Phase separation and self-assembly in vitrimers: hierarchical morphology of molten and semi-crystalline polyethylene/dioxaborolane maleimide systems

Vitrimers - a class of polymer networks which are covalently crosslinked and insoluble like thermosets, but flow when heated like thermoplastics - contain dynamic links and/or crosslinks that undergo an associative exchange reaction. These dynamic crosslinks enable vitrimers to have interesting mechanical/rheological behavior, self-healing, adhesive, and shape memory properties. We demonstrate that vitrimers can self-assemble into complex meso- and nanostructures when crosslinks and backbone monomers strongly interact. Vitrimers featuring polyethylene (PE) as the backbone and dioxaborolane maleimide as the crosslinkable moiety were studied in both the molten and semi-crystalline states. We observed that PE vitrimers macroscopically phase separated into dioxaborolane maleimide rich and poor regions, and characterized the extent of phase separation by optical transmission measurements. This phase separation can explain the relatively low insoluble fractions and overall crystallinities of PE vitrimers. Using synchrotron-sourced small-angle X-ray scattering (SAXS), we discovered that PE vitrimers and their linear precursors micro-phase separated into hierarchical nanostructures. Fitting of the SAXS patterns to a scattering model strongly suggests that the nanostructures - which persist in both the melt and amorphous fraction of the semi-crystalline state - may be described as dioxaborolane maleimide rich aggregates packed in a mass fractal arrangement. These findings of hierarchical meso- and nanostructures point out that incompatibility effects between network components and resulting self-assembly must be considered for understanding behavior and the rational design of vitrimer materials

The Impact of Protracted Peace Processes on Identities in Conflict

This open access book discusses the impact of protracted peace processes on identities in conflict. It is concerned with how lingering peace processes affect, in the long-term, patterns of othering in protracted conflicts, and how this relates with enduring violence. Taking Israel and Palestine as a case study, the book traces different representations of success and failure of the protracted peace process, as well as its associated policies, narratives, norms and practices, to analyze its impact on identity and its contribution to the maintenance and/or transformation of the cultural component of violence. On the one hand, drawing from an interdisciplinary approach comprising International Relations (IR), History and Social Psychology, this book proposes an analytical framework for assessing the specificities of the construction of identities in protracted conflicts. It identifies dehumanization and practices of reconciliation in ongoing conflicts – what is called peace-less reconciliation – as the main elements influencing processes of othering and violence in this kind of conflicts. On the other hand, the book offers an empirical historical analysis on how the protracted peace process has impacted identity building and representations made of the ‘other’ in the case of the Israeli-Palestinian conflict since the end of the 19th century to the present day