Synthesis and application of new polymers for agriculture : pesticide formulation

The objective of this work was to synthesise potential polymeric materials to use in agricultural applications, particularly as pesticide carriers. Synthesis of solid microcapsules, which contain hydrophobic pesticides, from functional polymers, was the primary goal. In addition, promising materials such as poly(dimethylsiloxane) (PDMS) and acid-labile containing polymers were also explored. The extraordinary reactivity of isocyanates towards nucleophiles offers an interesting synthetic tool as a catalyst-free reaction. Unfortunately, the high reactivity of isocyanate during the polymerisation process is a major concern, thus a facile approach in order to synthesise stable functional polymer was first investigated. Chapter 2 details the synthesis of two types of isocyanate side chain containing copolymers, poly(methyl methacrylate-co-isocyanatoethyl methacrylate) (P(MMAm-co-IEMn)) and poly(benzyl methacrylate-co-isocyanatoethyl methacrylate) P(BnMAm-co-IEMn), via Cu(0)-mediated controlled radical polymerisation. Both copolymers were functionalised with dibutylamine, octylamine, and (R)-(+)-α-methylbenzylamine, which further proved the successful incorporation of the isocyanate groups. Subsequently, P(BnMAm-co-IEMn) was used for the fabrication of liquid core microcapsules via an oil-in-water interfacial polymerisation with diethylenetriamine as a crosslinker. Furthermore, chapter 3 illustrates the synthetic route of solid microcapsules containing hydrophobic pesticides; this illustrates the incorporation of biodegradable materials, modern controlled radical polymerisation techniques and isocyanate chemistry. An α, ω-poly (ɛ-caprolactone) SET-LRP initiator is first prepared by esterification to obtain a degradable halide initiator. Subsequently, biodegradable P(BnMAn-co-IEMn) was polymerised via the conditions from chapter 2. An isocyanate-containing copolymer was used to fabricate a microcapsule which consists of imidacloprid (IMI), followed by water removal via spray dryer. Chapter 4 details an efficient tool to synthesise an amphiphilic copolymer containing PDMS. The versatility of hydrosilylation has been exploited for the preparation of an ABA block copolymer of PDMS and poly(ethylene glycol) methacrylate (PEGMA), which can be potentially used to prepare polymeric micelles. Also, to demonstrate the adaptability of this method, different methacrylates and vinyl terminated methacrylic macromonomers were applied to modified hydride terminated PDMS. Finally, the α, ω-hydroxyl terminated poly(acetal) SET-LRP initiator was synthesised from the condensation and esterification reaction. A favourable Cu(0)-mediated controlled radical polymerisation and degradation under an acidic conditions of acetal initiator was affirmed. Thus, this offers a great opportunity of using this initiator to synthesise isocyanate-containing copolymers, certainly, an acid-labile microcapsule to use as an agrochemical carrier is potentially achievable

Polyurea microcapsules from isocyanatoethyl methacrylate copolymers

The synthesis of two types of isocyanate side chain containing copolymers, poly(methyl methacrylate-co-isocyanatoethyl methacrylate) (P(MMA-co-IEM)) and poly(benzyl methacrylate-co-isocyanatoethyl methacrylate) (P(BnMA-co-IEM)), which were synthesized by Cu(0)-mediated radical polymerization, is reported. Polymerization proceeded to high conversion giving polymers of relatively narrow molar mass distributions. The incorporation of the bulky aromatic groups in the latter copolymer rendered it sufficiently stable toward hydrolysis and enabled the isolation of the product and its characterization by 1 H and 13C NMR, and FTIR spectroscopy and SEC. Both P(MMA-co-IEM) and P(BnMA-co-IEM) were functionalized with dibutylamine, octylamine, and (R)-(1)-a-methylbenzyl-amine, which further proved the successful incorporation of the isocyanate groups. Furthermore, P(BnMA-co-IEM) was used for the fabrication of liquid core microcapsules via oil-in-water interfacial polymerization with diethylenetriamine as crosslinker. The particles obtained were in the size range of 10–90 mm in diameter independent of the composition of copolyme

