Α-methyl Styrene Research Articles

Functionalized mesoporous silica supported copper(ii) and nickel(ii) catalysts for liquid phase oxidation of olefins

Highly ordered 2D-hexagonal mesoporous silica has been functionalized with 3-aminopropyltriethoxysilane (3-APTES). This is followed by its condensation with a dialdehyde, 4-methyl-2,6-diformylphenol to produce an immobilized Schiff-base ligand (I). This material is separately treated with methanolic solution of copper(II) chloride and nickel(II) chloride to obtain copper and nickel anchored mesoporous materials, designated as Cu-AMM and Ni-AMM, respectively. The materials have been characterized by Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance (DRS) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N(2) adsorption-desorption studies and (13)C CP MAS NMR spectroscopy. The metal-grafted mesoporous materials have been used as catalysts for the efficient and selective epoxidation of alkenes, viz. cyclohexene, trans-stilbene, styrene, α-methyl styrene, cyclooctene and norbornene to their corresponding epoxides in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant under mild liquid phase conditions.

Functionalization of polypropylene and compatibilization of polypropylene/nylon 6 blends with copolymers containing α-methyl styrene units

AbstractIn our earlier works, a new and viable strategy for bulk polymerization of methyl methacrylate (MMA) and styrene (St) with copolymers of poly(AMS-co- GMA) (PAG) of α-methyl styrene (AMS) and glycidyl methacrylate (GMA) has been reported. Herein, we report on the achievements of the compatibilization of the blend system of polypropylene (PP) and Nylon 6 (Ny6) and the functionalization of PP with PAG. The graft reactions of PAG onto PP in solution and molten state were investigated respectively, and the functionalized production was confirmed by the FT-IR spectra. Through SEM, the in-situ compatibilization of PP/Ny6 blends with PAG was observed. And the block copolymers of PP-b-PAG-b-Ny6 in the blends were characterized by FT-IR, which confirmed the “compatibilizing effect” of PAG in the blend system.

A Predictive Ligand-Based Bayesian Model for Human Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is one of the most important reasons for drug development failure at both preapproval and postapproval stages. There has been increased interest in developing predictive in vivo, in vitro, and in silico models to identify compounds that cause idiosyncratic hepatotoxicity. In the current study, we applied machine learning, a Bayesian modeling method with extended connectivity fingerprints and other interpretable descriptors. The model that was developed and internally validated (using a training set of 295 compounds) was then applied to a large test set relative to the training set (237 compounds) for external validation. The resulting concordance of 60%, sensitivity of 56%, and specificity of 67% were comparable to results for internal validation. The Bayesian model with extended connectivity functional class fingerprints of maximum diameter 6 (ECFC_6) and interpretable descriptors suggested several substructures that are chemically reactive and may also be important for DILI-causing compounds, e.g., ketones, diols, and α-methyl styrene type structures. Using Smiles Arbitrary Target Specification (SMARTS) filters published by several pharmaceutical companies, we evaluated whether such reactive substructures could be readily detected by any of the published filters. It was apparent that the most stringent filters used in this study, such as the Abbott alerts, which captures thiol traps and other compounds, may be of use in identifying DILI-causing compounds (sensitivity 67%). A significant outcome of the present study is that we provide predictions for many compounds that cause DILI by using the knowledge we have available from previous studies. These computational models may represent cost-effective selection criteria before in vitro or in vivo experimental studies.

The viscoelastic behavior of polymer/oligomer blends

The viscoelastic properties of poly(α-methyl styrene), its hexamer, and their athermal blends at various concentrations are studied. Master curves for the dynamic shear responses, G′ and G″, are successfully constructed for both the pure materials and the blends, indicating the validity of the time–temperature superposition principle for these systems. The temperature dependence of the shift factor follows the Vogel–Fulcher behavior over the temperature range studied, and the temperature dependence is slightly weaker for the blends. The rubbery plateau modulus scales with the polymer concentration as GN0∝ϕ2.04±0.32; the terminal relaxation time scales with the polymer concentration as τd∝ϕ1.35±0.33. The shape of the segmental dispersion appears unchanged by concentration, which differs from our calorimetric studies where mixtures show obviously temperature-broadened glass transitions and depressed enthalpy overshoots. The TNM (Tool-Narayanaswamy-Moynihan) model indicates that the change in the temperature dependence is not sufficient to account for the observed calorimetric broadening. We conclude that the temperature broadening of the glass transition for our blends is not due to a broadening of the dynamic spectrum or to changes in its temperature dependence. The possibility that the broadening is due to changes in the non-linearity parameter x in the TNM model is also considered. While the broadening could be due to a decreasing value of x, we found that this same decrease would lead to increasing enthalpy overshoots on heating, contrary to the experimental observations. The combination of the calorimetric results with the rheological measurements further indicates that the fundamental basis of the TNM-type of model of structural kinetics in glasses is potentially wrong.

