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

Published online by Cambridge University Press:  19 March 2013

Geoffrey Robert Mitchell
Affiliation:
Centre for Rapid and Sustainable Product Development, Institute Polytechnic Leiria, Marinha Grande, Portugal;
Daniel Bowron
Affiliation:
ISIS, Science and Technology Facility Council, Didcot, United Kingdom; OX11 0QX
Artur Mateus
Affiliation:
Centre for Rapid and Sustainable Product Development, Institute Polytechnic Leiria, Marinha Grande, Portugal;
Paulo Bartolo
Affiliation:
Centre for Rapid and Sustainable Product Development, Institute Polytechnic Leiria, Marinha Grande, Portugal;
Thomas Gkourmpis
Affiliation:
Innovation & Technology, Borealis AB, Stenungsund SE-444 86 Sweden;
Khamphee Phomphrai
Affiliation:
Department of Chemistry, Mahidol University, Bangkok, Thailand.
Daniel Lopez
Affiliation:
ICTP, Madrid, Spain;
Fred Davis
Affiliation:
Department of Chemistry, University of Reading UK RG6 6AD
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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.

Type
Articles
Copyright
Copyright © Materials Research Society 2013

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References

REFERENCES

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