Polymer-Grafted-Nanoparticles Nanocomposites: Dispersion, Grafted Chain Conformation, and Rheological Behavior

被引:284
作者
Chevigny, Chloe [1 ]
Dalmas, Florent [2 ]
Di Cola, Emanuela [3 ]
Gigmes, Didier [4 ,5 ,6 ,7 ]
Bertin, Denis [4 ,5 ,6 ,7 ]
Boue, Francois [1 ]
Jestin, Jacques [1 ]
机构
[1] CEA Saclay, Lab Leon Brillouin, F-91191 Gif Sur Yvette, France
[2] Univ Paris Est, CNRS, UMR 7182, Inst Chim & Mat Paris Est, F-94320 Thiais, France
[3] ESRF, F-38043 Grenoble, France
[4] CNRS, UMR 6264, Lab Chim Provence, F-13393 Marseille 20, France
[5] Univ Aix Marseille 1, F-13393 Marseille 20, France
[6] Univ Aix Marseille 2, F-13393 Marseille 20, France
[7] Univ Aix Marseille 3, F-13393 Marseille 20, France
关键词
MOLECULAR-WEIGHT; MECHANICAL-PROPERTIES; PROCESSING CONDITIONS; COPOLYMER MICELLES; MATRIX; REINFORCEMENT; HOMOPOLYMER; PARTICLES; DENSITY; SPHERES;
D O I
10.1021/ma101332s
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
We investigate the dispersion mechanisms of nanocomposites made of well-defined polymer (polystyrene, PS) grafted-nanoparticles (silica) mixed with free chains of the same polymer using a combination of scattering (SAXS/USAXS) and imaging (TEM) techniques. We show that the relevant parameter of the dispersion, the grafted/free chains mass ratio R tuned with specific synthesis process, enables to manage the arrangement of the grafted nanoparticles inside the matrix either as large and compact aggregates (R < 0.24) or as individual nanoparticles dispersion (R > 0.24). From the analysis of the interparticles structure factor, we can extract the thickness of the spherical corona of grafted brushes and correlate it with the dispersion: aggregation of the particles is associated with a significant collapse of the grafted chains, in agreement with the theoretical models describing the free energy as a combination of a mixing entropy term between the free and the grafted chains and an elastic term of deformation of the grafted brushes. At fixed grafting density, the individual dispersion of particles below the theoretical limit of R = 1 can be observed, due to interdiffusion between the grafted and the free chains but also to processing kinetics effects, surface curvature and chains poly dispersity. Mechanical analysis of nanocomposites show the appearance of a longer relaxation time at low frequencies, more pronounced in the aggregated case even without direct connectivity between the aggregates. Correlation between the local structure and the rheological behavior suggests that the macroscopic elastic modulus of the nanocomposite could be described mainly by a short-range contribution, at the scale of the interactions between grafted particles, without significant effect of larger scale organizations.
引用
收藏
页码:122 / 133
页数:12
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