Composition Gradient, Structure, and Mechanical Properties of Mono Epoxy Terminated Polydimethylsiloxanes Grafted Gelatin Films

Abstract

In present study, α-[3-(2,3-epoxy propoxy) propyl]-ω-butyl-polydimethylsiloxanes grafted gelatin (PGG) compositional gradient film was successfully fabricated by combining a solvent induced self-assembly procedure and the interaction between polymer and air/substrate induced migration. The variation of gelatin superstructures and the transformation of PGG aggregate structure with tuning volume ratio of water/ethanol studied by Atomic force microscopy (AFM), Fourier-transform infrared (FTIR) and High-resolution transmission electron microscopy (HR–TEM). At 1 : 3 vol/vol, gelatin chains self-assembled to cyclic aggregates that tended to deposit on the gelatin substrate, while PGG formed core–shell structure which should migrate to air-liquid interface driven by low free energy of PDMS chain during drying. X-ray photoelectron spectroscopy (XPS) showed that the surface of gradient film was covered with PDMS component and strong intermolecular interactions existed in between polymer and solvent molecules at 1 : 3 vol/vol. The gradients of PDMS composition along longitudinal orient in film were further confirmed by scanning electron microscopy-energy dispersive spectroscopy (SEM−EDS) with line scan. Contact angle results exhibited a successive decrease of hydrophobicity along longitudinal orient in gradient film. Dynamic mechanical analysis (DMA) results showed two tan δ and lower storage modulus in gradient than that of blank gelatin film, which led to good flexibility of gradient film.