Open Access

ARTICLE

Biobased Aromatic-Aliphatic Polyols from Cardanol by Photochemical Thiol-ene Reaction

Maha L. Shrestha^{1, 2,*}, Mihail Ionescu¹, Xianmei Wan¹, Zoran S. Petrović¹

1 Kansas Polymer Research Center, Pittsburg State University, Pittsburg, Kansas, USA 66762
2 Department of Chemistry, Pittsburg State University, Pittsburg, Kansas, USA 66762

*Corresponding author:

Journal of Renewable Materials 2018, 6(5), 504-516. https://doi.org/10.7569/JRM.2017.634187

Abstract

Biobased aromatic-aliphatic polyols were previously synthesized from a thermal thiol-ene reaction of propoxylated cardanol with 2-mercaptoethanol (ME) in the presence of azobisisobutyronitrile (AIBN) as a radical initiator. Cardanol used for this purpose was obtained as a dark-brown liquid (Gardner Color Reference ∼18). The photochemical thiol-ene reaction can also be used to prepare aromatic-aliphatic polyols by employing cardanol. Via the photochemical thiol-ene reaction, 2-mercaptoethanol was added successfully to C=C double bond of cardanol, suggesting that phenolic group may not play an inhibitory role in the radical thiol-ene reaction. However, we preferred to alkoxylate the phenolic hydroxyl group of cardanol, which is much more reactive with isocyanates than phenolic hydroxyls, to generate a new aliphatic hydroxyl group. Furthermore, the functionality of polyols was also improved by two methods: 1) using 1-thio-glycerol instead of 2-mercaptoethanol and 2) using alkoxylated cardanol with glycidol (Cardanol-GLY) instead of propoxylated cardanol (Cardanol-PO). These polyols were then used in preparation of rigid polyurethane foams that can be useful in various applications such as insulation of freezers, pipes and storage tanks in food and chemical industries.

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