Effect of nanoparticle size on the internal structure of copolymer-nanoparticles composite thin films studied by neutron reflection

Neutron reflection was used for the study of the composite films made of symmetric (d-PS-PBMA) diblock copolymer (molecular weight M_w = 170 and 135 K) with nanoparticles of γ-Fe₂O₃ (4 and 6 nm in diameter) incorporated in the deuterated PS-domains with different concentrations. From the neutron reflection experiment we determined the period of the lamellar structure and the position of the nanoparticles in the PS-layers. It is important to examine the effect of the particle size on the lamellar structure. We determined that the small nanoparticles (4 nm) concentrate close to d-PS-PBMA interfaces while larger nanoparticles (6 nm) localize in the center of PS domains. This effect is of considerable interest in the elaboration of new composite materials since it will give a control on the particle distribution inside the host domains.