A DSC-Study of Donor/Acceptor Side-Chain Polymers with Flourinated Taper-Shaped Tails

It is shown that insertion in methacrylic polymers of bulky electron donor/acceptor side-groups with taper-shaped flourinated tails promotes a self-organization of the respective side-chain polymers due to the space demands of the bulky D/A side-groups, leading to a columnar hexagonal mesophase. The presence of an Lc-phase is evidenced by DSC and identified by X-ray analysis. The orientation in the respective copolymers and polymer blends is additionally improved by the CT-interaction between the D/A side-groups. An increased packing effect due to this CT-orientation effect is evidenced in DSC by an increase of the respective transition temperatures. CT-interaction is responsible as well for a preferential polymerization of monomeric D/A-complexes leading to copolymers of alternating structures and for a zip-like arrangement along the main chain of the A/D-complexes between the interacting side-groups in polymer blends. Formation of mesophases is even observed in CT-interacting blends between the Lc-D/A side-chain polymethacrylates and the respective amorphous D/A side-chain polysiloxanes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Poly(cyclodiborazane)s

This paper summarizes our recent works on the synthesis and properties of the organoboron polymers, especially poly(cyclodiborazane)s. The polymers consist of boron–nitrogen four-membered rings, and are highly stable against air and moisture. The obtained polymers exhibited interesting properties as a novel type of π-conjugated polymers with intramolecular charge transfer structure. Their stability and potential as functional materials would be important and informative both in industry and boron chemistry.     

Poly(thioester)s

Syntheses and properties of aliphatic and aromatic polythioesters (PTEs) were reviewed including polythiocarbonates and polythiourethanes. The content is subdivided into the following sections: PTEs of aliphatic α‐mercapto carboxylic acid, PTEs of ω‐mercapto carboxylic acids, PTEs derived from α,ω‐dimercapto alkanes, aromatic poly(thioester)s, aliphatic poly(thiocarbonate)s, aliphatic poly(thiourethane)s and aromatic polythiocarbonates. The synthetic strategies reviewed in this article include anionic and cationic ring‐opening polymerizations, polycondensations in bulk, polycondensations in solutions, interfacial polycondensations and in vitro enzymatic polycondensations.     

聚甲基丙烯酸与修饰聚丙烯酰胺间的络合作用

利用荧光各向异性,荧光探针和荧光猝灭等静态光物理技术研究了稀水溶液中聚甲基丙烯酸（ＰＭＡＡ）与阳离子修饰聚丙烯酰胺（ＱＣＰＡＭ）间的络合作用。结果表明：在ｐＨ＝２－８范围内,ＰＭＡＡ与ＱＣＰＡＭ之间发生明显络合,但以ｐＨ为４时络合作用最大,最佳络合本比为１：１（单体单元比）,络合作用的发生大大地改变了ＰＭＡＡ的构象行为,ＰＭＡＡ构象对ｐＨ和络合作用的双重依赖性有可能在新型“智能”凝胶的设计合成上获     

Charge-Transfer Complexation for Spectrophotometric Assay of Certain Imidazole Antifungal Drugs

Abstract

A spectrophotometric method is described for the assay of some antifungal agents containing an imidazole ring: clotrimazole, econazole, ketoconazole and miconazole. The method is based on the formation of a charge-transfer complex between the drug as n-electron donor and iodine as [sgrave]-acceptor. The product exhibited two absorption maxima at 290 and 377 nm; measurements are made at 290 nm. Beer's law is obeyed in a concentration range of 1-40 μg/ml. The method is rapid, simple and sensitive and can be applied to the analysis of some commercial dosage forms without interference. A detailed investigation of the formed complex was made with respect to its composition, association constant and free energy change.

     

银离子与聚酰胺-胺型树形高分子配位作用的研究

The complexation between poly(amidoamine) (PAMAM) dendrimers and silver ion was studied in this paper. The results showed that generations and surface groups of dendrimers， reaction time， pH value， mole ratio of Ag⁺/PAMAM dendrimers， as well as reaction temperature strongly influence complexation between Ag⁺ and PAMAM dendrimers. The maximum complexing number of Ag⁺ that amino-， hydroxyl- and carboxylate- terminated PAMAM dendrimers could bind has been obtained. It has been found that the measured value of amino- and hydroxyl- ter-minated PAMAM is almost similar to the theory value， but to carboxylate- terminated PAMAM， there is a dis-crepancy between the measured value and theory value because of the electrostatic interaction between the silver ion and carboxyl group.     

