Size Controlled Polymer Coated Nanoparticles as Efficient Compatibilizers for Polymer Blends

Polymer-coated gold nanoparticles (Au) with controlled size and surface were successfully synthesized and applied to tailor the structures and properties of polytriphenylamine (PTPA) and polystyrene (PS) blends. Two different polymer-coated Au NPs with sizes of 5.9 nm (Au1) and 20.7 nm (Au2) were designed to be thermally stable above 200 $^{\circ}$C and neutral to both PS and PTPA phases. Hence, both Au NPs localize at the PS/PTPA interface and function as compatibilizers in the PS/PTPA blend. To show the compatibilizing effect of the particles, the morphological behaviors of PS/PTPA blends containing different particle volume fraction of Au NPs were observed using cross-sectional TEM, and for quantitative analysis, the size distribution of PTPA droplets in the PS matrix was obtained for each sample. The number-average droplet diameter (Dn) of the PTPA domain in the blend was dramatically reduced from 1.4 $\mu $m to 500 nm at a small volume fraction of 1.0 vol{\%} Au1. The same trend of decreasing Dn was also observed with the addition of larger Au2, but a higher volume fraction was required to obtain the same amount of reduction in the PTPA droplet size. To demonstrate the effectiveness of Au NPs as compatibilizers, PS-b-PTPA block copolymers were also synthesized and used as compatibilizers.