Polymers from Pristine and Modified Natural Monomers

Interest in polymers from renewable resources has been witnessing an incessant growth in both academia and industry with these blooming activities covering a progressively wider domain of sources and approaches worldwide. The association of these innovative scientific and technological investigations with the need of introducing a growing dose of green chemistry connotations in their conception is opening the way to an all-inclusive sustainability for this new generation of polymers, which justifies their vision as macromolecular materials for the XXI century. After the first comprehensive monograph dealing with these materials, published in 2008, [1] numerous reviews and books have appeared, mostly dealing with specific topics or brief analyses of the overall state of the art, [2,3] with a very recent update, [4] which was however aimed at highlighting trends, rather than at detailing the numerous papers covering different aspects of the vast field. Given the structure of this book, the present chapter concentrates exclusively on the use of biobased building blocks as potential monomers and on the recent studies dealing with their polymerizations and copolymerizations, as well as on the properties of the ensuing materials. Interestingly, moreover, the rate at which new interesting results are being published, amply justifies the coverage given here, since it also provides a “further update” of the mentioned “recent update”, [4] at least within its specific scope. Natural polymers (polysaccharides, lignin, suberin, proteins, natural rubber, etc.) and their modifications fall outside that scope and the reader will find information about the multitude of equally exciting and equally incessant studies and applications of these renewable resources in such materials as thermoplastics, thermosets, blends and composites, in other publications. [1-4] The topics discussed here are divided into two major sections, one dealing with polymers from pristine and chemically modified natural monomers, notably terpenes, rosin, sugars and vegetable oils, and the other dealing with polymers from monomers obtained from various vegetable biomass components, notably furans, diacids, diols, hydroxyacids and glycerol. The polymerizations involving classical fossil-derived monomers, such as ethylene and terephthalic acid, now also prepared from renewable resources, are obviously not discussed here, since the novelty of these systems only resides in the alternative mode of monomer synthesis. No attempt was made to cover each family of monomers exhaustively, but rather to concentrate on contributions that appeared to provide originality and hence potential follow-ups. This personal choice did not hinder a critical approach whenever it was deemed constructively appropriate. Given the modest amount of space allotted to this chapter, even some of the numerous interesting studies had to be sacrificed to avoid a list of cursory mentions and privilege instead a reasoned treatment of carefully selected examples.