Nanostructured polyamide by reactive blending. 2. Transition from nanovesicles to cucumber-like core-shell nanoobjects

Polyamide 12 (PA 12) has been nanostructured by reactive blending with 20 wt% of a symmetric anhydride end-capped polystyrene-b-polyisoprene (PS-b-PIP-anh) The liposome-like nanovesicles which are originally formed in the polyamide matrix (PA 12) are converted into cucumber-like core-shell nanoobjects upon increasing the volume fraction of PS by addi-j tion of homo PS of a molecular weight lower than the PS block. The key effect of the molecular weight of homoPS with respect to the PS bloc,k has been emphasized. The same nanoobjects can be prepared by direct blending of PA12 with 20 wt% of an asymmetric reactive PS-b-PIP-anh diblock with the same molecular weight and a higher PS content compared to the symmetric diblock. The interesting point is that the thickness of the rubbery envelope of the core-shell nanoobjects changes with the method used for their preparation at constant PA12/ PS/PIP composition, as result of a change in the molecular weight of the shell forming block.