Vegetable oil hybrid films cross-linked at the air–water interface: formation kinetics and physical characterization

Abstract

Vegetable oil based hybrid films were developed thanks to a novel solvent- and heating-free method at the air-water interface using silylated castor oil cross-linked via a sol-gel reaction. To understand the mechanism of the hybrid film formation, the reaction kinetics was studied in detail by using complementary techniques: rheology, thermogravimetric analysis, and infrared spectroscopy. The mechanical properties of the final films were investigated using nano-indentation, whereas their structure was studied using a combination of wide-angle X-ray scattering, electron diffraction, and atomic force microscopy. We found that solid and transparent films form in 24 hours and, by changing the silica precursor to castor oil ratio, their mechanical properties are tunable in the MPa-range by about a factor of twenty. In addition to that, a possible optimization of the cross-linking reaction with different catalysts was explored, and finally cytotoxicity tests were performed on fibroblasts proving the absence of film toxicity. The results of this work pave the way to a straightforward synthesis of castor-oil films with tunable mechanical properties: hybrid films cross-linked at the air-water interface combine an easy and cheap spreading protocol with the features of their thermal history optimized for possible future micro/nano drug loading, thus representing excellent candidates for the replacement of non-environmentally friendly petroleum-based materials.

Physico-chemical properties and surface characterization of renewable hybrid nanofilms interacting with model proteins

“…Consequently, the mechanical properties of the hybrid nanofilms could be tailored by changing the XR ratio obtaining Young moduli between 13<E(MPa)<62 and hardness between 2<H(MPa)<21. These results are compatible with the moduli measured with micrometric films [33], indicating that the spin-coating process did not affect the film's hardness and Young Modulus of the films.…”

“…In order to evaluate the water vapour transmission rate (WVTR) of the ICO films we created films with thickness of 188 ± 10 μm according to the method that we have reported recently. [33] These films were cut in circular shapes with an area of 9.08 10 -4 m 2 . A glass container was filled with water and afterwards the circular films were stabilized within the container at a distance of 1 cm from the surface of the water.…”

“…A series of castor oil-based hybrid coatings was prepared through a sol-gel process based on the direct functionalization of the triglycerides followed by a hydrolysis and condensation, avoiding epoxidation and subsequent ring-opening reactions. Nanometric-sized films were obtained using spin-coating contrary to our previous work where micrometric sized films were prepared at the air-water interface [33]. Moreover, the effect of the molar ratio between the silica precursor to castor oil (XR) on hydrophilicity and water-vapour transmission rate are here deeply studied, which are prerequisites to biomedical applications and food packaging.…”

Preparation and Spectroscopic Characterization of Si‐Coated Vegetable Oils and their Application in In Situ Curing of Hybrid Coatings

“…The catalyzed hydrosilylation of vegetable oils has been explored to reach mesoporous materials and biosiloxanes. [27,28] Another strategy has been investigated by Mandal et al using the reactivity of aminosilane with a polyurethane prepolymer bearing free isocyanate groups. [24,25] Such an approach has already been proposed for an epoxidized Prosopis juliflora oil by Tathe and Jagtap.…”

“…The authors combined both urethane and sol‐gel cross‐linking. A second route consists of the reaction between a silane‐bearing an isocyanate functional group with the free OH groups of castor oil . Another strategy has been investigated by Mandal et al using the reactivity of aminosilane with a polyurethane prepolymer bearing free isocyanate groups .…”