Morphology, Crystallization, and Melting of Single Crystals and Thin Films of Star-branched Polyesters with Poly(Îµ-caprolactone) Arms as Revealed by Atomic Force Microscopy

Nunez, E. and Vancso, G.J. and Gedde, U.W. (2008) Morphology, Crystallization, and Melting of Single Crystals and Thin Films of Star-branched Polyesters with Poly(Îµ-caprolactone) Arms as Revealed by Atomic Force Microscopy. Journal of Macromolecular Science, Part B: Physics, 47 (3). pp. 589-607. ISSN 0022-2348

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Abstract:	The morphology and thermal stability of different sectors in solution- and melt-grown crystals of star-branched polyesters with poly(Îµ-caprolactone) (PCL) arms, and of a reference linear PCL, have been studied by tapping-mode atomic-force microscopy (AFM). Real-time monitoring of melt-crystallization in thin films of star-branched and linear PCL has been performed using hot-stage AFM. A striated fold surface was observed in both solution- and melt-grown crystals of both star-branched and linear PCL. The presence of striations in the melt-grown crystals proved that this structure was genuine and not due to the collapse of tent-shaped crystals. The crystals of the star-branched polymers had smoother fold surfaces, which can be explained by the presence of dendritic cores close to the fold surfaces. The single crystals of linear PCL grown from solution showed earlier melting in the ${100}$ sectors than in the ${110}$ sectors, whereas no such sectorial dependence of the melting was found in the solution-grown crystals of the star-branched polymers. The proximity of the dendritic cores to the fold surface yields at least one amorphous PCL repeating unit next to the dendritic core and more nonadjacent and less sharp chain folding than in linear PCL single crystals; this evidently erased the difference in thermal stability between the ${110}$ and ${100}$ sectors. Melt-crystallization in thin polymer films at 53-55Â°C showed 4 times faster crystal growth along b than along a, and more irregular crystals with niches on the lateral faces in star-branched PCL than in linear PCL. Crystal growth rate was strictly constant with time. Multilayer crystals with central screw dislocation (growing with or without reorientation of the b-axis) and twisting were observed in both classes of polymers.
Item Type:	Article
Copyright:	© 2008 Taylor & Francis
Faculty:	Science and Technology (TNW)
Research Group:	Materials Science and Technology of Polymers (MTP)
Link to this item:	http://purl.utwente.nl/publications/60211
Official URL:	http://dx.doi.org/10.1080/00222340801955636
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