Significant counterion effect of the In(III)–pybox complex in highly enantioselective carbonyl-ene reactions of ethyl glyoxylate

A highly efficient enantioselective carbonyl-ene reaction of ethyl glyoxylate catalyzed by an In(III)–pybox complex, which is designed based on the counterion effect, is reported. Reactions of both aliphatic and aromatic 1,1-disubstituted olefins proceed smoothly to give enantioenriched homoallylic alcohols with excellent yields and enantioselectivities. In addition, electron-withdrawing as well as donating groups on the phenyl ring of α-methyl styrenes are tolerated in this reaction.

ChemInform Abstract: Asymmetric Diels-Alder and Ene Reactions Promoted by a Ti(IV) Complex Bearing a C2-Symmetric Tridentate Ligand.

Abstract A new Ti(IV) complex obtained from the C 2 -symmetric amino diol (1 R ,5 R )-3-aza-3-benzyl-1,5-diphenyl pentan-1,5-diol, (1 R ,5 R )- 1 , is used effectively as a Lewis acid promoter in asymmetric Diels–Alder reactions. Using various Evans' oxazolidinones as dienophiles and cyclopentadiene as the diene high yields of the adducts with moderate enantioselectivity, under different reaction conditions are achieved. The effects of solvent, temperature and ligand on the enantioselectivity of the Diels–Alder products are reported. Molecular modelling studies provide an understanding of the diastereofacial selectivity of the Diels–Alder reactions. Asymmetric carbonyl-ene reactions between various glyoxylate esters and α-methyl styrene are also described.

Monomer reactivity ratio and thermal performance of α-methyl styrene and glycidyl methacrylate copolymers

Synthesis and characterization of the copolymers (PAG) of α-methyl styrene (AMS) and glycidyl methacrylate (GMA) are presented. The copolymers of PAG were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR) and thermogravimetery (TG). Based on the copolymer compositions determined by 1H-NMR, the reactivity ratios of AMS and GMA were found to be 0.105 ± 0.012 and 0.883 ± 0.046 respectively by Kelen-Tudos method. TG revealed that thermal stability of the copolymers decreased with increasing the AMS content in the copolymers, which indicated that the degradation was mainly caused by the chain scission of AMS-containing structures. Under heating, the copolymers depolymerize at their weak bonds and form chain radicals, which could further initiate other chemical reactions.

The crystallinity and miscibility of syndiotactic polystyrene blends after mixing with low molar mass liquid crystal or commercial lubricant

The quantities of the crystallinity of syndiotactic polystyrene (SPS) blended with another polymer in the group of poly(α-methyl styrene), poly(n-butyl methacrylate) or poly(cyclohexyl acrylate) with or without the additives were measured by X-ray diffraction and calculated by Ruland’s method. The SPS was synthesized by using metallocene catalyst and modified-methylaluminoxane as cocatalyst. The additive of low molar mass liquid crystal chemical (cyclohexyl-biphenyl-cyclohexane (CBC33)) or lubricant (glycerol monostearate (GMS)) was individually added to the blends of SPS in order to investigate the effects on the crystallinity of the blended SPS. From the experimental results, it was found that the percent crystallinities of the blends decreased with decreasing the percent of SPS in the blend because of the dilution of SPS. The depression of the percent crystallinity was in the order of PaMS > PCHA > PBMA according to the compatibility with SPS. The addition of GMS or CBC33 slightly decreased the percent crystallinity of the pure SPS. The addition of GMS impeded the depression of the SPS crystallinity in the blends, because their percent depression from pure SPS is similar (at around 25%) regardless to the components of the blends. The blends with added CBC33 have the similar depression of crystallinity as the pure blends because of the low concentration of CBC33 and the good compatibility of CBC33 with the SPS.

