Special Cases of Castor Oil and Ricinoleic Acid

The fact that castor oil is a well-established industrial commodity because of the importance of some of its derivatives and macromolecular materials explains why so many studies on polymers derived from vegetable oils have focused on the use of ricinoleic acid, 10-undecenoic acid, and several other molecules based on their structures. Chapter 3 considered the context of direct polymerisation of this oil and its main fatty acid. This section is devoted to reviewing the most salient recent aspects of the vast realm of monomers and polymers based on their second-generation derivatives. Its treatment begins after the exhaustive review that Mutlu and Meier published in 2010 [124]. The impressive number of contributions since 2010 testifies to the relevance that this area has acquired. Some general notions are, however, needed to set the stage . 

Transesterification of castor oil with triethanolamine or glycerol was carried out to increase its hydroxyl functionality [125]. The ensuing polyols were used to prepare rigid vegetable oil foams with an apparent density of 50 kg/m and a compression strength =200 kPa. 

Inclusion of these structures into polyglycerols was met with a moderate outcome because of poor yields. 

A very recent contribution to materials based on ricinoleic acid [128] revived two main aspects. The first was a search for optimum conditions related to its homopolymerisation and copolymerisation with butylene succinate. This was attained by using titanium tetrabutoxide at 200 °C to yield products with high molecular weight. Secondly, these materials displayed high biocidal activity, which was enhanced further by appending imidazolium moieties to their macromolecules. 

This green-chemistry strategy provided the possibility of arriving at urethane moieties without use of standard unsafe methods based on phosgene. Polymers had molecular weights ranging between 11 and 31 kDa, Tg values of -29 to 55 C and a Tm of 110 °C, for those whose structure was sufficiently regular to promote some crystallisation. 

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