Radical copolymerization of acrylonitrile with 2,2,2‐trifluoroethyl acrylate for dielectric materials: Structure and characterization

Radical copolymerization based on acrylonitrile (AN) and 2,2,2‐Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN‐co‐ATRIF) copolymers were characterized by ¹H, ¹³C, and ¹⁹F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by ¹H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 °C from initial [AN]₀/[ATRIF]₀ molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer—polymer copolymerization curve, the Fineman–Ross and Kelen–Tüdos laws enabled to assess the reactivity ratios (r_AN= r₁ = 1.25 ± 0.04 and r_ATRIF = r₂ = 0.93 ± 0.05 at 70 °C) while the revised patterns scheme led to r₁₂ = r_AN = 1.03, and r₂₁ = r_ATRIF = 0.78 at 70 °C. In all cases, r_AN x r_ATRIF product was close to unity, which indicates that poly(AN‐co‐ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN‐ATRIF, AN‐AN, and ATRIF‐ATRIF dyads. The Q and e values for ATRIF were also assessed (Q₂ = 0.62 and e₂ = 0.93). The glass transition temperature values, T_g, of these copolymers increased from 17 to 61 °C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN‐co‐ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3856–3866     

Synthesis and adsorption on gold surfaces of a functionalized thiol: elaboration and test of a new nitroaromatic gas sensor

A new type of sensor was built by synthesizing a long-chain thiol functionalized with an aromatic head group and grafting it onto a gold surface. The synthesis route is here described, together with the IR, MS, and RMN analysis of the new product. Adsorption of the latter onto gold was assessed by a combination of RAIRS and XPS data. Those reveal that a monolayer of thiol is adsorbed and oriented with the benzene groups toward the external part of the layer. Detection tests were performed in various atmospheres by QCM. The response shows good sensitivity to 2,4-dinitrotrifluoromethoxybenzene as a model of nitroaromatic compound.     

An alkylzinc bromide and a lithium alkyldibromozincate containing tris(organosilyl)methyl groups

The lithium reagent (3) reacts with a molar equivalent of anhydrous zinc bromide to give the dimeric compound (2a), in which zinc is four-coordinate. The product from a similar reaction with Li{C(SiMe₃)₂(SiMe₂NPhMe)} is the lithium zincate [Li(THF)₂(μ-Br)₂Zn{C(SiMe₃)₂(SiMe₂NPhMe)}] (4), in which the zinc is only three-coordinate. The crystal structures of 2a and 4 have been determined.     

Silica/Polyamide Nanocomposite Synthesis via an Original Double Emulsification Process in Miniemulsion

Summary: A new method for the encapsulation of inorganic charges by an organic polymer by a reactive double emulsification process is proposed. This work is especially novel since it is highly unusual to encounter polymerization reactions in such a double emulsification process. Silica was first synthesized in cyclohexane using a sol–gel process in an inverse microemulsion in the presence of a non‐ionic surfactant (nonylphenyl ether polyoxyethylene), tetraethoxysilane, and concentrated ammonia. The coupling agent, 3‐aminopropyl triethoxysilane, was then grafted onto the surface of the silica nanoparticles. In a third step, direct miniemulsions were prepared from the microemulsion containing the functionalized silica nanoparticles. The miniemulsions were prepared using sodium dodecylsulfate as the surfactant and cetyl alcohol as the costabilizer. Finally, an interfacial polycondensation occurred between a diamine added to the external phase and sebacoyl chloride in solution in the dispersed phase. The formation of polyamide latexes was proven using infrared spectroscopy, and observation of the nanocomposites by transmission electron microscopy showed mean diameters of 100 nm.

TEM micrograph of silica/polyamide nanocomposite particles     

A convenient synthesis of pyrazolidine and 3‐amino‐6,7‐dihydro‐1H,5H‐pyrazolo[1,2‐a] pyrazol‐1‐one

A convenient four‐step synthesis of the aminobicyclopyrazolone hydrochloride 1 ·HC1 was achieved starting from di‐tert‐butyl hydrazodiformate (8) . The route entails cyclization of 8 with 1,3‐dibromopropane under phase transfer conditions followed by deprotection of 1,2‐di‐tert‐butoxycarbonylpyrazolidine (9) to give pyrazolidine hydrochloride ( 2 ·HC1). Cyanoacetylation of the latter and ring closure of the resulting cyanoacetyl pyrazolidine (7) gave 1·HC1. This novel synthesis circumvents distillation of pyrazolidine (2) and flash chromatography to provide the hydrochloride of 1 in 35–46% overall yields compared to 6% yield for the patent procedure.     

Purification of crude DNA oligonucleotides by solid-phase extraction and reversed-phase high-performance liquid chromatography

Purification of target oligodeoxyribonucleotides from failure sequence by-products of synthesis is often required for polymerase chain reaction primers, DNA sequencing and other oligonucleotide applications. We have developed purification protocols based on a reversed-phase mechanism ("trityl on" purification) using a 96-well Oasis HLB extraction plate. The Oasis HLB sorbent combines excellent pH stability with a high loading capacity allowing for single-step purification of 0.2 microM scale synthesis. After sample loading and washing, the oligonucleotide trityl group is cleaved on the plate with 2% trifluoroacetic acid. Target DNA is eluted with acetonitrile-0.36 mM triethylamine acetate, pH 11.3 (10:90, v/v). Typical yield of purified product is 60-95%. Final purity, measured by capillary gel electrophoresis, was found to be 90% or greater. Alternatively, highly pure oligonucleotides can be obtained by a RP-HPLC "trityl off" method using an XTerra C18 column. The use of volatile triethylamine acetate buffer as an ion-pair for RP-HPLC eliminates the need for further desalting.     

Contribution to the analysis of the predissociated rovibronic structure of the symmetric isotopomers 16O3 and 18O3 of ozone near 10,400 cm-1): [3A2(3(2)(0)) <-- X1A1(0(0)(0))] and 3B2 <-- X1A1

The absorption spectrum of ozone was recorded at low temperatures (down to -135 degrees C) by high resolution Fourier transform spectrometry and intra cavity laser absorption spectroscopy (ICLAS) near 10,400 cm-1. A preliminary analysis of the rotational structure of the absorption spectra of 16O3 and 18O3 shows that this spectral region corresponds to a superposition of two different electronic transitions, one with a very broad rotational structure, showing for the first time the asymmetric stretching frequency mode nu3 of the electronic state 3A2, the other formed by a completely diffuse band, probably the 2(1)(0) band of a new transition due to the triplet electronic state 3B2. Predissociation effects induce large broadening of the rotational lines for the transition centered at 10,473 cm-1 identified as the 3(2)(0) band of the 3A2 <-- X1A1 electronic transition. The rotational structure cannot be analyzed directly but instead the band contour method was used to confirm the symmetry of the transition and to estimate the spectroscopic constants for the 16O isotopomer. The origin of the band is at 10,473 +/- 3 cm-1 and the value of the 16O3(3A2) antisymmetric stretching frequency mode is equal to 460 +/- 2 cm-1. We believe that the diffuse band is due to the 3B2 state and is located at about 10,363 +/- 3 cm-1 for 16O3 and 10,354 +/- 3 cm-1 for 18O3. The isotopic rules confirm the different results obtained for 18O3 and 16O3.