Abstract
Polyethylene glycol-based nanocomposites containing an organo-modified hydrotalcite with loadings ranging from 0.5 to 5 wt.% were prepared by melt mixing performed just above the melting point of the polymer matrix. In these conditions, the dispersion of the nanofiller within the polymer matrix was quite homogeneous as revealed by TEM analyses. The effect of various thermal treatments and filler loadings was thoroughly investigated by means of rheological, morphological and gas chromatography-mass spectrometry, hyphenated to thermogravimetry analysis tests. Unfilled polyethylene glycol exhibited a continuous decrease in complex viscosity upon heating. In contrast, the complex viscosity of nanocomposites containing nanofiller loadings higher than 1 wt.% showed first a decrease, followed by an increase in the complex viscosity as the temperature increases, exhibiting a minimum between 130 and 140 °C. Annealing at 180 °C for different times further increased the viscosity of the system. This unusual behavior was explained by the occurrence of grafting reactions between the –OH terminal groups of the polyethylene glycol chains and the hydroxyl groups of the organo-modified filler, thus remarkably affecting the relaxation dynamics of the system.
Highlights
Polymer-based nanocomposites have attracted a growing attention in the last few years, as the introduction of solid nanoparticles into a soft polymeric matrix allows for multi-functional materials with tailored and controlled properties, potentially suitable for advanced applications [1,2,3]
Oscillatory dynamic measurements were carried out within the material linear viscoelastic regime to evaluate the effect of different amounts of LDHs on the relaxation dynamics of polyethylene glycol (PEG)
On the annealing temperature [38], which results in 300 h when the annealing temperature is 140 ◦ C [35] but just some hours [36] when the grafting temperature is 180 ◦ C. These results suggest that a grafting reaction between the hydroxyl terminal groups of the polyethylene glycol chains and the hydroxyl groups of the hydrotalcite occurs when the nanocomposites are annealed at temperatures higher than 135 ◦ C
Summary
Polymer-based nanocomposites have attracted a growing attention in the last few years, as the introduction of solid nanoparticles into a soft polymeric matrix allows for multi-functional materials with tailored and controlled properties, potentially suitable for advanced applications [1,2,3]. The full potential of this large interface can be effectively exploited only when the polymer-nanoparticle interactions are strong enough to overcome the intrinsic tendency of nanoparticles to self-aggregate [6]. The dispersion and distribution of the incorporated nanoparticles, as well as the extent of interaction between the two components, is crucial to control the final properties of the resulting nanocomposite [7,8]. The viscoelastic behavior of polymer-based materials impacts on both the processing technology and conditions [11] and on the final properties [12]
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