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Schmalz, Holger ; Müller, Alejandro J. ; Abetz, Volker:
Crystallization in ABC triblock copolymers with two different crystalline end blocks : Influence of confinement on self-nucleation behavior.
In: Macromolecular Chemistry and Physics.
Bd. 204
(2003)
Heft 1
.
- S. 111-124.
ISSN 1521-3935
DOI: https://doi.org/10.1002/macp.200290063
Volltext
Abstract
The influence of different confinements active during crystallization within polybutadiene-block-polyisoprene-block-poly(ethylene oxide) (PB-b-PI-b-PEO) and the corresponding hydrogenated polyethylene-block-poly(ethylene-alt-propylene)-block-poly(ethylene oxide) (PE-b-PEP-b-PEO) triblock copolymers on the self-nucleation behavior of the crystallizable PEO and PE blocks is investigated by means of differential scanning calorimetry (DSC). In triblock copolymers with PEO contents less than or equal to20 wt.-% crystallization of I PEO is confined within small isolated microdomains (spheres or cylinders), and PEO crystallization takes place exclusively at high supercoolings. Self-nucleation experiments reveal an anomalous behavior in comparison to the classical self-nucleation behavior found in semicrystalline homopolymers. In these systems, domain II (exclusive self-nucleation domain) vanishes, and self-nucleation can only take place at lower temperatures in domain IIISA, when annealing is already active. The self-nucleation behavior of the PE blocks is significantly different compared with that of the PEO blocks. Regardless of the low PE content (10-25 wt.-%) in the investigated PE-b-PEP-b-PEO triblock copolymers a classical self-nucleation behavior is observed, i.e., all three self-nucleation domains, usually present in crystallizable homopolymers, can be located. This is a direct result of the small segmental interaction parameter of the PEP and PE segments in the melt. As a consequence, crystallization of PE occurs without confinement from a homogeneous mixture of PE and PEP segments.