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Hydrogen-bonded complexation between high-molecular-weight poly(N-vinylpyrrolidone) (PVP, = 650 kDa) and poly(acrylic acid) (PAA) with weight-average molar weights between 0.9 and 50 kDa, is studied in dilute, salt-free aqueous solution. The onset of complexation, aggregation, and the structure of the formed particles are strongly influenced by PAA molecular weight, solution composition, and the method of sample preparation. With increasing poly(acrylic acid) chain length, IPCs show higher stability against aggregation. IPCs based on high-molecular-weight PAA show core-corona architecture ensuring good sterical stabilization, whereas for those containing the shortest polyacid a loose soft-sphere structure without distinct borders of different chain densities is found.

pH-sensitive PVP–PAA hydrogels have been prepared by electron-beam-induced irradiation at pH close to pKa of carboxylic groups. Protonation of these groups promoted the formation of hydrogen bonds between the PAA and PVP segments within the crosslinked structure and caused interpolymer complex formation. To demonstrate possible future application of such gels, we tested them as simple chemical detectors. When loaded with glucose oxidase, the PAA–PVP gel's turbidity and shrinkage was triggered by the presence of glucose due to a drop in pH caused by the enzymatic reaction.

Porous coordination polymers, in particular flexible porous coordination polymer networks that change their network structure on guest adsorption, have enormous potential in applications involving selective storage, separation and sensing. Despite the expected significant differences in their adsorption properties, porous coordination polymer nanocrystals remain largely unexplored, and there have been no reports about studies on flexible porous coordination polymer nanocrystals, mainly due to a lack of preparation methods. Here, we present a new technique for the rapid preparation of porous coordination polymer nanocrystals that combines non-aqueous inverse microemulsion with ultrasonication. Uniform nanocrystals of {[Zn(ip)(bpy)]}(n) (ip = isophthalate, bpy = 4,4'-bipyridyl; CID-1), a flexible porous coordination polymer, have been prepared by this method and analysed using field-emission scanning electron microscopy, energy-dispersive X-ray analysis, infrared spectroscopy, Raman spectroscopy and X-ray powder diffraction. A model for particle formation and growth is presented and discussed. Adsorption experiments with methanol show that the overall adsorption capacities of nanoparticles and bulk are almost identical, but the shapes of the sorption isotherms differ significantly and the adsorption kinetics increase dramatically.

High-molecular-weight polymers with defined architectures are generally prepared by atom transfer radical polymerization. In order to prepare biodegradable structures different polymerization techniques have to be used. Here we present the successful synthesis of biodegradable starlike poly(glycidol-graft-ϵ-caprolactone) copolymers by a combination of anionic and coordinative ring-opening polymerization, their characterization by static and dynamic light scattering and their visualization by scanning force microscopy.

Pluronic F127, a tri-block copolymer of poly(ethylene oxide) and poly(propylene oxide) of a nominal formula EO100-PO65-EO100, when subjected to the action of ionizing radiation in oxygen-free, N2O-saturated aqueous solution, undergoes predominantly cross-linking by intermolecular recombination of polymer-derived radicals. This manifests itself as an increase in average molecular weight and, at sufficiently high doses, as a formation of permanent hydrogel. Cross-linking occurs with high yields. Side reactions include chain scission and traces of oxidation processes. Polymer concentration and temperature influence the yields of radiation-induced reactions. This indicates that radiolysis mechanism depends on the spatial arrangement of Pluronic molecules, which can be organized into single chains, micelles, and physical gel. Macroscopic hydrogels of Pluronic are thermo-sensitive (phase transition temperature behavior with the transition temperature, at the tested conditions, of ca. 27 °C). Pluronic gels are prone to oxidative degradation, both in an aqueous environment and in the dry state, especially at elevated temperatures. Copyright © 2006 John Wiley & Sons, Ltd.

Interpolymer complexes were obtained using high-molecular-weight polyvinylpyrrolidone and oligomeric poly(acrylic acid) as substrates. Turbidimetric and viscometric studies indicate that complexation is most pronounced at a molar PAA fraction of ca. 0.8, and that the critical pH values for complex formation are in the range 3.7–4.0, depending on the molar ratios of components. Irradiation of PAA–PVP complex structures by pulses of fast electrons in dilute, deoxygenated solutions induces intramolecular (intra-complex) cross-linking, evidenced by decrease in viscosity and radius of gyration, leading to the formation of permanent PAA–PVP nanogels.