Sterically Stabilized Diblock Copolymer Nanoparticles Enable Convenient Preparation of Suspension Concentrates Comprising Various Agrochemical Actives

Abstract

It is well known that sterically stabilized diblock copolymer nanoparticles can be readily prepared using polymerization-induced self-assembly. Recently, we reported that such nanoparticles can be employed as a dispersant to prepare micron-sized particles of a widely used fungicide (azoxystrobin) via ball milling. In the present study, we examine the effect of varying the nature of the steric stabilizer block, the mean nanoparticle diameter, and the glass transition temperature ( T g ) of the core-forming block on the particle size and colloidal stability of such azoxystrobin microparticles. In addition, the effect of crosslinking the nanoparticle cores is also investigated. Laser diffraction studies indicated the formation of azoxystrobin microparticles of approximately 2 μm diameter after milling for between 15 and 30 min at 6000 rpm. Diblock copolymer nanoparticles comprising a non-ionic steric stabilizer, rather than a cationic or anionic steric stabilizer, were determined to be more effective dispersants. Furthermore, nanoparticles of up to 51 nm diameter enabled efficient milling and ensured overall suspension concentrate stability. Moreover, crosslinking the nanoparticle cores and adjusting the T g of the core-forming block had little effect on the milling of azoxystrobin. Finally, we show that this versatile approach is also applicable to five other organic crystalline agrochemicals, namely pinoxaden, cyproconazole, difenoconazole, isopyrazam and tebuconazole. TEM studies confirmed the adsorption of sterically stabilized nanoparticles at the surface of such agrochemical microparticles. The nanoparticles are characterized using TEM, DLS, aqueous electrophoresis and 1 H NMR spectroscopy, while the final aqueous’ suspension concentrates comprising microparticles of the above six agrochemical actives are characterized using optical microscopy, laser diffraction and electron microscopy.

Efficient Synthesis of Hydrolytically Degradable Block Copolymer Nanoparticles via Reverse Sequence Polymerization‐Induced Self‐Assembly in Aqueous Media

“…Optical microscopy studies confirmed a substantial reduction in mean particle size (Figures 9a and 9b) while laser diffraction studies indicated that the final azoxystrobin microparticles had a mean diameter of 2.0 μm (Figure 9c). These observations are very similar to those obtained when using non‐degradable methacrylic nanoparticles as a dispersant [10,11] . In principle, such hydrolytically degradable nanoparticles could be used to prepare more environmentally‐friendly next‐generation agrochemical formulations.…”

“…Unfortunately, this precludes their use for this agrochemical application and is also problematic for other potential applications in personal care and cosmetics formulations. Nevertheless, in a follow‐up study we established the fundamental design rules for using nanoparticle dispersants in the context of various agrochemical compounds (including five fungicides and a pesticide) [10,11] . Bearing the latter results in mind, we decided to evaluate the new hydrolytically degradable PDMAC 30 ‐PCL 16 ‐PDMAC 30 nanoparticles as a dispersant for azoxystrobin.…”

Amphiphilic Polymers for Color Dispersion: Toward Stable and Low-Viscosity Inkjet Ink

“…The self-organizing behaviors of amphiphilic polymers have attracted considerable attention in polymer chemistry, , supramolecular chemistry, − and biochemistry. − Moreover, the application of amphiphilic polymers in the industry has recently become an important subject. For example, amphiphilic polymers have been utilized as dispersants − of nanoparticles. Recent progress in the use of amphiphilic polymers can be found in the effective dispersion of colorants in aqueous media .…”

Efficient Synthesis of Hydrolytically Degradable Block Copolymer Nanoparticles via Reverse Sequence Polymerization‐Induced Self‐Assembly in Aqueous Media

“…fundamental design rules for using nanoparticle dispersants in the context of various agrochemical compounds (including five fungicides and a pesticide). [10,11] Bearing the latter results in mind, we decided to evaluate the new hydrolytically degradable PDMAC 30 -PCL 16 -PDMAC 30 nanoparticles as a dispersant for azoxystrobin.…”