Living radical graft polymerization of methyl methacrylate to polyethylene film with typical and reverse atom transfer radical polymerization

Nickel‐mediated atom transfer radical polymerization (ATRP) and iron‐mediated reverse ATRP were applied to the living radical graft polymerization of methyl methacrylate onto solid high‐density polyethylene (HDPE) films modified with 2,2,2‐tribromoethanol and benzophenone, respectively. The number‐average molecular weight (M_n) of the free poly(methyl methacrylate) (PMMA) produced simultaneously during grafting grew with the monomer conversion. The weight‐average molecular weight/number‐average molecular weight ratio (M_w/M_n) was small (<1.4), indicating a controlled polymerization. The grafting ratio showed a linear relation with M_n of the free PMMA for both reaction systems. With the same characteristics assumed for both free and graft PMMA, the grafting was controlled, and the increase in grafting ratio was ascribed to the growing chain length of the graft PMMA. In fact, M_n and M_w/M_n of the grafted PMMA chains cleaved from the polyethylene substrate were only slightly larger than those of the free PMMA chains, and this was confirmed in the system of nickel‐mediated ATRP. An appropriate period of UV preirradiation controlled the amount of initiation groups introduced to the HDPE film modified with benzophenone. The grafting ratio increased linearly with the preirradiation time. The graft polymerizations for both reaction systems proceeded in a controlled fashion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3350–3359, 2002     

New Emivirine (MKC-442) Analogues Containing a Tetrahydronaphthalene at C-6 and their Anti-HIV Activity

Summary. An 5-ethyl-2-thiouracil derivative with a 6-(tetrahydronaphthalen-1-yl)methyl substituent was synthesized by condensation of thiourea with an adequate β-ketoester which in turn was synthesized in a single step from (tetrahydronaphthalen-1-yl)acetonitrile. The latter starting material was also used to synthesize an analogously substituted tetrahydronaphthalen-1-yl substituted uracil with a locked conformation. Only the non-nucleoside derivatives prepared from the desulfurized substituted 2-thiouracil showed moderate activity against HIV whereas a corresponding non-nucleoside derivative was devoid of activity against HIV.     

Synthesis and Crystal Structure of N,N＇-Dimethyldithio-arbamato-Copper（Ⅰ） Polymer {[Cu（Me2dtc）]2}n

Reactions of CuSCN with tetramethylthiuram disulfide in CH₃CN in the presence of styrene and N,N,N′,N″,N″‐pentamethyldiethylenetriamine gave rise to a new copper(I) complex ofN,N′‐dimethyldithiocabamate ([CU(S₂CNMe₂)]₂)_n. The title compound crystallized in the triclinic P‐1 space group with lattice parameters a=0.7610(4) nm, b=0.8911(4) nm, c=0.9268(5) nm, α=68.66(1)°, β=83.88(2)°, γ=79.31(2)°, V=0.5748(5) nm³, Z=2. The compound has a unique 1D chain structure composed of CuSCSCuSCS eight‐membered rings and a pair of CU? S bonds, the structure of which has been determined by singlecrystal X‐ray crystallography. The isolation of this compound may provide some helpful information for the cause of the induction periods of the reverse atom transfer radical polymerization.     

Nonconventional lecithin gels in hydrocarbon oils

Nonconventional gels formed by lecithin in hydrocarbon oils containing a small amount of water have been studied with the help of temperature- and water-content-dependent phase transitions,³¹P NMR and FT-IR techniques. Gels are obtained in cyclohexane,n-octane, andn-dodecane. Addition of cholesterol in lecithin/water/oil ternary system either eliminates the gelation or shifts the transition temperature to higher values. The gels are thermoreversible, optically clear and are not birefringent. The composition of these gels indicates that the gelation takes place even at 15 weight % of lecithin and water. The lateral motion of the phosphate part of lecithin head group along surfactant monolayer, as well as the tumbling motion of the entangled assemblies of the rodshaped aggregates are fast enough to average out the chemical shift anisotropy of³¹P NMR spectra. From the FT-IR studies, it has been concluded that the gel formation involves the conformational changes in the polar head part of lecithin molecules in such a way that further hydration of phosphate group is drastically hindered.This paper is respectfully dedicated to the sixtieth birthday of Professor Hans F. Eicke, University of Basel, Switzerland     

Nanocrystallite Titanium Dioxide Films Made by the Sol-Gel Method Using Reverse Micelles

Reverse micelles have been made by dissolving Triton X-100 in cyclohexane and adding water. Titanium isopropoxide was then introduced in the solution under vigorous stirring yielding a clear sol. If left at ambient temperature the sol gels in a time of a few hours. Gelation has been studied by fluorescence probing. When a glass slide was dipped in the sol at an early stage of gelation, a thin, photometrically uniform film formed, containing both TiO₂ and surfactant. The organic substances could then be burned out at 400–450°C. Heating secured total TiO₂ formation and permanent attachment to the glass substrate. The ensuing film was studied by electron and AFM microscopy. The film possessed a mesoporous structure characterized by uniformity and particle size monodispersity. It also possessed a high capacity for adsorption of a variety of inorganic particle and ionic species.     

Influence of temperature on the reactivity of phosphorus acid esters in reverse micellar systems based on sodium bis(2-ethylhexyl)sulfosuccinate

A change in the reactivity of ethyl p-nitrophenyl chloromethylphosphonate in the sodium bis(2-ethylhexyl)sulfosuccinate-n-nonane-water system around the percolation threshold was found. Study of location sites of the reactants by NMR self-diffusion and optical spectroscopy and modeling of the kinetic data in terms of the pseudophase approach demonstrated that below the percolation threshold, the reaction occurs in the surface layer. The observed rate constant for substrate hydrolysis in a microemulsion below the percolation threshold is described by the Arrhenius equation, like that in aqueous solutions. Above the percolation threshold, the slope of the Arrhenius plot sharply changes, which is apparently due to a change in the reactant location pattern and, hence, the microscopic properties of the medium in the region of their solubilization. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1407–1414, June, 2005.     

逆向工程中基于NURBS的曲面重构

曲面重构是逆向工程中的关键技术.根据非均匀有理B样条曲面矩阵表达式,对于造型曲面上的(2m+1)×(2n+1)个型值数据点,推导了一个仅利用型值点数据反算二次非均匀有理B样条曲面控制顶点的算法.数值算例表明了该算法的有效性.     

Star-shaped alkylated poly(glycerol methacrylate) reverse micelles: Synthesis and evaluation of their solubilizing properties in dichloromethane

Amphiphilic star-shaped polymers were synthesized by atom transfer radical polymerization (ATRP). Four-, 5-, and 6-arm ATRP initiators were prepared and used to polymerize glycidylmethacrylate. The resulting polymers were hydrolyzed to yield poly(glycerolmethacrylate)s (PG_OHMAs), and then partially esterified with lauroyl or stearoyl chloride (40–60 mol % vs. hydroxyl groups). Alkylated PG_OHMAs were found to assemble into 20–60 nm aggregates in dichloromethane (DCM) above a critical concentration. Particle size essentially depended on the branching degree of the polymer. The micelles were extremely efficient in extracting Congo red from water into DCM, with the highest incorporations (97 mg/g) obtained for the 6-arm polymer modified with stearoyl chloride (60 mol %). The entrapment efficiency for the latter was further improved in alkaline solution. The high level of incorporation achieved for these amphiphilic multiarm polymers suggests that such reverse micelles could be potentially useful as drug delivery systems and nanoreactors in catalytic organic reactions or for water purification. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2425–2435, 2007