Effects of a chemically reacting, 2nm size heterogeneity on polymerization: A dielectric relaxation study

Khouri, Joseph; Johari, G. P.

doi:10.1016/j.tca.2012.04.012

Cited by 2 publications

(2 citation statements)

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“…25,26 Their chemical structures and the impurity content have been described previously, 25,26 and, for convenience, their structures are given in Fig. 1.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…It should be noted that chemical reactions in the production process of POSS yield batches containing different distribution of the sizes of the POSS molecules, different number (up to 12) of Si-atom vertices, different numbers of groups attached to the vertices and different amount of impurities, as described previously. 25,26 As a result, the POSS liquid taken from different batches may differ slightly in its composition and properties. The POSS liquids, like DGEBA, also have a shelf life.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Effects of 2 nm size added heterogeneity on non-exponential dielectric response, and the dynamic heterogeneity view of molecular liquids

Johari

Khouri

2012

The Journal of Chemical Physics

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To investigate how non-exponential response could vary under different conditions, we studied the effects of adding 2 nm size polyhedral oligomeric silsesquioxane (POSS) to diglycidyl ether of bisphenol-A, whose molecules have the same terminal (epoxide) dipoles as the tentacle-like side chains attached to the silsesquioxane core of the POSS molecule. Dielectric relaxation spectra show that, on initial addition, the POSS nano-heterogeneity decreases the non-exponential response parameter β, which is consistent with the dynamic heterogeneity view, but it also decreases the relaxation time τ(m), which is inconsistent with that view. The variations in β and τ(m) with the composition have a thermal equivalence. Despite the lack of translational diffusion required for dynamic heterogeneity, plastic crystals show non-exponential response and non-Arrhenius dynamics. Measurements of β and τ(m) seem more appropriate than using probe molecules or modeling nonlinear response data as a sum of linear responses for testing the dynamic heterogeneity view. Data on molecular liquid mixtures is not generally consistent with this view, and adding a solute does not always decrease β. Studies of mixtures of different size rigid molecules with identical dipolar groups, including polymers, may be useful for comparing the relative effects of temperature and molecular size on β and τ(m).

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“…25,26 Their chemical structures and the impurity content have been described previously, 25,26 and, for convenience, their structures are given in Fig. 1.…”

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%