Bismaleimide Resins Containing Urethanic Moieties

Abstract

A series of novel bismaleimide (BMIs) resins were prepared from 4-maleimidophenyl isocyanate and oligoether diols and oligoester diols. All the BMIs were characterized by IR, ¹H-NMR spectra and elemental analysis. DSC studies indicated that the thermal polymerization of the BMIs carried out in the 80–260°C range, and their curing behavior was significantly affected by the molecular weight of the BMIs. The poly(aminobismaleimide) resins (V1a-e, V2a-e) obtained by Michael addition of 4,4′-diaminodiphenylmethane and 4,4′-oxydianiline in 1-methyl-2-pyrrolidinone, led to elastic films showing good mechanical properties and better thermal stability than the traditional polyurethane elastomers.     

Heterocyclic Poly(Bismaleimide)s. II. Synthesis and Characterization of New Poly(Ether-Bismaleimide)s Containing Parabanic Rings

Abstract

New poly(ether-bismaleimide)s containing parabanic rings were obtained by the nucleophilic substitution reactions of 1,3-bis(4-dichloromaleimido-phenyl)parabanic acid (4) with various bisphenols. The structures of the resulting polymers were confirmed by IR and elemental analysis. The polymers are soluble in aprotic dipolar solvents and showed lower thermal stability than other polymers without parabanic rings.     

Synthesis of a novel crosslinked superabsorbent copolymer with diazacyclooctadecane crown ether and its sorption capability

A novel crosslinked poly(acrylic acid-copolymer-Kryptofix-22-DM) superabsorbent copolymer, poly(AA-co-Kry22-DM), was synthesised by the reaction of 4,13-dimethylacryloyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (Kyrptofix-22-DM) and acrylic acid (AA). Characterisation of the polymers was achieved by FTIR and ¹H NMR techniques. Sorption capacity of the crosslinked poly(AA-co-Kry22-DM) superabsorbent copolymer was investigated for Pb²⁺, Cu²⁺, Cr³⁺, Cd²⁺, Mn²⁺, Zn²⁺, and Ni²⁺ heavy metal ions at different pH values using Freundlich and Langmuir isotherms. Swelling ratio, q_v, and distribution ratio, log D, values of the crosslinked poly(AA-co-Kry22-DM) superabsorbent copolymer were calculated at various pH values.     

A note on the Poisson boundary of lamplighter random walks

The main goal of this paper is to determine the Poisson boundary of lamplighter random walks over a general class of discrete groups Γ endowed with a “rich” boundary. The starting point is the Strip Criterion of identification of the Poisson boundary for random walks on discrete groups due to Kaimanovich (Ann. Math. 152:659–692, 2000). A geometrical method for constructing the strip as a subset of the lamplighter group \mathbb Z₂\wr G{\mathbb {Z}_{2}\wr \Gamma} starting with a “smaller” strip in the group Γ is developed. Then, this method is applied to several classes of base groups Γ: groups with infinitely many ends, hyperbolic groups in the sense of Gromov, and Euclidean lattices. We show that under suitable hypothesis the Poisson boundary for a class of random walks on lamplighter groups is the space of infinite limit configurations.     

Necessary and sufficient conditions for inclusion relations for absolute summability

We obtain a set of necessary and sufficient conditions for to imply for 1 <k ≤ s < ∞. Using this result we establish several inclusion theorems as well as conditions for the equivalence of and .     

Polymers containing phenylquinoxaline rings

The synthesis and properties of poly(phenylquinoxalines) containing hexafluoroisopropylidene or silylene units in the backbone are described. The polymers have been prepared by polycondensation of aromatic diamines containing preformed phenylquinoxaline rings with a dianhydride or diacid chlorides containing hexafluoroisopropylidene groups, or with a dianhydride or diacid chlorides containing silylene units. The solubility, thermal stability, film forming ability, and electric insulating, mechanical, and electroluminescent properties of the thin films are discussed and compared with those of related heterocyclic polymers. Potential applications of poly(phenylquinoxalines) are outlined.Based on the report presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1739–1748, September, 2004.     

Determination of Abacavir, Lamivudine and Zidovudine in Pharmaceutical Tablets, Human Serum and in Drug Dissolution Studies by HPLC

A simple, accurate, precise and fully automated method for the simultaneous determination of abacavir, lamivudine and zidovudine in pharmaceutical tablets, human serum samples and drug dissolution studies has been developed. Separation was performed on a 5 μm Zorbax^® C₁₈ column (150 × 4.6 mm ID) with methanol:water:phosphate buffer at pH 5.65 (80:10:10; v/v/v) isocratic elution in less than 7 min with a flow rate of 0.6 mL min^?1.Good sensitivity for all analytes was observed with UV detection at 275 nm. The method allowed quantitation over the 500–3,000 ng mL^?1 range for abacavir and 500–5,000 ng mL^?1 range for lamivudine and zidovudine. The method has been applied, without any interference from excipients or endogenous substances, for the simultaneous determination of these three compounds in tablets. Human serum and drug dissolution studies.     

Synthesis and characterisations of Au-nanoparticle-doped TiO2 and CdO thin films

In the present study, pure and gold nanoparticle (Au NP)-doped titanium dioxide (TiO₂) and cadmium oxide (CdO) thin film were prepared by the sol–gel method, and the effect of Au NP doping on the optical, structural and morphological properties of these thin films was investigated. The prepared thin films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectra. While the optical band increases from 3.62 to 3.73 for TiO₂ thin films, it decreases from 2.20 to 1.55 for CdO thin films with increasing Au doping concentration. Analysis of XRD indicates that the intensities of peaks of the crystalline phase have increased with the increasing Au NP concentrations in all thin films. SEM images demonstrate that the surface morphologies of the samples were affected by the incorporation of Au NPs. Consequently, the most significant results of the present study are that the Au NPs can be used to modify the optical, structural and morphological properties of TiO₂ and CdO thin films.