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SANS/WANS Time-resolving Neutron Scattering Studiesof Polymer Phase Transitions Using NIMROD

  • Geoffrey Robert Mitchell (a1), Daniel Bowron (a2), Artur Mateus (a1), Paulo Bartolo (a1), Thomas Gkourmpis (a3), Khamphee Phomphrai (a4), Daniel Lopez (a5) and Fred Davis (a6)...

Abstract

We use new neutron scattering instrumentation to follow in a single quantitative time-resolving experiment, the three key scales of structural development which accompany the crystallisation of synthetic polymers. These length scales span 3 orders of magnitude of the scattering vector. The study of polymer crystallisation dates back to the pioneering experiments of Keller and others who discovered the chain-folded nature of the thin lamellae crystals which are normally found in synthetic polymers. The inherent connectivity of polymers makes their crystallisation a multiscale transformation. Much understanding has developed over the intervening fifty years but the process has remained something of a mystery. There are three key length scales. The chain folded lamellar thickness is ∼ 10nm, the crystal unit cell is ∼ 1nm and the detail of the chain conformation is ∼ 0.1nm. In previous work these length scales have been addressed using different instrumention or were coupled using compromised geometries. More recently researchers have attempted to exploit coupled time-resolved small-angle and wide-angle x-ray experiments. These turned out to be challenging experiments much related to the challenge of placing the scattering intensity on an absolute scale. However, they did stimulate the possibility of new phenomena in the very early stages of crystallisation. Although there is now considerable doubt on such experiments, they drew attention to the basic question as to the process of crystallisation in long chain molecules. We have used NIMROD on the second target station at ISIS to follow all three length scales in a time-resolving manner for poly(e-caprolactone). The technique can provide a single set of data from 0.01 to 100Å-1 on the same vertical scale. We present the results using a multiple scale model of the crystallisation process in polymers to analyse the results.

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References

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1. Keller Philos, A.. Mag., Ser. 8, 2, 11711175 1957
2. Heeley, EJ, Maidens, AV, Olmsted, PD, Bras, W, Dolbnya, IP, Fairclough, JPA, Terrill, NJ, and Ryan, AJ, Macromolecules 36 (2003) 36563665
3. Strobl, G., Rev. Mod. Phys. 81, 1287 2009
4. Mitchell, G.R. Neutron Diffraction to Soft Matter in Essentials of Neutron Techniques for Soft Matter Eds Imae, Toyoko et al 2011
5. Mitchell, G.R., Rosi, B. and Ward Philos, D.J.. Trans. Roy. Soc.. (London) Series A 348 97115 1994
6. Gkourmpis, T. and Mitchell, G.R. MRS Symposium 2012
7. Mitchell, G.R. in ‘Ecosustainable Polymer nanomaterials for food packaging’ Eds C.Silvestre and S.Cimmino Taylor and Francis 2013

Keywords

SANS/WANS Time-resolving Neutron Scattering Studiesof Polymer Phase Transitions Using NIMROD

  • Geoffrey Robert Mitchell (a1), Daniel Bowron (a2), Artur Mateus (a1), Paulo Bartolo (a1), Thomas Gkourmpis (a3), Khamphee Phomphrai (a4), Daniel Lopez (a5) and Fred Davis (a6)...

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