Synthesis and thermal properties of linear amphiphilic diblock copolymers of L-lactide and 2-dimethylaminoethyl methacrylate

in Macromolecules (2011), 44(13), 5209-5217

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA ... [more ▼]

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA using 4-isopropylbenzyl alcohol and tin octoate as the initiating system, conversion of the OH-terminated PLLA into Br-terminated macroinitiators (5, 13, and 19 kg/mol), followed by atom transfer radical polymerization of DMAEMA (to obtain one-half, equal, and twice the molecular weight of each PLLA block). Compositional analysis and molecular weight characterization were done using NMR, SEC–LS, TGA, polarimetry, and PDMAEMA quaternization/precipitation to test for residual PLLA homopolymer. DSC investigations indicate that low molecular weight amorphous PLLA or PDMAEMA blocks (less than or equal to ca. 5000 g/mol) are miscible in the second block. Compared to the parent PLLA homopolymers, PLLA crystallization in the block copolymers is significantly retarded, whereas the degree of crystallinity is only mildly affected and melting points are reduced only for the low molecular weight miscible blocks. [less ▲]

Synthesis ans structural studies of a new class of heterocyclic compounds: 1,2,4-pyridothiadiazine 1,1-dioxides, pyridyl analogues of 1,2,4-benzothiadiazine 1,1-dioxides

in Tetrahedron (1995), 51

Synthesis by sol-gel process of visible light sensitive-TiO2 for the degradation of pollutants and microorganisms

Poster (2011)

Since the discovery of photocatalytic decomposition of water on TiO2 electrodes by Fujishima and Honda [1], heterogenous photocatalysis has been widely studied for environmental applications ... [more ▼]

Since the discovery of photocatalytic decomposition of water on TiO2 electrodes by Fujishima and Honda [1], heterogenous photocatalysis has been widely studied for environmental applications. Photocatalytic processes are new technologies for waste water treatment because new compounds (alkanes, pesticides, dyes, etc.) in effluents are not readily degraded by the conventional treatments [2]. Oxidative processes can completely destroy organic pollutants [3] or microorganisms (bacteria, viruses, fungi, etc.) [4,5]. At this moment, the commercial Degussa P25 is the mostly used photocatalyst. Nevertheless, it requires UV light to be activated, that is why scientists try to activate TiO2 under visible light. The aim of this study is to synthesize photocatalysts activated by visible light and to evaluate their activity for the degradation of pollutants and microorganisms. The sol-gel process allows the direct introduction of visible light sensitive species like porphyrins inside the TiO2 matrix during the synthesis [6]. Two tetracarboxyphenyl porphyrins are synthesized for the sensitization of TiO2 to visible light : the metal free tetracarboxyphenyl porphyrin and the nickel tetracarboxyphenyl porphyrin. These porphyrins are characterized by 1H NMR, FT-IR and UV/Vis spectroscopies. They are introduced during the sol-gel synthesis of TiO2 matrix. Diffuse reflectance and FT-IR spectroscopies are used to ensure that porphyrins are incorporated inside the matrix of TiO2. Indeed, characteristic porphyrins peaks appear on spectra. The cristallinity and specific surfaces of catalysts are also determined by XRD and nitrogen adsorption-desorption measurements respectively. The depolluting efficiency of photocatalysts is evaluated for the degradation in water of p-nitrophenol, which is listed as one of the 114 organic pollutants by the Environmental Protection Agency in the US. After 6 h under visible light, 40 % of p-nitrophenol are degraded with some catalysts. The activity is influenced by i) the presence of porphyrins : the photoactivity increases with the amount of porphyrins ; ii) the nature of porphyrins : nickel porphyrins are more active than free metal porphyrins ; and iii) the crystallinity of catalysts : amorphous catalysts are less active than crystallized samples. The photocatalysts with the highest degradation rating of dyes will be selected for the degradation in water of Escherichia coli and Lactobacillus acidophilus. [1] A. Fujishima, K. Honda, Nature 238, 37-38 (1972) [2] P. Gogate, A. Pandit, Advances in Environmental Research 8, 501-551 (2004). [3] D. Chen, A. Ray, Water Research 32, 3223-3234 (1998) [4] R. Watts, S. Kong, M. Orr, G. Miller, B. Henry, Water Research 29, 95-100 (1995). [5] J. Hong, M. Otaki, Journal of Bioscience and Bioengineering 101, 185-189 (2006). [6] C. Wang, J. Li, G. Mele, G.M. Yang, F.-X. Zhang, L. Palmisano, G. Vasapollo, Applied catalysis 78, 218-226 (2007). [less ▲]

