Ultrahigh Loading of Nanoparticles into Ordered Block
Copolymer Composites
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Abstract
Phase
selective, ultrahigh loading of nanoparticles into target
domains of block copolymer composites was achieved by blending the
block copolymer hosts with small molecule additives that exhibit strong
interactions with one of the polymer chain segments and with the nanoparticle
ligands via hydrogen bonding. The addition of d-tartaric
acid to poly(ethylene oxide-<i>block</i>-<i>tert</i>-butyl acrylate) (PEO-<i>b</i>-PtBA) enabled the loading
of more than 150 wt % of 4-hydroxythiophenol-functionalized Au nanoparticles
relative to the mass of the target domain (PEO + tartaric acid), which
corresponds to greater than 40 wt % Au by mass of the resulting well-ordered
composite as measured by thermal gravimetric analysis. The additive,
tartaric acid, performs three important roles. First, as evidenced
by small-angle X-ray scattering, it significantly increases the segregation
strength of the block copolymer via selective interaction with the
hydrophilic PEO block. Second, it expands the PEO block and enhances
the number and strength of enthalpically favorable interactions between
the nanoparticle ligands and the host domain. Finally, it mitigates
entropic penalties associated with NP incorporation within the target
domain of the BCP composite. This general approach provides a simple,
efficient pathway for the fabrication of well-ordered organic/nanoparticle
hybrid materials with the NP core content over 40 wt %