Formation of higher-order structures of chiral poly(ethynylpyridine)s depending on size, temperature, and saccharide recognition

Amphiphilic 2,6-pyridylene ethynylene "meta-ethynylpyridine" polymers having chiral oligo(oxyethylene) side chains were developed as hosts for saccharide recognition. The polymers were prepared via a Sonogashira reaction and fractionated by gel permeation chromatography (GPC). They showed circular dichroism (CD) activity due to their higher-order chiral helical structures, and their CD and UV-vis spectra changed depending on not only saccharide recognition but also molecular size, temperature, and metal cation recognition.     

Polysalt formation with poly(carboxylic acid)s

Polysalts have been prepared from poly(acrylic acid), poly(itaconic acid) and two alternating copolymers of maleic anhydride with propene and α-methyl styrene, acting as the polyanions, and several polycations. The stoichiometry and water retention values of the polysalts have been determined and compared with those prepared using carboxymethyl cellulose (CMC). It was observed that “nonstoichiometric” polysalts were formed if the “theoretical” carboxyl content was used to calculate the composition. Stoichiometric polysalts were obtained with CMC. The results are discussed in terms of the acid strength and distribution of the anionic groups in the polymers; it is concluded that both factors can influence the composition of the polysalts formed.     

Counterion binding by poly(styrenesulfonate)

Binding isotherms of poly(styrenesulfonate) with hydrogen and selected alkali ions have been determined by dialysis equilibrium and dye spectroscopy, employing Pb²⁺, Mg²⁺, and Ca²⁺ as the competing divalent ions. The observed degrees of counterion binding, Θ_z, defined as the number of bound counterfoils of valence z per poly ion site-group, agree quite well with those predicted by Manning's two variable theory. The binding preference follows the order Cs⁺ > Rb⁺ > K⁺ > Na⁺ > H⁺ >Li⁺, indicating that the binding process is of a territorial nature. Independently performed light scattering measurements show that a plot of the radius of gyration, >S _z>, against the actual polyion charge gives a sigmoidal curve. This result is taken to indicate that (1) a polyion is, in general, not completely neutralized in the Θ-state and that (2) a polyion may be not fully stretched when the polyion charge density is largest.     

Mesomorphic phase formation of poly (macromonomer)s of polystyrene macromonomers

The liquid crystalline phase formation of poly(macromonomer)s associated with the specific multibranched architecture of high branch density was investigated. The poly(macromonomer)s were prepared by radical chain polymerizations of ω‐methacryloyloxyethyl polystyrene macromonomers. It was confirmed that the mesomorphic phase formation depended on the branching architecture, where sufficient length of the branch chains as well as the backbone chain is crucial for the formation of the mesomorphic phase. Formation of the optically anisotropic mesophase also depended on the nature of solvent. The mesophase was observed in the cast films prepared from p‐xylene, toluene, tetrahydrofuran, carbon disulfide and chloroform but not observed for cyclohexane. The effects of the branched structure and the solvent nature were explained by repulsive interaction between the polystyrene branch chains of high branch density. The repulsive interaction increases the chain stiffness of the central backbone and also prevents the interpenetration of the polystyrene branches of different molecules in solution, which allow poly(macromonomer) molecules to arrange with the orientational order. Copyright © 2000 John Wiley & Sons, Ltd.     

Conformational studies of basic poly (α-amino acid)s in reversed micelles

The conformation of various basic poly (-amino acid)s was investigated by CD measurements in aqueous solutions containing bis (2-ethylhexyl)sodium sulfosuccinate (AOT) as well as in the AOT reversed micelles. The addition of AOT into an aqueous solution of poly(L-lysine) induces the conformational transition from coil to ordered structure, followed by aggregation. On the other hand, poly(L-lysine) assumes-structure in the reversed micelles at low w_ovalue (w_o=[H₂O]/[AOT]). Similarly to poly(L-lysine), poly(L-ornithine) takes an ordered structure in the aqueous solution containing AOT and-structure in the reversed micelles. In this case, however, these ordered structures are not so stable, compared with that of poly(L-lysine). Poly(L-arginine) undergoes the conformational transition from coil to helix by addition of AOT into the aqueous solution. Further addition of AOT allows transformation into-structure. Copoly(L-lysyl-L-leucine) with 63% leucine residue was shown to take a stable helical conformation even in pure water. In the reversed micelles, however, this ordered structure is significantly changed probably because the hydrophobic interaction among the leucyl residues is lowered in the reversed micelles.     

Determination of binding constants of hydrophobically end-capped poly(ethylene glycol)s with beta-cyclodextrin by affinity capillary electrophoresis

The formation of inclusion complexes between methoxypoly(ethylene glycol)s (MPEG)s bearing one hydrophobic group (phenyladamantyl) per chain and beta-cyclodextrin (beta-CD) was studied by capillary electrophoresis (CE). The effect of highly sulphated beta-CD (HS-beta-CD) on the migration behaviour of the phenyladamantyl-modified MPEG (MPEG-PhAd) analyte was investigated. It was established that the interaction between the modified PEG and beta-CD involved a 1:1 stoichiometry. Non-linear regression and three usual linearization methods (y-reciprocal, x-reciprocal and double reciprocal) were employed to estimate the binding constants. It was demonstrated that the binding constants were similar (around 400 M(-1)) for two MPEG-PhAd having different chain lengths (2000 and 5000 g/mol).     

