Direct Relationship between Dispersion and Crystallization Behavior in Poly(ethylene oxide)/Poly(ethylene glycol)-g-Silica Nanocomposites
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Date
2021-02-08Author
Wen, Xiangning
Su, Yunlan
Liu, Guoming
Li, Shaofan
Kumar, Sanat K.
Wang, Dujin
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Macromolecules 54(4) : 1870-1880 (2021)
Abstract
The inclusion of polymer-grafted nanoparticles (PGNPs) can impart various
functional properties to polymer nanocomposites (PNCs). For semicrystalline
polymers, we can control the spatial dispersion of PGNPs and presumably use it to
modulate the nucleation rate of the polymer. In this work, the correlation between the
dispersion quality of poly(ethylene glycol) (PEG) grafted silica (PEG-g-SiO2)
nanoparticles and the crystallization ability of poly(ethylene oxide) (PEO)
nanocomposites is systematically investigated by varying the grafting density (σ,
chains/nm2) and the value of P/N (P: molecular weight of matrix chains, N: molecular
weight of grafted chains). The variation of PEG-g-SiO2 dispersion state was studied
by morphological characterization and small-angle X-ray scattering (SAXS). It was
found that, in contrast to the unmodified SiO2 and poly(methyl methacrylate) grafted
silica (PMMA-g-SiO2), PEG-g-SiO2 (high σ and low P/N) can increase the nucleation
rate of PEO even under conditions where they are well dispersed in the PEO matrix.
Evidently, the nature of the graft, i.e., amorphous PMMA vs. crystallizable PEO, has
profound consequences in this context, a novel result that has not been anticipated
based on previous work. NP aggregation occurs at higher P/N values and limits the
effectiveness of the grafted PEG on the crystallization ability of PEO nanocomposites.
Based on differential scanning calorimetry (DSC) and polarized light optical
microscopy (PLOM) characterization, we deduced that the increased nucleation
density at high σ and low P/N has a strong impact on accelerating the overall
crystallization of PEO nanocomposites.