Self-assembly of Anacardic Acid Derived Cation-modified Montmorillonite into 'Arthropodal' Branched Nanofibers

Montmorillonite (MMT) was organo-modified with tri-(2-carboxy-3-pentadeca-8,11,14]-trienylphenoxy) aminopropylsilyl sulfate cation, synthesized from anacardic acid (AA), a biomonomer by cation exchange and characterized. The modified product (AAM) showed a decreased crystallinity with an increase in d-spacing of MMT from 1.47 nm to 2.29 nm attributed to intercalation by modification. AAM solution in the water-acetone mixture at 3.0 mg mL(-1) showed an organization into 'arthropodal' branched nanofibers of about 30-60 nm diameter and 10-20 mm length. These results were attributed to rolling of AAM into grain like morphology stabilized by hydrogen bonded interactions induced by the carboxyl group and end to end assembly of the grains. Though acidic pH stabilized the morphology, an increase in pH to 8.0 marked the absence of any assembly attributed to lack of hydrogen bonding. The effect of the carboxyl group in the assembly was further established by the absence of any assembly in the case of MMT modified with cardanol, the decarboxylated product of AA. A simple strategy for the synthesis of biocompatible hybrid silicate nanofibers is demonstrated here.