Solid-state structure of gelatin-mono epoxy terminated polydimethylsiloxane polymer: effect of electrostatic and hydrophobic interactions

In this study, a hybrid synthetic gelatin-mono epoxy terminated polydimethylsiloxane polymer (PDMS-E grafted gelatin (PGG)) was successfully synthesized on a large scale. Supramolecular structure of gelatin, which was decided by the sophisticated inter- and intra-molecular interactions, significantly affected the self-assembly and phase behavior of PGG. Interestingly, the supramolecular organization of PGG could be tuned finely by negatively charged surfactants, such as sodium dodecyl sulfate (SDS) and sodium tetradecyl sulfonate (STSo), as revealed by high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), light microscopy (LM), and atomic force microscopy (AFM). SEM images exhibited the presence of spherical aggregates in PGG/SDS films while hexagonal array was observed in PGG/STSo films. The results of LM revealed that when PGG/STSo solution was dried, a successive structural transformation from spheres to hexagons, via sticks and butterfly-shaped aggregates as intermediates, was observed. However, the morphologies of the aggregates formed in PGG/SDS system did not exhibit any obvious change upon drying. Attenuated total reflection-Fourier transform infrared spectra combined with AFM observations indicated that the secondary structure and aggregation behavior of gelatin was modified with the change in the electrostatic and hydrophobic interactions, leading to the formation of diversified solid-state structures of PGG.