磺化聚苯乙烯／聚吡咯复合膜

磺化聚苯乙烯（ＳＰＳ）／聚吡咯（ＰＰｙ）复合膜是通过毗咯单体在ＳＰＳ基体中原位聚合方法制成的．用ＦＴＩＲ研究ＳＰＳ／ＰＰｙ复合膜分子间的相互作用，特别是ＳＰＳ中ＳＯ３阴离子在１２００ｃｍ－１不对称伸缩振动港带的分裂，说明了聚吡咯是以阳离子的形式作用于ＳＰＳ中ＳＯ３阴离子上，产生强的离子－离子相互作用．同时还研究了在复合过程中，引起ＳＰＳ基体的微区结构与性能的变化．ＳＰＳ由于吡咯单体的胀入和聚合，导致了ＳＰＳ微相分离，复合膜在动态力学性能测试中出现了两个Ｔｇ转变，分别在１２４和１４５℃．     

Titanium complexes bearing aromatic-substituted β-enaminoketonato ligands: Syntheses, structure and olefin polymerization behavior

A series of titanium complexes [(Ar)NC(CF₃)CHC(R)O]₂TiCl₂ (4b: Ar = -C₆H₄OMe(p), R = Ph; 4c: Ar = -C₆H₄Me(p), R = Ph; 4d: Ar = -C₆H₄Me(o), R = Ph; 4e: Ar = α-Naphthyl, R = Ph; 4f: Ar = -C₆H₅, R = t-Bu; 4g: Ar = -C₆H₄OMe(p); R = t-Bu; 4h: Ar = -C₆H₄Me(p); R = t-Bu; 4i: Ar = -C₆H₄Me(o); R = t-Bu) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4b, 4c and 4h adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b-c and 4f-i are active catalysts for ethylene polymerization and ethylene/norbornene copolymerization, and produce high molecular weight polyethylenes and ethylene/norbornene alternating copolymers. In addition, the complex 4c/MMAO catalyst system exhibits the characteristics of a quasi-living copolymerization of ethylene and norbornene with narrow molecular weight distribution.     

KINETICS OF SUSPENDED EMULSION POLYMERIZATION OF METHYL METHACRYLATE

The kinetics of suspended emulsion polymerization of methyl methacrylate (MMA), in which water acted as the dispersed phase and the mixture of MMA and cyclohexane as the continuous phase, was investigated. It showed that the initial polymerization rate (Rp0) and steady-state polymerization rate (Rp) were proportional to the mass ratio between water and oil phase, and increased as the polymerization temperature, the potassium persulphate concentration ([I]) and the Tween20 emulsifier concentration ([S]) increased. The relationships between the polymerization rate and [I] and [S] were obtained as follows: Rp0 ∝ [I]0.73[S]0.32 and Rp ∝ [I]0.71[S]0.23. The above exponents were close to those obtained from normal MMA emulsion polymerization. It also showed that the average molecular weight of the resulting poly(methyl methacrylate) decreased as the polymerization temperature, [I] and [S] increased. Thus, MMA suspended emulsion polymerization could be considered as a combination of many miniature emulsion polymerizations proceeding in water drops and obeyed the classical kinetics of MMA emulsion polymerization.     

Fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) for fuel cell applications

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10⁻² S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10⁻¹ and 1.78 × 10⁻¹ S/cm at 100 °C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.     

Characteristics of Heterophase Graft Copolymerizations

Abstract

Persulfate-initiated graft copolymerizations of glutaraldehyde crosslinked gelatin with acrylic acid, acrylamide, vinyl acetate, and methyl methacrylate in the aqueous phase were investigated. It was observed that percentage grafting, molecular weights of the grafts, and grafting efficiencies were greatly influenced by the nature of the monomers. Hydrophilic monomers gave a higher frequency of grafting but lower molecular weights. While the frequency of grafting with hydrophobic monomers was low, the molecular weights of the grafts were comparatively high. The results are explained in terms of microdomain kinetics, similar to those encountered in emulsion or suspension polymerizations.     

