We have found that not only block copolymers but also ionomers can self-assemble in a selective solvent to form surfactant-free nanoparticles. The self-assembly can be induced by chemical reaction, polymer-polymer complexation, and microphase inversion in addition to the temperature. A recently developed microwave method for the preparation of uniform surfactant-free polymeric nanoparticles is also reviewed. Our results have revealed that for a given dispersion, the particle surface area occupied per stabilizer (surfactant, polymer chains, and ionic groups) is close to a constant.

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A slow‐release and superabsorbent nitrogen fertilizer (SSNF) was synthesized by aqueous solution copolymerization of acrylic acid and maleic anhydride using N,N′‐methylene bisacrylamide as a crosslinker, ammonium persulfate and sodium sulfite as an initiator in the presence of urea. The effects on water absorbency such as amount of crosslinker, initiator, urea and maleic acid, degree of neutralization, etc. were investigated. To improve slow release and water retention properties, the product was surface‐crosslinked with trihydroxymethyl propane glycidol ether (6360). The nitrogen content of the SSNF synthesized under optimal conditions was 28.5%, and the water absorbencies were about 900 (g/g) in distilled water and 180 (g/g) in tap water. The nitrogen slow release behavior of the SSNF in water and water retention capacity of the soil with SSNF were also investigated. The results showed that the surface‐crosslinked product not only had good slow release property but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. The results of the present work indicated that the SSNF could be found an application in agriculture and horticulture, especially in drought‐prone areas where the availability of water is insufficient. Copyright © 2006 John Wiley & Sons, Ltd.

A superabsorbent, slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea. The polymer was characterized using infrared spectral analysis, and network structural parameters such as molecular weight between crosslinks (Mc) and crosslink density (q) were calculated. The effects of reaction conditions, such as reaction time, reaction temperature, initiator, crosslinker and the degree of neutralization of acrylic acid, on water absorbency were investigated. The nitrogen content of SSRNF synthesized under optimal conditions was 22.7%, and the water absorbencies were about 965 g g−1 in distilled water and 185 g g−1 in tap water. The nitrogen slow release behaviors of the SSRNF in water and water retention capacity of soil with the SSRNF were also investigated. A possible slow release mechanism was proposed and the release rate constant K and the diffusion coefficient D of urea in the hydrogel was calculated. The results showed that the product not only had good slow release properties but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. Therefore, the SSRNF is a multifunctional water managing material, which would find application in agriculture and horticulture, especially in drought‐prone areas where the availability of water is limited. Copyright © 2006 Society of Chemical Industry

We present a combined 1H-NMR and small angle neutron scattering in situ study of the anionic polymerization of butadiene using t-butyllithium as the initiator. Both initiation and propagation phases were explored. This combined approach allows the structural and kinetic characteristics to be accessed and cross compared. The use of the D22 instrument (ILL Grenoble) permits the attainment of Q approximately equal to 2 x 10(-3) A. This, in turn, led to the identification of coexisting large-scale and smaller aggregates during all stages of the polymerization. The smaller aggregates contain most of the reacted monomers. Their structure changes from high functionality wormlike chains at early stages of the reaction to starlike aggregates where the crossover occurs at a degree of polymerization of approximately equal to 40. The initiation event involved these small, high functionality (approximately equal to 120) aggregates that apparently consisted of cross-associated t-butyllithium with the newly formed allylic-lithium head groups. As the initiation event progressed the initiation rate increased while the functionality of these small aggregates decreased and their size increased. Propagation, in the absence of initiation, was found to have a rate constant that was molecular weight dependent. At approximately 11 kg/mol the measured polymerization rate was found to increase while no further structural changes were seen.

ABSTRACT:To improve the utilization of fertilizer and water resource at the same time, a new type of slow-release fertilizer with superabsorbent and moisture preservation was developed, with the combination of slow-release technique and superabsorbent polymers. The coatings were formed by the inverse phase polymerization technique. The element analysis results showed that the product contained 22.58% nitrogen element, and the water absorbency of the product was 94 times its own weight if it was allowed to swell in tap water at room temperature for 2 h. The results of the slow-release behavior of N and the water absorbency and retention properties in soil showed that the product not only had good slow-release property but also had excellent water absorbency and water retention capacity, which was a significant advantage over the normal slow-release or controlled-release fertilizers. The effects of the amount of initiator, crosslinker, reaction time, and the degree of neutralization of acrylic acid on water absorbency were investigated and optimized. At the same, a rather new and simple method was used to make homogeneous urea-formaldehyde granules.

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