Propargyl-PEG1-SS-PEG1-t-butyl ester is a Click Chemistry-ready crosslinker containing a propargyl group, a cleavable disulfide bond and a t-butyl protected carboxyl group. The propargyl groups can be reacted with azide-bearing compounds or biomolecules via copper catalyzed azide-alkyne Click Chemistry to yield stable triazole linkages. The t-butyl protected carboxyl group (COOH) prevents self coupling or polymerization under standard acid/amine or acid/hydroxyl coupling conditions. The protected acid can be deprotected by acidic or basic hydrolysis.