Effect of meta-carborane on segmental dynamics in a bimodal poly(dimethylsiloxane) network

Lewicki, J.P. and Maxwell, R.S. and Patel, M. and Herberg, J.L. and Swain, A.C. and Liggat, J.J. and Pethrick, R.A. (2008) Effect of meta-carborane on segmental dynamics in a bimodal poly(dimethylsiloxane) network. Macromolecules, 41 (23). pp. 9179-9186. ISSN 0024-9297 (https://doi.org/10.1021/ma801570e)

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Abstract

Bimodal networks of polydimethylsiloxane (PDMS) filled with varying amounts of icosahedral meta-carborane (m-CB) have been developed and characterized by broadband dielectric spectroscopy (BDS) and static 1H multiple quantum nuclear magnetic resonance (MQ NMR). Both BDS and MQ NMR showed evidence for a decrease in the polymer chain dynamics. BDS spectra quantified a normal-mode relaxation near 40 Hz at 40 °C. The frequency maximum observed for filled samples decreased with increasing m-CB content until contents greater than 5 wt %. The width of the relaxation spectrum increased with the addition of small quantities of filler and decreased with filler contents greater that 5 wt %. Agglomeration effects were observed at loadings greater than 5 wt % as manifest by the onset of low frequency Maxwell-Wagner-Sillars (MWS) processes. The MQ NMR data allowed the characterization of distributions of the residual dipolar couplings, <Ωd> and, thus, in the dynamic order parameter, Sb, consistent with the bimodal network architecture expected from the synthesis protocol used. Upon addition of less than 10 wt % m-CB filler, the mean <Ωd> for the longer chains increased by 46% and the width of the distribution increased by 33%. The mean <Ωd> for the shorter chains increased by much less, indicative of preferential dispersion of the filler particles in the long chain domains of the network structure. We conclude that the mechanism of reinforcement is likely free volume space filling at low loadings transitioning to complex molecular filler and polymer chain interaction phenomena at higher loadings.

ORCID iDs

Lewicki, J.P., Maxwell, R.S., Patel, M., Herberg, J.L., Swain, A.C., Liggat, J.J. ORCID logoORCID: https://orcid.org/0000-0003-4460-5178 and Pethrick, R.A.;
  • Item type:Article
    ID code:17009
    Dates:
    Date
    Event
    9 December 2008
    Published
    Notes:http://suprimo.lib.strath.ac.uk/primo_library/libweb/action/display.do?ct=display&doc=SUSFX954925421108&indx=3&mode=Basic&vid=SUVU01&vl(96071691UI1)=all_items&dscnt=0&vl(54032236UI0)=lsr02&srt=rank&ct=facet&frbg=&fctV=include%20only%20journals%20or%20serials&scp.scps=scope%3A(SU)&indx=1&dum=true&dstmp=1269949636895&fctN=facet_fmt&fn=search&vl(freeText0)=Macromolecules&tab=local
    Subjects:Science > Science (General)
    Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Strathprints Administrator
    Date deposited:30 Mar 2010 11:13
    Last modified:11 Nov 2024 09:23
    URI:https://strathprints.strath.ac.uk/id/eprint/17009
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