The application of Taft-Hancock steric constants to the free-radical initiated copolymerization of N-alkylmaleimides with α-methylstyrene

Summary The rates of free-radical initiated alternating copolymerization of -methylstyrene with N-alkylmaleimides (RMI) decrease in the following order: Me>Et>n-Prn-Bun-Hex>iso-Pr>tert-Bu. A linear relationship was established in the plots of log(k_R/k_Me) against polar substituent constants ^*, true steric factors E_S and corrected steric factors E_S ^C. The best fit was obtained in plots of log (k_R/k_Me) against ^* and E_S ^C while a large scattering of results was observed in the plot of log(k_R/k_Me) against E_S.     

Copolymerization ofα-methylstyrene with 4′-N-(benzo-15-crown-5)maleimide

Summary 4-N-(Benzo-15-crown-5)maleimide (I) was prepared by dehydration of the corresponding maleamic acid (IV). The complexation constant, K=0.07 L mol^–1, between I and -methylstyrene (-MeSt) was determined by modified Benesi-Hildebrand NME method. The copolymerization of -MeSt with homopolymerizable I at different monomer-to-monomer ratios in the feed was performed up to high conversion in Calvet microcalorimeter. It was found that in the copolymerization of -MeSt with an excess of I, the alternating copolymerization precedes the homopolymerization. The mixture of alternating copolymer and homopolymer of I has a single Tg, thus indicating the miscibility on molecular level.     

Solvent effect on the equilibrium polymerization of α-methylstyrene

The Flory-Huggins interaction parameter χ has been determined from static vapour-pressure measurements for four binary mixtures: α-methylstyrene in p-dioxane or cyclohexane, and poly(α-methylstyrene) in p-dioxane or cyclohexane. For the first system, measurements were carried out at 25 and 40°C, yielding values between 0.12 and 0.18 for χ. The second one was investigated at 30, 35 and 40°C leading to χ values between 0.50 and 0.58. The values at 40°C for the third system lie between 0.40 and 0.46 when the polymer volume fraction varies from 0.10 to 0.35. The last system, also at 40°C, has χ values of 0.49 and 0.60 for polymer volume fraction of 0.10 and 0.27, respectively. These parameters were used to compute the equilibrium compositions of monomer and polymer, at any solvent concentration, for the polymerization of α-methylstyrene in different solvents.     

Kinetics and Mechanism of Copolymerization of α-terpineol with Methylmethacrylate in Presence of Azobisisobutyronitrile as an Initiator

The radical copolymerization of -terpineol with methyl-methacrylate in xylene at 80±0.1C for 50 minutes in the presence of azobisisobutyronitrile (AIBN) follows ideal kinetics and results in the formation of a functional and random copolymer. The activation energy is 33 KJ/mole. The IR spectrum and NMR spectra of the copolymer(s) shows the bands at 1750 and 3400 cm^–1 for ester group of methylmethacrylate and alcoholic group of -terpineol and peaks at 3 to 4 for methoxy group and at 6.5 to 7.5 due to alcoholic group of methylmethacrylate and -terpineol repectively. The values of reactivity ratios, calculated by Kelen–Tüdos method, are r ₁ (MMA) = 0.18 and r ₂ (-terpineol) = 0.046. The Alfrey-Price; Q–e parameters for -terpineol has been calculated as 0.149 and 2.486. The mechanism of copolymerization has been elucidated and it is concluded that the double bond present in the monocyclic ring of -terpineol is an active site for copolymerization and the alcoholic group of -terpineol remain to give functional copolymer.     

Three-phase catalytic hydrogenation of α-methylstyrene in supercritical carbon dioxide

The three-phase catalytic hydrogenation (TPCH) of α-methylstyrene using supercritical carbon dioxide (scCO₂) in a slurry reactor is reported. Kinetic data are presented for the reaction at 323 K over the range of pressure from 7.0 to 13.0 MPa using a carbon-supported palladium catalyst. The experimental data are fitted to a first-order power-law model. A detailed explanation of the methodology used to isolate the effect of CO₂ on the rate of reaction is presented. Particular attention is given to the phase behaviour of the reaction system and the volumetric expansion of the liquid phase with CO₂. It is shown that scCO₂ significantly enhances the rate of reaction. This effect is attributed to the enhancement of the solubility of hydrogen in the liquid phase.     

