Triazole-based cross-linkers in radical polymerization processes: tuning mechanical properties of poly(acrylamide) and poly(-dimethylacrylamide) hydrogels.

Triazole-based cross-linkers with different spacer lengths and different functional end groups (acrylamides, methacrylamides, maleimides and vinylsulfonamides) were synthesized, investigated for cytotoxic and antibacterial activity, and incorporated into poly(acrylamide) (PAAm) and poly(,-dimethylacrylamide) (PDMAAm) hydrogels by free-radical polymerization. Hydrogels prepared with different cross-linkers and cross-linker contents between 0.2% and 1.0% were compared by gel yields, equilibrium degrees of swelling () and storage moduli ('). Generally with increasing cross-linker content, ' values of the hydrogels increased, while values decreased. The different polymerizable cross-linker end groups resulted in a decrease of ' in the following order for cross-linkers with C spacers: acrylamide > maleimide > methacrylamide > vinylsulfonamide. Longer cross-linker alkyl spacer lengths caused an increase in ' and a decrease in . Independent of the cross-linker used, a universal correlation between ' and equilibrium polymer volume fraction was found. For PAAm hydrogels, ' ranged between 4 kPa and 23 kPa and between 0.07 and 0.14. For PDMAAm hydrogels, ' ranged between 0.1 kPa and 4.9 kPa and between 0.02 and 0.06. The collected data were used to establish an empirical model to predict ' depending on . ' of PAAm and PDMAAm hydrogels is given by ' = 4034 kPa and ' = 4297 kPa , respectively.