Front Cover: Co‐continuous nanostructured semi‐crystalline blends, in which long graft chains are incorporated, are obtained by reactive blending of functional polyethylene and bi‐modal molecular weight polyamides. The short chains react more readily to form graft copolymers that facilitate both grafting of long chains and formation of nanostructures. Further details can be found in the article by L. Gani, S. Tencé‐Girault,* M. Milléquant, S. Bizet, and L. Leibler .
Reactive blending is used as a tool for the synthesis of graft copolymers of poly(methyl methacrylate)
and polyamide-6 (PMMA-g-PA). The grafting reaction occurs between the amino end group of PA and glutaric
anhydride units randomly distributed along the PMMA backbone. The anhydride units are formed by thermal
treatment (typically above 180 °C) of a precursor PMMA bearing a low fraction of methacrylic acid units (5 or
10 mol %). With this method, it is possible to control the amount of anhydride units without degradation or
cross-linking of the PMMA chains. The resulting blends with PA are characterized by size exclusion
chromatography in benzyl alcohol at 130 °C and selective extraction of ungrafted PMMA chains. Combining
these techniques, we were able to estimate the fraction and the average composition of the graft copolymers
synthesized in situ during the blending process. High fractions of graft copolymer (35−75 wt %) are obtained in
all the blends studied in this work. A higher amount of graft copolymer is obtained by increasing the amount of
PA in the blend or the anhydride content on a functionalized PMMA. Optimum grafting is also influenced by the
remaining acid groups on the PMMA chain. These groups are expected to contribute to the reversible interactions
(hydrogen bonding) between PMMA and PA at the interface.
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