Cross-dimerization of α-methylstyrene with isoamylene and aldol condensation of cyclohexanone using a cation-exchange resin and acid-treated clay catalysts

The utility of cation-exchange resin and acid-treated clay catalysts was investigated for two non-aqueous reaction systems, viz. the cross-dimerization of α-methylstyrene with isoamylene and the aldol condensation of cyclohexanone. A systematic investigation of the cross-dimerization of α-methylstyrene with isoamylene was carried out in the temperature range 40–100°C employing different reactant molar ratios. The effect of these parameters on the selectivity for cross-dimerization as compared to the dimerization of the individual reactants was studied. In the liquid-phase aldol condensation of cyclohexanone, special emphasis was laid on the selectivity for 2-(1-cyclohexen-1-yl)cyclohexanone, an intermediate in the manufacture of o-phenylphenol. The effect of the temperature was studied in the range 100–160°C. The efficacy of the acid-treated clay over cation-exchangers has been highlighted. The experimental data were analysed and correlated by heterogeneous models. The cross-dimerization reaction was found to follow Rideal-Eley kinetics, while the condensation reaction conformed to the Langmuir-Hinshelwood mechanism.     

Copolymerization of butadiene and isoprene with TMEDA as modifier

以正丁基锂(n-BuLi)为引发剂,N,N,N',N＇-四甲基乙二胺(TMEDA)为调节剂,环己烷为溶剂,通过负离子聚合制备了丁二烯和异戊二烯的共聚物.结果表明,随着TMEDA用量的增加,聚合速度加快,丁二烯单体竞聚率增加,异戊二烯单体竟聚率减少,二者差值逐渐增大,在TMEDA/n-BuLi(摩尔比)不小于0.8时,这种变化趋势变缓,表明共聚物分布不均匀程度增加.     

Heteropolyacid-catalyzed dimerization of α-methylstyrene; on the efficiency and selectivity dependence

In the presence of catalytic amounts of a Keggin (H₃PW₁₂O₄₀), Wells–Dawson (H₆P₂W₁₈O₆₂) or Preyssler (H₁₄NaP₅W₃₀O₁₁₀) heteropolyacid, α-methylstyrene (1) leads to dimers. The efficiency and the selectivity toward 2,4-diphenyl-4-methyl-1-pentene (2), 2,4-diphenyl-4-methyl-2-pentene (3) and 1,1,3-trimethyl-3-phenylindan (4) depend on the reaction temperature and the nature of both the catalyst and the solvent. Thus, 2, 3 and 4 can be produced in 45%, 50% and 97% yields, respectively.     

Volumetric expansion and vapour–liquid equilibria of α-methylstyrene and cumene with carbon dioxide at elevated pressure

Volumetric expansion data and vapour-liquid equilibria (VLE) for α-methylstyrene (AMS) with CO₂ are reported at temperatures of 308 and 323 K and pressures approaching the mixture critical point. Similar data are reported for the mixture of carbon dioxide and cumene at a temperature of 323 K. It is shown that the volumetric expansion data for the various systems coincide when plotted as a function of the solubility of CO₂ in the liquid phase. A procedure is described for calculating the molar volume of the liquid phase from the phase compositions and volumetric expansion data. The experimental VLE data are correlated with the Peng-Robinson (PR) equation of state and the interaction parameter for each binary system is obtained by regression. The interaction parameter is subsequently used to predict the liquid molar volume for each binary system. The use of a single interaction parameter with the PR equation of state provides a satisfactory correlation of the liquid molar volume.     

