## 1 Introduction  
In recent years, 3D printing or rapid prototyping as a flexible additive manufacturing technique became very popular because of its simplicity, relatively low cost, and unlimited creativity. This process enables the creation of complex three-dimensional objects which cannot be cut, assembled or carved. It is possible because of Computer-Aided Design (CAD) modeling, where various objects are generated and files are transmitted for the printing of 3D items [1]. Stereolithography (SLA) is a process which obtains a high printing accuracy and speed, simple and low raw material usage technology [2]. It is a layer by layer photopolymerization method, where the photosensitive resin is polymerized by UV/VIS light. Epoxy and acrylic resins are the most popular materials in optical 3D printing. Printed epoxy polymers have low shrinkage and high structural stability, while acrylates have high light sensitivity, low critical energy and viscosity, controllable mechanical properties and relatively high dependence on temperature and humidity changes [3]. While epoxides have higher structural stability, acrylates possess higher photosensitivity due to which they are more popular in the SLA process. Most of the photosensitive resins for optical 3D printing are made from acrylic oligomers, acrylic monomers and/or reactive diluents, photoinitiator and UV stabilizers/blockers [4]. Photopolymerized acrylates are in an irregular molecular structure because of high curing speed. Petroleum-derived acrylic resins such as polyesters, polyether oligomers or diglicidylether bisphenol A acrylates are those that are mostly used for optical 3D printing [5]. Due to decreasing petroleum recourses, it became crucial to search for alternative materials such as renewable resources [6]. Natural oils are one of the best alternatives for petroleum-derived resins [7; 8; 9]. Due to their richness in double bonds which can be polymerized or converted to other functional groups, biodegradability and renewability, natural oils became a popular target of researchers [10; 11]. Soybean oil is one of the most promising materials to replace petroleum-derived resins. It contains a high amount of unsaturated fatty acids such as monounsaturated oleic acid (C-18:1, \(\sim\)23%), polyunsaturated \(\alpha\)-linoleic acid (C-18:3, 7-10%), and linoleic acid (C-18:2, \(\sim\)51%) [12; 13]. Carbon-carbon double bonds of fatty acids can be oxidized [14], polymerized [15; 16] or converted to various reactive groups [17; 18; 19]. Acrylated epoxidized soybean oil (AESO) is produced by the epoxidation of fatty acid double bonds followed by epoxy ring acrylation [20; 21; 22; 23]. Due to the high amount of various functional groups such as the acrylic, epoxy and hydroxy groups, AESO is widely used in industry and is commercially available under Ebecryl 860 trademark [24]. AESO can be polymerized by UV/VIS light using appropriate photoinitiators and can form a cross-linked polymer network. AESO is already photopolymerized with polycaprolactone diacrylate and polyethylenglycol diacrylate [25], tetrahydrophuryl acrylate [26; 27], myrcene [28], and various thiols [29; 30]. The addition of comonomers improved the mechanical and thermal properties as well as solvent resistance of the resulted polymers. Due to AESO fatty acid long aliphatic chains, cross-linked polymers are soft and mechanically resistless. To improve the polymer mechanical properties, aromatic comonomers are added. Such compounds such as styrene [31; 32], divinylbenzene (DVB) [33; 34], dicyclopentadiene [35] and acrylepoxymethylester [36] were used as stiffening agents for AESO polymers. But these materials are petroleum-derived and harmful to health [37; 38; 39]. Initially, we selected the plant-derived vanillin acrylates to replace the petroleum-derived aromatic compounds because of their aromatic structure, renewability and reactivity [40]. Vanillin dimethacrylate (VDM) or methacylated vanillin alcohol is produced from lignin, one of the most abundant natural polymers [41].