Synthesis of 3‐substituted‐2‐cyanoacrylates: Their evaluation as cross‐linkers in cyanoacrylate adhesive compositions

Abstract

SYNOPSISAlkyl 2-cyano-2,4-pentadienoates and alkyl 2-cyano-2,4-hexadienoates were synthesized and characterized by spectroscopic methods. These were then evaluated as cross-linkers in 2-cyanoacrylate adhesive compositions to improve the heat stability of their adhesive bonds between various metal surfaces. 0 1993 John Wiley & Sons, Inc. I N T R O D U C T I O N3-Substituted-2-cyanoacrylates have been used from time to time either as cross-linkers for alkyl 2-cyanoacrylates or on their own as adhesives apart from other acrylic monomers. These esters are recommended to use in the alkyl2-cyanoacrylate adhesive compositions, aiming at improvement of the joint bond strength under higher-temperature conditions.'-6 Most of the literature available on their synthesis and their compounding with alkyl 2-cyanoacrylates is in the form of patents that are often misleading. In the present communication, the synthesis of 3-substituted-2-cyanoacrylates such as alkyl2-cyano-2,4-pentadienoates, and hexadienoates and their effect in alkyl 2-cyanoacrylate adhesive composition on heat aging of adhesive bond strength has been discussed. EXPERIMENTAL Synthesis of AlkylDifferent alkyl 2-cyano-2,4-pentadienoates were prepared by reacting corresponding cyanoacetate with acrolein in the presence of a zinc chloride catalyst: Zinc chloride (0.037 mol) and dioxane (40 mL) were taken in a two-neck round-bottom flask, and this mixture was stirred for about 30 min while heating at 70°C using an oil bath. Then, this mixture was cooled to room temperature (25°C). Alkyl cyanoacetate (0.06 mol) and acrolein (0.075 mol) were added slowly to this mixture. The reaction mixture was stirred for 3 h at 25°C. The product was isolated by taking the product in 50 mL of hexane and further extracting with cold dilute hydrochloric acid in ( 3 X 100 mL) portions. the organic layer was separated and dried and the solvent removed under reduced pressure. The crude product was recrystallized from a petroleum ether-ethyl ether (1 : 1) mixture. Attempts to check the purity by the GLC technique have failed due to the polymerization of these compounds over the column at 180°C. The purity of the compounds was therefore checked by spectroscopic methods. Synthesis of Alkyl 2-Cyano-2,4-hexadienoatesAlkyl 2-cyano-2,4-hexadienoates were prepared by reacting crotanaldehyde (0.15 mol) with the corresponding cyanoacetate (0.12 mol) in the presence of a zinc chloride catalyst (0.074 mol) in dioxane (80 mL ) as the solvent medium: 1387

PEG‐Biscyanoacrylate Crosslinker for Octyl Cyanoacrylate Bioadhesive

“…Crosslinking is often used to improve the mechanical properties of tissue adhesives. CA adhesives have also been crosslinked by photo and free radical crosslinking of allyl or 3′‐substituted cyanoacrylates . Biscyanoacrylate has also been reported as comonomer and crosslinking agent: first time in 1978 by Buck, to more recent applications as CA nanocapsules by Gross‐Heitfeld et al They controlled the membrane permeability of these nanocapsules through interfacial crosslinking using biscyanoacrylates.…”

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Effect of Addition of Various Acrylates on the Performance of Ethyl Cyanoacrylate Adhesive

“…These adhesives require no heat, pressure, or addition of catalysts to cure. There are some general ways to increase the heat resistance of polymers (5)(6)(7). The cyanoacrylate esters are distinguished from the other olefinic monomers by their ability to undergo rapid anionic polymerization initiated by mild nucleophiles, even in the presence of contaminants like water and oxygen, which efficiently inhibit most other anionic polymerizations (3).…”