Synthesis and characterization of terpene-based gels

Nowadays, the two most fundamental problems facing the polymer industry are the depletion of resources obtained from fossil fuels and the damage they cause to the environment. Considering this problem, the need to diversify polymer resources has arisen and for this reason, the use of natural polymers is increasing both in scientific research and industrial applications. In the last decade, the use of terpenes to produce renewable polymers has constituted a broad area of research. The design and synthesis of terpene-based polymers involve the application of various chemical strategies and polymerization techniques by exploiting the structure of terpene molecules. Terpenes are an important component of the essential oils of many plants. The simple derivation of these bio-based organic compounds from essential oils of plants has made terpenes one of the widely preferred sustainable materials in fragrance, cosmetics, food, pharmaceuticals and inhalation products. High internal phase emulsions (HIPEs) are concentrated emulsion systems in which the internal phase volume constitutes at least 74% of the total emulsion volume. High internal phase emulsions generally consist of two phases, the continuous phase and the internal phase. PolyHIPEs are obtained by polymerizing the emulsion continuous phase or both phases, followed by removal of the internal phase. Gels are cross-linked polymeric structures that can be defined as structures composed of water-insoluble homopolymers or copolymers. These structures are insoluble in water, but they can absorb large amounts of water into their structure, and they are also swellable. They are also materials whose properties change under the influence of environmental factors. These factors include temperature, pH, ionic strength, electric and magnetic fields. Gels react to changes in these environmental factors by reversible volumetric expansion. In this study, porous polymer gels were prepared with linalool and geraniol, a terpene derivative. In this context, crosslinking of linalool in high internal phase emulsions was carried out using ethylene glycol dimethacrylate (EGDMA) and 2-hydroxyethyl methacrylate (HEMA), whereas crosslinking of geraniol in high internal phase emulsions was carried out using diurethane dimethylacrylate (DUDMA) and HEMA. Thus, polyHIPE gels with porous structure were obtained. The pore morphology, thermal stability, mechanical strength and physicochemical properties of the obtained polyHIPE gels were extensively investigated.