Trichloroacetyl Groups Research Articles

Straightforward synthesis of complex polymeric architectures with ultra-high chain density.

Synthesis of complex polymeric architectures (CPAs) via reversible-deactivation radical polymerization (RDRP) currently relies on the rather inefficient attachment of monofunctional initiation/transfer sites onto CPA precursors. This drawback seriously limits the overall functionality of the resulting (macro)initiators and, consequently, also the total number of installable polymeric chains, which represents a significant bottleneck in the design of new polymeric materials. Here, we show that the (macro)initiator functionality can be substantially amplified by using trichloroacetyl isocyanate as a highly efficient vehicle for the rapid and clean introduction of trichloroacetyl groups (TAGs) into diverse precursors. Through extensive screening of polymerization conditions and comprehensive NMR and triple-detection SEC studies, we demonstrate that TAGs function as universal trifunctional initiators of copper-mediated RDRP of different monomer classes, affording low-dispersity polymers in a wide molecular weight range. We thus unlock access to a whole new group of ultra-high chain density CPAs previously inaccessible via simple RDRP protocols. We highlight new opportunities in CPA synthesis through numerous examples, including the de novo one-pot synthesis of a novel "star-on-star" CPA, the preparation of β-cyclodextrin-based 45-arm star polymers, and facile grafting from otherwise problematic cellulose substrates both in solution and from surface, obtaining effortlessly ultra-dense, ultra-high-molecular weight bottle-brush copolymers and thick spatially-controlled polymeric coatings, respectively.

Hybrid polyacrylamide chiral stationary phases for HPLC prepared by surface-initiated photopolymerization

Two hybrid polyacrylamide chiral stationary phases (CSPs) for HPLC have been synthesized by a new surface-initiated photo-induced radical polymerization approach of enantiopure N,N'-diacryloyl derivatives of (1R,2R)-diaminocyclohexane (CSP1) and (1R,2R)-diphenylethylenediamine (CSP2). This system is based on the activation of mesoporous silica microparticles by chemically bonded trichloroacetyl groups and dimanganese decacarbonyl as catalyst. UV irradiation was performed using a lab-made quartz photochemical reactor, ad hoc designed for the photo-induced polymerization process on the surface of microparticles. The two phases were evaluated and compared as chromatographic supports for the enantioselective HPLC of model chiral compounds. Their physico-chemical properties and chromatographic performances were also evaluated in comparison with those exhibited by the homologue CSPs obtained by the grafting-from thermal-induced process (CSP3 and CSP4). The new photopolymerization approach yielded higher grafting density than the thermal-induced one, especially in the case of the less reactive monomer (the diacryloyl derivative of (1R,2R)-diphenylethylenediamine), good chromatographic efficiency and a broad application field under normal phase and polar organic mode conditions.

Efficient alternative for the reduction of N-trichloroacetyl groups in synthetic chondroitin oligosaccharide intermediates

Abstract An efficient alternative for the reduction of N -trichloroacetyl groups in chondroitin oligosaccharides is reported. It involves the use of Zn–Cu couple in acetic acid, and was successfully applied to a large panel of synthetic intermediates useful for the preparation of chondroitin oligomers, a class of natural products with numerous relevant biological functions.

Methodological problems in determining TCAA in soils—the discovery of novel natural trichloroacetyl containing compounds and their interference with a common method for determining TCAA in soil and vegetation

Trichloroacetic acid (TCAA) is a pollutant with several sources and is also formed naturally in soil. We show that almost all investigated environmental compartments (soil, soil water, groundwater, spruce needles and throughfall, but not rain) contain compounds, which make false positives in the thermal decarboxylation method often used for determination of TCAA in environmental samples. The compounds are dominating quantitatively over TCAA in soil, soil water and groundwater, while TCAA is dominating in needle and throughfall samples. The compounds behave differently from TCAA with regard to the velocity and the pH-dependence of the chloroform release. We did not manage to reveal the whole chemical structure of the compounds, but a trichloroacetyl group seems to be the only plausible structure giving rise to CHCl(3) both upon heating and under alkaline conditions. Besides the trichloroacetyl group, the compounds did in general contain a carboxylic acid group, although in needle and throughfall samples, trichloroacetyl compounds with a neutral charge at pH 7.5 seemed to co-exist with the carboxylic acids. Trichloroacetyl groups in humic substances and possibly other macromolecular structures contribute to the major portion of the total trichloroacetyl-CHCl(3) in topsoil, but smaller molecules with less UV-VIS absorption seem to constitute the major part of trichloroacetyl-CHCl(3) in soil water and groundwater. The trichloroacetyl containing compounds are most likely naturally occurring compounds formed in the natural chlorination processes in soil, but additional studies are needed to substantiate this hypothesis.

