Acids aliphatic unsaturated diacids

The materials in this group are linear copolyesters. One of the dicarboxylic acids is an aliphatic unsaturated diacid. The unsaturation is introduced into the polymer backbone for the purpose of subsequent crosslinking. Unsaturated polyester technology was developed for use in glass fiber laminates, thermosetting molding compositions, casting resins, and solventless lacquers. 

The development of unsaturated polyanhydrides responded to the necessity of improving the mechanical properties of the polymers in applications such as the temporary replacement of bone. " Unsaturated polyanhydrides, prepared by melt or solution polymerization, include homopolymers of fumaric acid (FA), acetylene-dicarboxylic acid (ACDA), and 4,4 -stilbenzenedi-carboxylic acid (STDA). The chemical structures of poly(FA) and poly(ACDA) are shown in Table 1. These polymers are highly crystalline and insoluble in common organic solvents. The double bonds of these monomers make them suitable for further crosslinking to improve mechanical properties of polyanhydrides. When copolymerized with aliphatic diacids, less crystalline polymers with enhanced solubility in chlorinated solvents result. 

Novel PA were prepared by polycondensation between diacids and diamines catalysed by l,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in a very interesting study described by Meier and Mutlu [16]. In this study, unsaturated C20 chain PA with a Tm 180-226 °C were synthesised by polycondensation of the SM product of 10-undecenoic acid and various diamines. Fradet and colleagues studied various diamines (aliphatic, cycloaliphatic, benzylic) and used the same methodology [17, 18]. 

The first approach involved the amide formation with the 10-undecanoic acid (3) and the diamine 4 to create the monomer 5 which was then polymerized further by metathesis, as shown in Figure 14.6. A second approach to the synthesis of polyamide Nylon involved forming the polymer using the diacid 6, which was polymerized with the aliphatic diamine 4 in the presence of strong bases. Both these methods were able to use the biorenewable starting material and a metathesis step, and both led to the production of the unsaturated PAX, 20 polyamide [39]. Overall, Meier and coworkers found that the synthesis of the diacid first, followed by polymerization with TBD (1,5,7-triazabicyclo[4.4.0]dec-l-ene), was the most efficient route and had some advantages over classical methods, such as avoiding the use of an acid chloride. 

As reported, AABB type PEAs of fumaric acid display limited solubility in common organic solvents. In most cases the polymerization solution turns to gel, due to partial crosslinking (10). We have observed that unsaturated PEA (UPEA) copolymers with less than 35 % mol. ratio of fumaric acid to aliphatic diacid maintain reactivity during radical reactions and remain soluble over long storage periods. 

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