Synthesis of polyacrylonitrile via reverse atom transfer radical polymerization catalyzed by FeCl3/isophthalic acid

FeCl₃ coordinated by isophthalic acid was first used as a catalyst in the azobisisobutyronitrile‐initiated reverse atom transfer radical polymerization of acrylonitrile. N,N‐Dimethylformamide was used as a solvent to improve the solubility of the ligand. An FeCl₃‐to‐isophthalic acid ratio of 0.5 not only gave the best control of the molecular weight and its distribution but also provided rather a rapid reaction rate. The effects of different solvents on the polymerization of acrylonitrile were also investigated. The rate of the polymerization in N,N‐dimethylformamide was faster than that in propylene carbonate and toluene. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in N,N‐dimethylformamide. The rate of polymerization increased with increasing polymerization temperature, and the apparent activation energy was calculated to be 59.9 kJ mol^?1. Reverse atom transfer radical polymerization was first used to successfully synthesize acrylonitrile polymers with a molecular weight higher than 80,000 and a narrow polydispersity as low as 1.22. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 219–225, 2006     

Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol

The copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as a ligand was performed even at ?78°C with a number‐average molecular weight (M_n) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured M_n's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr₂) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]₀/[methyl α‐bromoisobutyrate]₀/[CuBr]₀/[CuBr₂]₀/[Me₆TREN]₀ = 200/1/1/0.2/1.2 at ?20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of Cu^IBr/Me₆TREN in HFIP, there were [Cu(Me₆TREN)Br]⁺ and [Cu(Me₆TREN)OCH(CF₃)₂]⁺, indicating that HFIP should coordinate to the Cu^I/Me₆TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for ?78°C, 77% for ?30°C, 75% for ?20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006     

Synthesis of A2B star block copolymers from a heterotrifunctional initiator

We described the obtention of A₂B star block copolymers through the use of a new heterotrifunctional initiator. That way, well‐defined (PCL)₂‐arm‐PtBuMA and (PCL)₂‐arm‐PS star block copolymers have been synthesized from a heterotrifunctional initiator bearing two hydroxyl groups able to initiate ROP of CL (with AlEt₃ or Sn(Oct)₂ as coinitiator) and a bromide function able to initiate ATRP of tBuMA or styrene. Firstly, we have proceeded using a sequential process (two‐steps), leading to an intermediate macroinitiator. Secondly, attempt to polymerize these two monomers in a simultaneous process (one‐step), that is directly from the mixture of monomers, initiator, coinitiators, and solvent, has been realized and has shown that some interferences between the two polymerizations occurred, leading to an inhibition of ATRP when Sn(Oct)₂ was used and an unexpected increase in control when AlEt₃ was used as catalyst for the ROP (obtention of well‐defined (PCL)₂‐arm‐PtBuMA with pdi of 1.18). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1796–1806, 2006     

Block copolymer mediated synthesis of amphiphilic gold nanoparticles in water and an aqueous tetrahydrofuran medium: An approach for the preparation of polymer–gold nanocomposites

The synthesis of polymer‐matrix‐compatible amphiphilic gold (Au) nanoparticles with well‐defined triblock polymer poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] and diblock polymers poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], polystyrene‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], and poly(t‐butyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] in water and in aqueous tetrahydrofuran (tetrahydrofuran/H₂O = 20:1 v/v) at room temperature is reported. All these amphiphilic block copolymers were synthesized with atom transfer radical polymerization. The variations of the position of the plasmon resonance band and the core diameter of such block copolymer functionalized Au particles with the variation of the surface functionality, solvent, and molecular weight of the hydrophobic and hydrophilic parts of the block copolymers were systematically studied. Different types of polymer–Au nanocomposite films [poly(methyl methacrylate)–Au, poly(t‐butyl methacrylate)–Au, polystyrene–Au, poly(vinyl alcohol)–Au, and poly(vinyl pyrrolidone)–Au] were prepared through the blending of appropriate functionalized Au nanoparticles with the respective polymer matrices {e.g., blending poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate‐stabilized Au with the poly(methyl methacrylate)matrix only}. The compatibility of specific block copolymer modified Au nanoparticles with a specific homopolymer matrix was determined by a combination of ultraviolet–visible spectroscopy, transmission electron microscopy, and differential scanning calorimetry analyses. The facile formation of polymer–Au nanocomposites with a specific block copolymer stabilized Au particle was attributed to the good compatibility of block copolymer coated Au particles with a specific polymer matrix. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1841–1854, 2006     

Comprehensive study on the formation of polyelectrolyte complexes from (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] and poly(2‐acrylamido‐2‐methylpropane sodium sulfonate)

Polyelectrolyte complexes (PECs) have been prepared from well‐defined (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) and high molecular weight poly(2‐acrylamido‐2‐methylpropane sodium sulfonate) (PAMPSNa) after a thorough study of their viscometric properties. The effect of pH and quaternization degree of PDMAEMA on PECs stoichiometry has been examined. PEC‐based materials have been characterized in terms of thermal stability, equilibrium swelling degree, and free/bound water composition. The stoichiometry and swellability of the physically crosslinked hydrogels obtained from fully quaternized PDMAEMA/PAMPSNa complexes do not depend on pH. In contrast, PECs made of non quaternized PDMAEMA and PAMPSNa are highly affected by pH, and could reversibly disintegrate at pH ≥ 9. Partially quaternized PDMAEMA/PAMPSNa PECs exhibit intermediate properties and form stable loose structures in the whole investigated pH range. Finally, stable dispersions of PECs nanoparticles have been successfully produced from dilute solutions of the complementary polyelectrolytes. The nanoparticle average diameter as determined by dynamic light scattering proved to depend on the molar fraction of DMAEMA‐based subunits and on the initial polyelectrolyte concentration. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5468–5479, 2006     

