Dye conjugation to linseed oil by highly-effective thiol-ene coupling and subsequent esterification reactions

• Dye-conjugated linseed oil was synthesised in a two-step reaction.
• Thiol-ene coupling and subsequent esterification reactions were performed.
• 39.1% of carbon–carbon double bonds in linseed oil were used for the dye-conjugation.
• The product exhibited a hypsochromic shift relative to the unbound dye.
• The proposed method is of significance for the production of dye-conjugated oils.

Linseed oil, a renewable material obtained from the ripened seeds of the flax plant, was conjugated with C. I. Disperse Red 1 to yield a coloured macromolecule in two experimentally-simplistic coupling steps. Firstly, the abundant presence of carbon–carbon double bonds in linseed oil was exploited to introduce carboxylic acid functionality to linseed oil via a thiol-ene reaction between linseed oil and 3-mercaptopropionic acid. C. I. Disperse Red 1 was then grafted to the carboxylic acid units now present via esterification, offering a coloured product in high yields. On average, 39.2% of the carbon–carbon double bonds in each linseed oil molecule were furnished with a C. I. Disperse Red 1 molecule. The remaining carbon–carbon double bonds may therefore be further exploited for chemical crosslinking, ensuring that the product formed is of potential significance as a coloured, bio-based, surface coating product.

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