Phase-separated and self-assembled co-network materials offer a simple route to bicontinuous morphologies, which are expected to be highly beneficial for applications such as ion, charge, and oxygen transport. Despite these potential advantages, the programmed creation of co-network structures has not been achieved, largely due to the lack of well-controlled chemistries for their preparation. Here, a thiol-ene end-linking platform enables the systematic investigation of phase-separated poly(ethylene glycol) (PEG) and polystyrene (PS) networks in terms of the molecular weight and relative volume fractions of precursor polymers. The ion conductivity and storage modulus of these materials serve as probes to demonstrate that both phases percolate over a wide range of compositions, spanning PEG volume fractions from ∼0.3-0.65. Small angle X-ray scattering (SAXS) shows that microphase separation of these co-networks yields disordered structures with d-spacings that follow d∼Mn0.5, for 4.8 kg/mol

Using ternary blends of polystyrene (PS), poly(methyl methacrylate) (PMMA), and Janus particles (JPs) with symmetric PS and PMMA hemispheres, we demonstrate the stabilization of dispersed and bicontinuous phase-separated morphologies by the interfacial adsorption of Janus particles during demixing upon solvent removal. The resulting blend morphology could be varied by changing the blend composition and JP loading. Increasing particle loading decreased the size of phase-separated domains, while altering the mixing ratio of the PS/PMMA homopolymers produced morphologies ranging from PMMA droplets in a PS matrix to PS droplets in a PMMA matrix. Notably, bicontinuous morphologies were obtained at intermediate blend compositions, marking the first report of highly continuous domains obtained through demixing in a polymer blend compatibilized by Janus particles. The JPs were found to assemble in a densely packed monolayer at the interface, allowing for the stabilization of bicontinuous morphologies in films above the glass transition temperature by inhibiting coarsening and coalescence of the phase-separated domains. The rate of solvent evaporation from the drop-cast films and the molecular weights of the homopolymers were found to greatly affect blend morphology. ■ INTRODUCTIONBlending immiscible polymers to produce materials that combine properties of the individual components is an appealing strategy to generate high-performance materials. If the polymer blends can be produced with bicontinuous morphologies, systems with useful transport properties 1,2 are enabled, and routes to mechanically reinforced soft, functional materials become possible. 3 Because of the inherent immiscibility of most polymer pairs, however, surface-active agents are often necessary to prevent macroscopic phase separation. These surfactants decrease interfacial tension and inhibit coalescence of domains by suppressing capillary bridge formation and providing steric stabilization, 4−6 thereby allowing control over the size scale and structure of the phase-separated morphology.Surfactants such as block copolymers (BCPs) and colloidal particles with homogeneous surface chemistry have received extensive attention as compatibilizers in polymer blends. Block copolymer compatibilizers are effective at hindering coarsening in blends with both dispersed and bicontinuous morphologies 7−10 and have also been used to create thermodynamically stable bicontinuous polymeric microemulsions. 11,12 The overall performance of a BCP compatibilizer involves striking a balance between its diffusion rate (i.e., its ability to reach the interface over the relevant time scale for coalescence of domains), tendency to form micelles, and ability to provide effective steric stabilization. Reactive compatibilization, wherein block copolymers are formed in situ at the interface via reaction of end groups, solves the problem of BCP micellization but adds complexity with respect to synthesis and processing. 13,14 Colloidal particles with homogeneous surface chemistry have a...

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We present a detailed study of the dynamics of cadmium sulfide nanoparticles suspended in polystyrene homopolymer matrices using X-ray photon correlation spectroscopy for temperatures between 120 and 180 °C. For low molecular weight polystyrene homopolymers, the observed dynamics show a crossover from diffusive to hyper-diffusive behavior with decreasing temperatures. For higher molecular weight polystyrene, the nanoparticle dynamics appear hyperdiffusive at all temperatures studied. The relaxation time and characteristic velocity determined from the measured hyper-diffusive dynamics reveal that the activation energy and underlying forces determined are on the order of 2.14 × 10 −19 J and 87 pN, respectively.

The static structure and dynamic behavior of cadmium sulfi de nanoparticles suspended in block copolymer matrix are investigated using transmission electron microscopy, small-angle X-ray scattering, and X-ray photon correlation spectroscopy. The transmission electron microscopy study shows that cadmium sulfi de nanoparticles are preferentially segregated within the polyisoprene domain of a poly(styrene-block -isoprene) diblock copolymer. For the dynamics study, X-ray photon correlation spectroscopy captures the relaxation process of cadmium sulfi de nanoparticles. The measured characteristic relaxation time reveals that the observed dynamics are hyperdiffusive. The characteristic velocity and corresponding activation energy, which are hallmarks of a hyperdiffusive system, are determined from the relationship between the characteristic relaxation time and the wavevector.the BCP provide a means to precisely control the spatial organization of the NPs. Theoretical investigations have suggested that a synergetic interaction between NPs and a self-organizing BCP matrix could produce hierarchically structured functional hybrid materials. [1][2][3] We refer to these nanocomposites as NP-BCPs. Such material design fl exibility is utilized to tune the electrical, [ 4 ] magnetic, [ 5 ] or biomedical [ 6 ] properties of targeted NP-BCPs. Despite recent progress on the fabrication techniques and contemporary applications of NP-BCPs, the equilibrium state and structural dynamics of these materials still remains poorly understood. This is in part because NP-BCPs compound the diffi culties caused by the entropic and enthalpic interactions between NPs and the BCP domain. In addition, many of the key methods for structural elucidation are less useful for characterizing dynamic behavior.The unique self-assembling features of the BCP can be used to synthesize NPs. Specifi cally, poly(styrene-block -2 vinylpyridine) (S2VP) or poly(styrene-block -4 vinylpyridine) (S4VP), which are solvent-selective diblock copolymers, provide a micellar structure for metal/semiconductor