Single electron transfer–degenerative chain transfer living radical polymerization of N‐butyl acrylate catalyzed by Na2S2O4 in water media

Living radical polymerization of n‐butyl acrylate was achieved by single electron transfer/degenerative‐chain transfer mediated living radical polymerization in water catalyzed by sodium dithionate. The plots of number–average molecular weight versus conversion and ln[M]₀/[M] versus time are linear, indicating a controlled polymerization. This methodology leads to the preparation of α,ω‐di(iodo) poly (butyl acrylate) (α,ω‐di(iodo)PBA) macroinitiators. The influence of polymerization degree ([monomer]/[initiator]), amount of catalyst, concentration of suspending agents and temperature were studied. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right‐angle light scattering (RALLS), a differential viscometer (DV), and refractive index (RI). The methodology studied in this work represents a possible route to prepare well‐tailored macromolecules made of butyl acrylate in an environmental friendly reaction medium. Moreover, such materials can be subsequently functionalized leading to the formation of different block copolymers of composition ABA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2809–2825, 2006     

Structural anisotropy in friction‐deposited layers of polystyrene

Friction‐deposited layers of atactic polystyrene (PS) on inert and OH‐grafted gold substrates were the subject of this study to establish a relationship between the friction process and the resulting anisotropy of the transferred polymer chains. We show, by using polarization‐modulation infrared reflection‐absorption spectroscopy that the deposited PS chains involve an anisotropy in which PS main backbone is rather perpendicular to the friction support, fact that is surprising when compared with the majority of polymers where the anisotropy is along the sliding direction. Moreover, our calculation of the orientation angles revealed that PS chains are more perpendicular in the transferred layers than in spin‐coated films. This particular anisotropy is probably due to a parallel reorientation of the phenyl ring on the friction support whatever the surface chemistry is. On the other hand, this study was useful to rectify the assignment of infrared bands unclearly reported in the literature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3272–3281, 2006     

Decomposition of multiattribute expected-utility functions

This paper integrates and extends the theory of the decomposition of multiattribute expected-utility functions based on utility independence. In a preliminary section, the standard decision model of expected utility is briefly discussed, including the fact that the decision maker's preference forlotteries with two outcomes determines the utility function uniquely. The decomposition possibilities of a utility function are captured by the concept ofautonomous sets of attributes, an affine separability of some kind known as generalized utility independence.Overlapping autonomous sets lead to biaffine-associative, i.e.multiplicative oradditive decompositions. The multiplicative representation shows that autonomy has strongerclosure properties than utility independence, for instance with respect to set-theoretic difference. Autonomy is also a concept with a wider scope since it applies to the decomposition of Boolean functions, games and a number of other topics in combinatorial optimization. This relationship to the well-known theory ofsubstitution decomposition in discrete mathematics also reveals a kind of discrete core behind the decomposition of utility functions. The entirety of autonomous sets can be represented by a compact data structure, the so-calledcomposition tree, which frequently corresponds to a natural hierarchy of attributes. Multiplicative/additive ormulti-affine functions correspond to the hierarchy steps. The known representation of multi-affine functions is shown to be given by aMoebius inversion formula. The entire approach has the advantage that it allows the application of more sophisticated representation methods on a detailed level, whereas it employs onlyfinite set theory andarithmetic on the main levels in the hierarchy.     

煤中有机硫形态结构和热解过程硫变迁特性的研究

利用热解 质谱并结合固定床热解反应装置，对煤中有机硫的形态主其对加氢热解过程 变迁特性的影响，进行了较系统的研究。结果表明，煤中有机硫的形态结构在褐煤中主要以脂肪族、芳香族硫化物为主，而在 煤中则主要以各种不同芳构化程度的噻吩结构为主，初步表明煤中有机硫形态结构随煤变质程度的变迁呈较强的连续递变性。煤热解过程中硫在呼产物中的变迁和分布与煤中有机硫的形态结构特点密切相关。较高芳构化噻吩结构不完全的氧     

Transfer activity coefficient of the proton in water-pyridine mixtures. A comparison of some extrathermodynamic assumptions

Various water-pyridine mixtures have been selected in order to compare several of the most popular extrathermodynamic assumptions involved in the determination of the transfer activity coefficient of the proton, _t(H⁺). Two techniques have been utilized for this purpose: voltammetry [study of the ferrocene, ferricyanide, or thallium(1) systems] and potentiometry at equilibrium (emf measurements of various galvanic cells, including liquid junctions and hydrogen electrode or silver electrode as a test electrode). The assumptions have been classified into various groups [e.g., _t(Z^p+)=_t(Z^q+) or _t(X^–)=_t(Y⁺)], and the values of _t(H⁺) have been experimentally determined in each case. The results vary depending upon the basic assumption (several pH units); less important differences (e.g., 0.5 pH unit) occur within a given group, and this may be assigned to the nature of the reference species chosen. A simple model of solvation has been also examined; the application of the law of mass action to the corresponding equilibrium provides results close to the _t(X^–) =_t(Y⁺)type of assumptions which ultimately leads to most self-consistent results.