END GROUP TRANSFORMATION OF POLYMERS PREPARED BY ATRP,SUBSTITUTION TO AZIDES

Polystyrenes, polyacrylates and poly(methyl methacrylate) prepared by atom transfer radical polymerization (ATRP) have predictable molecular weights, low polydispersities and well-defined halogen end groups. The halogen end groups have been substituted by other functionalities such as azides and amines. In order to predict the feasibility and selectivity of nucleophilic substitution reactions, the reactivities of the end groups of the different polymers were studied. First, model studies with benzyl halide (BzX), 1-phenylethyl halide (1-PEX), methyl 2-halopropionate (MXP), ethyl 2-bromoisobutyrate (EBiB) and 2-halopropionitrile (2-XPN) were performed. The models compounds were dissolved in DMF and after adding sodium azide (1.1 eq.), the reaction mixtures were stirred at 25°C. The relative magnitude of the rate constants for the reactions with the chlorinated substrates were found to be BzCl > MClP > 1-PECl ≈ 2-ClPN:22 > 6 > 1. Increased substitution at the carbon center decreased the rate of reaction, benzyl chloride reacted 22 times faster than 1-phenylethyl chloride. The brominated substrates reacted very fast. The rate constant of 1-PEBr, determined by competition experiments, was 4.5 times higher than the rate constant of benzyl chloride. Based on these results, the bromine end groups of different polymers were substituted under reaction conditions simular to those used for the model reactions. The end-functionalized polymers were characterized by ¹H-NMR, IR and MALDI-TOFMS.     

Mechanochemical Formation,Solution Rearrangements,and Catalytic Behavior of a Polymorphic Ca/K Allyl Complex

Without solvents present, the often far-from-equilibrium environment in a mechanochemically driven synthesis can generate high-energy, non-stoichiometric products not observed from the same ratio of reagents used in solution. Ball milling 2 equiv. K[A’] (A’=[1,3-(SiMe₃)₂C₃H₃]⁻) with CaI₂ yields a non-stoichiometric calciate, K[CaA’₃], which initially forms a structure ( 1 ) likely containing a mixture of pi- and sigma-bound allyl ligands. Dissolved in arenes, the compound rearranges over the course of several days to a structure ( 2 ) with only η³-bound allyl ligands, and that can be crystallized as a coordination polymer. If dissolved in alkanes, however, the rearrangement of 1 to 2 occurs within minutes. The structures of 1 and 2 have been modeled with DFT calculations, and 2 initiates the anionic polymerization of methyl methacrylate and isoprene; for the latter, under the mildest conditions yet reported for a heavy Group 2 species (one-atm pressure and room temperature).     

Monodisperse Crosslinked Microsphere Polymer Particles by Dispersion Copolymerization of Glycidyl Methacrylate and Divinylbenzene

Monodisperse polyglycidyl methacrylate (PGMA) microsphere particles crosslinked with divinylbenzene crosslinker were prepared by single-stage dispersion copolymerization in ethanol medium. 1 wt% of DVB was successfully incorporated due to the costabilizing effect of GMA as a surface-active monomer. This behavior may indicate that the fast formation of stable primary particle leads to monodispersity. The average particle sizes and the particle size distributions increased with the DVB crosslinker concentration. The effects of two different variables (initiator concentration, crosslinker concentration) on the rate of dispersion copolymerization have been investigated. With the initiator concentration, the polymerization procedure mainly depended on the dual natures of general dispersion polymerization, in the crosslinked state. Up to 1 wt% DVB, the particle growth was controlled by the monomer diffusion from the continuous phase into the particle phase.     

Preparation of dibromopyridines having -(CH2)m-SO3Na groups as monomers for new polypyridines

Dibromopyridines or dibromopyridone with -(CH₂)_m-SO₃Na group(s) has been prepared via the reactions of the corresponding dibromopyridines with -OH and -NH₂ groups with sultone. These compounds were converted into polymers with the -(CH₂)_m-SO₃H groups via organometallic polycondensation. The polymer showed proton conducting properties and high stability toward oxidation.     

Early/Late Heteronuclear Complexes Bridged by Bifunctional Phosphorus-Based Ligands

Substituted bifunctional phosphorus-based ligands HX(CRR') n PR"H (or -PR" 2 ) [where X = O, S, NR', (substituted) cyclopentadienyl; n = 1, 2, 3; R, R', R" = alkyl, aryl, H] were employed as bridging ligands in the synthesis of early/late bridged transition metal complexes. Synthetic routes to the bifunctional ligands were also developed. First, mononuclear complexes, such as [TpZr(OCH 2 PPh 2 ) 3 ] (Tp = trispyrazolylborato), [Cp 2 Zr(1-O-2-PHR-C 6 H 10 )(Me)] (R = 2,4,6-Pr i 3 C 6 H 2 (Tipp)), [Cp 2 Zr(SCH 2 CH 2 PHR) 2 ] (R = Ph, Mes, Tipp), and phosphinoferrocene derivatives, were prepared. These complexes are suitable precursors for the introduction of a second metal (as in, for example, [TpZr( w -OCH 2 PPh 2 ) 3 Mo(CO) 3 ]).