molecular weight distribution ( M _(w) / M _(n) ) of 5.3. They showed good solubility in aprotic organic solvents, such as N -methylpyrrolidone and N , N -dimethylacetamide at a concentration of 2 mg mL ~(?1) . The glass transition temperatures ( T _(g) ) of the c -PG polymers were in the range 359 °C–392 °C, approximately 160 °C higher than those of counterpart polymers ( i.e. , with no aza-calixarene-based PG ( l -PG)). The coefficients of thermal expansion (CTEs) of the c -PG polymers were 29.7–48.1 ppm K ~(?1) (at 100 °C–150 °C), much lower than those of l -PG samples, i.e. , 59.1–85.1 ppm K ~(?1) . Transparent and almost colorless c -PG films were successfully prepared by a solution casting method, showing maximum tensile strength ( σ _(S) ), modulus ( E _(γ) ), and elongation at break ( E _(b) ) values of 151 MPa, 6.3 GPa, and 4.4%, respectively, for the c -PG polymer from m PDA _(2) CyC _(2) and 4,4′-oxydianiline monomers. The corresponding l -PG film exhibited σ _(S) , E _(γ) , and E _(b) values of just 76 MPa, 5.4 GPa, and 1.6%, respectively. These outstanding thermal and mechanical properties of the c -PG polymers can be attributed to their multiple hydrogen bonding interaction between m PDA _(2) CyC _(2) residues in the polymer backbone. This interaction was identified by infrared spectroscopy measurements at the broad absorption band around 3000–3400 cm ~(?1) .