Suchergebnisse

Despite the growing application of nanostructured polymeric materials, there still remains a large gap in our understanding of polymer mechanics and thermal stability under confinement and near polymer-polymer interfaces. In particular, the knowledge of polymer nanoparticle thermal stability and mechanics is of great importance for their application in drug delivery, phononics, and photonics. Here, we quantified the effects of a polymer shell layer on the modulus and glass-transition temperature (T) of polymer core-shell nanoparticles via Brillouin light spectroscopy and modulated differential scanning calorimetry, respectively. Nanoparticles consisting of a polystyrene (PS) core and shell layers of poly(n-butyl methacrylate) (PBMA) were characterized as model systems. We found that the high T of the PS core was largely unaffected by the presence of an outer polymer shell, whereas the lower T of the PBMA shell layer decreased with increasing PBMA thickness. The surface mobility was revealed at a temperature about 15 K lower than the T of the PBMA shell layer. Overall, the modulus of the core-shell nanoparticles decreased with increasing PBMA shell layer thickness. These results suggest that the nanoparticle modulus and T can be tuned independently through the control of nanoparticle composition and architecture. ; E.K., B.G., and G.F. acknowledge the financial support by ERC Advanced Grant Smartphon (No. 694977). B.G. acknowledges the support from the First Team project (POIR.04.04.00-00- 5D1B/18-00) granted by the Foundation for Polish Science. R.D.P. acknowledges the support of the National Science Foundation (NSF) Materials Research Science and Engineering Center Program through the Princeton Center for Complex Materials (DMR-1420541) and NSF CBET1706012. D.C. acknowledges financial support from the Basque Government (Grant No. IT-1175-19).