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Issue 4, 2016
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Solvent transport through hard–soft segmented polymer nanocomposites

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Abstract

We conducted transport studies of a common solvent (toluene) in its condensed state, through a model hard–soft segmented polyurethane–clay nanocomposite. The solvent diffusivity is observed to be non-monotonic in a functional relationship with a filler volume fraction. In stark contrast, both classical tortuous path theory based geometric calculations and free volume measurements suggest the normally expected monotonic decrease in diffusivity with increase in clay volume fraction. Large deviations between experimentally observed diffusivity coefficients and those theoretically estimated from geometric theory are also observed. However, the equilibrium swelling of a nanocomposite as indicated by the solubility coefficient did not change. To gain an insight into the solvent interaction behavior, we conducted a pre- and post swollen segmented phase analysis of pure polymers and nanocomposites. We find that in a nanocomposite, the solvent has to interact with a filler altered hard–soft segmented morphology. In the altered phase separated morphology, the spatial distribution of thermodynamically segmented hard blocks in the continuous soft matrix becomes a strong function of filler concentration. Upon solvent interaction, this spatial distribution gets reoriented due to sorption and de-clustering. The results indicate strong non-barrier influences of nanoscale fillers dispersed in phase segmented block co-polymers, affecting solvent diffusivity through them. Based on pre- and post swollen morphological observations, we postulate a possible mechanism for the non-monotonic behaviour of solvent transport for hard–soft segmented co-polymers, in which the thermodynamic phase separation is influenced by the filler.

Graphical abstract: Solvent transport through hard–soft segmented polymer nanocomposites

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Publication details

The article was received on 28 Jul 2015, accepted on 09 Dec 2015 and first published on 16 Dec 2015


Article type: Paper
DOI: 10.1039/C5CP04432D
Phys. Chem. Chem. Phys., 2016,18, 2682-2689

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    Solvent transport through hard–soft segmented polymer nanocomposites

    S. K. Rath, S. S. Edatholath, T. U. Patro, K. Sudarshan, P. U. Sastry, P. K. Pujari and G. Harikrishnan, Phys. Chem. Chem. Phys., 2016, 18, 2682
    DOI: 10.1039/C5CP04432D

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