**2.5 Transformation of soybean oil to self-healing material**

An attempt was made on preparation of self–healing material using dimerized fatty acids. In the present study, dimerization of fatty acids has been initiated by use of soy triacylglycerol (STAG) in the presence of lipase (Fungal lipase, Sigma, USA), metal salts (alkali, alkaline earth and transition; Merck, India), monosaccharide and oligopeptides (HiMedia, India) in addition to biosurfactants and under agitation condition (200 rpm, Remi, India). And then self-assembly of dimers in the presence of biosurfactants (Lipopepetide, Sigma, USA) results with the transformation STAG to STLM (Soft Tissue like material).

**Stages of self-healing within 4 days**

An attempt was made on preparation of self–healing material using dimerized fatty acids. In the present study, dimerization of fatty acids has been initiated by use of soy triacylglycerol (STAG) in the presence of lipase (Fungal lipase, Sigma, USA), metal salts (alkali, alkaline earth and transition; Merck, India), monosaccharide and oligopeptides (HiMedia, India) in addition to biosurfactants and under agitation condition (200 rpm, Remi, India). And then self-assembly of dimers in the presence of biosurfactants (Lipopepetide, Sigma, USA) results with the transformation STAG to STLM (Soft Tissue like

**material Starting** 

**vii viii ix**

**Stages of self-healing within 4 days**

Fig. 5. Self-healing pattern of delamination damages of STLM.

**ii iii iv v Delamination stages**

**x i**

**Self-healed** 

 A B Fig. 4. Colloidosomes from (A) Soybean oil; (B) Sunflower oil.

**2.5 Transformation of soybean oil to self-healing material** 

material).

**material**

**vi**

The obtained STLM was creamy-white in colour with soft nature, partially soluble in polar and non-polar solvents, however, completely soluble in ethylacetate and methanol. STLM showed layered, honeycombed, porous structure with channeled network in Scanning electron microscope. Different damages mode such as cracking, punching, cutting and delamination were made. Since minor damages like cracking healed at the very faster rate (24 hours) and however, healing of punching, cutting and delamination damages, took more than 96 hours and the healing rate differs with the depth of the damage. Figure 5 illustrates the self-healing pattern of delamination damages of STLM.

However, STLM obtained in the present study, heal upon various damages (punching, delamination and cutting) without any inducers and also demonstrate more flexibility upon ageing (more than six months). Further, we found, surface rearrangement, diffusion and reunion of the self-healing material in the presence of aqueous atmosphere as evidenced through spread test conducted. The lower surface tension moieties at the end of the chain make the molecules migrate to the surface, and the diffusion and the interface results in the cross-linking and self-healing property. As reported by Wool (2008), healing of polymers proceeded with various stages of healing mechanisms, viz., surface rearrangement, wetting, diffusion and randomization and also suggest, the fibrillar morphology, nature of molecules at the end of the chain and *in situ* oxidation – reduction reactions.

Further, wetting and spreading of the fluid on the surface of the material, enhances the healing process (Brochard, 1986). In the present study, while damaging the self-assembled tissue like material, the released imbibed materials (hydrophobic and hydrophilic) diffuse through cut ends and trigger the repairing and healing process. The attractive force between the molecules present inside the material and on the surface of the material assembles by itself due to the Van der Waals forces. Here, the driving forces were the hydrophobic components (free fatty acid and unhydrolyzed oil) present in multilayered channeled structures.

With regard to wetting and dewetting processes of semi solid and liquid materials, in general, wetting makes the material to spread over the surface of the water, and in dewetting, the material shrinks and again wetting, spreading of a material transform the substrate to a very thin film (Scheludko, 1968 and lsraelachvili, 1985). However, in contradict to the said natural phenomena of wetting and dewetting, in the present study, we observed, a complete wetting (soaking), make STLM to shrink and the partial wetting, make it to spread. In the partial wetting state, (i) hydrostatic pressure makes the polymer to migrate towards the edge of the petriplate, which, (ii) further triggered by non-covalent bonding between the layers of the material and the hydrophobic components imbibed; (iii) the interface between the water and the material also acting as a driving force; (iv) Surface tension between the air and water interface also pull the material towards the edge. Presence of intramolecular bonding between the dimerized molecules gives the stability and it helps in the structure retrieval.
