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University of Technology of Compiègne, France

Nawaz Q.,Domaine University 38041 | Rharbi Y.,Domaine University 38041
Langmuir | Year: 2010

Film formation from aqueous suspensions of polymer nanoparticles is an important process in many environmental friendly applications and particularly for waterborne coatings. This process occurs via three mains steps: concentration, sintering, and interdiffusion. During the sintering step, the particles in close-packed morphology deform and the interstices between them close under Laplace pressure. This step is crucial in the film formation process since it is where the suspension turns into a uniform, defect-free film. Most of the experimental and theoretical studies on sintering assume that the interstices close uniformly over the entire film. We use small-angle neutron scattering to probe void closure between polystyrene nanoparticles. We show that the voids close simultaneously and uniformly throughout the annealing process in large particles. For particles with a diameter smaller than 60 nm, we interpret the results to show that the interstices close heterogeneously at the nanoscopic level: in the beginning of annealing, some interstices close while others enlarge, and eventually they all vanish, The difference between the behavior of large and small particles is related, to the high polydispersity of small particles compared to the larger ones. © 2009 American Chemical Society. Source


Rharbi Y.,Domaine University 38041 | Yousfi M.,Domaine University 38041 | Porcar L.,Laue Langevin Institute | Nawaz Q.,Domaine University 38041
Canadian Journal of Chemistry | Year: 2010

Motivated by the recent advances in new technologies, a lot of effort has been dedicated to developing methods for quantifying the dynamic of nanoconfined polymers. Particularly, polymers confined in nanoparticles are an important system for several environment-friendly applications such as waterborne coatings and nanoblends. In this work, we discuss two methods to probe the large scale dynamic of nanoconfined polymers in nanoparticles in two situations: (i) nanoblends and (ii) the close-packed structure. In the methods we apply stress at the nanoscopic level around the polystyrene particles and we probe their deformation in real time using small-angle neutron scattering. These methods give new possibilities to probe, in a nonintrusive manner, the dynamic of confined polymers in nanoparticles, which could ultimately bring conclusive insight to this field. Source

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