This tutorial review could serve as an introduction of cardanol into the world of soft nanomaterials; it is a biobased lipid-mixture obtained from the plant Anacardium occidentale L. Cardanol is a renewable raw material derived from a byproduct of cashew nut processing industry: Cashew Nut Shell Liquid (CNSL). Cardanol is a rich mixture of non-isoprenoic phenolic compounds that is a valuable raw material for generating a variety of soft nanomaterials such as nanotubes, nanofibers, gels and surfactants. These nanostructures may then serve as templates for the synthesis of additional nanomaterials. The wealth and diversity of cardanol-derived functional nanomaterials has urged us to present an article that will give readers a taste of a new class of cardanol-derived functional amphiphiles, along with their ability to generate hierarchical functional nanomaterials through non-covalent soft-chemical routes. In this concise review, we discuss selected examples of novel biobased surfactants, glycolipids, and polymers derived from cardanol, and their subsequent self-assembly into functional soft materials.

Adaptive response in functional systems of nature is best exemplified by the homeostasis (homeoviscous alterations) or the tropism observed in flora and fauna. The term "homeoviscous alteration" describes the process whereby the fluidity of the membrane is adjusted in response to a perturbation such as temperature, pressure, etc. [1,2] Most of the natural lipids utilize their characteristic unsaturations as a tool to execute such elegant processes. The biophysical properties of the membranes thus depend on the subtle adjustments in the structure and composition of the alkyl chains that are attached to glycerol backbones. [3] Chilling sensitivity in plants is the direct repercussion of the membrane dynamics in plants that involves conformational changes and variations in unsaturation component of the lipid membranes.[4] Deciphering the stimuli-responsive character in such biological systems not only sheds light on the underlying mechanism in the race for survival of the fittest, but also provides clues to generate unique functional materials in the laboratory. Amphiphilic molecules rich in unsaturations in their side chain are expected to display such interesting phenomena and provide vistas for new soft materials.[5] Taking cue from this, we designed an amphiphile from a naturally available raw material-cardanol-that possesses structural features akin to natural lipidic systems.Cardanol is a biobased non-isoprene lipid obtained from cashew nut shell liquid (CNSL). It consists of a rich mixture of phenolic lipids: 5 % of 3-(pentadecyl)phenol, 49 % of 3-(8Z-pentadecenyl)phenol, 17 % of 3-(8Z,11Z-pentadecadienyl)-phenol and 29 % of 3-(8Z,11Z,14-pentadecatrienyl)phenol. [6] The unique feature of cardanol is that it contains 1) lipid chains with varying degree of allylic cis double bonds, 2) alkyl chains with odd numbers of carbon atoms, 3) a reactive phenolic group in the meta position for further functionalization, and 4) saturated/unsaturated versions of hydrocarbon chains. Hence one can envision an amphiphilic building block from cardanol, which show a stimuli-responsive behavior that could be utilized to reconfigure them into functional architectures. Herein, we report vesicle formation and vesicular adhesion from a biobased surfactant, N-cardanyl tauramide (NCT), obtained by the judicious combination of cardanol as the hydrophobic part and taurine (a vital aminosulfonic acid) as the hydrophilic head group. The molecular structure of NCT is shown in Figure 1 c.NCT behaved as a surfactant in aqueous solution with a critical micelle concentration (CMC) of 1.2 mm at 25 8C. Typically, when a 5 mm micellar solution was warmed to 55 8C and annealed, the solution transformed into a viscous phase at 45 8C with a restricted flow. Upon reaching room temperature, the solution resumed back to the micellar phase. Interestingly, the viscous phase appeared elastic and could be pulled into a "wet string" (Figure 1 d). In order to understand this behavior, we performed a cryo-TEM analysis of the sample at 45 8C in the cooling ...

Adaptive response in functional systems of nature is best exemplified by the homeostasis (homeoviscous alterations) or the tropism observed in flora and fauna. The term "homeoviscous alteration" describes the process whereby the fluidity of the membrane is adjusted in response to a perturbation such as temperature, pressure, etc. [1,2] Most of the natural lipids utilize their characteristic unsaturations as a tool to execute such elegant processes. The biophysical properties of the membranes thus depend on the subtle adjustments in the structure and composition of the alkyl chains that are attached to glycerol backbones. [3] Chilling sensitivity in plants is the direct repercussion of the membrane dynamics in plants that involves conformational changes and variations in unsaturation component of the lipid membranes. [4] Deciphering the stimuli-responsive character in such biological systems not only sheds light on the underlying mechanism in the race for survival of the fittest, but also provides clues to generate unique functional materials in the laboratory. Amphiphilic molecules rich in unsaturations in their side chain are expected to display such interesting phenomena and provide vistas for new soft materials. [5] Taking cue from this, we designed an amphiphile from a naturally available raw material-cardanol-that possesses structural features akin to natural lipidic systems.Cardanol is a biobased non-isoprene lipid obtained from cashew nut shell liquid (CNSL). It consists of a rich mixture of phenolic lipids: 5 % of 3-(pentadecyl)phenol, 49 % of 3-(8Zpentadecenyl)phenol, 17 % of 3-(8Z,11Z-pentadecadienyl)phenol and 29 % of 3-(8Z,11Z,14-pentadecatrienyl)phenol. [6] The unique feature of cardanol is that it contains 1) lipid chains with varying degree of allylic cis double bonds, 2) alkyl chains with odd numbers of carbon atoms, 3) a reactive phenolic group in the meta position for further functionalization, and 4) saturated/unsaturated versions of hydrocarbon chains. Hence one can envision an amphiphilic building block from cardanol, which show a stimuli-responsive behavior that could be utilized to reconfigure them into functional architectures. Herein, we report vesicle formation and vesicular adhesion from a biobased surfactant, N-cardanyl tauramide (NCT), obtained by the judicious combination of cardanol as the hydrophobic part and taurine (a vital aminosulfonic acid) as the hydrophilic head group. The molecular structure of NCT is shown in Figure 1 c.NCT behaved as a surfactant in aqueous solution with a critical micelle concentration (CMC) of 1.2 mm at 25 8C. Typically, when a 5 mm micellar solution was warmed to 55 8C and annealed, the solution transformed into a viscous phase at 45 8C with a restricted flow. Upon reaching room temperature, the solution resumed back to the micellar phase. Interestingly, the viscous phase appeared elastic and could be pulled into a "wet string" (Figure 1 d). In order to understand this behavior, we performed a cryo-TEM analysis of the sample at 45 8C in the cooling r...

Gelation of amphiphiles due to the formation of networks of cylindrical chains of reverse micelles is observed.