Kinetic and mechanistic studies of the oxidation of poly(o‐toluidine) doped with 5‐sulfosalicylic acid

Protonation of poly(o‐toluidine) base form (POT‐EB) with 5‐sulfosalicylic acid (SSA) was proved experimentally and computationally. Molecular mechanics (MM+) calculations showed that the potential energy (PE) of the optimum molecular geometric structure of SSA‐doped POT is 4.703 × 10³ kcal mol^?1 or at least three orders of magnitude higher than the PE of the molecular geometric structure of the same matrix. These calculations indicate that the optimization of this matrix is necessary for understanding the stability. Dark green coloration (λ ～800 nm) after addition of SSA into POT‐EB matrix (dark blue, λ ～600 nm) revealed that the SSA was working as a protonating agent to convert POT base form (POT‐EB) to salt form (SSA‐doped POT). The change of the dark green color of SSA‐doped POT to dark brown (λ ～500 nm) after addition of oxidant (K₂CrO₄) was due to the highest oxidized form of the matrix obtained (the quinoid one), which undergoes a hydrolysis reaction to produce p‐hydroquinone (H₂Q) by a mechanism similar to Schiff‐base hydrolysis. Kinetic parameters of the oxidation reaction were deduced employing a computer‐aided kinetic analysis of the absorbance (A) at ～800 nm against the hydrolysis time (t) data. The results obtained indicate that the rate controlling process may be governed by the Ginstling–Brounshetin equation for three‐dimensional diffusion (D4). The proposed mechanism for the oxidation of SSA‐doped POT matrix is also supported by MM+ calculations. Activation parameters for the rate of the oxidation process of acid‐doped POT matrix have been computed and discussed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 260–272, 2003     

Poly[aquaneodymium(III)‐μ5‐2‐oxido‐5‐sulfonatobenzoato]

The title compound, [Nd(C₇H₃O₆S)(H₂O)]_n or [Nd(SSA)(H₂O)]_n (H₃SSA is 5‐sulfosalicylic acid), was synthesized by the hydrothermal reaction of Nd₂O₃ with H₃SSA in water. The compound forms a three‐dimensional network in which the asymmetric unit contains one Nd^III atom, one SSA ligand and one coordinated water mol­ecule. The central Nd^III ion is eight‐coordinate, bonded to seven O atoms from five different SSA ligands [Nd—O = 2.405 (4)–2.612 (4) Å] and one aqua O atom [Nd—OW = 2.441 (4) Å].     

Starch?Sulfuric Acid (SSA) as Catalyst for a One‐Pot Synthesis of 1,5‐Diaryl‐1H‐pyrazoles

Protocols with starch? sulfuric acid (SSA) as reusable catalyst for the synthesis of aryl‐1H‐pyrazoles are described. SSA acted as an efficient and environmentally friendly catalyst for the regioselective condensation of Baylis? Hillman adducts 1 with phenylhydrazine hydrochloride leading to the new 1,5‐diaryl‐1H‐pyrazole 2a – 2e in excellent yields (Scheme and Table 1).     

Application of SSA thermal fractionation and X‐ray diffraction to elucidate comonomer inclusion or exclusion from the crystalline phases in poly(butylene succinate‐ran‐butylene azelate) random copolymers

Poly(butylene succinate‐ran‐butylene azelate) random copolyesters were thermally fractionated by successive self‐nucleation and annealing (SSA). The samples before and after SSA were analyzed by differential scanning calorimetry (DSC) and X‐ray diffraction (WAXS and SAXS). WAXS results indicate that a small degree of comonomer inclusion is present in the crystalline phases that are formed in the copolymers depending on composition: a PBS‐like unit cell or/and a PBAz‐like unit cell, thus confirming the isodimorphic behavior of the samples. SSA on the other hand demonstrated that the degree of comonomer exclusion during crystallization is far larger than comonomer inclusion, as judged by the increase in fractionation degree with compositions leading to the pseudo‐eutectic point. Furthermore, WAXS, SAXS, and SSA results show that the isodimorphic behavior is not highly dependent on kinetic factors, as the degree of comonomer inclusion or exclusion in the samples was not significantly altered by SSA thermal fractionation, a thermal treatment that promotes annealing and molecular segregation of defects to the amorphous regions of the material. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2346–2358     

