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Octa-OH-functional POSS has been incorporated into a model polyurethane elastomer as a comparatively massive and notionally "robust" 3-dimensional cross-linking core. The effects of this cross-linking moiety on the morphology and molecular dynamics of the system are studied over a range of size and time scales. Microscopy, scattering, spectroscopic, thermal, and dielectric techniques, in agreement with each other, show that the covalent inclusion of the crosslinking particles restricts microphase separation, inhibits the formation of hard-block domains, and decelerates the motional dynamics of the polyurethane backbone. The effects on both the morphology and the dynamics of the polyurethane system are not continuous but occur in a steplike manner in the loading region of 4−6 wt % POSS. This critical region is thought to correspond to a sterically induced transition from one dominant morphology (microphase segregated) to an increasingly homogeneous nanophase segregated domain morphology. Contrary to expectations, cross-linking, even by the presumably rigid siliceous nanoparticles, reduces the mechanical modulus. In conjunction with the reduction of microphase separation, this observation indicates that the hard microdomains reinforce the polymer more effectively than the chemical cross-links.

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Polyhedral oligomeric silsesquioxane moieties with poly­(ethylene glycol) groups attached on the cage (PEG–POSS) were blended with an elastomeric polyurethane matrix, in contents up to 10 wt %. Several experimental techniques in agreement with each other show that the PEG–POSS moieties disperse well on the molecular level and act as diluents plasticizing the molecular dynamics. Although the degree of microphase separation is only weakly affected in all the compositions, changes in the macromorphology related to the POSS moieties have an impact on the matrix properties, decreasing the storage modulus. The PEG–POSS themselves display segmental dynamics, glass transition, and crystallinity; however, none of these properties are observed in the blends, providing additional support for excellent miscibility with the matrix. The results are compared to those of previous works where different synthesis approaches resulting in different POSS topologies were used.

In the present work, the thermomechanical performance of linear low‐density polyethylene (LDPE) reinforced with multi‐walled carbon nanotubes (CNTs) is investigated by means of scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, tensile and electrical testing. The ball milling and melt mixing procedure, employed for the nanocomposites preparation provided improvement of the thermomechanical properties. The findings are encouraging for a wider application of linear LDPE. The nanocomposites’ elastic behaviour was further described by three different micromechanics models. It was found that the model based on the effective continuum fiber was capable of describing the Young's modulus for all CNTs concentrations, revealing also the micromorphology and the dispersion quality of the nanocomposites examined. POLYM. COMPOS., 39:E1118–E1128, 2018. © 2017 Society of Plastics Engineers