Nanostructured Polyethylene-POSS Copolymers:  Control of Crystallization and Aggregation

Nanoscale structure formation in copolymers of polyethylene (PE) and polyhedral oligomeric silsesquioxane (POSS) with norbornene and cyclopentyl side-groups can be controlled through choice of crystallization conditions. Aggregates of both crystalline PE and crystalline POSS are found when crystallized from the melt. A self-assembled, two-phase crystalline structure, consisting of POSS crystalline domains molecularly connected to PE crystalline domains, is formed. Constraints on domain growth arise from molecular architecture, likely leading to anisotropy in the shape of POSS domains. Considerable suppression of POSS crystallization is found on precipitation from solution. The origin of the frustration of crystal growth and the introduction of disorder is discussed. Structural investigative methods include X-ray diffraction and transmission electron microscopy. Degradation temperatures are found to be dependent on the morphology of the nanocomposites, with possible implications for improved thermal resistance.