DOI: 10.1021/la100785r 17843 Langmuir 2010, 26(23), 17843–17851 Published on Web 05/13/2010 pubs.acs.org/Langmuir © 2010 American Chemical Society Biorefinery: A Design Tool for Molecular Gelators George John,* Balachandran Vijai Shankar, Swapnil R. Jadhav, and Praveen Kumar Vemula † Department of Chemistry, The City College of New York, The Graduate School and University Center of The City University of New York, The CUNY Institute for Macromolecular Assemblies (MMA), New York, New York 10031. † Present address: Kauffman Foundation Entrepreneur Postdoctoral Fellow, Harvard-MIT Division of Health Sciences & Technology, 65 Landsdowne Street, PRB 325, Cambridge, Massachusetts 02139. Received February 23, 2010. Revised Manuscript Received April 23, 2010 Molecular gels, the macroscopic products of a nanoscale bottom-up strategy, have emerged as a promising functional soft material. The prospects of tailoring the architecture of gelator molecules have led to the formation of unique, highly tunable gels for a wide spectrum of applications from medicine to electronics. Biorefinery is a concept that integrates the processes of converting biomass/renewable feedstock and the associated infrastructure used to produce chemicals and materials, which is analogous to petroleum-based refinery. The current review assimilates the successful efforts to demonstrate the prospects of the biorefinery concept for developing new amphiphiles as molecular gelators. Amphi- philes based on naturally available raw materials such as amygdalin, vitamin C, cardanol, arjunolic acid, and trehalose that possess specific functionality were synthesized using biocatalysis and/or chemical synthesis. The hydrogels and organogels obtained from such amphiphiles were conceptually demonstrated for diverse applications including drug- delivery systems and the templated synthesis of hybrid materials. Introduction The ubiquity of functional soft materials in nature is best exemplified in the plethora of intriguing, naturally occurring jelly materials, common example being the jelly pith of the aloe vera plant that retains water (Figure 1) and the whole body of a jelly- fish. Via an intricate yet proficient bottom-up strategy, the produc- tion of gels in natural systems occurs for diverse but essential biological functions. In the quest to develop man-made multi- functional gels, the materials research community is involved in mimicking such biological jelly materials as well as in extending the logistics to other solvent systems. The recent trend has been shift- ing toward the development of monomeric low-molecular-weight building blocks rather than polymers for crafting such gels. 1 The gels resulting from such small molecules are called molecular gels. Increasing interest in such systems is evident from the ample variety of low-molecular-weight gelators being developed. The recent demonstrations of molecular gels in applications such as scaffolds for regenerative medicines, electronic and photonic appli- cations, and art conservation illustrate their potential utility. 2-4 The ability of molecular gelators (MGs) to immobilize solvent molecules (organic liquids or water) stems from the propensity to undergo supramolecular self-assembly processes. MGs hierarchi- cally self-assemble to form a 3D self-assembled fibrillar network (SAFIN) by utilizing weak intermolecular forces such as hydro- gen bonding, donor-acceptor interactions, π-π stacking, and van der Waals interactions in which the liquid medium is efficiently entrapped by surface tension. 5 This has proven to be a versatile, simple bottom-up fabrication strategy for generating not only novel but also unique, highly tunable materials. 6,7 In addition, nature offers structurally diverse raw materials such as sugars, fatty acids, and lipids that can be exploited to tailor specific recog- nition events at the molecular level and in turn develop morpho- logically rich nanoscale architectures. Thus, diversity in nature can be utilized to control the gel network exquisitely for various uses. 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