Role of polymer structure and ceiling temperature in polymer roughening and degradation during plasma processing: a beam system study of P4MS and PαMS

The degradation and roughening of polymers during plasma processing are important for the understanding of patterning of critical dimension features for both current and future lithographic techniques. Recently, the role of plasma-generated VUV photons in both the roughening and smoothing of current generation 193 nm photoresist (PR) has been investigated. However, a general understanding of the importance of polymer chemistry and structure on the degradation and roughening of polymers during plasma processing, which could be useful for polymer selection for next generation lithography, is currently lacking. Through the use of a beam system approach, the effects of ion bombardment and VUV radiation during plasma processing are investigated for two polymers with the same composition but different structure: poly(4-methyl styrene) (P4MS) and poly(α-methyl styrene) (PαMS). PαMS degrades under VUV radiation when heated above room temperature while P4MS is stable up to 70 °C, the maximum temperature studied. Both polymers undergo a drastic reduction in ion sputter yield at an ion fluence of 1 × 1016 ions cm−2, associated with the formation of a highly modified near-surface region. Almost no surface roughness is generated after VUV radiation, with moderate surface roughness formed on PαMS after ion bombardment at 70 °C. In contrast, extreme levels of surface roughness (∼10 nm rms) are observed for PαMS after simultaneous exposure to VUV photons and ion bombardment at 70 °C. Similarities to the synergistic roughening of current generation 193 nm PR under simultaneous VUV photons and ion bombardment are discussed.

Effect of Gas and Liquid Superficial Velocities on the Performance of Monolithic Reactors

The effect of gas and liquid velocities on the rate of hydrogenation of α-methyl styrene (AMS) in a monolithic reactor has been investigated at different washcoat loadings. The catalyst used was 0.5 wt % Pd/Al2O3. To cover a wide range of velocities, reaction studies were conducted in multichannel as well as single-channel monolith blocks. The liquid channel velocity was varied from 0.5 cm/s to 22 cm/s, and the gas channel velocity was varied from 1.2 cm/s to 22 cm/s. To study the effect of internal diffusional resistance, the washcoat thickness was varied from 11 μm to 62 μm. Under these operating conditions, both external mass-transfer and internal diffusional resistance affected the rate of reaction. At low liquid velocities (<2 cm/s), the measured rate of reaction was not significantly affected by the gas velocity, whereas at high liquid velocities, the measured reaction rate passed through a maximum with increasing gas velocity. The highest reaction rates were obtained for gas and liquid velocities in the range of 5−10 cm/s. At higher liquid velocities (>10 cm/s), the rate of reaction decreased with liquid velocity, most probably because of the increase in liquid slug length and film thickness around the gas bubble. The overall effectiveness factor of the monolith catalyst was determined from the measured rate of reaction and the published intrinsic kinetics. Using the approximation of Gottifredi et al. for nonlinear kinetics [Gottifredi et al. Chem. Eng. Sci. 1981, 36, 313−317], the internal effectiveness factor and overall mass-transfer coefficient were determined. The overall mass-transfer coefficients determined from the reaction-rate data have been compared with the values calculated using the available correlations.

Dependence of Pentacene Crystal Growth on Dielectric Roughness for Fabrication of Flexible Field-Effect Transistors

The dependence of pentacene nanostructures on gate dielectric surfaces were investigated for flexible organic field-effect transistor (OFET) applications. Two bilayer types of polymer/aluminum oxide (Al(2)O(3)) gate dielectrics were fabricated on commercial Al foils laminated onto a polymer back plate. Some Al foils were directly used as gate electrodes, and others were smoothly polished by an electrolytic etching. These Al surfaces were then anodized and coated with poly(alpha-methyl styrene) (PAMS). For PAMS/Al(2)O(3) dielectrics onto etched Al foils, surface roughness up to approximately 1 nm could be reached, although isolated dimples with a lateral diameter of several micrometers were still present. On PAMS/Al(2)O(3) dielectrics (surface roughness >40 nm) containing mechanical grooves of Al foil, average hole mobility (mu(FET)) of 50 nm thick pentacene-FETs under the low operating voltages (|V| < 6 V) was approximately 0.15 cm(2) V(-1) s(-1). In contrast, pentacene-FETs employing the etched Al gates exhibited mu(FET) of approximately 0.39 cm(2) V(-1) s(-1), which was comparable to that of reference samples with PAMS/Al(2)O(3) dielectrics onto flat sputtered Al gates. Conducting-probe atomic force microscopy and two-dimensional X-ray diffraction of pentacene films with various thicknesses revealed different out-of-plane and in-plane crystal orderings of pentacene, depending on the surface roughness of the gate dielectrics.

