# Emulsion Polymerization of Tung Oil-Based Latexes with Asolectin as a Biorenewable Surfactant
## 1 Introduction  
The development of bio-based materials as an alternative to traditional polymers and composites from non-renewable resources has gained significant attention in the past couple of decades due to economical and environmental factors. As a result, numerous vegetable oil-based thermosetting resin systems have been recently studied [1; 2; 3; 4; 5; 6]. Vegetable oil-based resins recently developed include polyester amides [7], and cyanate esters [8]. Due to their abundance, low cost, readily availability, and renewable nature, vegetable oils have been used for the preparation of films, coatings, and thermosetting resins with interesting thermo-mechanical properties [9; 10]. With over 80% of its fatty acid chains bearing a conjugated triene, tung oil can react with vinyl co-monomers via cationic, thermal, or free radical polymerizations without the need of any structural modification of the triglyceride [9; 10; 11]. The resulting materials from the polymerization of tung oil consist of highly crosslinked thermosets. Whenever vegetable oil-based thermosetting resins are reinforced with materials exhibiting a polar surface, there is an intrinsic incompatibility between the hydrophobic resin and the hydrophilic reinforcement, which can be overcome by the addition of compatibilizers to the resin formulation [3; 12]. Very recently, the successful use of asolectin as a natural compatibilizer for cellulose-reinforced tung oil-based composites has been reported [13]. Asolectin consists of a mixture of phospholipids from soybeans containing 76% of polyunsaturated fatty acids [14]. Indeed, the mixture contains approximately 25% of phosphatidylcholine, 25% of cephalin, and 25% of phosphatidylcholine(Figure 1), with the remainder consisting of small amounts of other phospholipids from soybeans [15]. Due to its amphiphilic nature, asolectin interacts withthe non-polar resin components through its fatty acid chains and with the hydrophilic reinforcement through the phosphate and ammonium groups [13]. The polyunsaturated fatty acids in asolectin enable the phospholipid to be free radically crosslinked to other reactive and compatible olefins upon cure [13]. Due to obvious similarities in the structures of phospholipids and triglycerides, a copolymer of tung oil and asolectin is readily formed in the presence of a free radical initiator [13]. When cellulose/tung oil-based composites are prepared with asolectin, improved thermo-mechanical properties are obtained in comparison to composites prepared without asolectin [13]. The preparation of latexes and emulsions containing bio-based polymers allow for smooth film depositions leading to bio-based coatings [15; 16]. Vegetable oil-based anionic [15], and cationic [16] polyurethane latexes with uniform particle sizes have been previously prepared. In these instances, the final polyurethane latexes were obtained by the co-polycondensation of vegetable oil-based polyols and diisocyanates in a water medium [15; 16]. Polyurethane-acrylic hybrid systems have been developed with a similar concept [17]. In such systems, unreacted carbon-carbon double bonds from the vegetable oil-based polyols were crosslinked with acrylic co-monomers through free radical emulsion polymerization, resulting in hybrid latexes [17; 18]. In such hybrid systems, the polyurethane forms a polar shell that serves as a high molecular weight emulsifier, while the vinyl polymers form a non-polar core [19]. Typically, emulsifiers are required in order to achieve successful free radical emulsion polymerization in solvent mixtures containing water [20]. In this work, asolectin is used for the first time as an effective bio-based emulsifier for the emulsion free radical co-polymerization of tung oil, divinylbenzene, and \(n\)-butyl methacrylate in a xylene/water mixture. The incorporation of asolectin in the crosslinked polymer results in stable bio-based polymeric vesicles with potential application in drug delivery and/or nano-catalyst encapsulation/stabilization.