# Bio-Based Polymers with Potential for Biodegradability
## 2 Bio-Based Polymers
### Vegetable Oils  
Over the past decade, various polymeric systems have been developed based on the crosslinking of vegetable oils through free radical or cationic polymerization reactions [12; 31]. It has been observed that oils bearing conjugated carbon-carbon double bonds are more reactive towards polymerization [32]. More recently, ring-opening metathesis polymerization (ROMP) and acyclic diene metathesis polymerization (ADMET) have also been used in the synthesis of vegetable oil-based polymeric materials [16; 33]. In a more elaborate approach, the modification of soybean oil with acrylate groups resulted in acetylated epoxidized soybean oil (AESO), which was crosslinked with styrene and reinforced with multi-walled carbon nanotubes and soot [34]. Poly(AESO)-_co_-polystyrene has been reinforced with flax fibers to demonstrate the action of butyrate lignin as a compatibilizer [35]. Similarly, red oak leaves were introduced onto a commercial maleated AESO (MAESO)-based resin resulting in bio-based composites [36]. In the preparation of bio-based cationic composites, glass fibers were added to a resin composed of corn oil (COR), styrene (ST), and divinylbenzene (DVB), with crosslink density and the overall material's properties being directly dependent on DVB content [37]. It has also been observed that replacement of COR with conjugated corn oil (CCO) resulted in improved properties [37]. Similar cationic thermosetting resins have also been prepared from conjugated soybean oil (CSO) and conjugated low-saturation soybean oil (CLS) [38]. When reinforcing these resins with ligno-cellulosic materials, a switch from cationic to free radical cure was necessary to avoid quenching of the cationic initiator by the polar reinforcement. When these composites are compression molded, the presence of the natural filler helps to minimize shrinkage and prevent extended cracking of the piece [39]. It was also observed that substitution of \(n\)-butyl methacrylate (BMA) and DVB with dicyclopentadiene (DCPD) results in lower mechanical properties and micro phase separation [39]. Recent improvements in the mechanical properties of free radical bio-based composites have been achieved upon use of maleic anhydride as a compatibilizer [40; 41]. Evaluation of the resin composition revealed that conjugated linseed oil (CLO)-based resins exhibit better properties than CSO-based resins due to their higher number of unsaturations [40]. Similar results have been obtained with cationic resins [42]. With a different approach, the thermoset obtained from the ROMP of DCPD and Dilulin(r) was reinforced with glass fibers [43]. Polyurethane coatings have also been prepared from vegetable oils [44]. As a matter of fact, bio-based polyols can react with diisocyanates to result in polyurethane dispersions (PUDs) [45]. Castor oil and ricinoleic acid have been used as starting materials for the preparation of PUDs [46; 47]. Sunflower, canola, soybean, corn, and linseed oils-based polyols have been used for the synthesis of polyurethane [18]. Methoxylated soybean oil polyols (MSOLs) [48], and castor oil-, MSOL-, and AESO-based polyols have been employed in the synthesis of anionic PUDs [26]. Protonation of amine groups in anionic PUDs results in cationic PUDs with high adhesionto leather and glass [26]. These materials are also antimicrobial, being intentionally designed to be less susceptible to microbial activity [49]. Improvement of anionic PUDs' mechanical properties has been obtained through copolymerization with acrylates, resulting in bio-based hybrid latexes [50; 51]. Surfactant-free, core-shell hybrid latexes were prepared from soybean oil [52]. Other vegetable oil-based systems include polyesters [53] and polyamides [54; 55]. The reaction of Nahar seed oil monoglyceride with anhydrides resulted in polyesters for use in composite applications [17].