Propargyl-PEG1-SS-PEG1-t-butyl ester is a Click Chemistry crosslinker containing a propargyl group that can react with azide-bearing compounds or biomolecules via copper catalyzed azide-alkyne Click Chemistry to yield stable triazole linkages. The t-butyl protected carboxyl group prevents self coupling or polymerization under standard acid/amine or acid/hydroxyl coupling condition, t-butyl can be deprotected under acidic conditions.