Network dynamics in nanofilled polymers.
It is well accepted that adding nanoparticles (NPs) to polymer melts can result in significant property improvements. Here we focus on the causes of mechanical reinforcement and present rheological measurements on favourably interacting mixtures of spherical silica NPs and poly(2-vinylpyridine), complemented by several dynamic and structural probes. While the system dynamics are polymer-like with increased friction for low silica loadings, they turn network-like when the mean face-to-face separation between NPs becomes smaller than the entanglement tube diameter. Gel-like dynamics with a Williams-Landel-Ferry temperature dependence then result. This dependence turns particle dominated, that is, Arrhenius-like, when the silica loading increases to ∼31 vol%, namely, when the average nearest distance between NP faces becomes comparable to the polymer's Kuhn length. Our results demonstrate that the flow properties of nanocomposites are complex and can be tuned via changes in filler loading, that is, the character of polymer bridges which 'tie' NPs together into a network.
Foundation for Research and Technology - Hellas (FORTH), Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece.
Guilhem P
GP
Baeza
Foundation for Research and Technology - Hellas (FORTH), Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece.|Department of Materials Science and Technology, University of Crete, Heraklion, Crete 71003, Greece.
Claudia
C
Dessi
Foundation for Research and Technology - Hellas (FORTH), Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece.|Department of Materials Science and Technology, University of Crete, Heraklion, Crete 71003, Greece.
Salvatore
S
Costanzo
Department of Chemical Engineering, Columbia University, New York, New York 10027, USA.
Dan
D
Zhao
Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Shushan
S
Gong
Departamento de Física de Materiales y Centro de Física de Materiales CSIC-UPV/EHU, Universidad del País Vasco UPV/EHU, San Sebastian E-20018, Spain.
Angel
A
Alegria
Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Ralph H
RH
Colby
Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.
Michael
M
Rubinstein
Foundation for Research and Technology - Hellas (FORTH), Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece.|Department of Materials Science and Technology, University of Crete, Heraklion, Crete 71003, Greece.
Dimitris
D
Vlassopoulos
Department of Chemical Engineering, Columbia University, New York, New York 10027, USA.
Sanat K
SK
Kumar
D017276:Friction; D053761:Nanocomposites / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012212:Rheology; D012822:Silicon Dioxide / Q000737:chemistry; D013696:Temperature
D011108:Polymers; D012822:Silicon Dioxide