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2006-06-02 - Article/Dans un journal avec peer-review - Anglais - 13 page(s)

Hamley I.W., Parras P., Castelletto V., Castillo Reina Veronica, Müller Alejandro J, Pollet E., Dubois Philippe , Martin C., "Melt structure and its transformation by sequential crystallization of the two blocks within poly(L-lactide)-b-poly(e-caprolactone) double crystalline diblock copolymers" in Macromolecular Chemistry and Physics, 207, 11, 941-953

  • Edition : Wiley-VCH, Weinheim (Germany)
  • Codes CREF : Chimie macromoléculaire (DI1315), Catalyses hétérogène et homogène (DI1334)
  • Unités de recherche UMONS : Matériaux Polymères et Composites (S816)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
Texte intégral :

Abstract(s) :

(Anglais) Sequential crystallization of poly(L-lactide) (PLLA) followed by poly(e-caprolactone) (PCL) in double crystalline PLLA-b-PCL diblock copolymers is studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). Three samples with different compositions are studied. The sample with the shortest PLLA block (32 wt.-% PLLA) crystallizes from a homogeneous melt, the other two (with 44 and 60% PLLA) from microphase separated structures. The microphase structure of the melt is changed as PLLA crystallizes at 122?°C (a temperature at which the PCL block is molten) forming spherulites regardless of composition, even with 32% PLLA. SAXS indicates that a lamellar structure with a different periodicity than that obtained in the melt forms (for melt segregated samples). Where PCL is the majority block, PCL crystallization at 42?°C following PLLA crystallization leads to rearrangement of the lamellar structure, as observed by SAXS, possibly due to local melting at the interphases between domains. POM results showed that PCL crystallizes within previously formed PLLA spherulites. WAXS data indicate that the PLLA unit cell is modified by crystallization of PCL, at least for the two majority PCL samples. The PCL minority sample did not crystallize at 42?°C (well below the PCL homopolymer crystallization temperature), pointing to the influence of pre-crystallization of PLLA on PCL crystallization, although it did crystallize at lower temperature. Crystallization kinetics were examined by DSC and WAXS, with good agreement in general. The crystallization rate of PLLA decreased with increase in PCL content in the copolymers. The crystallization rate of PCL decreased with increasing PLLA content. The Avrami exponents were in general depressed for both components in the block copolymers compared to the parent homopolymers.

Notes :
  • (Anglais) Lecture en ligne: http://onlinelibrary.wiley.com/doi/10.1002/macp.200600085/pdf
  • (Anglais) Publié en ligne le 23 mai 2006
Identifiants :
  • DOI : 10.1002/macp.200600085