Control of interfacial interactions leads to a dramatic change in shape and morphology for particles based on poly(styrene-b-2-vinylpyridine) diblock copolymers. Key to these changes is the addition of Au-based surfactant nanoparticles (SNPs) which are adsorbed at the interface between block copolymer-containing emulsion droplets and the surrounding amphiphilic surfactant to afford asymmetric, ellipsoid particles. The mechanism of formation for these novel nanostructures was investigated by systematically varying the volume fraction of SNPs, with the results showing the critical nature that the segregation of SNPs to specific interfaces plays in controlling structure. A theoretical description of the system allows the size distribution and aspect ratio of the asymmetric block copolymer colloidal particles to be correlated with the experimental results.

We herein report a new facile strategy to ellipsoidal block copolymer nanoparticles exhibiting a pH-triggered anistropic swelling profile. In a first step, elongated particles with an axially stacked lamellae structure are selectively prepared by utilizing functional surfactants to control the phase separation of symmetric PS-b-P2VP in dispersed droplets. In a second step, the dynamic shape change is realized by crosslinking the P2VP domains, hereby connecting glassy PS discs with pH-sensitive hydrogel actuators.

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We herein report a new facile strategy to ellipsoidal block copolymer nanoparticles exhibiting a pH-triggered anistropic swelling profile. In a first step, elongated particles with an axially stacked lamellae structure are selectively prepared by utilizing functional surfactants to control the phase separation of symmetric PS-b-P2VP in dispersed droplets. In a second step, the dynamic shape change is realized by crosslinking the P2VP domains, hereby connecting glassy PS discs with pHsensitive hydrogel actuators.© Wiley-VCH Verlag GmbH &co. KGaA, Weinheim Supporting information for this article is available on the WWWunder http://dx.doi.org/10.1002/anie.201xxxxxx. The ability of nature to precisely control the shape and functionality of nanoparticles in a range of biological systems has long motivated researchers to strive for similar control in synthetic nanomaterials. [1] This challenge has been partially fulfilled in inorganic systems where the ability to tailor shape and size in order to tune properties has been extensively studied. [2] In direct contrast, the toolbox for controlling the shape and functionality of polymer-based nanoparticles is still in its infancy [3] with future success being critical to the preparation of bio-inspired materials with applications ranging from drug-delivery systems to artificial camouflage. [1c] In addressing this need, the development of dynamic, shape-changing polymer particles requires three main structural features to be incorporated into a single system: shape anisotropy, spatial control over internal morphology and the introduction of stimuliresponsiveness to the nanoparticles. Unfortunately, current examples address each aspect separately with multifunctional, dynamic systems not being realized. [3] Anisotropic particles, for instance, have been prepared by a multistep procedure which relies on the stretching of spherical particles. [3a, 4] Even though such elongated particles show interesting properties [5] only a few examples combine shape anisotropy with either well-defined internal morphologies [6] or stimuli-responsive properties. [7] For example, we have recently reported the use of tailored Au nanoparticles as surface active agents for the preparation of shape anisotropic particles with an internally structured morphology. [8] While the potential of block copolymer self-assembly in colloidal systems is promising, [9] the use of Au nanoparticles represents a significant synthetic limitation and did not lead to a dynamic, stimuli-responsive material. As a result, the facile formation of multifunctional nanoparticles that combine all three mentioned features (shape anisotropy, internal morphology, and stimuli-responsiveness) remains a major challenge. NIH Public AccessHerein, we report the development of a facile and powerful new strategy for the preparation of functional particles that serves as a broad platform for nanoscale materials. Key to the success of this strategy is the use of functional surfactant mixtures to control the phase separat...

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A series of porous block copolymer (BCP) particles with controllable morphology and pore sizes was fabricated by tuning the interfacial behavior of BCP droplets in oil-in-water emulsions. A synergistic adsorption of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) BCPs and sodium dodecyl sulfate (SDS) to the surface of the emulsion droplet induced a dramatic decrease in the interfacial tension and generated interfacial instability at the particle surface. In particular, the SDS concentration and the P4VP volume fraction of PS-b-P4VP were key parameters in determining the degree of interfacial instability, leading to different types of particles including micelles, capsules, closed-porosity particles, and open-porosity particles with tunable pore sizes ranging from 10 to 500 nm. The particles with open-porosity could be used as pH-responsive, high capacity delivery systems where the uptake and release of multiple dyes could be achieved.

Functionalization of reactive precursor particles allows the preparation of amphiphilic nanogel libraries with tunable network hydrophobicity and comparable colloidal features.

Solution-exchange lithography is a new modular approach to engineer surfaces via sequential photopatterning. An array of lenses reduces features on an inkjet-printed photomask and reproduces arbitrarily complex patterns onto surfaces. In situ exchange of solutions allows successive photochemical reactions without moving the substrate and affords access to hierarchically patterned substrates.