Effect of Tricarboxylic Acids on the Formation of Hydrogels with Melem or Melamine: Morphological, Structural and Rheological Investigations.

Pradip Kumar Sukul,Sudip Malik,Puspendu Das,Lalmohan Das,Gopal Lal Dhakar

doi:10.3390/gels8010051

Pradip Kumar Sukul, Sudip Malik + Show 3 more

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https://doi.org/10.3390/gels8010051

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Abstract

Herein, aggregation behaviors of melem or melamine in the presence of three symmetric carboxylic acids (1,3,5-tris(4-carboxyphenyl)benzene (TPCA), 1,3,5-benzene-tri-carboxylic acid (BTA) and 1,3,5-cyclohexane-tri-carboxylic acid (CHTA)) have been performed to check the influence of acid on the formation of aggregated structures which have been investigated by optical microscopy, FESEM, FTIR, XRD and viscoelastic properties have been explored with rheological studies. Interestingly, melem, that has limited solubility in aqueous medium, forms aggregation that leads to the formation of hydrogels with TPCA. More significantly, hydrogel is formed here by matching the size selectivity. Melem forms hydrogel with only large tricarboxylic acid, whereas melamine produces hydrogel with any kind of its counterpart from small to large tricarboxylic acid derivatives. Present investigations and results provide the strategy of design of organic self-assembled materials having two component systems.

Highlights

Hydrogels are three-dimensional polymeric networks, which are hydrophilic and crosslinked via covalent or noncovalent interactions [1,2,3,4,5]
We have rationally picked up two triamines melamine (MM) as well as melem (MEM) and three tricarboxylic acids (TPCA: 1,3,5-tris(4-carboxyphenyl)benzene, BTA: 1,3,5-benzene tricarboxylic acid, and CHTA: 1,3,5-cyclohexane tricarboxylic acid) for the gelation study in which all have C3 symmetric functional groups (Scheme 1). and we have explored that symmetrical position of complementary interactions and recognition of site and size are crucial for the creation of one-dimensional self-assembled fibrils that eventually lead to the formation of gelation in aqueous medium
Aggregations and gelation ability of different triamines and tricarboxylic acid derivatives have been investigated in the present manuscript

Summary

Introduction

Hydrogels are three-dimensional polymeric networks, which are hydrophilic and crosslinked via covalent or noncovalent interactions [1,2,3,4,5]. Physical (noncovalent) hydrogels are generally less stable and have poorer mechanical properties compared to covalent hydrogels [13]. Two components in the hydrogel may interact with each other to form a complex utilizing hydrogen bonding [14,15], electrostatic action [16], donor–acceptor interactions [17] and metal coordination [18], further aggregate via intercomplex interactions, e.g., hydrogen bonding, π–π interactions or van der Waals forces, to generate the fully three-dimensional networks that eventually produce the formation of semi-solid gel

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