Synthesis of (Na1-xLix)MnFe3+2(PO4)3 (with x = 0 to 1) compounds with the alluaudite structure type : the crystallochemical role of lithium

in Terra Nova (1998), 10

Synthesis of 1-vinyl-3-ethylimidazolium-based ionic liquid (co)polymers by cobalt-mediated radical polymerization

in Macromolecules (2011), 44(16), 6397-6404

The cobalt-mediated radical polymerization (CMRP) of 1-vinyl-3-ethylimidazolium bromide (VEtImBr) is described. Polymerizations were performed at 30 °C in solution either in dimethylformamide (DMF) or in ... [more ▼]

The cobalt-mediated radical polymerization (CMRP) of 1-vinyl-3-ethylimidazolium bromide (VEtImBr) is described. Polymerizations were performed at 30 °C in solution either in dimethylformamide (DMF) or in methanol (MeOH) or in a mixture of both solvents, using a preformed alkyl–cobalt(III) adduct, CH3OC(CH3)2CH2–C(CH3)(CN)–(CH2–CHOAc)<4–Co(acac)2, as the mediating agent. Excellent control over molecular weights and dispersities (Mw/Mn 1.05–1.06) was achieved in MeOH, with a linear increase of experimental molecular weights with the monomer conversion. Substituting methanol for DMF induced much faster polymerization process, even under quite high diluted conditions: for instance, about 80% monomer conversion was reached in 30 min in DMF, compared to 10 h in MeOH. However, size exclusion chromatography (SEC) traces of PVEtImBr samples synthesized in DMF revealed a side population in the high molecular weight region, presumably due to the occurrence of irreversible coupling reactions of a small proportion of growing chains. Well-defined diblock copolymers featuring both a poly(vinyl acetate) (PVAc) block and a PVEtImBr-based poly(ionic liquid) block, PVAc-b-PVEtImBr, were next obtained by sequential CMRP of VAc and VEtImBr. To this end, a PVAc-Co(acac)2 was first prepared by CMRP and employed as a macroinitiator for the polymerization of VEtImBr either in methanol or in a mixture of DMF and MeOH (2/1: v/v) at 30 °C. Finally, cobalt-mediated radical coupling (CMRC) of the aforementioned PVAc-b-PVEtImBr diblock copolymers, using isoprene as a simple coupling agent, led to unprecedented and structurally well-defined PVAc-b-PVEtImBr-b-PVAc triblock copolymers. [less ▲]

Synthesis of 2-aminoquinazoline-4(3H)-one derivatives as potential potassium channel openers

in Journal of Heterocyclic Chemistry (2000), 37

The synthesis of 6-[18F]fluoro-L-dopa by chiral catalytic phase-transfer alkylation.

in Journal of Labelled Compounds & Radiopharmaceuticals (1999), 42

Synthesis of [18F]4-(4-fluorophenyl)-1,2,4-triazole-3,5-dione: an agent for specific radiolabelling of tyrosine.

in Flagothier, Jessica (Ed.) Journal of Labelled Compounds and Radiopharmaceuticals (2013, May 14)

Objectives: Metal-free and mild tyrosine modification reactions are an attractive alternative to the commonly used lysine and cysteine modification protocols for peptide and proteins labelling. Recently ... [more ▼]

Objectives: Metal-free and mild tyrosine modification reactions are an attractive alternative to the commonly used lysine and cysteine modification protocols for peptide and proteins labelling. Recently, Ban and co-workers have reported a tyrosine bioconjugation through ene-type reactions. Cyclic diazodicarboxamides, which are electrophilic compounds, react selectively in o-position on the phenol side chain of tyrosine in mild aqueous conditions and the 1,2,4-triazolidine-3,5-dione linkage is hydrolytically and thermally stable. We herein present the synthesis of [18F]4-(4-fluorophenyl)-1,2,4-triazole-3,5-dione and the coupling with N-acyl tyrosine methylamide. Methods: The N,N,N-trimethyl-4-nitrobenzeneammonium trifluoromethanesulfonate 1 was prepared following a procedure previously reported [2]. The [18F]prosthetic group 6, [18F]4-(4-fluorophenyl)-1,2,4-triazole-3,5-dione, was synthesized in five steps. Results: The synthesis of the [18F]prosthetic group has been realized with a decay-corrected radiochemical yield of 20% in 90 minutes. The radiochemical yield of the coupling with N-acyl tyrosine methylamide is 40% (DC). This presented synthetic pathway should be easily automated: particulary because the purifications between the different steps are exclusively done on SPE cartridges. Conclusions: We successfully developed an efficient bioconjugation method for fluorine-18 labelling of tyrosine without prior modifications of the peptide in very mild conditions. [less ▲]

Synthesis of [18F]fluorinated a-methyl-a-amino acids by phase transfer catalysis for potential PET application.

in Journal of Labelled Compounds & Radiopharmaceuticals (2003), 46

Synthesis of a fluorinated analogue of L-threo-3-(3,4-dihydroxyphenyl)serine: 6-fluoro-L-threo-DOPS.

in Journal of Labelled Compounds & Radiopharmaceuticals (1997), 40