Complexation of Nickel Ions by Boric Acid or (Poly)borates

An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel–boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70 °C. The calculated enthalpy and entropy at 25 °C for the formation of the complex from boric acid and Ni²⁺ ions are respectively equal to (65.6 ± 3.1) kJ·mol^?1 and (0.5 ± 11.1) J·K^?1·mol^?1. The results of this study suggest that complexation of nickel ions by borates can significantly enhance the solubility of nickel metal and nickel oxide depending on the concentration of boric acid and pH. First principles calculations were investigated and tend to show that the complex is thermodynamically stable and the nickel cation in solution should interact more strongly with the \( {\text{B}}_{3} {\text{O}}_{3} \left( {\text{OH}} \right)_{4}^{ - } \) than with boric acid.     

以聚丙二醇二苯甲酸酯为给电子体的丙烯聚合催化剂

 采用聚丙二醇二苯甲酸酯(PPGDB)为内给电子体制备了一种新的丙烯聚合催化剂MgCl2/PPGDB/TiCl4. 该催化剂用于丙烯聚合时,除了具有与以邻苯二甲酸二异丁酯为给电子体的催化剂相当的活性和立体定向性外,其特点在于所得产物的分子量分布较宽(Mw/Mn＞8.0). 采用红外光谱研究了催化剂中PPGDB与MgCl2的作用机制,结果表明PPGDB中的酯官能团和醚官能团可同时与MgCl2配位. 这种双官能团的配位作用是所得聚合物分子量分布较宽的主要原因.     

苯并双噁唑类聚合物的合成

详细介绍了以4,6-二氨基间苯二酚盐酸盐(DADHB)为原料,采用多聚磷酸法、三甲基硅烷基化法、中间相聚合法、单体成盐法合成聚对苯撑苯并双噁唑(PBO),还有以4,6-二硝基间苯二酚(DNR)为原料,先选择还原制得4-氨基-6-硝基间苯二酚盐酸盐,进而与对甲氧羰基苯甲酰氯进行缩环合获得苯并噁唑化合物,再催化加氢合成AB型PBO新单体2-(对甲氧羰基苯基)-5-氨基-6-羟基苯并噁唑,最后自缩聚反应制备PBO的新路线.另外,本文还介绍了直链烯烃型、直链脂肪烷烃型、稠环芳烃型、联苯取代基型、杂环型、聚醚型等苯并双噁唑类聚合物的合成方法.     

Well-defined Poly(lactic acid)s Containing Poly(ethylene glycol) Side-chains

Poly(ethylene glycol) (PEG) side-chain functionalized lactide analogues have been synthesized in four steps from commercially available L-lactide. The key step in the synthesis is the 1,3-dipolar cycloaddition between PEG-azides and a highly strained spirolactide-heptene monomer, which proceeds in high conversions. The PEG-grafted lactides analogues were polymerized via ring-opening polymerization using triazacyclodecene as organocatalyst to give well-defined tri- and hepta-(ethylene glycol)-poly(lactide)s (PLA) with molecular weights above 10 kDa and polydispersity indices between 1.6 and 2.1. PEG-poly(lactide) (PLA) with PEG chain M(n) 2000 was also prepared but GPC analysis showed a bimodal profile indicating the presence of starting macromonomer. Cell adhesion assays were performed using MC3T3 E-1 osteoblast-like cells demonstrating that PEG-containing PLA reduces cell adhesion significantly when compared to unfunctionalized PLA.     

Poly(aryl ether amide)s

A general method for the preparation of poly(aryl ether amide)s has been developed where the generation of an aryl ether linkage is the polymer-forming reaction. The amide linkage was found to be sufficiently electron-withdrawing to activate halo-substituents towards nucleophilic aromatic substitution analogous to conventional activating groups (i.e., sulfone, ketone, etc.). Model reactions demonstrated that the amide-activated displacement occurred with high selectivity in near quantitative yield and was judged suitable as a polymer-forming reaction. Appropriately fluoro-substituted amides were prepared and subjected to displacement polymerization with bisphenoxides in a N-methyl-2-pyrrolidone (NMP)/N-cyclohexyl-2-pyrrolidone (CHP) solvent mixture. High molecular weight polymers with glass transition temperatures in the 200–225°C range were obtained. © 1993 John Wiley & Sons, Inc.     

