No abstract

Plant oils are already one of the most important platform chemicals for the chemical industry due to its universal availability, inherent biodegradability, and low price. Nowadays, plant oils are already a commercial source of multifunctional monomers and oligomers for polyurethane synthesis, and the design of novel biobased polyols derived from them is an active area of research. By taking advantage of the wide variety of possibilities for chemical modification of plant oils, there is a broad palette of strategies to functionalize its structure with hydroxyl groups. The purpose of this review is to comprehensively overview recent developments on the preparation of biobased polyols from plant oils, covering from the general epoxidation and ring-opening approach to novel routes based on thiol-ene click chemistry as well as to highlight the properties of polyurethanes obtained from them.

Oligomeric polyether polyols were obtained through the acid‐catalyzed ring‐opening polymerization of epoxidized methyl oleate and the subsequent partial reduction of ester groups to give primary alcohols. The oligomers were characterized with titration, spectroscopic techniques (Fourier transform infrared and nuclear magnetic resonance), matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, size exclusion chromatography, and differential scanning calorimetry. Depending on the degree of reduction, polyols of different hydroxyl content values were obtained and were reacted with 4,4′‐methylenebis(phenyl isocyanate) to yield polyurethanes. These materials, which were characterized by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis, could behave as hard rubbers or rigid plastics. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 634–645, 2006

Natural vegetable oils have been transformed in polymers following three main routes. The first is the direct polymerization through the double bonds of the fatty acid chain. The cationic copolymerization of soybean oil with styrene, divinylbenzene, and different amounts of styrenic monomers containing Si allows producing materials with improved mechanical and flame retardant properties. The second route is the functionalization of the triglyceride double bonds to introduce readily polymerizable groups: The singlet oxygen photoperoxidation-dehydration of the allylic positions of the high oleic sunflower oil allows producing enone-containing triglycerides that are chemically crosslinked with aromatic diamines through aza-Michael reactions. At high temperatures, this curing reaction proceeds through a complex mechanism leading to quinoline moieties. This new crosslinking approach can be also applied to aldehyde containing triglycerides. The third route consists of using plant oil-derived chemicals like 10-undecenoic acid to produce tailor made monomers. Acyclic diene metathesis polymerization has been applied to allyl 10-undecenoate, 10-[2 0 ,5 0 -bis(10-undecenoyloxy)phenyl]-9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide, and 1,3-bis(10-undecenoyl)glycerol to prepare a set of polyesters with different phosphorus and hydroxyl contents. Moreover thiol-ene ''click'' coupling of allyl 10-undecenoate with mercaptoethanol, 3-mercaptopropanoic acid, and 3-mercaptopropyltrimethoxysilane has been used to produce difunctional telechelic polyesters.

Vegetable oils are excellent renewable raw materials for thermosetting polymers. By the direct polymerization of triglyceride C=C, we obtained organic-inorganic hybrid materials with promising properties for optical applications by the hydrosilylation of alkenyl-terminated fatty acid derivatives. The presence of double bonds in triglycerides makes it possible to attach some functional groups through chemical modification, and we describe various chemical pathways for functionalizing triglycerides and fatty acids. Epoxidation is one of the most interesting chemical modifications that leads to epoxidized vegetable oils. We report the preparation of biobased polyhedral oligomeric silsesquioxanes-nanocomposites from epoxidized linseed oil. Moreover, we describe the preparation of a new family of epoxidized methyl oleatebased polyether polyols, which were used in the synthesis of polyurethanes with specific applications: silicon-containing polyurethanes with enhanced flame-retardant properties and polyurethane networks with potential applications in biomedicine. An enone-containing triglyceride derivative was obtained, by an environmentally friendly chemical procedure from high oleic sunflower oil that could be cross-linked with diamines. In a similar way, triglycerides containing secondary allylic alcohols can be obtained that can be further functionalized with acrylate or phosphorus-containing derivatives to obtain flame-retardant thermosets.

This mini-review focuses on the recent efforts to replace petro-based feedstocks with polybenzoxazine precursors.

Novel biobased aromatic triols (1,3,5-(9-hydroxynonyl)benzene and 1,3,5-(8-hydroxyoctyl)-2,4,6-octylbenzene) were synthesized through the transition-metal-catalyzed cyclotrimerization of two alkyne fatty acid methyl esters (methyl 10-undecynoate and methyl 9-octadecynoate) followed by the reduction of the ester groups to give terminal primary hydroxyl groups. A series of biobased segmented polyurethanes based on these triols, 1,4-butanediol as a chain extender and 4,4'-methylenebis(phenyl isocyanate) as a coupling agent, were synthesized. Samples were prepared with hard-segment contents up to 50%. The morphologies and thermal properties of these polyurethanes were studied by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. Partial crystallinity and phase separation were detected in samples with hard-segment content of 50%.

A series of poly(ether urethane) networks were synthesized from epoxidized methyl-oleate-based polyether polyol and 1,3-propandiol using l-lysine diisocyanate as a nontoxic coupling agent. Polyurethanes with different hard segment contents were prepared to tune the final properties of the materials. The polyurethanes were fully chemically and physically characterized, including water uptake and in vitro hydrolytic degradation measurements. The weight loss of the polyurethanes was traced, and the changes in the surface morphology with the degradation time were examined by scanning electron microscopy. The experimental results revealed that the hard segment content is the main factor that controls the physical, mechanical, and degradation properties of these polymers. The observed diversity in material properties suggests that these polyurethanes may be useful for a wide range of biomedical polymer applications.