Effect of the γ‐form crystal on the thermal fractionation of poly(propylene‐co‐ethylene)

The effect of the γ‐form crystal on the thermal fractionation of a commercial poly(propylene‐co‐ethylene) (PPE) has been studied by differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) techniques. Two thermal fractionation techniques, stepwise isothermal crystallization (SIC) and successive self‐nucleation and annealing (SSA), have been used to characterize the molecular heterogeneity of the PPE. The results indicate that the SSA technique possesses a stronger fractionation ability than that of the SIC technique. The heating scan of the SSA fractionated sample exhibits 12 endothermic peaks, whereas the scan of the SIC fractionated sample only shows eight melting peaks. The WAXD observations of the fractionated PPE samples prove that the content of the γ‐form crystals formed during the thermal treatment of the SIC technique is much higher than that of the SSA treatment. The former is 57.4%, whereas the later is 12.6%. The effect of theγ‐form crystals on thermal fractionation ability is discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4320–4325, 2004     

Electrospun poly(ε‐caprolactone)‐based composites using synthesized β‐tricalcium phosphate

Non‐woven hybrid membranes based on poly(ε‐caprolactone) (PCL) and as‐synthesized β‐tricalcium phosphate (β‐TCP) were obtained by the electrospinning technique. A wide range of composition was investigated, the filler content spanning between 2 and 60 wt%. The synthesis of the β‐TCP powder was accomplished by titration of calcium hydroxide with phosphoric acid followed by calcination of the resulting precipitate at 1100°C. The as‐dried calcium phosphate was characterized by Inductive Coupled Plasma (AES‐ICP), thermal analysis (TG‐DTA), Fourier Transform Infrared Spectroscopy (FT‐IR), Scanning Electron Microscopy (SEM), and high temperature X‐ray diffraction analysis (HT‐XRD). The specific surface area (SSA) was evaluated by N₂ adsorption. Microstructure of PCL/TCP membranes was investigated by SEM, energy dispersion spectroscopy (EDS), XRD analysis, and SSA measurements. The average fiber diameter ranged between 1 and 2 µm, the porosity was 80–90%, and the SSA 16 m²/g. Mechanical properties were determined by uniaxial tensile test. A remarkable enhancement of the tensile modulus was observed for composites containing up to 4 wt% β‐TCP. The ultimate tensile strength ranged between 2 and 3 MPa for samples loaded up to 8 wt%. For most of the samples, the elongation at break was in the range 100–150%. Copyright © 2010 John Wiley & Sons, Ltd.     

Probing the early stages of thermal fractionation by successive self‐nucleation and annealing performed with fast scanning chip‐calorimetry

The thermal fractionation kinetics of a linear low‐density polyethylene (LLDPE) during Successive Self‐Nucleation and Annealing (SSA) is investigated by fast scanning chip‐calorimetry (FSC), by systematically varying the holding times (t_s) at each fractionation temperature (T_s). The range of explored fractionation times spans four orders of magnitude, from 0.001 to 10 s. Discernible thermal fractions are already detected in the very early stages of the process, at t_s shorter than one second. As t_s increases, the melting endotherm after SSA indicates a progressive lamellar thickening and narrowing of the thicknesses distribution of the various crystalline fractions. The largest variations are observed for the families of crystals containing the longest crystallizable sequences, which also undergo a change of their relative content as a consequence of self‐nucleated crystallization at T_s. The quality of the thermal fractionation obtained in 10 seconds with FSC is equivalent to that of conventional differential scanning calorimetry SSA (t_s = 300 s). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2200–2209     

Iron‐mediated AGET ATRP of MMA with sulfosalicylic acid as a ligand

Iron‐mediated atom transfer radical polymerizations with activators generated by electron transfer of methyl methacrylate in N,N‐dimethylformamide solution in the presence and absence of a limited amount of air, using FeCl₃·6H₂O as the catalyst, ethyl 2‐bromoisobutyrate (EBiB) as the initiator, vitamin C as the reducing agent, and a commercially available organic acid, sulfosalicylic acid (SSA), as the ligand were investigated. Addition of SSA as the ligand could enhance the polymerization rate, and produce poly(methyl methacrylate) with controllable molecular weights and narrow molecular weight distributions (M_w/M_n = 1.30–1.50). The effect of [FeCl₃·6H₂O]₀/[SSA]₀ on the polymerization was studied by cyclic voltammetry characterization. Chain extension was performed to confirm the “living”/controlled nature of the polymerization system. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Solvent‐Free One‐Pot Synthesis of Amidoalkyl Naphthols Catalyzed by Silica Sulfuric Acid