Chemical assembling of silica surface using a reaction of catalytic hydrosilylation

Chemical assembling of the silica surface modified by dimethylchlorosilane was performed by the catalytic hydrosilylation of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, α-methyl styrene, acetophenone, allyl butyl and allyl glycidyl ethers with dimethylchlorosilane. The effect of the nature of complexes of platinum, palladium, rhodium and ruthenium on the parameters of hydrosilylation was studied. It was shown that the maximum rate of hydrosilylation was observed in the reaction with allyl glycidyl ether, and minimum, with α-methylstyrene; the most effective catalyst of hydrosilylation was [Rh(CO)2(acac)].

THE INITIATION OF A MACROINITIATOR

The initiation of a novel macroinitiator is presented.The oligomers of α-methyl styrene(AMS)and glycidyl methacrylate(GMA)(designated as PAG)were used as macroinitiator in the bulk polymerization of methyl methacrylate(MMA)and styrene(St).The polymerization of MMA was carried out at 90℃ and that of St at 100℃,respectively.The resulting copolymers were characterized by Fourier transform infrared spectroscopy(FTIR)and gel permeation chromatography(GPC).The results indicated that the copolymers can be prepared by simply heating PAG in the presence of the second monomer,without any other initiator.During the process of polymerization of MMA,the higher AMS content in PAG led to higher monomer conversion,which suggested that the polymerization reaction was initiated by PAG.Under the certain reaction time,copolymers can be obtained from the reaction system of St and PAG,but there had nothing in the system of pure St.Also,the copolymers gained by polymerization of MMA initiated with PAG have the reinitiating reactivity,and the curve of molecular weight with reaction time(M_n-t)has a well linear relation,as well as that of molecular weight with yield of copolymers(M_n-Y%).Based on the research results,the possible reaction mechanism has been put forward.This simple method is expected to be applied to some other monomers,and it might be suitable even for industrial applications.

Experimental evidence against the existence of an ideal glass transition

Abstract The absolute liquid heat capacity of poly(α-methyl styrene) was determined at temperatures far below T g and T K in previous work by use of pentamer/polymer athermal mixtures. Here the data is compared to data compiled by Wunderlich and coworkers from 0 K to above T g in order to obtain the absolute entropy for the polymer in its equilibrium state at temperatures as much as 180 K below the glass temperature or 130 K below the Kauzmann temperature. The results provide no evidence of a second-order transition or of a smeared transition in the entropy. In addition, we find no evidence that the entropy would become negative at a finite temperature.

Synthesis and Polymerization of Bismaleimide Derived from 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane

The acid-catalyzed dimerization of α-methyl styrene led to the formation of trimethyl phenyl indane, which on nitration followed by reduction using hydrazine hydrate gave 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane. This aromatic diamine was used to synthesize bismaleamic acid and imidized to yield bismaleimide. The bismaleamic acid was converted to prepolymer directly by imidizing it in refluxing toluene. All the materials synthesized were characterized using FTIR, 1H and 13C NMR. The direct inlet mass spectral characterizations were carried out for bismaleamic acid, bismaleimide and bismaleimide prepolymer. The fragmentation pattern was discussed in detail and the structure proposed was confirmed. The thermogravimetric studies were done for all the materials and kinetic parameters (energy of activation and frequency factor) were calculated using Dharwadkar and Kharkhanavala method. The structural changes occurring in the thermally polymerized bismaleimide and bismaleimide prepolymer were discussed.

Accelerating effect of arsonium ylide for the copolymerization of acrylonitrile and α-methyl styrene

p-Acetyl benzylidene triphenyl arsonium ylide (p-ABTAY) accelerates α,α-azobisisobutyronitrile (AIBN) initiated copolymerization of acrylonitrile (AN) and α-methyl styrene (α-MS) in DMF at 65 ± 0.1 °C by reducing the rate of termination. The value of energy of activation in the presence and absence of p-ABTAY is 11.0 and 9.8 kJ/mol, respectively.

