Colloidal assembly by ice templating

Abstract

We investigate ice templating of aqueous dispersions of polymer coated colloids and crosslinkers, at particle concentrations far below that required to form percolated monoliths. Freezing the aqueous dispersions forces the particles into close proximity to form clusters, that are held together as the polymer chains coating the particles are crosslinked. We observe that, with an increase in the particle concentration from about 10(6) to 10(8) particles per ml, there is a transition from isolated single particles to increasingly larger clusters. In this concentration range, most of the colloidal clusters formed are linear or sheet like particle aggregates. Remarkably, the cluster size distribution for clusters smaller than about 30 particles, as well as the size distribution of linear clusters, is only weakly dependent on the dispersion concentration in the range that we investigate. We demonstrate that the main features of cluster formation are captured by kinetic simulations that do not consider hydrodynamics or instabilities at the growing ice front due to particle concentration gradients. Thus, clustering of colloidal particles by ice templating dilute dispersions appears to be governed only by particle exclusion by the growing ice crystals that leads to their accumulation at ice crystal boundaries.

Perspective: Outstanding theoretical questions in polymer-nanoparticle hybrids

“…This new functionality allows them to self-assemble into a variety of superstructures reflecting their hydrophilic/hydrophobic balance. [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] Other methods to facilitate miscibility are to use processing (e.g., use of solvents, extrusion) to drive these systems into long-lived metastable states with favorable properties 38,[69][70][71] or to push them into far-from quiescent, but still equilibrium, states under the action of electric/magnetic fields. [72][73][74] While many of the theoretical developments are discussed below, we only offer a limited, personal perspective of what is necessarily a very broad field.…”

Light‐Triggered, Spatially Localized Chemistry by Photoinduced Electron Transfer

“…Therefore, we investigated the effect of irradiation of chain like assemblies where colloidal particles are held together by a crosslinked PEI mesh. We have previously demonstrated the formation of such linear colloidal assemblies using ice‐templating (Details of colloidal chain preparation by ice‐templating in Section F, Supporting Information). Briefly, a dilute aqueous dispersion of colloidal f‐PS particles, PEI and crosslinker (polyethylene oxide diglycidyl ether) is frozen.…”

Light‐Triggered, Spatially Localized Chemistry by Photoinduced Electron Transfer

“…[45] In systems such as ours with an amine as electron donor, the high reactivity of the radical species can cleave C À Ha nd C À Cb onds. We have previously demonstrated the formation of such linear colloidal assemblies using icetemplating [47] (Details of colloidal chain preparation by icetemplating in Section F, Supporting Information). We have previously demonstrated the formation of such linear colloidal assemblies using icetemplating [47] (Details of colloidal chain preparation by icetemplating in Section F, Supporting Information).…”