Synthesis and Characterization of Modified Cellulose Acetate Propionate Nanocomposites via Sol-Gel Process

In this study novel organic-inorganic hybrid nanocomposites were synthesized from modified cellulose acetate propionate (MCAP) via sol-gel reaction at ambient temperature. The inorganic phase was introduced in situ by hydrolysis-condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in the presence of organic polymer dissolved in acetone. The chemical modification of CAP was monitored by infrared spectroscopy (IR). The nanocomposites structure was characterized by IR analysis and solid state 29Si NMR studies. The spectral data revealed that organic and inorganic phases are linked through covalent bound. Surface morphology of the samples and the degree of dispersion of inorganic phase in the polymer matrix were investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The actual incorporation of the inorganic component into the hybrid nanocomposites was deducted from the residual weight according to thermogravimetric analysis (TGA). 1. Introduction Organic-inorganic polymer hybrids are rapidly expanding area of research. Such materials offer the opportunity to combine the desirable properties of organic polymers (toughness, elasticity, and formability) with those of inorganic solids (hardness, chemical resistance, and strength). Sol-gel techniques generating nanosized silica particles within a polymer matrix have been widely used for the preparation of organic-inorganic hybrid nanocomposites. The advantage of sol-gel route is the ability to prepare organic-inorganic nanostructured materials at ambient temperature and the possibility to control morphology of the growing inorganic phase by the subtle control of various reaction conditions. Sol-gel technique involves hydrolysis of the precursor (metal alkoxide) followed by condensation reactions of the resulting hydroxyl groups. Hydrolysis of metal alkoxide and condensation of the hydroxyl groups and residual alkoxyl groups occur simultaneously. Once the hydrolysis reaction has been initiated, condensation takes place parallel to hydrolysis and occurs even if not all of the alkoxyl groups are hydrolyzed. Considering the nature of the interface between the organic and inorganic phases, hybrid materials can be categorized into two different classes. The first class corresponds to not covalently bound networks of inorganic and organic phases. These hybrids show weak interactions between the polymer matrix and inorganic phase, such as van der Waals, hydrogen bonding, or weak electrostatic interactions, and can be prepared by physical mixing of