An efficient, inexpensive, and mild method for the synthesis of amidoalkyl naphthols, catalyzed by ‘silica sulfuric acid’ (SSA), was elaborated under solvent‐free conditions at room temperature. Various amidoalkyl naphthols were synthesized in high yields from aromatic or aliphatic aldehydes, α‐ or β‐naphthols, and amides or urea or thiourea.     

Synthesis of gem-Dihydroperoxides from Ketones and Aldehydes Using Silica Sulfuric Acid as Heterogeneous Reusable Catalyst

Silica sulfuric acid (SSA) was found to efficiently catalyze the conversion of aldehydes and ketones directly into the corresponding gem-dihydroperoxides (DHPs) on treatment with aqueous 30% H₂O₂ at room temperature. Mild reaction conditions, good to excellent yields, short reaction times, low environmental impact, and recyclability of the catalyst are the main advantages of this synthetic method.     

Structural effects of dopants and polymerization methodologies on the solid‐state ordering and morphology of polyaniline

The solid‐state three‐dimensional ordering of polyaniline–dopant complexes was investigated with four structurally different sulfonic acid dopants. The doped materials were produced in three different ways: polyaniline emeraldine base doped with sulfonic acid (aqueous route), in situ polymerization at the organic–water solvent interface (interfacial route), and in situ polymerization in organic and aqueous solvent mixtures (bilayer route). p‐Toluenesulfonic acid (PTSA), 5‐sulfosalicilic acid (SSA), camphorsulfonic acid (CSA), and dodecylbenzene sulfonic acid (DBSA) were employed as dopants. The conductivity of the aqueous‐route samples showed 10 and 100 times higher conductivity than the interfacial and bilayer routes, respectively. WXRD studies suggested that the crystallinity of the doped samples was dependent on both the structure of the dopants and the polymerization techniques. DBSA increases the polyaniline interplanar distance and produced highly crystalline materials via the aqueous and bilayer routes but failed with the interfacial route because of poor solubility in water. CSA, PTSA, and SSA produced highly crystalline samples by the interfacial route but failed with the aqueous (except for CSA) and bilayer routes. SEM analysis revealed that the doped materials of the interfacial route had excellent continuous morphology and uniform submicrometer‐size particle distributions in comparison with those of the aqueous and bilayer routes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1321–1331, 2005     

High‐molar‐mass polypropene with tunable elastic properties by hafnocene/borate catalysts

Elastic polypropene has gained growing industrial and academic interest as a thermoplastic elastomer. In this study, “rac”‐ and “meso”‐dimethylsilyl(3‐benzylindenyl)(2‐methylindenyl)hafnium dichloride complexes (Hfr and Hfm, respectively), activated with [NHMe₂Ph][B(C₆F₅)₄]/triisobutyl aluminum, were used in propene polymerization. Using these catalyst systems, we obtained polymers with high molar masses, up to 550 kg/mol, and moderate isotacticities between 34 and 52%. By varying the polymerization conditions, we could modify the polymer microstructure and molar mass. ¹³C NMR was used to calculate the polymer pentad sequence distributions. The crystalline parts of the polymers were analyzed with the differential scanning calorimetry successive self‐nucleation and annealing (SSA) technique. The SSA thermograms revealed that Hfr produced polypropene with a more uniform lamellar structure than Hfm. The mechanical properties were tested with dynamic mechanical analysis creep‐recovery tests. In the series, the polymers with the lowest isotacticities and therefore lowest crystallinities showed the best elastic properties. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4743–4751, 2006     

Improved accuracy of quantitative XPS analysis using predetermined spectrometer transmission functions with UNIFIT 2004