Preparation of Antibacterial Polymer-Grafted Silica Nanoparticle and Surface Properties of Composites Filled with the Silica (2)

Antibacterial polymer was grafted onto silica nanoparticle and the surface properties of various composites filled with the silica were investigated. The grafting of antibacterial polymer, poly(vinylbenzyltributylphosphonium chloride) (poly(St-CH2P+(Bu) 3Cl−)), onto silica surface was achieved by two methods: one is treatment of poly(vinylbenzylchloride) (poly(St-CH2Cl))-grafted silica with tributylphosphine and the other is direct grafting of poly(St-CH2P+ (Bu)3Cl−) by radical graft polymerization of the corresponding monomer. The grafting of poly(St-CH2Cl) and poly(St-CH2P+ (Bu)3Cl−) onto silica surface were initiated by the system consisting of trichloroacetyl groups on the silica surface and Mo(CO) 6. Trichloroacetyl groups were introduced onto the silica surface by the reaction of amino groups on the silica surface with trichloroacetyl isocyanate. The percentage of poly(St-CH2Cl) grafting during the graft polymerization initiated by the system increased with progress of the polymerization reached 116%. The grafting of poly(St-CH2P+ (Bu)3Cl−) onto silica surfaces was confirmed by FT-IR spectra, thermal decomposition gas chromatograms and mass spectra (GC-MS), and 13C-CP/MAS NMR. The surfaces of silicone rubber, polystyrene film, and paints filled with the poly(St-CH2P+ (Bu)3Cl−)-grafted silica shows strong antibacterial activity. These composites retained the antibacterial activity even after the boiling in water for 24 h.

Grafting of branched polymers onto the surface of vapor grown carbon fiber and their electric properties

The grafting of branched polymers onto vapor grown carbon fiber (VGCF) surface and their electric properties of the composite prepared from the branched polymer-grafted VGCF were investigated. In the first step, the grafting of copolymers having pendant peroxy groups onto VGCF was achieved by the copolymerization of 1-(t-butylperoxy-i-propyl)-3-i-propenylbenzene (BPPB) with vinyl monomers initiated by the system consisting of Mo(CO)6 and trichloroacetyl groups previously introduced onto the surface. In the second step, the postpolymerization of vinyl monomers was initiated by pendant peroxy groups of grafted poly(vinyl monomer-co-BPPB) on the surface to give branched vinyl polymer-grafted VGCF. The dispersibility of VGCF in THF was remarkably improved by grafting of branched polymers onto the surface. The electric resistance of composites prepared from the branched polymer-grafted VGCF suddenly increased when the composites were transferred into solvent vapors and suddenly decreased when they were transferred to dry air.

Acid-catalysed rearrangement of glycosyl trichloroacetimidates: a novel route to glycosylamines

A novel route to glycosylamines has been developed. Treatment of glycosyl trichloroacetimidates with TMSOTf under glycosylation conditions, but in the absence of an acceptor, resulted in complete rearrangement of the trichloroacetimidates into the corresponding N-protected-glycosylamines. Reductive cleavage of the trichloroacetyl groups using sodium borohydride provided the desired glycosylamine products.

