Soft polyethylene oxide/chitosan mixtures, reinforced with hard titanate nanotubes (TiNT) by co-precipitation from aqueous solution, have been used to produce compact coatings by the "drop-cast" method, using water soluble polyethylene oxide (PEO) polymer and stable, aqueous colloidal solutions of TiNT. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young's modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 minutes) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young's modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 hour) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.
A colloidal dispersion of titanate nanotubes (TiNT) and polyamic acid (PAA) in dimethylformamide (DMF) was electrospun and chemically converted to polyimide (PI) -titanate nanotube (PI-TiNT) composite nanofibres of 500-1000nm diameter. The dispersion of nanotubes in the polymer was addressed by two different approaches, namely an in-situ method (when TiNT was coated with one of the monomers) and an ex-situ one (when TiNT reacted directly with PAA). SEM images showed bead formation on samples from the in-situ approach, while ex-situ samples showed the absence of such features. Good distribution and some alignment of TiNT within the polymer fibres from in-situ or ex-situ approaches were observed by TEM imaging. Addition of titanate nanotubes into the polyimide significantly decreased the viscosity of polyamic acid solution and increased the glass transition temperature of the composite.
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