Cationic polymerization of α-methylstyrene in liquid sulfur dioxide initiated by p-methoxybenzyl chloride

Summary The cationic polymerization of -methylstyrene (-MeSty) in liquid sulfur dioxide initiated by benzyl chloride and p-methoxybenzyl chloride was investigated at different temperatures. The p-methoxybenzyl chloride (p-MOBCl) was found to be effective in initiating -MeSty polymerization while benzyl chloride yielded only traces of polymer under all conditions. Polymers with narrow molecular weight distribution were obtained indicating rapid exchange between p-MOBCl dormant species and the corresponding carbenium ion. The reaction seems to be controlled by termination.     

Copolymerization via zwitterion of 2-ethyl-2-oxazoline with β-methylhydrogenitaconate

Summary 2-Ethyl-2-oxazoline (ETOX) as a nucleophilic monomer and -methylhydrogenitaconate (MHI) as electrophilic monomer were copolymerized in solution in the absence of initiator at various feed mole ratios. Copolymers were characterized by elemental analysis, FT-IR and ¹H NMR spectroscopy. The copolymer composition was determined by elemental analysis and by ¹H NMR spectroscopy. The copolymerization reaction occurs with a termination reaction which is evidenced by the end double bond at the ¹H NMR spectra.     

Copolymerization of ethylene with α-olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

The data on the effect of comonomer (propylene and 1-hexene) on molecular weight (M_w), molecular weight distribution (MWD), and content of terminal double bonds were obtained for ethylene/α-olefin copolymers produced over a supported titanium–magnesium catalyst (TMC) upon polymerization in the absence of hydrogen. The experimental data on the effect of comonomer concentration on M_w of polymers were used to calculate the ratios between the effective rate constants of chain transfer with monomer and the propagation rate constant. It was shown that the effective rate constant of chain transfer with monomers increases in the row of monomers: ethylene < 1-hexene < propylene. Meanwhile, the data on the effect of copolymers on content of terminal double bonds of various types demonstrate that different reactions of chain transfer with comonomer may simultaneously occur during copolymerization. It results in simultaneous formation of terminal vinylidene and trans-vinylene bonds. Therefore, the calculated rate constants of chain transfer with comonomer are complex values, which include the rate constants of chain transfer with comonomer occurring via different mechanisms. The data on MWD, short chain branching (SCB) and terminal double bonds content of different types were obtained by molecular weight fractionation of copolymers followed by the analysis of narrow fractions. The analysis of the data on MWDs of SCB and terminal double bonds shows that active sites of the TMC are considerably heterogeneous with respect to the rates of different chain transfer reactions with monomers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rheological behavior of liquefied α-cellulose with phenol

The steady rheological behavior of phenol-liquefied cellulose product (LCP) at varying liquefaction times was investigated at three testing temperatures. The LCP presented interesting rheological behavior. When liquefaction time was longer than 45?min, the LCP showed stronger shear-thinning behavior with increasing temperature, and the viscosity at high testing temperature was higher than that at low testing temperature at low shear rates. An experiment with a heating and cooling cycle indicated that LCP would form reversible association structures when temperature increased. The mechanism of the reversed rheological behavior of LCP may be attributed to the association of alkyl chain parts of liquefied cellulose when heating.     

Hydrogenation of α-enaminoketones with cobalt phosphine-modified catalysts

The synthesis of α-enamines and hydrogenation of these compounds were studied using cobalt-modified complexes. Cobalt complexes were characterized by ¹H, ¹³C and ³¹P NMR, elemental analysis and IR spectroscopy. Furthermore, the molecular structures of complexes C1–C2 and C4–C5 have been determined by single-crystal X-ray diffraction. All cobalt complexes investigated were active catalysts for the hydrogenation reaction. The best catalytic activity was obtained with an ortho-substituent in the phosphine ligand. Noteworthy, the reduction was chemoselective over the double bond.     