Preparation and properties of biocompatible polymer-grafted silica nanoparticle

Grafting of biocompatible polymer onto the surface of silica nanoparticles was achieved by radical graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC), initiated by azo groups previously introduced onto the surface or by a system consisting of Mo(CO) 6 and trichloroacetyl groups on the silica surface. Both of these systems have the ability to initiate graft polymerization of MPC, resulting in the formation of poly(MPC)-grafted silica, but the percentage of poly(MPC) grafting for the latter initiating system was much higher than that of the former. The amount of moisture that could be adsorbed onto the silica surface was found to increase with increasing poly(MPC) grafting. This indicates that grafting of poly(MPC) onto the silica surface markedly increases the hydrophilic nature of the surface. The contact angle of water in composites prepared from poly(vinyl alcohol) and poly(MPC)-grafted silica was found to decrease with increasing poly(MPC)-grafted silica content. When poly(MPC)-grafted silica was added to water containing a small amount of chloroform, it was found to act as stabilizer for droplets of chloroform. In addition, according to tests by the Lee–White method, poly(MPC)-grafted silica shows non-thrombogenic characteristics.

Preparation of Antibacterial Polymer-grafted Nano-sized Silica and Surface Properties of Silicone Rubber Filled with the Silica

Antibacterial polymer was grafted onto nano-sized silica surface and the surface properties of silicone rubber filled with the silica were investigated. The grafting of antibacterial polymer was carried out by two-step reactions as follows. Poly(p-styrene sodium sulfate) (poly(St-SO3−Na+)) was successfully grafted onto nano-sized silica surface by the radical polymerization of St-SO3−Na+ initiated by the system consisting of trichloroacetyl groups on the silica surface and Mo(CO)6: trichloroacetyl groups were introduced onto the silica surface by the reaction of amino groups with trichloroacetyl isocyanate. The percentage of poly(St-SO3−Na+) grafting increased with progress of the polymerization and reached about 30%. The poly(St-SO3−Na+)-grafted silica was treated with tributyltetradecylphosphonium chloride (Bu3RP+Cl−) to convert the SO3−Na+ groups to alkyl phosphonium salt, SO3−P+Bu3R, groups. The grafting of poly(St-SO3−P+Bu3R) onto the silica surface was confirmed by IR spectra. The poly(St-SO3−P+Bu3R)-grafted silica gave a stable dispersion in DMSO and poly(dimethylsiloxane). It was found that silicone rubber filled with the poly(St-SO3−P+Bu3R)-grafted silica shows extremely strong antibacterial activity. The silicone rubber surface has an ability to inhibit the reproduction of a Staphylococcus aureus and an Escherichia coli.

Preparation and properties of hyperbranched poly(amidoamine) grafted onto a colloidal silica surface

Grafting of hyperbranched poly(amidoamine) (PAMAM) onto a colloidal silica surface was achieved in a solvent-free dry system and in a methanol solvent system using dendrimer synthesis methodology. The hyperbranched PAMAM was grown from amino groups on the colloidal silica surface by repetition of two steps: (1) Michael addition of methyl acrylate (MA) to amino groups on the surface and (2) amidation of the resulting terminal ester groups with ethylenediamine (EDA). The extent of PAMAM grafting in the solvent-free system and in the methanol solvent system were determined to be 60.4 and 62.8%, respectively. However, both of these values were considerably smaller than the previously calculated theoretical values. This indicates that propagation of PAMAM from the colloidal silica surface did not take place in the manner theoretically predicted; instead, due to steric hindrance, the polymer was grafted in hyperbranched fashion. The terminal amino groups of hyperbranched PAMAM-grafted silica were found to be effective in curing epoxy resin. The gel fraction of the cured resin increased as the proportion of PAMAM on the silica surface increased. Vinyl polymers were postgrafted to the terminal groups of the hyperbranched grafted PAMAM by radical polymerization, which was initiated by a system consisting of hyperbranched PAMAM-grafted silica with terminal trichloroacetyl groups (Silica–PAMAM–COCCl 3) and Mo(CO) 6.