Multifunctional Poly(ethylene glycol)s

In the rapidly evolving multidisciplinary field of polymer therapeutics, tailored polymer structures represent the key constituent to explore and harvest the potential of bioactive macromolecular hybrid structures. In light of the recent developments for anticancer drug conjugates, multifunctional polymers are becoming ever more relevant as drug carriers. However, the potentially best suited polymer, poly(ethylene glycol) (PEG), is unfavorable owing to its limited functionality. Therefore, multifunctional linear copolymers (mf‐PEGs) based on ethylene oxide (EO) and appropriate epoxide comonomers are attracting increased attention. Precisely engineered via living anionic polymerization and defined with state‐of‐the‐art characterization techniques—for example real‐time ¹H NMR spectroscopy monitoring of the EO polymerization kinetics—this emerging class of polymers embodies a powerful platform for bio‐ and drug conjugation.     

Comparative Spectrophotometrc Analysis of Rifampicin by Chelate Formation and Charge-Transfer Complexation

Abstract

Simple, rapid, and accurate spectrophotometrc procedures for the determination of the antibiotic rifampicin, in capsules, are presented. A chelate formation of the antibiotic with cupric ion and charge-transfer complexation with halogenated quinones are carried out. Linear correlations between absorbance and concentration over the range of 40-100 μg ml^?1 were computed. The reaction pathways were proposed. The utility of copper chelate as a stability indicating procedure as well as a method to determine rifampicin In spiked urine samples is demonstrated.     

Micellization and Thermogelation of Poly(ether urethane)s Comprising Poly(ethylene glycol) and Poly(propylene glycol)

A series of multiblock poly(ether urethane)s comprising poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. Their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 8 to 12 wt%. The composition and structural information of the copolymers were studied by GPC and ¹H NMR. The critical micellization concentration (CMC) and thermodynamic parameters for micelle formation were determined at different temperatures. The temperature response of the copolymer solutions were studied and found to be associated with the composition of the copolymers.     

Complexation of poly(acrylic acid)s with uranyl ion

The complexation of uranyl ion (UO₂²⁺) in aqueous solution with polymers containing carboxylic acid groups was studied potentiometrically. Overall formation constants of the uranyl complexes with poly(methacrylic acid) and crosslinked poly(acrylic acid) were much larger than those with the corresponding low molecular carboxylic acids. Decrease in the viscosity of the polymer solution on adding uranyl ion indicated that poly(acrylic acid) forms intra-polymer chelates with uranyl ion. The crosslinked poly(acrylic acid) adsorbed uranyl ions at higher efficiency than transition metal ions.     

Improving Gene Delivery Efficiency of Bioreducible Poly(amidoamine)s via Grafting with Dendritic Poly(amidoamine)s

Dendritic poly(amidoamine)s (PAMAM)s were introduced into the side chains of disulfide‐containing poly(amidoamine)s via repetitive Michael addition and amidation. The bioreducible poly(amidoamine)s grafted with dendritic polyamidoamines showed high buffer capacity, low cytotoxicity and strong DNA binding ability at low N/P ratio. They were able to condense DNA into small sized polycation/DNA complexes, which degraded and released the incorporated DNA under reductive conditions. In comparison to the original disulfide‐containing poly(amidoamine) with aminoethyl side chain, the grafting of the bioreducible poly(amidoamine) with dendrimer greatly improved the transfection efficiencies of 293T and HeLa cells with foreign DNA at various N/P ratios. The structure–gene delivery property relations of dendrimer‐grafted polycations will provide valuable insight into the design of highly efficient and less toxic polycationic gene carriers.

     

Oxidations of 3,6-diamino-1,2,4,5-tetrazine and 3,6-bis(s,s-dimethylsulfilimino)-1,2,4,5-tetrazine

Oxidation of 3,6-diamino-1,2,4,5-tetrazine ( 1 ) with most peracids gave 3,6-diamino-1,2,4,5-tetrazine 1,4-dioxide ( 3 ) as the major product; however, treatment of 1 with peroxytrifluoroacetic acid (PTFA) gave 3,6-diamino-1,2,4,5-tetrazine 1-oxide ( 4 ) as the major product along with a small amount of 3-amino-6-nitro-1,2,4,5-tetrazine 2,4-dioxide ( 5 ). Oxidation of 3,6-bis(S,S-dimethylsulfilimino)-1,2,4,5-tetrazine ( 6 ) with 3-chloroperoxybenzoic acid (MCPBA) gave 3-S,S-(dimethylsulfilimino)-6-nitroso-1,2,4,5-tetrazine ( 7 ), which was oxidized further with dimethyldioxirane to 3-(S,S-dimethylsulfoximino)-6-nitro-1,2,4,5-tetrazine ( 8 ). All attempts to obtain 3,6-dinitro-1,2,4,5-tetrazine ( 2 ) by further oxidation of 7 or 8 failed.