Photocatalytic activities for partial oxidation of α-methylstyrene over zeolite-supported titanium dioxide and the influence of water addition to reaction solvent

The photocatalytic reaction in the partial oxidation of α-methylstyrene (α-MS) to acetophenone (AP) was investigated for TiO₂ supported on H-ZSM-5 (H-MFI), H-mordenite (H-MOR), and H-Y-type (H-FAU) zeolites. XRD results demonstrated that the anatase was the stable phase of TiO₂ supported on zeolites. Photocatalytic activities of supported catalysts decreased in the following order: TiO₂/H-MFI >> TiO₂/H-MOR > (TiO₂) > TiO₂/H-FAU >> (blank). TiO₂/H-MFI catalyst exhibited the best performance for photocatalytic oxidation of α-MS to AP. The maximal activity was obtained by 25 wt% TiO₂/H-ZSM-5. The addition of water to the reaction solvent resulted in significantly lowering the photocatalytic activity for TiO₂/H-ZSM-5 catalyst, although its activity for TiO₂ and TiO₂ + H-ZSM-5 mechanical mixture was little influenced by the amount of water added to reaction solvent.     

Partial Peptide of α-Synuclein Modified with Small-Molecule Inhibitors Specifically Inhibits Amyloid Fibrillation of α-Synuclein

We have previously reported that pyrroloquinoline quinone (PQQ) prevents the amyloid formation of α-synuclein, amyloid β_1–42 (Aβ_1–42), and mouse prion protein. Moreover, PQQ-modified α-synuclein and a proteolytic fragment of the PQQ-modified α-synuclein are able to inhibit the amyloid formation of α-synuclein. Here, we identified the peptide sequences that play an important role as PQQ-modified specific peptide inhibitors of α-synuclein. We demonstrate that the PQQ-modified α-Syn_36–46 peptide, which is a partial sequence of α-synuclein, prevented α-synuclein amyloid fibril formation but did not inhibit Aβ_1–42 fibril formation. In addition, the α-synuclein partial peptide modified with other small-molecule inhibitors, Baicalein and epigallocatechin gallate (EGCG), prevented α-synuclein fibril formation. Currently reported quinone amyloid inhibitors do not have selectivity toward protein molecules. Therefore, our achievements provide a novel strategy for the development of targeted specific amyloid formation inhibitors: the combination of quinone compounds with specific peptide sequence from target proteins involved in amyloid formation.     

Syntheses and characterizations of copolymers of dicyanoquinone methides with α-acetoxystyrenes

Summary 7,7-Dicyanoquinone methides (1a-b) copolymerized spontaneously with substituted -acetoxystyrenes (2a-b) in benzene at 60 °C to give alternating copolymers (poly(1a-b-co-2a-b)) with the molecular weights of 8–60×10⁴ in 42–66% yields. When these copolymers were heated under nitrogen, they eliminated acetic acid quantitatively at around 200 °C to be converted to the copolymers (poly(3a-d)) with olefinic bonds, which were characterized by infrared and nuclear magnetic resonance spectroscopy. Alternating copolymers and the corresponding copolymers with olefinic bonds were amorphous, and capable of being cast from their chloroform solutions into transparent, tough films.     

Lewis Acid – Complexed Tetramethylene Biradicals Can Initiate the Thermal Copolymerization of Indene with Acrylonitrile

Summary To clarify the mechanism of the spontaneous copolymerization of styrene with acrylonitrile, the corresponding reaction of its analog, indene, was investigated. The spontaneous free radical copolymerization of indene with acrylonitrile was promoted by Lewis acids. Spontaneous copolymerization rates comparable to those of styrene with acrylonitrile were found. For indene, the Mayo [⁴+²] initiation mechanism, initially postulated for the spontaneous polymerization of styrene, cannot occur. Therefore the Flory mechanism, postulating a tetramethylene biradical initiating species, is proposed.     

Alkylation of α-Methylnaphthalene with Long-Chain Olefins over Large-Pore Zeolites

The liquid-phase alkylation of -methylnaphthalene with long-chain olefins (C_11–12) has been investigated firstly in the presence of H-Y and H-Beta zeolites with different pore architectures. The H-Y zeolites exhibited outstanding catalytic performances. The influences of various reaction parameters like temperature, pressure, mole ratio of -methylnaphthalene to olefins (n _rea), solvent concentration, volume hour space velocity (VHSV) and time on stream on the reaction were studied in detail. Under the optimal reaction parameters, more than 90% conversion of olefins and 100% selectivity for the desired mono-alkyl methylnaphthalene were achieved.