The accuracy of quantitative XPS analysis can be improved using predetermined transmission functions. Two different calibration methods are used for estimating the transmission function T(E) of a photoelectron spectrometer, applying a survey spectra approach (SSA) and a quantified peak‐area approach (QPA) to minimize the quantification error. For the SSA method, Au, Ag and Cu spectra measured with the Metrology Spectrometer II have been used. The new QPA method was built up from Au 4f, Au 4d, Au 4p_3/2, Ag 3d, Ag 3p_3/2, Cu 3p, Cu 2p_3/2, Ge 3p and Ge 2p_3/2 standard peak areas, applying adequate ionization cross‐sections and mean free path lengths for different pass energies (10 and 50 eV), lens modes (large area, large area XL, small area 150) and x‐ray sources (Al/Mg Twin and Al Mono). In the energy range 200–1500 eV a transmission function T(E) = a₀ + b₁E (where a₀, b₁ and b₂ are variable parameters) was found to give an appropriate approximation for eight tested spectrometer settings, implementing the largest changes in the case of pass energy variations. Determination and application of the transmission functions were integrated in the XPS analysis software (UNIFIT 2004) and tested by means of an Ni90Cr10 alloy. The results demonstrate the practicability of the SSA and QPA methods, giving decreased errors of <8% in comparison with errors up to 38% obtained using Wagner's sensitivity factors. Copyright © 2005 John Wiley & Sons, Ltd.     

Proton conducting grafted/crosslinked membranes prepared from poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) copolymer

Poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) (P(VDF‐co‐CTFE)) backbone was grafted with crosslinkable chains of poly(hydroxyl ethyl acrylate) (PHEA) and proton conducting chains of poly(styrene sulfonic acid) (PSSA) to produce amphiphilic P(VDF‐co‐CTFE)‐g‐P(HEA‐co‐SSA) graft copolymer via atom transfer radical polymerization (ATRP). Successful synthesis and microphase‐separated structure of the copolymer were confirmed by ¹H NMR, FT‐IR spectroscopy, and TEM analysis. Furthermore, this graft copolymer was thermally crosslinked with sulfosuccinic acid (SA) to produce grafted/crosslinked membranes. Ion exchange capacity (IEC) increased continuously with increasing SA contents but the water uptake increased up to 6 wt% of SA concentration, above which it decreased monotonically. The membrane also exhibited a maximum proton conductivity of 0.062 S/cm at 6 wt% of SA concentration, resulting from competitive effect between the increase of ionic groups and the degree of crosslinking. XRD patterns also revealed that the crystalline structures of P(VDF‐co‐CTFE) disrupted upon graft polymerization and crosslinking. These membranes exhibited good thermal stability at least up to 250°C, as revealed by TGA. Copyright © 2009 John Wiley & Sons, Ltd.     

Proton conductivity in crosslinked hydrophilic ionic polymer system: Competitive hydration,crosslink heterogeneity,and ineffective domains

High proton conductivity in hydrophobic backbone‐based polymers such as Nafion is known to be due to the formation of organized ionic clusters and channels upon hydration. However, a lower proton conductivity in hydrophilic, ionic polymers and the role played by the microstructure are not well understood. In this work, we demonstrate the importance of heterogeneity in crosslinked ionic polymer networks in explaining proton conductivity. Poly(vinyl alcohol) (PVA) crosslinked with sulfosuccinic acid (SSA) is used as the model polymer system for the study. Evolution of the microstructure with hydration and the effect on proton conductivity are analyzed using ATR‐FTIR spectroscopy, dielectric spectroscopy, and small‐angle neutron scattering. We show that the presence of the two hydrophilic groups in PVA‐SSA (hydroxyl and sulfonic acid), as opposed to Nafion, results in competition for water and a lower proton conductivity. The crosslinked polymer–water system contains heterogeneous domains of crosslink nodes which are conductive. These domains (of size 20–35 Å) interconnect with each other and form tortuous percolating domains through which proton conduction takes place. The presence of hydroxyl groups results in some of the domains being ineffective for proton transport, resulting in a lower conductivity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1087–1101     

A facile preparation method for synthesis of silica sulfuric acid/poly(o‐methoxyaniline) core–shell nanocomposite