Postgrafting of vinyl polymers onto hyperbranched poly(amidoamine)-grafted nano-sized silica surface

To prepare polymer-grafted nano-sized silica with hydrophilic core and hydrophobic shell and with higher percentage of grafting, the postgraft polymerization of vinyl polymers onto hyperbranched poly(amidoamine)-grafted (PAMAM-grafted) nano-sized silica initiated by the system consisting of Mo(CO) 6 and terminal trichloroacetyl groups of PAMAM-grafted silica was investigated. The introduction of trichloroacetyl groups onto PAMAM-grafted silica surfaces was readily achieved by the reaction of trichloroacetyl isocyanate with terminal amino groups of PAMAM-grafted silica. It was found that the polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and glycidyl methacrylate (GMA) was successfully initiated by the system consisting of Mo(CO) 6 and terminal trichloroacetyl groups of PAMAM-grafted silica. In the polymerization, the corresponding vinyl polymers were effectively postgrafted onto PAMAM-grafted silica, based on the propagation of polymer from surface radicals formed by the reaction of terminal trichloroacetyl groups with Mo(CO) 6: the percentage of PMMA postgrafting onto PAMAM-grafted silica reached to 400% after 30 min, but the formation of gel was observed after 35 min. The formation of gel tends to decrease by use of hyperbranched PAMAM-grafted silica with higher percentage of grafting. The vinyl polymer-postgrafted nano-sized silica gave a stable colloidal dispersion in various organic solvents.

Grafting of vinyl polymers onto VGCF surface and the electric properties of the polymer-grafted VGCF

The graft polymerization of vinyl monomers onto vapor grown carbon fibers (VGCF) initiated by the system consisting of molybdenum hexacarbonyl (Mo(CO)6) and trichloroacetyl (COCCl3) groups introduced onto the surface was investigated. The introduction of trichloroacetyl groups onto VGCF surface was successfully achieved by the reaction of carboxyl groups on VGCF surface with trichloroacetyl isocyanate. It was found that the radical graft polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and glycidyl methacrylate (GMA) is successfully initiated by the system consisting of Mo(CO)6 and COCCl3 groups introduced onto the surfaces. In the polymerization, the corresponding vinyl polymers were effectively grafted onto the VGCF surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mo(CO)6: the percentage of PMMA grafting reached 40%. Polymer-grafted VGCF gave a stable colloidal dispersion in good solvents for grafted polymer. The electric resistance of composite prepared from the polymer-grafted VGCF suddenly increased in organic solvent vapor over 103 times, and returned to initial resistance when it was transferred into dry air. These results indicate that such composites can be used as novel gas sensors.

Indium-mediated chemoselective deprotection of trichloroethoxycarbonyl and trichloroacetyl groups

A new, mild, and chemoselective method for the deprotection of trichloroethoxylcarbonyl and trichloroacetyl groups is described.

Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10

Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10

Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10

AbstractThe effective grafting of vinyl polymers onto an ultrafine silica surface was successfully achieved by the photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface with Mn2(CO)10 under UV irradiation at 25 °C. The introduction of trichloroacetyl groups onto the surface of silica was achieved by the reaction of trichloroacetyl isocyanate with surface amino groups, which were introduced by the treatment of silica with 3‐aminopropyltriethoxysilane. During the polymerization, the corresponding polymers were effectively grafted onto the surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mn2(CO)10. The percentage of poly(methyl methacrylate) grafting onto the silica reached 714.6% after 90 min. The grafting efficiency (proportion of grafted polymer to total polymer formed) in the polymerization of methyl methacrylate was very high, about 80%, indicating the depression of formation of ungrafted polymer. Polymer‐grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2157–2163, 2001

トリクロロアセチル基を導入したシリカとMo (CO) 6とを組み合わせた系によるアクリレート樹脂の硬化反応

シリカ粒子表面へ導入したトリクロロアセチル基と, マンガンヘキサカルボニル (Mo (CO) 6) とを組み合わせた系によるアクリレート樹脂の硬化反応について検討した。シリカ表面へのトリクロロアセチル基の導入は, γ-アミノプロピルトリエトキシシランで処理してシリカ表面へ導入したアミノ基と, トリクロロアセチルイソシアナートとの反応により行った。トリクロロアセチル基を導入したシリカとMo (CO) 6とを組み合わせた系では, アクリレート樹脂の硬化反応が進行することがわかった。このような結果は, トリクロロアセチル基とMo (CO) 6との反応により, 粒子表面に生成したラジカルからアクリレート樹脂の硬化反応が進行していることを示唆している。したがって, このような系では, 硬化膜中へ化学結合を介してシリカ粒子が組み込まれることが推察された。また, この系で得られた硬化膜は吸水率が低いこともわかった。

