Effect of hybrid nanoparticles on glass transition temperature of polymer nanocomposites

Abstract

Changes in the glass transition temperatures of composites based on polystyrene and nanosized macromolecular nanostructures (molecular silicasols, dendrimers) are reported. Silicasols are nanosized particles consisting of a silica core and an ethyl phenyl shell; dendrimers are formed using a carbosilane core with ethyl phenyl end groups. It has been observed that the glass transition temperatures of the composites (T gc ) may be either above or below the glass transition temperature of polystyrene, depending on the size of the filler particles. A theoretical model based on the relation between the glass transition temperature and the configurational entropy of the composite, which satisfactorily describes the experimental dependence, was developed. It is found that the effect of the size of the hybrid nanoparticles on T gc was determined using two factors. First, the presence of an organic layer on the surface of nanoparticles increases the number of degrees of freedom and the entropy of the system, thereby reducing T gc . Second, the particles present in the polymer reduce the number of configuration states of macromolecules, which reduces the disorientation entropy. This effect leads to an increase T gc . The competition between these two main factors determines the sign of the glass transition temperature deviation. The size of the particles and their organic surface layer play the key roles in the thermodynamic properties of the composites. POLYM. COMPOS., 37:1978-1990

Dynamics heterogeneity in silica‐filled nitrile butadiene rubber

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Polymer-Based Nanocomposite Coatings for Anticorrosion Applications

“…Rolldughin et al [ 56 ] modeled the glass transition temperature ( T g ) of polystyrene-based nanocomposites incorporating silicasol nanoparticles. Each silicasol particle consisted of a silica core and an ethyl phenyl shell.…”

The effect of size and concentration of nanoparticles on the glass transition temperature of polymer nanocomposites

“…A thermodynamic approach to the analysis of concentrationdependent changes in T g of nanocomposites based on amorphous polymer and nanoparticles with a core-shell structure, which includes the internal conguration entropy of the hybrid nano-inclusions was developed earlier. 16 To describe the concentration-dependent change in the glass transition temperature of a polymer lled with polyphenylene dendrimers, we use the approaches proposed earlier 16 assuming the structural uniformity and monodispersity of the particles. In this case, the equation describing the glass transition temperature of the composite takes the form:…”

“…Upon the calculation of the glass transition temperature of PS/dendrimer composites, the value of parameter Z, which characterizes the coordination number of segments of the PS macromolecule, was taken equal to 9. 16,31 Fig. 3 shows the obtained dependences of the T g changes on the content of rigid dendrimers.…”

“…[13][14][15] This effect disguises the effect of the nanoparticle itself on the composition properties. Thus, based on the results of thermodynamic analysis of polymer/ hybrid nanoparticles systems with a core-shell structure, it was shown that the increase or decrease in T g depends on the competition of two main factors: 16 -An increase in the number of degrees of freedom and the system entropy because of the presence of an organic layer on the surfaces of nanoparticles; -A decrease of the system entropy and the number of conguration states of the macromolecules in the presence of nanoinclusions.…”