A new nanocomposite of poly(o‐methoxyaniline) (POMA) is introduced by overlayer formation of POMA on silica. The key appealing feature of the synthesis is the role of silica sulfuric acid (SSA) both as solid acid dopant and template in overlayer self‐assembly of POMA on silica surface. Hereon siloxide group (Si―O^?) of silica surface is replaced with dopant anion of SSA (≡Si―O―SO₃^?), which leads to formation of a overlayer of POMA on the silica surface. The composite particles are spherical in the nanoscale range of 50 nm without application of any external template (no‐template synthesis). Nanocomposite was fully characterized by various instrumentation methods: Fourier transform infrared (FT‐IR), ultraviolet–visible (UV–vis), thermogravimetric analysis (TGA), diffrential thermal analysis (DTA), elemental analysis (CHNS), energy dispersive X‐ray (EDX), X‐ray photoelectron spectroscopy (XPS) and X‐ray difraction (XRD). Based on XPS and CHNS results, it is demonstrated that the doping level of POMA is as high as 50% and for the first time the ratio of 4:2:2 is obtained for ―NH― (amine): ―HN^.+― (polarons): ?HN⁺― (bipolarons), respectively. In fact, bipolarons may also coexist with polarons with a 1:1 ratio of them. Moreover, the synthesis benefits from the perspective of green chemistry which is preparation under solid‐state (solvent‐free) condition. Copyright © 2015 John Wiley & Sons, Ltd.     

A One‐Pot Tandem Ugi Multicomponent Reaction (MCR)/Click Reaction as an Efficient Protecting‐Group‐Free Route to 1H‐1,2,3‐Triazole‐Modified α‐Amino Acid Derivatives and Peptidomimetics

By a one‐pot tandem Ugi multicomponent reaction (MCR)/click reaction sequence not requiring protecting groups, 1H‐1,2,3‐triazole‐modified Ugi‐reaction products 6a – 6n (Scheme 1 and Table 2), 7a – 7b (Table 4), and 8 (Scheme 2) were synthesized successfully. i.e., terminal, side‐chain, or both side‐chain and terminal triazole‐modified Ugi‐reaction products as potential amino acid units for peptide syntheses. Different catalyst systems for the click reaction were examined to find the optimal reaction conditions (Table 1, Scheme 1). Finally, an efficient Ugi MCR+Ugi MCR/click reaction strategy was elaborated in which two Ugi‐reaction products were coupled by a click reaction, thus incorporating the triazole fragment into the center of peptidomimetics (Scheme 3). Thus, the Ugi MCR/click reaction sequence is a convenient and simple approach to different 1H‐1,2,3‐triazole‐modified amino acid derivatives and peptidomimetics.     

Accelerated stochastic simulation of the stiff enzyme-substrate reaction

The enzyme-catalyzed conversion of a substrate into a product is a common reaction motif in cellular chemical systems. In the three reactions that comprise this process, the intermediate enzyme-substrate complex is usually much more likely to decay into its original constituents than to produce a product molecule. This condition makes the reaction set mathematically "stiff." We show here how the simulation of this stiff reaction set can be dramatically speeded up relative to the standard stochastic simulation algorithm (SSA) by using a recently introduced procedure called the slow-scale SSA. The speedup occurs because the slow-scale SSA explicitly simulates only the relatively rare conversion reactions, skipping over occurrences of the other two less interesting but much more frequent reactions. We describe, explain, and illustrate this simulation procedure for the isolated enzyme-substrate reaction set, and then we show how the procedure extends to the more typical case in which the enzyme-substrate reactions occur together with other reactions and species. Finally, we explain the connection between this slow-scale SSA approach and the Michaelis-Menten [Biochem. Z. 49, 333 (1913)] formula, which has long been used in deterministic chemical kinetics to describe the enzyme-substrate reaction.     

Synthesis of 5‐aryl and 5‐amidocamptothecins

A variety of 5‐aryl‐(20S)‐camptothecin derivatives were synthesized by the reaction of 5‐hydroxy‐(20S)‐camptothecin with aromatic hydrocarbons under Friedel‐Craft reaction conditions in moderate to good yield as diastereomeric pairs. The methodology was then extended for the synthesis of 5‐amido‐(20S)‐camptothecin derivatives by reacting 5‐hydroxy‐(20S)‐camptothecin with alkyl and aryl nitriles under Ritter type reaction conditions. The reaction is presumed to proceed through an iminium ion intermediate under Friedel Craft and Ritter type reaction condition, which is further trapped by nucleophile present in the reaction medium. J. Heterocyclic Chem., 00 , 00 (2011).