Synthesis and properties of novel poly(N-oxyimide)s

Novel poly(N-oxyimide)s (PNOI) were synthesized by the room temperature polycondensation of N,N′-dihydroxypyromellitimide (I) with dichloro compounds in N,N-dimethylformamide (DMF) in the presence of triethylamine both as base as well as catalyst. The dichloro compounds used were 1,4-bis(chloromethyl)-2,5-dimethylbenzene (II), 1,5-bis(chloromethyl)-2,4-dimethylbenzene (III), 1,4-bis(chloromethyl)-2,5-dimethoxybenzene (IV) and 1,4-dichlorobut-2-yne (V). Polymer synthesis, characterization, and properties such as density, viscosity, solubility, crystallinity, and thermal stability were described. Two model compounds, viz. (i) MNOI-1 from N-hydroxyphthalimide and a dichloro compound (III), (ii) MNOI-2 from I and benzyl chloride were also synthesized to confirm the formation of polymers. The polymers thus obtained had high intrinsic viscosities in the range 1.09–1.18 dl/g. The thermal decomposition of the polymers started around 260°C with 20–25% decomposition and about 50% weight loss was observed at 400°C.     

Synthesis and characterization of polyesters containing heterocyclic thiaxanthone units

Several polyesters containing thiaxanthone rings were prepared from 2,7-dichloroformylthiaxanthone-5,5′-dioxide ( IVa ), 2,8-dichloroformylthiaxanthone-5,5′-dioxide ( IVb ), and bisphenols by solution polycondensation. The 2,8-diethoxycarbonylthiaxanthone-5,5′-dioxide ( V ) was prepared and characterized by spectral methods to confirm the formation of 2,8-thiaxanthonedicarboxylic acid-5,5′-dioxide ( IVb ). Prior to polymer synthesis two model compounds,2,7-diphenoxycarbonylthiaxanthone-5,5′-dioxide (MDE-1) and 2,8-diphenoxycarbonylthiaxanthone-5,5′-dioxide (MDE-2), were synthesized and characterized by spectral methods. The polyesters were obtained in 62–78% yield and had inherent viscosities in the range 0.42–0.90 dL/g. The effect of thiaxanthone rings on solubility, crystallinity, and thermal stability of the polyesters are also discussed. The polyesters have decomposition temperatures in the range 372–438°C.     

The Incorporation of Titania into Modified Silicates for Solar Photodegradation of Aqueous Species

A new class of sol-gel-derived photocatalytic materials has been synthesized and used in solar-assisted photodegradation studies. The materials are comprised of a homogeneous dispersion of commercial TiO₂ powder into silica and organically modified silicate (Ormosil) hosts. The efficiency of the photocatalytic properties of these TiO₂-containing materials was determined by their relative performance in the solar photodecomposition of aqueous rhodamine B. The improved adsorption properties of the modified materials compared to commercial TiO₂ increase the photodecomposition rate and the buoyancy properties, although excess hydrophobicity decreases the wetted section of the catalyst and its photocatalytic performance. These materials can be used as floatable catalysts for solar-assisted water purification.     

Studies on the formation of manganese molybdate

The reaction of MoO₃ with various oxides of manganese (MnO, Mn₂O₃, Mn₃O₄ and MnO₂) and with MnCO₃ has been studied in air and nitrogen atmospheres employing DTA, TG and X-ray diffraction methods, with a view to elucidating the conditions for the formation of MnMoO₄. Thermal decomposition of MnCO₃ has also been studied in air and nitrogen atmospheres to help understand the mechanism of the reaction between MnCO₃ and MoO₃. The studies reveal that, whereas MnO, Mn₂O₃ and MnO₂ react smoothly with MoO₃ to form MnMoO₄, Mn₃O₄ does not react with MoO₃ in the temperature range investigated (48O–6OO°C). An equimolar mixture of MnCO₃ and MoO₃ reacts in air to yield MnMoO₄, while only a mixture of Mn₃O₄ and MoO₃ remains as final product when the same reaction is carried out in nitrogen. Marker studies reveal that manganese ions are the main diffusing species in the reaction between MoO₃ and manganese oxides that result in MnMoO₄.     

Superpositions of chiral states in the presence of electric dipole, magnetic dipole, and electric quadrupole interactions

This paper is a straightforward generalization of Maierle-Harris proposal regarding parity implications on the superpositions of chiral states of a molecule. It is shown that the inclusion of electric quadrupole and magnetic dipole interactions removes several of restrictions on the preparation of superpositions of mid R:L and mid R:R states of a chiral molecule. It is also found that the dephasing of mid R:L and mid R:R superpositions, due to the spontaneous emission from the chiral molecule, has opposing contributions from electric quadrupole-magnetic dipole and electric dipole interactions.     

Correction: Click activated protodrugs against cancer increase the therapeutic potential of chemotherapy through local capture and activation

Correction for ‘Click activated protodrugs against cancer increase the therapeutic potential of chemotherapy through local capture and activation’ by Kui Wu et al., Chem. Sci., 2021, 12, 1259–1271, DOI: 10.1039/D0SC06099B.

The authors regret that the reference to the bond-breaking bioorthogonal chemistry, termed ‘click-to-release’ was omitted from the original article. In addition, we would like to include a reference describing the synthesis of compound 1, which is an intermediate to the protodrugs described in the original article. These references are listed below as ref. 1 and 2.The Royal Society of Chemistry apologizes for these errors and any consequent inconvenience to authors and readers.     

Superconvergence error estimates of discontinuous Galerkin time stepping for singularly perturbed parabolic problems

Numerical Algorithms - A parabolic convection-diffusion-reaction problem is discretized by the non-symmetric interior penalty Galerkin (NIPG) method in space and discontinuous Galerkin (DG) method...     

Surface properties of laser processed ductile iron

On laser melt treatment,Sliding Wear of pearlitic ductile iron reduced from severe metallic wear to oxidative mild wear by nearly two orders of magnitude at 7.5 ms^–1 over a load range of 14–31 kg cm^–2; resistance toCavitation Erosion improved by a factor ofseven in corrosive media and surface hardness increased from 20–22 to 40–58 HR_c. Laser melting could effectively reduceCorrosion rates in dilute acids by nearly 40%.These improvements were caused by the ultrafine microstructure (1–41 ,DAS), microhardness (700–900,HV _0,1) and the consequent high resistance to plastic flow and subsurface crack initiation.In this investigation, pin-on-disc adhesive wear, ultrasonic vibratory cavitation erosion and potentiodynamic corrosion in synthetic sea water and 0.01 N H₂SO₄, were assessed after laser surface melting or transformation hardening of hyper-eutectic ductile iron, typically employed in automotive and marine engine components by using CO₂ CW or Nd-YAG pulsed high power laser. Also the processing parameters viz, beam power (P), scan rate (U), and specific energy intensity (P/UD _b ² ) for threshold and specific depth of transformation hardening or melting have been determined.