Enhancement in microporosity and catalytic activity on grafting silica and organosilica moieties in lamellar titanium phosphate framework

New silica-grafted analogs of lamellar semicrystalline titanium phosphate (sc-TiOP), silicotitanium phosphate (STP) and organic–inorganic hybrid silicotitanium phosphate (HSTP) have been synthesized under hydrothermal condition without the assistance of any template or structure-directing agent under acidic pH conditions. These materials were characterized by elemental analysis, powder XRD, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N2 sorption and spectroscopic studies. N2 adsorption studies revealed that the surface area increased significantly when the Si atoms were incorporated into the layered titanium phosphate framework. The surface area improves further with the grafting of organosilane moiety in HSTP material. Fourier-transformed infrared (FT IR), UV–vis and X-ray photoelectron spectroscopic (XPS) results suggested the presence of Si–O–P, Ti–O–Si bonds and octahedral coordination of Ti(IV) in these novel microporous materials. Si- and Si–CH2CH2–Si-grafted materials showed considerable enhancement in catalytic activity towards the liquid phase partial oxidation of styrene, α-methyl styrene, cyclohexene and acrylic acid using dilute H2O2 as an oxidant. These materials also showed excellent catalytic activity and selectivity in ammoximation of cyclohexanone to cyclohexanone oxime in the presence of aqueous ammonia and dilute aqueous H2O2 with reference to the silica-free sc-TiOP analogue.

Selective cis-dihydroxylation of olefins using recyclable homogeneous molybdenum acetylide catalyst

Selective cis-dihydroxylation of various olefins has been carried out using molybdenum acetylide complex CpMo(CO) 3(C CPh) ( 1) as catalyst and hydrogen peroxide as an efficient and environmentally benign oxidant. In case of cyclohexene, very high conversion (95%) and selectivity (86%) for cis-dihydroxylated product has been achieved using H 2O 2 as an oxidant and t-butanol as a solvent. cis-Dihydroxylation of other substrates like styrene, α-methyl styrene, limonene and cyclopentene has also been carried out with very high selectivity for diol. The catalyst and intermediate species have been characterized using FT-IR, UV–vis spectral analysis and XPS studies as well as cyclic voltametric studies. These studies suggest that molybdenum oxo–peroxo complex is the catalytically active species. The intermediate blue complex when characterized by ESI MS suggested the formation of dimeric molybdenum complex and XPS and cyclic voltametric studies confirm the presence of mixed valence Mo(V) and Mo(VI) in the reaction intermediate. Based on the characterization results possible mechanism for dihydroxylation is proposed. Interestingly, even though the catalyst is homogeneous; it could be recovered quantitatively by extraction in aqueous phase and recycled five times without any appreciable loss in cyclohexene conversion and selectivity for cis-1,2-cyclohexanediol.

Low‐Voltage Organic Thin‐Film Transistors with High‐k Nanocomposite Gate Dielectrics for Flexible Electronics and Optothermal Sensors

Organic field effect transistors with a nanocomposite gate of ZrO2 and poly(α-methyl styrene) (see figure, left) show performances close to the theoretically possible limit, with interface trap densities comparing favorably with the current state of the art in silicon microelectronics. They are not only key elements in flexible electronics, but also in low-cost, high-end sensors, as demonstrated with optothermal sensing elements (see figure, right).

Asymmetric Glyoxylate-Ene Reactions Catalyzed by Chiral Pd(II) Complexes in the Ionic Liquid [bmim][PF6

The room temperature ionic liquid [bmim][PF6] was employed as the reactionmedium in the asymmetric glyoxylate-ene reaction of α-methyl styrene (4a) with ethylglyoxylate using chiral palladium(II) complexes as the catalysts. [Pd(S-BINAP)(3,5-CF3-PhCN)2](SbF6)2 (1b) showed the highest catalytic activity. Under the reaction conditionsof 40 oC, 0.5 h, and 1b/4a molar ratio of 0.05, ethyl α-hydroxy-4-phenyl-4-pentenoate wasobtained in excellent chemical yield (94 %) with high enantioselectivity (70 %). Otherα-hydroxy esters can also be obtained in high chemical yields and enantioselectitiesthrough the glyoxylate-ene reactions of alkenes with glyoxylates catalyzed by 1b in[bmim][PF6]. Moreover, the ionic liquid [bmim][PF6] which contained the palladium(II)complex could be recycled and reused several times without significant loss of the catalyticactivity.