Graft polymerization of vinyl monomers from initiating groups introduced onto polymethylsiloxane-coated titanium dioxide modified with alcoholic hydroxyl groups

The grafting of vinyl polymers onto the surface of polymethylsiloxane-coated titanium dioxide modified with alcoholic hydroxyl groups (Ti/Si–R–OH) were investigated. The introduction of azo and trichloroacetyl groups onto the surface of Ti/Si–R–OH was achieved by the reaction of the surface alcoholic hydroxyl groups with 4,4′-azobis(4-cyanopentanoic acid) and trichloroacetyl isocyanate, respectively. The radical polymerizations of vinyl monomers were successfully initiated by the azo groups introduced onto the surface and by the system consisting of Mo(CO) 6 and Ti/Si–R–COCCl 3. During the polymerization, the corresponding polymers were effectively grafted onto the titanium dioxide surface through propagation from surface radicals formed by the decomposition of azo groups and by the reaction of Mo(CO) 6 with trichloroacetyl groups on the surface. The percentage of grafting and grafting efficiency in the graft polymerization initiated by the system consisting of Ti/Si–R–COCCl 3 and Mo(CO) 6 were much larger than those initiated by azo groups. The polymer-grafted titanium dioxide was found to produce a stable colloidal dispersion in good solvents for the grafted polymer. The dispersibility of poly( N, N-diethylacrylamide)-grafted titanium dioxide in water was controlled by temperature. In addition, the wettability of the surface of titanium dioxide to water was readily controlled by grafting of hydrophilic or hydrophobic polymers.

X-Ray and 35Cl NQR Studies on the Trichloroacetyl Group in Covalent and Ionic Compounds of L-Valine and DL-Valine

Abstract The crystal structures and 35Cl NQR of trichloroacetyl-DL-valine (1), trichloroacetyl-L-valine (2), as well as the salts of trichloroacetic acid with DL-valine (3) and L-valine (4) have been investigated. Crystal data are for (1): Monoclinic, C2/c, a= 15.835(4) Å, b= 10.481 (3) Å, c = 14.046(4) Å, β = 103.28(1), Z = 8; (2): Orthorhombic, P212121, a = 12.117(3) Å, 6=10.896(3) Å, c= 8.718(2) Å, Z = 4; (3): Triclinic, P1̄, a= 17.269(3) Å, 6 = 8.504(3) Å, c = 10.427(4) A, a = 105.38(2), β = 96.98(2), γ = 96.24(2), Z = 2; (4): Monoclinic, P21, a = 10.378(4) Å, b = 20.349(8) Å, c= 11.890(5) Å, β = 95.28(2), Z = 8. The onset of rotational motion within the trichloroacetyl groups bleaches out 35Cl NQR lines between 115 K and 185 K for (1)-(4). While TCA-L-valine (1), TCA-DL-valine (2), and TCA(-) · DL-valine(+) (3) do not show any phase transition in the temperature range 77 K to 295 K, TCA(-) · L-valine(+) (4) shows more than one phase transition above 77 K before the three NQR signals bleach out at 164 K.

Grafting of polymers onto ultrafine inorganic particle surface: graft polymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and molybdenum hexacarbonyl

The graft polymerization of vinyl monomers initiated by the system consisting of Mo(CO) 6 and trichloroacetyl groups introduced onto ultrafine silica, titanium oxide, and carbon black was investigated. The introduction of trichlbroacetyl groups onto these surfaces was readily achieved by use of trichloroacetyl isocyanate. It was found that the polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and glycidyl methacrylate is successfully initiated by the system consisting of Mo(CO) 6 and surface trichloroacetyl groups introduced onto these surfaces. In the polymerization, the corresponding polymers were effectively grafted onto these surfaces, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mo(CO) 6: the percentage of polyMMA grafting onto silica, titanium oxide, and carbon black reached to 744,1, 150.5, and 35.4% respectively. These values were extremely larger than that obtained from the radical graft polymerization initiated by surface azo and peroxyester groups introduced onto these surfaces. Polymer-grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer.