Reaction kinetics of epoxy resin modified with reactive and nonreactive thermoplastic copolymers

An epoxy resin system based on a triglycidyl p‐amino phenol (MY0510) was crosslinked using stoichiometric amounts of 4,4′‐diaminodiphenyl sulfone. The epoxy was modified with random copolymers, polyethersulfone‐poly(ether‐ethersulfone) (PES:PEES), with either amine or chlorine end groups, at 10 and 20 wt %. The reaction kinetics for both unmodified and modified epoxy systems were studied using differential scanning calorimetry in isothermal and dynamic conditions. The results show that the degree of conversion in thermoplastic‐modified epoxies at any reaction time is smaller compared with the unmodified resin. Gel point (GP) determination was done from rheological measurements. The modified system containing 20% of the PES:PEES additive showed considerable increase in the GP. The reaction rate shows the characteristic of an autocatalytic reaction where the product acts as catalyst. The activation energy, E_a calculated from the isothermal reaction depends on the extent of conversion and increases with increasing PES:PEES content. For unmodified epoxy system, the average E_a is 67.8 ± 4.1 kJ mol^?1 but for systems modified with 20 wt % of amine and chlorine PES:PEES, the value increased to 74.1 ± 3.3 and 77.9 ± 4.4 kJ mol^?1, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of copolymers of poly(ether ether sulfone)/semiaromatic polyamides (PEES/PA)

Poly(ether ether sulfone) (PEES) containing semi‐aromatic polyamides with methylene units and ether linkage were synthesized through the copolymerization of m‐dihydroxybenzene, 4,4‐dichlorodiphenylsulfone (DCDPS) and 1,6‐N, N′‐bis(4‐fluorobenzamide) hexane (BFBH) by the method of nucleophilic polymerization. The inherent viscosities of the resultant different proportion of copolymers were in the range of 0.39–0.78 dL/g. These copolymers were found to have excellent thermal properties with glass transition temperatures (T_g) of 121–177°C, and initial degradation temperatures (T_d) of 417.5–432.5°C. These copolymers showed good mechanical properties with tensile strengths of 45–83 MPa, storage modulus of 1.8–2.6 GPa. The complex viscosities of pure Poly(ether ether sulfone) (PEES) was in the range of 176,000–309.8 Pas from 0.01 to 100 Hz, the complex viscosities of the copolymers decreased significantly with the increase of semi‐aromatic amide content, the copolymers of 20% decreased from 4371 to 142.4 Pas (from 0.01 to 100 Hz), and the copolymers of 70% dropped from 634.6 Pas to 55.97 Pas (from 0.01 Hz to 100 Hz). All copolymers exhibited non‐Newtonian and shear‐thinning behavior. These results suggested the resultant copolymers possess better melt flowability that is beneficial for the materials’ melt processing. POLYM. ENG. SCI., 56:44–50, 2016. © 2015 Society of Plastics Engineers     

Removal of aldehydes by amino acids and their salts in ambient air

The removal of gaseous aldehydes by amino acids and by their sodium salts and hydrochlorides was studied in ambient air with the relative humidity of 30% at 25°C. Amino acid sodium salts, diamino acids, sodium p-aminobenzoate (PABANa), and o-aminobenzoate (OABANa), and p-aminobenzoic acid (PABA) on sepiolite, both having a carboxylato functionality (? COO^?) together with an amino (? NH₂) group, were highly reactive with aldehydes. In contrast, PABA which has free carboxylic acid functionality (? COOH: dimeric) was not so reactive with aldehydes. Normal amino acids and their hydrochlorides having ammonio (? NH₂⁺) and ? COO^? or ? COOH (dimeric) groups were less reactive with aldehydes. The reactivity was closely related to the degree of dissociation of carboxylate anion; as the degree of dissociation increases, the compound becomes more reactive. p-Aminobenzoic acid hydrochloride (PABA · HCl), having ? NH₃⁺ and ? COOH (monomeric) groups, was the most reactive (with ethanal) of all the amino acids and their salts examined. Amino acid sodium salts, diamino acid, PABANa, OABANa, and PABA on sepiolite are proved to be excellent removers of aldehydes in ambient air. Among them, PABA · HCl is particularly good for ethanal.     

Thermal behavior of PES/PEES copolymers with different sequence distribution: Comparative study of the kinetics of degradation

The degradation of three aromatic thermoplastics copolymers of polyethersulfone (PES) and polyetherethersulfone (PEES) with the same composition but different sequence distribution was performed in a thermogravimetric analyzer in both nitrogen and air environments, in isothermal and dynamic heating conditions. The obtained results suggest that the degradations started by random chain scission under all the experimental conditions. Under N₂ flow, branching and crosslinking were superimposed on the initial process, whereas complete oxidative degradation occurred in air. The apparent activation energies associated with the first degradation stage were evaluated and correlated with the sequence linkages present in the copolymer chains. The obtained values indicated that the chemical reactions occurring under nitrogen were different from those in air. In addition, a comparison of activation energies of PES/PEES copolymers with different sequence distribution was also reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of chitosan films mixed with superabsorbent polymer and evaluation of its haemostatic and antibacterial activities

In this study, polycaprolactone/C₆₀ (PCL/C₆₀) hybrids were prepared via a melt‐blending method. To enhance the compatibility between PCL and C₆₀, the acrylic acid‐grafted polycaprolactone (PCL‐g‐AA) was first transformed to PCL? NH₂ by mixing with 1,6‐diaminohexane, while C₆₀ was oxidized using a mixture of H₂SO₄/HNO₃ and NaOH to derive C₆₀ fullerol (C₆₀? OH). Thereafter, C₆₀? OH and PCL? NH₂ were used to replace PCL and C₆₀, respectively. The resulting products were characterized using FTIR, solid‐state ¹³C‐ and ¹H‐ NMR, TGA, DMA, SEM, TEM, and Instron mechanical testing. Because of the formation of ? NHCO groups through the reaction between amino groups of PCL? NH₂ and hydroxyl groups of C₆₀? OH, thermal and mechanical properties of the PCL? NH₂/C₆₀? OH composite were significantly superior to those of PCL/C₆₀. The optimal blend was the 5 wt % C₆₀? OH with PCL? NH₂, producing an 84°C increase in initial decomposition temperature (IDT). C₆₀? OH in excess of 5 wt % aggregated and caused separation of the organic and inorganic phases, lowering their compatibility.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

IR spectroscopy approach for the study of interactions between an oxidized aluminium surface and a poly(propylene-g-acrylic acid) film

In this paper, we report the study of the interactions between a poly(propylene-g-acrylic acid) and an oxidized aluminium surface by IR spectroscopy. A deposit of a pure poly(acrylic acid) on the same surface is used as a model. Under free acid form (COOH) we demonstrate the formation of hydrogen bondings between the acrylic carboxyl groups and OH functions located at the surface of alumina. This is characterized by an IR absorption [v_(c?o)] at 1733 or 1743 cm^?1 when we observe the metal surface either after peeling of a PPg(OH) film initially pressed on it or after a deposit of PAA(OH). Under the carboxylate form (COO^?), we observe two modes of interaction, the one purely ionic between COO^? and Al³⁺ with an absorption located near 1550 cm^?1 and the other of complex form between COO^? and Al³⁺ giving a band near 1610 cm^?1. The water molecules can play a major part, in particular in the first case (COOH) where they destroy hydrogen bondings in favor of the formation of ? COO^? groups, interacting with the metal surface according to ionic or complex modes as above. © 1993 John Wiley & Sons, Inc.     

Heterogeneous production of Cl2 from particulate chloride: Effects of composition and relative humidity

Reactions initiated by chlorine atoms can enhance the formation of ozone (O₃) and secondary organic aerosol (SOA) in the troposphere. Environmental chamber experiments were conducted to quantify heterogeneous Cl₂ production from NH₄Cl and NaCl particles exposed to O₃ and hydroxyl radicals (?OH). Observations are inconsistent with models of Cl₂ production resulting solely from surface‐mediated reactions of ?OH and suggest that O₃ plays a significant role. The production of Cl₂ increased with relative humidity and decreased in the presence of SOA or nitric oxides (NO_x). Heterogeneous reactive uptake coefficients for the production of Cl₂ from O₃ on pure NH₄Cl ( ) averaged 1.4 ± 1.0 × 10^?3. Cl₂ production was six times more efficient on NH₄Cl aerosol than on NaCl aerosol. Model calculations under atmospheric conditions suggest this heterogeneous Cl₂ production could increase peak daily O₃ concentrations by over 10%. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3151–3158, 2018     

Study on hot air aging and thermooxidative degradation of peroxide prevulcanized natural rubber latex film

The air‐aging process at 120°C and the thermooxidative degradation of peroxide prevulcanized natural rubber latex (PPVL) film were studied with FTIR and thermal gravity (TG) and differential thermal gravity (DTG) analysis, respectively. The result of FTIR shows that the ? OH and ? COOH absorption of the rubber molecules at IR spectrum 3600–3200 cm^?1, the ? C?O absorption at 1708 cm^?1, and the ? C? OH absorption of alcohol at 1105 and 1060 cm^?1 increased continuously with extension of the aging time, but the ? CH₃ absorption of saturated hydrocarbon at 2966 and 2868 cm^?1, the ? CH₃ absorption at 1447 and 1378 cm^?1, and the C?C absorption at 835 cm^?1 decreased gradually. The result of TG‐DTG shows that the thermal degradation reaction of PPVL film in air atmosphere is a two‐stage reaction. The reaction order (n) of the first stage of thermooxidation reaction is 1.5; the activation energy of reaction (E) increases linearly with the increment of the heating rate, and the apparent activation energy (E₀) is 191.6 kJ mol^?1. The temperature at 5% weight loss (T_0.05), the temperature at maximum rate of weight loss (T_p), and the temperature at final weight loss (T_f) in the first stage of degradation reaction move toward the high temperature side as the heating rate quickened. The weight loss rate increases significantly with increment of heating rate; the correlation between the weight loss rate (α_p) of DTG peak and the heating rate is not obvious. The weight loss rate in the first stage (α_f1) rises as the heating rate increases. The final weight loss rate in second stage (α_f2) has no reference to heating rate; the weight loss rate of the rubber film is 99.9% at that time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3196–3200, 2004     

Synthesis, Characterization and Properties of New Lauryl Amidopropyl Trimethyl Ammoniums

A new lauryl amidopropyl trimethyl ammonium methyl carbonate with the formula CH₃(CH₂)₁₀CONH(CH₂)₃N⁺(CH₃)₃CH₃CO₃ ^? was synthesized via a high pressure process with tertiary amines and dimethyl carbonate, and its chemical structure was confirmed using ¹H-NMR spectra, mass spectral fragmentation, and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions X^? (X^?=HCO₃ ^?, HCOO^?, CH₃COO^?, CH₃CH(OH)COO^?) were also synthesized by the ion exchange reaction of methyl carbonate quaternary ammoniums with corresponding acids. The surface activities of these compounds were measured, including surface tension (??), critical micelle concentration and minimum surface area (A _min) at 25?°C. Adsorption and micellization free energies of these quaternary ammonium salts in their solutions showed a good tendency towards adsorption at interfaces. The antimicrobial activities are reported for the first time against representative bacteria and fungi for lauryl amidopropyl trimethyl ammoniums. It was found that the antimicrobial potency was Gram-positive bacteria?>?fungi?>?Gram-negative bacteria.     

Structural characterization and thermal behaviour of block copolymers of polydimethylsiloxane and polyamide having trichlorogermyl pendant groups

Block copolymers having a pendant trichlorogermyl group as a part of polyamide segment? (CO? R′? CO? NH? Ar? NH? )_xCO? R′? CO? and polydimethylsiloxane of general formula [(? CO? R′? CO? HN? Ar? NH)_x? CO? R′? CO? NH(CH₂)₃SiO(CH₃)₂ ((CH₃)₂SiO)_ySi(CH₃)₂(CH₂)₃ NH? ]_n (where R′ = CH₂CH(GeCl₃), CH(CH₃)CH(GeCl₃), CH(GeCl₃)CH(CH₃); Ar = C₆H₄, (? C₆H₃? CH₃)₂, (? C₆H₃? OCH₃)₂, 2,5‐(CH₃)₂? C₆H₂, C₆H₄? O? C₆H₄) were prepared by a polycondensation reaction and characterized using CHN and Ge analysis, Fourier transform infrared (FTIR) and ¹H NMR spectroscopy, thermogravimetric analysis (TGA) and molecular weight determination. They have a lamellar structure with weight‐average molecular weight in the range 1.21 × 10⁵–4.79 × 10⁵ g mol^?1. These copolymers display two glass transition temperatures and have an average decomposition temperature of 489 °C. TGA, FTIR and gas chromatography/mass spectrometry studies indicate that degradation of these block copolymers results in carbon monoxide, oligomeric siloxanes and polyamide fragments. They are thermally stable due to the hydrogen bonded interlinked chains of polyamide, while they absorb water due to the presence of Ge? Cl bonding. Copyright © 2010 Society of Chemical Industry     

Effects of electrolytes upon potential—pH relation of electrolytic gamma manganese dioxide

Potential-pH relations of two electrolytic gamma manganese dioxides were determined in NH₄Cl (pH 1–8), ZnCl₂ (pH 0–5), and C₂H₅)₄ (pH 1–8) solutions in order to examine how the supporting electrolytes affect upon both magnitude and pH-response of potential. There was no significant difference in the effects of those electrolytes. The pH-response of ?0.060 V .pH^?1 obtained was very close to the theoretical value of ?0.059 V .pH^?1 at 25°C estimated from the following reaction,

Ion-exchange adsorption found for Zn²⁺ and NH₄⁺ ions did not have any effect upon the pH-response, though a remarkable effect was expected. Another pH-response of ?0.075 ～ 0.100 V .pH^?1 was obtained in NH₄ClHCl (pH 1–3) and (C₂H₅)₄ NClO₄  HClO₄ (pH.1–2.5) solutions. This response was found to be caused by soluble Mn²⁺ ions formed by the wellknown disproportionation reaction of Mn(III) being present in the MnO₂ samples.     

Role of 2‐hydroxyethyl end group on the thermal degradation of poly(ethylene terephthalate) and reactive melt mixing of poly(ethylene terephthalate)/poly(ethylene naphthalate) blends

In an attempt to minimize the acetaldehyde formation at the processing temperatures (280–300°C) and the outer–inner transesterification reactions in the poly (ethylene terephthalate) (PET)–poly(ethylene naphthalate) (PEN) melt‐mixed blends, the hydroxyl chain ends of PET were capped using benzoyl chloride. The thermal characterization of the melt‐mixed PET–PEN blends at 300°C, as well as that of the corresponding homopolymers, was performed. Degradations were carried out under dynamic heating and isothermal conditions in both flowing nitrogen and static air atmosphere. The initial decomposition temperatures (T_i) were determined to draw useful information about the overall thermal stability of the studied compounds. Also, the glass transition temperature (T_g) was determined by finding data, indicating that the end‐capped copolymers showed a higher degradation stability compared to the unmodified PET and, when blended with PEN, seemed to be efficient in slowing the kinetic of transesterification leading to, for a finite time, the formation of block copolymers, as determined by ¹H‐NMR analysis. This is strong and direct evidence that the end‐capping of the ? OH chain ends influences the mechanism and the kinetic of transesterification. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

A novel “plane-line-plane” nanostructure of the sandwich-like CNTs@SnO2/Ti3C2Tx 3D nanocomposite as a promising anode for lithium-ion batteries

As one of the novel two-dimensional metal carbides, Ti₃C₂T_x has received intense attention for lithium-ion batteries. However, Ti₃C₂T_x has low intrinsic capacity due to the fact that the surface functionalization of F and OH blocks Li ion transport. Herein a novel “plane-line-plane” three-dimensional (3D) nanostructure is designed and created by introducing the carbon nanotubes (CNTs) and SnO₂ nanoparticles to Ti₃C₂T_x via a simple hydrothermal method. Due to the capacitance contribution of SnO₂ as well as the buffer role of CNTs, the as-fabricated sandwich-like CNTs@SnO₂/Ti₃C₂T_x nanocomposite shows high lithium ion storage capabilities, excellent rate capability and superior cyclic stability. The galvanostatic electrochemical measurements indicate that the nanocomposite exhibits a superior capacity of 604.1 mAh g^?1 at 0.05?A?g^?1, which is higher than that of raw Ti₃C₂T_x (404.9 mAh g^?1). Even at 3?A?g^?1, it retains a stable capacity (91.7 mAh g^?1). This capacity is almost 5.6 times higher than that of Ti₃C₂T_x (16.6 mAh g^?1) and 58 times higher than that of SnO₂/Ti₃C₂T_x (1.6 mAh g^?1). Additionally, the capacity of CNTs@SnO₂/Ti₃C₂T_x for the 50th cycle is 180.1 mAh g^?1 at 0.5?A?g^?1, also higher than that of Ti₃C₂T_x (117.2 mAh g^?1) and SnO₂/Ti₃C₂T_x (65.8 mAh g^?1), respectively.     

Supercapacitor device performances of polycarbazole/graphene and polycarbazole/nanoclay/graphene nanocomposites

In this study, graphene oxide (GO) is chemically reacted with sodium borohydride (NaBH₄) to form reduced graphene oxide (rGO). rGO, polycarbazole (PCz)/rGO and PCz/nanoclay/rGO materials were obtained by chemical polymerisation method. These three materials were characterised by Fourier-transform infra-red spectroscopy-attenuated transmission reflectance, scanning electron microscopy, energy-dispersive X-ray analysis, cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy. The PCz/nanoclay/rGO nanocomposite shows significantly improved capacitance (C_sp?=?187.78?F?g^?1) compared to that of PCz/rGO (C_sp?=?74.18?F?g^?1) and rGO (C_sp?=?20.78?F?g^?1) at the scan rate of 10?mV?s^?1 by CV method. The supercapacitor device performance results show high power density (P?=?1057.81?W?kg^?1) and energy density (E?=?1.7?Wh?kg^?1) obtained from Ragone plot for PCz/nanoclay/rGO material. Stability tests were also examined by the CV method for 1000 cycles.     

Matrix tacticity controlled tuning of microstructure,constitutive behavior and rheological percolation effect of melt‐mixed amino‐functionalized MWCNT/PP nanocomposites

Amino‐functionalized multi walled nanotube (MWCNT‐NH₂) filled isotactic PP and isotactic‐syndiotactic (70:30) mixed PP based melt‐mixed nanocomposites have been comparatively evaluated with regard to morphological, rheological and thermo‐mechanical properties. The ratio of mean free space lengths (L_f) to infiltrated mean free space lengths (L_inf) between nanotubes in isotactic‐syndiotactic (70:30) blended matrix based nanocomposites increased relatively indicating a dispersed‐morphology. The rheological percolation threshold increased up to a higher extent of MWCNT‐NH₂ loading (from ø_c ～ 2.3 × 10^?4 in isotactic to ø_c ～ 11 × 10^?4 in iso‐syndio blend) accompanied with the formation of a mechanically responsive network structure. van‐GurpPalmen plot showed a transition in the rheological response as a consequence of network morphology getting shifted to higher concentration of MWCNT‐NH₂ in the isotactic‐syndiotactic mixed PP based nanocomposites than in the isotactic based one. Constitutive modeling of complex viscosity response of the nanocomposites led to functional correlation between the percolation and relaxation dynamics of polymer chains. POLYM. ENG. SCI., 58:1115–1126, 2018. © 2017 Society of Plastics Engineers     

On the electrochemical behavior of H2O2 AT Ag in alkaline solution

Electrochemical oxidation and reduction of H₂O₂ on Ag were studied in alkaline solution of 10^?3?0.3 M H₂O₂ and 2 × 10^?3 ?1.0 M KOH under N₂ bubbling. Steady i-φ curves obtained by a cyclic potential sweep method in a potential range where no electrode oxidation takes place, lead to the following results: (1) i^c_d (A cm^?2) (cathodic limiting current density) = 1.0 × [H₂O₂]^1.0_T (M), (2) i¹_d (A cm^?2 (anodic limiting one) = i^c_d ([KOH] ? [H₂O₂]_T) or 1.0 × [KOH] < [H₂O₂]_T), (3) φ_m (V) (mixed potential) = 0.126-0.060 log [KOH]^1.0 and (4) (?φ/?i)_φ=φm (Ωcm²) (reaction resistance at φ = φ_m) = 0.057 × [H₂O₂]^?1.0_T (M^?1), where [H₂O₂]_T designates a total H₂O₂ concentration and the others have their usual meanings.The above results are explained by the following mechanism; HO^?₂ formed by the reversible chemical reaction, H₂O₂ + OH ? HO^?₂ + H₂O, is oxidised in anodic reaction by two steps: HO^?₂

HO₂ (a) + e^? and HO₂(a) + OH^? → O₂ + H₂O + e^?, whereas in cathodic reaction, H₂O₂ is reduced by H₂O₂ + e^?

OH(a) + OH^?, OH(a) + e^? → OH^?. Here,

designates a rate determining step,Catalytic decomposition of H₂O₂ on the electrode is also discussed.     

Synthesis and characteristics of a novel aliphatic polycarbonate,poly[(propylene oxide)‐co‐(carbon dioxide)‐co‐(γ‐butyrolactone)]

A novel aliphatic polycarbonate, poly[(propylene oxide)‐co‐(carbon dioxide)‐co‐(γ‐butyrolactone)] [P(PO? CO₂? GBL)], was synthesized by the copolymerization of carbon dioxide, propylene oxide (PO) and γ‐butyrolactone (GBL). The resulting copolymers were determined by FTIR and NMR spectral analysis with viscosity‐average molecular weights (M_v) from 50 000 to 120 000 g mol^?1. According to elemental analysis, the calculated data of elemental contents in P(PO? CO₂? GBL)44 were close to the found data. The result showed that GBL was inserted into the backbone of poly[(propylene oxide)‐co‐(carbon dioxide)] successfully. GBL offered an ester structural unit that gave the copolymer better degradability. The correlations between reaction conditions and properties were studied. When GBL content increased, the M_v and the glass transition temperature (T_g) of the copolymers improved relative to an identical copolymer without GBL. Prolonging the reaction time of the copolymerization resulted in increases in M_v and T_g. P(PO? CO₂? GBL) exhibited a high T_g above 40 °C. The rate of backbone degradation increased with increasing GBL content. Copyright © 2005 Society of Chemical Industry     

Effect of polyphenylene sulfide containing amino unit on thermal and mechanical properties of polyphenylene sulfide/glass fiber composites

Three kinds of high‐molecular‐weight compatibilizers [copoly(1,4‐phenylene sulfide)‐poly(2,5‐phenylene sulfide amine)] (PPS‐NH₂) containing different proportions of amino units in the side chain) were synthesized by the reaction of dihalogenated monomer and sodium sulfide via nucleophilic substitution polymerization under high pressure. The intrinsic viscosity of the obtained copolymers was 0.354–0.489 dL/g and they were found to have good thermal performance with melting point (T_m) of 271.3–281.0 °C and initial degradation temperature (T_d) of 490.0–495.7 °C. There was an excellent physical compatibility between PPS‐NH₂ and the pure industrial PPS. The results of dynamic mechanical analysis and macro‐ and micromechanical test showed that the selective compatibilizer PPS‐NH₂ (1.0) (1.0% mol aminated ratio) can improve the mechanical and interfacial properties of polyphenylene sulfide/glass fiber (PPS/GF) composite. The macro‐optimal tensile strength, Young's modulus, bending strength, and notched impact strength of 5%PPS‐NH₂ (1.0)/PPS/GF composite raised up to 141 MPa, 1.98 GPa, 203 MPa, and 6.15 kJ/m², which increased 12.8%, 9.4%, 4.1%, and 13.8%, respectively, comparing with the pure PPS/GF composite (125 MPa, 1.81 GPa, 195 MPa, and 5.40 kJ/m², respectively). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45804.     

Synthesis and properties of poly(ether ether ketone ketone)–poly(ether sulfone) block copolymers

Poly(ether ether ketone ketone)-poly(ether sulfone) (PEEKK/PES) block copolymers were prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction, and the M _n of the PEEKK segment was fixed at 12,000, while the M _n's of the PES segment ranged from 250 to 12,680. The different properties of the copolymers were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The results showed that the relationship between T_g and compositions of copolymers approximately followed the formula 1/T_g = W₂/T_g2. The PES content and the segment length of the copolymers had a significant influence on their melting points and crystallization behavior. The thermal properties and dynamic mechanical behavior of the copolymers were also studied. In the study of isothermal crystallization, the copolymers have the same nucleation mechanism and crystal growth as that of pure PEEKK. Owing to the introduction of the PES segment into the PEEKK main chain, it increases the free energy which forms the critical crystal nucleus and produces a resistant action to the whole crystallization process of the PEEKK segment. © 1996 John Wiley & Sons, Inc.     

Synergistic Excited State Involved Catalytic Reduction of (NH3-trz)[Fe(dipic)2] Complex by SnO2/TiO2 Nanocomposite

In this study, cost-effective, environmentally friendly well-fabricated SnO₂/TiO₂ nanocomposite synthesized via hydrothermal route and the photocatalytic activity was validated using the (NH₃-trz)[Fe(dipic)₂] complex under ultra-violet illumination. The structural features of (NH₃-trz)[Fe(dipic)₂] complex and catalysts were systematically examined by various characteristics. The photoreactivity of the model compound (NH₃-trz)[Fe(dipic)₂] in water/binary solvent systems was investigated. The rate of photoreaction (k) of nanocomposite (0.1432 s^?1) is higher than the SnO₂ (0.0373 s^?1) and TiO₂ (0.1422 s^?1) in H₂O:PrⁱOH (70:30%) than the rest of the solvents system. The pathways, mechanistic feature of accumulated reactive species on nanocomposite to induce adherent [Fe(dipic)₂]^? anion and photo-reductive products were studied.

Graphical Abstract