Synthesis of Polysiloxane-Immobilized Monoamine,Diamine, and Triamine Ligand Systems in the Presence of CTAB and Their Applications

Abstract

Polysiloxane-immobilized monoamine, diamine, and triamine ligand systems of the general formula P-(CH₂)₃-X [where P represents a polysiloxane three-dimension silica like network, and X represents monoamine(-NH₂), diamine (-NH(CH₂)₂NH₂), or triamine (-NH(CH₂)₂NH(CH₂)₂NH₂) functional ligand groups] were prepared by hydrolytic polycondensation of the tetraethylorthosilicate (TEOS) and the appropriate amine silane coupling agent (RO)₃Si-(CH₂)₃X in the presence of cetyltrimethylammonium bromide (CTAB) as surfactant using the sol-gel method. The polysiloxane-immobilized amine ligand systems exhibit a higher potential for divalent metal ions (Cu²⁺, Ni²⁺, Co²⁺) when CTAB was used as surfactant than those of the corresponding polysiloxane ligand systems prepared without CTAB. X-ray Photoelectron Spectroscopy (XPS) analyses show a significant change in the surface composition as resulting from the incorporation of CTAB, which can be related to the increase in the uptake of metal ions.     

Unexpected Formation of Cyclic Hydroxamic Acids from O-(2-Aminobenzoyl) Hydroxylamine

Cyclic hydroxamic acids 3 and 4 are the unexpected products in the reaction of 0-(2-aminobenzoyl) hydroxylamine 1 and orthoesters, acid chlorides, ethyl chloroformate.     

Modified interdigitated arrays by novel poly(1,8-diaminonaphthalene)/carbon nanotubes composite for selective detection of mercury(II)

This study describes a novel type of interdigitated arrays (IDA), microfabricated by electropolymerizing structured Poly(1,8-diaminonaphthalene)/functionalized multi-walled carbon nanotubes (PDAN/CNT) thin film onto a silicon chip for square wave voltammetry (SWV) multi-element heavy metal ion detection. The structure of PDAN/CNT was characterized by Raman, FE-SEM and AFM techniques. Analysed experiments reveal that the uptake of Hg²⁺ by PDAN/CNT is quite specific and it can be used advantageously for electrochemical sensing of Hg²⁺ thanks to original feature of (Hg²⁺/Hg₂²⁺) redox potential with the respect to that of PDAN/CNT. As-developed IDA type electrode can extend its utility in other sensing applications.     

Synthesis and characterization of poly[(4-vinylphenyl)dimethyl- silane]-b-polybutadiene-b-poly[(4-vinylphenyl)dimethylsilane] (PVPDMS-b-PBd-b-PVPDMS)

The novel functionalized triblock copolymers,poly[(4-vinylphenyl)dimethylsilane]-b-polybutadiene-b-poly[(4-vinylphenyl)-dimethylsilane] (PVPDMS-b-PBd-b-PVPDMS),were synthesized by anionic polymerization method using high vacuum technique. The hydrocarbon-soluble dilithium initiator synthesized from l,3-di[l-(methylphenyl)ethenyl]benzene(MPEB) was used to synthesize polybutadiene(PBd) precursors and the triblock copolymers in the presence of sec-BuOLi.The precursors and copolymers were characterized by size exclusion chromatography(SEC),~1HNMR and DSC techniques.     

Construction of a carbon nanocomposite electrode based on amino acids functionalized gold nanoparticles for trace electrochemical detection of mercury

A simple, highly sensitive and selective carbon nanocomposite electrode has been developed for the electrochemical trace determination of mercury. This mercury nanocomposite sensor was designed by incorporation of thiolated amino acids capped AuNps into the carbon ionic liquid electrode (CILE) which provides remarkably improved sensitivity and selectivity for the electrochemical stripping assay of Hg(II). Mercury ions are expected to interact with amino acids through cooperative metal–ligand interaction to form a stable complex which provides a sensitive approach for electrochemical detection of Hg(II) in the presence of other metal ions. The detection limit was found to be 2.3 nM (S/N = 3) that is lower than the permitted value of Hg(II) reported by the Environmental Protection Agency (EPA) limit of Hg(II) for drinkable water. The proposed nanocomposite electrode exhibits good applicability for monitoring Hg(II) in tap and waste water.     

High-Density Polyethylene with In-Chain Photolyzable and Hydrolyzable Groups Enabling Recycling and Degradation

Polyethylenes endowed with low densities of in-chain hydrolyzable and photocleavable groups can improve their circularity and potentially reduce their environmental persistency. We show with model polymers derived from acyclic diene metathesis polymerization that the simultaneous presence of both groups has no adverse effect on the polyethylene crystal structure and thermal properties. Post-polymerization Baeyer–Villiger oxidation of keto-polyethylenes from non-alternating catalytic ethylene-CO chain growth copolymerization yield high molecular weight in-chain keto-ester polyethylenes (M_n≈50.000 g mol⁻¹). Oxidation can proceed without chain scission and consequently the desirable materials properties of HDPE are retained. At the same time we demonstrate the suitability of the in-chain ester groups for chemical recycling by methanolysis, and show that photolytic degradation by extended exposure to simulated sunlight occurs via the keto groups.     

New task-specific ionic liquids as bifunctional organocatalysts; Synthesis,characterization, and computational insights

A new class of functionalized imidazolium-based Task-Specific Ionic Liquids (TSILs) is designed as low-cost bifunctional organocatalyst. New alkoxymethylimidazolium ILs are efficiently synthesized under solvent free conditions and extensively characterized by physical and spectral studies. The newly synthesized ILs demonstrate excellent catalytic potential in condensation reactions of high importance, such as the Biginelli reaction for the synthesis of medicinally important dihydropyrimidiones. The effect of the alkoxy group and counter-ions in the imidazolium salts were evaluated in detail. Moreover, computational studies were employed to explore the structural dynamics and physicochemical properties of the prepared ionic liquids. 3-(iso-butoxymethyl)-1-methyl-1H-imidazol-3-ium tetrafluoroborate (ⁱBOMMIMBF₄ 7) exhibited the highest catalytic ability due to the combined influence of the alkoxy group structure, counterion nature, high electrophilicity index, and availability of the reactive C2-H. Some notable advantages of the new TSILs include efficient catalyst preparation, simple work-up procedure, recyclability, short reaction times, and excellent yields.