1,4-Butanediol diglycidyl ether (BDDE) is a viscous liquid, which is hygroscopic in nature. BDDE is the most commonly used homobifunctional epoxide compound. BDDE may react with amines, hydroxyls, sulfhydryl groups to produce secondary amines, ether or thioether bonds respectively. BDDE is a cross linking agent used • for preparing amylose, xylan and hydroxyethyl-cellulose • to cross link polyethylenimine which also serves as a hole-blocking layer in organic solar cells • to cross link hyaluronic acid (HA) into hydrogels • for the activation of soluble dextran polymers. • Amine or hydroxyl containing bis-epoxy supports are reacted with BDDE to form particles containing terminal epoxide group for immobilization reactions. In most commercial products, HA is crosslinked to increase its longevity, and the crosslinking agent used has an important effect on the properties of the final product; BDDE is the crosslinking agent used in the majority of the market-leading HA fillers, and its stability, biodegradability, and long safety record spanning more than 15 years are what make it the industry standard, ahead of other crosslinkers such as divinyl sulfone and 2,7,8-diepoxyoctane. Its ability to crosslink is attributed to the reactivity of the epoxide groups present at the two ends of the molecule. Under basic (pH > 7) conditions, these epoxide groups preferentially react with the most accessible primary alcohol in the HA backbone, forming an ether bond connection. The superior stability of the ether bond (relative to the ester or amide bond) is one of the reasons that BDDE-crosslinked HA fillers have a clinical duration that can reach or exceed 1 year. In addition, BDDE has a significantly lower toxicity than other ether-bond crosslinking chemistry based agents (e.g., divinyl sulfone), is biodegradable, and has been well studied.