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Issue 38, 2013
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Multiple nucleation events and local dynamics of poly(ε-caprolactone) (PCL) confined to nanoporous alumina

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Abstract

The crystallization and local dynamics of poly(ε-caprolactone) (PCL) confined to self-ordered nanoporous alumina (AAO) were studied as a function of pore size, pore surface functionality, molecular weight and cooling/heating rate by differential scanning calorimetry (DSC), wide-angle X-ray diffraction and dielectric spectroscopy. In contrast to the bulk, PCL located inside nanoporous alumina crystallizes via several distinct nucleation mechanisms. All mechanisms display pronounced rate dependence. At low undercoolings, the usual heterogeneous nucleation of bulk PCL was suppressed at the expense of two additional mechanisms attributed to heterogeneous nucleation initiated at the pore walls. At higher undercoolings a broad peak was observed in DSC which we attribute to crystallization initiated by homogeneous nucleation. At high cooling rates, the critical nucleus size is smaller than the smallest diameter of pores. Thus, PCL is able to crystallize within the smallest pores, despite the lower degree of crystallinity. Inevitably, homogeneous nucleation is strongly coupled to the local viscosity and hence to the local segmental dynamics. Dielectric spectroscopy revealed that confinement affected both the rate of segmental motion with a lowering of the glass temperature as well as a broader distribution of relaxation times.

Graphical abstract: Multiple nucleation events and local dynamics of poly(ε-caprolactone) (PCL) confined to nanoporous alumina

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Article information


Submitted
02 Apr 2013
Accepted
24 Jun 2013
First published
24 Jun 2013

This article is Open Access

Soft Matter, 2013,9, 9189-9198
Article type
Paper

Multiple nucleation events and local dynamics of poly(ε-caprolactone) (PCL) confined to nanoporous alumina

Y. Suzuki, H. Duran, W. Akram, M. Steinhart, G. Floudas and H. Butt, Soft Matter, 2013, 9, 9189
DOI: 10.1039/C3SM50907A

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