Cu(0)-RDRP of methacrylates in DMSO: importance of the initiator

The controlled radical polymerization of methacrylates via Cu(0)-mediated RDRP is challenging in comparison to acrylates with most reports illustrating higher dispersities, lower monomer conversions and poorer end group fidelity relative to the acrylic analogues. Herein, we present the successful synthesis of poly(methyl methacrylate) (PMMA) in DMSO by judicious selection of optimal reaction conditions. The effect of the initiator, ligand and temperature on the rate and control of the polymerization is investigated and discussed. Under carefully optimized conditions enhanced control over the molecular weight distributions is obtained furnishing methacrylic polymers with dispersities as low as 1.10, even at very high conversions. A range of methacrylates were found to be tolerant to the optimized polymerization conditions including hydrophobic, hydrophilic and functional methacrylates including methyl and benzyl methacrylate, ethylene glycol methyl ether methacrylate and glycidyl methacrylate. The control retained during the polymerization is further highlighted by in situ chain extensions yielding well-defined block polymethacrylates

Polymerisation of 2-acrylamido-2-methylpropane sulfonic acid sodium salt (NaAMPS) and acryloyl phosphatidylcholine (APC) via aqueous Cu(0)-mediated radical polymerisation

The scope of aqueous Cu(0)-mediated living radical polymerisation has been expanded with the preparation of poly(2-acrylamido-2-methylpropane sulfonic acid sodium salt (P(NaAMPS)) and poly(acryloyl phosphatidycholine) (PAPC). Manipulation of the reaction conditions furnishes polymers capable of undergoing chain extension and supporting the synthesis of block copolymers at 0 °C

Absolut “copper catalyzation perfected”; robust living polymerization of NIPAM : Guinness is good for SET-LRP

The controlled polymerization of N-isopropyl acrylamide (NIPAM) is reported in a range of international beers, wine, ciders and spirits utilizing Cu(0)-mediated living radical polymerization (SET-LRP). Highly active Cu(0) is first formed in situ by the rapid disproportionation of [Cu(I)(Me6-Tren)Br] in the commercial water–alcohol mixtures. Rapid, yet highly controlled, radical polymerization follows (Đ values as low as 1.05) despite the numerous chemicals of diverse functionality present in these solvents e.g. alpha acids, sugars, phenols, terpenoids, flavonoids, tannins, metallo-complexes, anethole etc. The results herein demonstrate the robust nature of the aqueous SET-LRP protocol, underlining its ability to operate efficiently in a wide range of complex chemical environments

Faculty Guide Committee -- Interpretation of Article 10.3.c.10

Hydrosilylation is a well-established reaction for the preparation of organo-silicon compounds, in which vinyl groups react with silanes (Si–H) usually catalysed by late transition metal complexes, most often Pt(II) complexes. Hydrosilylation of functional methacrylates provides access to functional poly(dimethylsiloxane)s (PDMS), from appropriate hydride terminated and functional PDMS, in very high yielding reactions without the formation of any side products, odour and without the need for labor-intensive purification. Herein, commercially available telechelic PDMS hydrides (h2PDMS) have been modified with a range of different methacrylates using very low catalytic amounts of commercial Pt(II) catalysts. The products have been characterized by 1H and 13C NMR, SEC, IR and MALDI-ToF MS demonstrating high selectivity and very high reaction yields. The versatility of hydrosilylation has been exploited for the preparation of ABA triblock copolymers using poly(ethylene glycol) methacrylate and more structurally demanding vinyl terminated methacrylic macromonomers as obtained by catalytic chain transfer polymerization (CCTP). 1H NMR revealed the formation of solely anti-Markovnikov products and the high tolerance of the reaction towards other functionalities, such as epoxides present in glycidyl methacrylate. The specific Si–H signals in 1H NMR (4.8 ppm) and IR (2126 cm−1) from the Si–H group allow for facile monitoring of the progress of the reaction. SEC and MALDI-ToF MS investigations further highlighted the formation of well-defined polymer systems with near perfectly matching molecular compositions

Absolut “copper catalyzation perfected”; robust living polymerization of NIPAM: Guinness is good for SET-LRP

The controlled polymerization of N-isopropyl acrylamide (NIPAM) is reported in a range of international beers, wine, ciders and spirits utilizing Cu(0)-mediated living radical polymerization (SET-LRP). Highly active Cu(0) is first formed in situ by the rapid disproportionation of [Cu(I)(Me6-Tren)Br] in the commercial water–alcohol mixtures. Rapid, yet highly controlled, radical polymerization follows (Đ values as low as 1.05) despite the numerous chemicals of diverse functionality present in these solvents e.g. alpha acids, sugars, phenols, terpenoids, flavonoids, tannins, metallo-complexes, anethole etc. The results herein demonstrate the robust nature of the aqueous SET-LRP protocol, underlining its ability to operate efficiently in a wide range of complex chemical environments.ISSN:1759-9962ISSN:1759-995