We systematically investigated the structure formation pathways and transient morphologies involved in the formation of mesoporous membranes by the self-assembly of block copolymers during nonsolvent-induced phase separation. Using AFM, SEM, and in situ synchrotron SAXS, we mapped the topological paths and characteristic transient structures into a ternary phase diagram. We focused on the stability region of an ordered pore phase which is relevant for the generation of integral asymmetric isoporous membranes. We could identify several characteristic morphologies, i.e., spinodal networks, sphere percolation networks, ordered pore structures, and disordered and ordered cylinder arrangements together with transient structures connecting their stability regions. With given evaporation rates for the pure solvents, we calculated the corresponding composition trajectories in the phase diagram to identify suitable experimental conditions in terms of initial polymer volume fraction, solvent composition, and immersion time to trap the desired pore structure.

Amphiphilic diblock copolymers can spontaneously form integral asymmetric isoporous membranes by evaporation-induced self-assembly. The critical structural evolution steps occur within the first hundred seconds after solvent casting. By using synchrotron X-ray scattering employing a specially designed solvent casting apparatus, we were able to follow the kinetics of the structural evolution in situ. At an initial time of 20 s after solvent-casting we observe the first structural features on length scales d of 30−70 nm, signaled by a weak maximum in the low-q region of the measured scattering curves. During the subsequent period the length scales increase continuously until after around 100 s they reach a plateau value d ∞ of 80−120 nm, the size depending on the molecular weight of the block copolymer. Interestingly, the time evolution of the characteristic length scales follow a simple exponential saturation curve for all block copolymers, irrespective of molecular weight, composition, and addition of ionic additives, in agreement with theoretical models on two-dimensional ordered block copolymer domain formation. In addition, we could show that immersion in water during solvent evaporation leads to a nearly instantaneous increase of the characteristic length scale to its plateau value. The addition of salts such as Cu 2+ leads to compaction of the structures with smaller characteristic length scales, but still following the same kinetic evolution.

Polymer nanocomposites for optical applications require high optical transparency at high filling ratios of nanoparticles. The nanoparticles provide optical functionality but unfortunately have a strong tendency to aggregate in polymer matrices leading to strong turbidity and reduced optical transmission, particularly at high filling ratios. We report a general route to nonaggregated highly filled, optically transparent polymer nanocomposites. It is based on using nanoparticles that have been coated with polymers forming spherical brushlike layers providing thermodynamic miscibility with the polymer matrix over the complete range of nanoparticle volume fractions. The polymers are attached via a versatile ligand exchange procedure which enables to prepare a wide range of optically transparent polymer nanocomposites up to weight fractions of 45%. This is demonstrated for a broad range of metal and semiconductor nanoparticles in optically transparent polymer matrices relevant for selective light/UV absorption, photoluminescence, and high/low refractive index polymer materials. ■ INTRODUCTIONPolymer nanocomposites are currently of immense interest in fundamental research as well as in a large variety of industrial applications. Nanoparticles provide new or largely enhanced material properties, but unfortunately their agglomeration mostly prevents these enhancements and often deteriorates material properties. Therefore, generally less than 5−10 wt % of nanoparticles can be dispersed into polymer matrices without sacrificing material properties by aggregation. 1 Promising experimental studies 2 and theoretical investigations 3 have been reported to understand or control nanoparticle aggregation. This is a critical issue especially for optical applications that take advantage of the optical properties of nanoparticles. These are integrated into transparent polymers for ease of processing and protection, 4 but often at the cost of agglomeration which causes turbidity and strongly reduces optical transmission and efficiency.Since the first reports of polymer−gold nanocomposites for optical applications, 5,6 nanocomposites consisting of inorganic metal or semiconducting nanoparticles and transparent polymer matrices have been continuously investigated toward applications based on selective light absorption in the UV/vis range, photoluminescence, and high/low refractive index polymeric materials. For nanocomposites used as UV-photoprotective materials, high transparency in the visible range and steep absorption in the near UV-range (λ < 400 nm) are required. The most promising inorganic materials are ZnO and TiO 2 nanoparticles, which have bulk band gap energies of around 3 eV. These nanoparticles are preferably incorporated into poly(methyl methacrylate) (PMMA) or other transparent polymer matrices. 7−9 For photoluminescent materials, semiconductor nanoparticles are particularly attractive, since they show wavelength-tunable light emission due to the quantum size effect and possess high photostability and a narrow emission...

There are various methods to synthesize superparamagnetic nanoparticles (SPIONs) useful for MPI (magnetic particle imaging) and in therapy (Hypothermia) such as co-precipitation, hydrothermal reactions etc. In this research, the focus is to analyse the effects of crucial parameters such as effect of molecular mass of dextran and temperature of the co-precipitation. These parameters play a crucial role in the inherent magnetic properties of the resulting SPIONs. The amplitude spectrum and hysteresis curve of the SPIONs is analysed with MPS (magnetic particle spectrometer). PCCS (photon cross-correlation spectroscopy) measurements are done to analyse the size distribution of hydrodynamic diameter the resulting SPIONs.