Complex formation of daunomycin with poly(vinylpyrrolidone) and poly(ethylene glycol)

Russian Journal of General Chemistry - Complexes of the anthracycline antitumor antibiotic daunomycin with biocompatible polymer carriers, poly(vinylpyrrolidone) and poly(ethylene glycol), have...     

Palladium-catalyzed synthesis of poly(bromoalkoxy- and bromoalkanoyloxymethylsiloxane)s from poly(hydromethylsiloxane)s

Palladium-catalyzed synthesis of poly(bromoalkoxymethyl- and bromoalkanoyloxymethylsiloxane)s from poly(hydromethylsiloxane)s was studied. Treatment of poly(hydromethylsiloxane)s with mixtures of allyl bromide and cyclic ethers in the presence of a catalytic amount of PdCl₂ gave the corresponding poly[(bromoalkoxy)methylsiloxane]s in good yield. A similar reaction with γ-butyrolactone produced poly[(bromobutanoyloxy)methylsiloxane], although the polymer was highly moisture-sensitive and could not be separated from the reaction mixture. Transformation of the bromoalkoxy unit in the resulting siloxane polymer into an aminoalkoxy group was also examined.     

Synthesis of poly(benzoxazinone)s by direct polycondensation of dicarboxylic acids with bis(anthranilic acid)s

A convenient method for the synthesis of poly(benzoxazinone)s of high molecular weights has been developed. These polymers were prepared readily by direct polycondensation of aromatic dicarboxylic acids containing phenyl ether structures with bis(anthranilic acid)s using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensations proceeded smoothly and were completed within several hours at 140°C to produce poly(benzoxazinone)s with inherent viscosities up to 2.6 dL/g. The synthesis of 2-substituted benzoxazinones by the reaction of aromatic carboxylic acids or dicarboxylic acid with anthranilic acid in PPMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(benzoxazinone)s showed 10% weight loss in air and nitrogen around at 440 and 460°C, respectively.     

Synthesis of poly(cyanurate)s by a novel polyaddition of bis(epoxide)s with triazine dichloride

Poly(cyanurate)s (P‐1–P‐4) containing triazine groups in the main chain and pendant chloromethyl groups in the side chain were synthesized by the polyaddition of bis(epoxide)s with 2,4‐dichloro‐6‐(diphenylamino)‐s‐triazine (DPAT) using quaternary onium salts as catalysts. The polyaddition of diglycidyl ether of bisphenol‐A (DGEBA) with DPAT proceeded smoothly in chlorobenzene at 100 °C for 12 h to give P‐1 with M_n = 19,000 in a 92% yield, when tetrabutylammonium chloride (TBAC) was used as a catalyst. However, no reaction occurred without a catalyst or with triethylamine alone under the same reaction conditions. Polyadditions of other bis(epoxide)s with DPTA also proceeded smoothly using 5 mol % of TBAC as a catalyst in chlorobenzene to produce corresponding polymers (P‐2≈P‐4) in high yields under similar reaction conditions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4006–4012, 2000     

Synthesis of poly(Schiff-base)s by organometallic processes

Some new monomers with Schiff-base structures and bromine final atoms were obtained by combining condensation reactions of dialdehydes or diamines with p-bromoaniline or p-bromobenzaldehyde. The corresponding polymers were synthesized by Ni- or Pd-catalyzed polycondensation reactions in combination with 2,5-dihexylbenzene-1,4-diboronic acid. The new structures were characterized by spectral methods (¹H NMR, IR, UV-vis) as well as by thermal analyses (TGA, DSC).     

Effect of copolymer composition on interpolymer complex formation of (co)poly(vinyl ether)s with poly(acrylic acid) in aqueous and organic solutions

The complex formation between vinyl ether of poly(ethylene glycol‐co‐vinyl butyl ether) with poly(acrylic acid) has been considered in aqueous and isopropanol solutions. The effect of copolymer composition on the complex formation process was clarified. It has been shown that the incorporation of hydrophobic fragments into macromolecules enhances the hydrophobic stabilization of polycomplexes in aqueous solutions. In organic media this effect disappears. The stability of polycomplexes formed both in aqueous and in organic solutions in respect to the addition of dimethylformamide has been studied.     

Fluorine containing poly(amide-imide)s: synthesis and formation of Langmuir-Blodgett monolayers

Soluble fluorine containing poly(amide-imide)s, PAI(1-4), were synthesized from diimide-dicarboxylic acid, 2,2-bis[N-(4-carboxyphenyl)-phthalimide-1,4-yl]hexafluoropropane with various diamines by direct polycondensation in N-methyl-2-pyrrolidone (NMP) containing CaCl₂ and using triphenyl phosphite and pyridine as condensing agents. The polymers were readily soluble in aprotic polar solvents such as NMP, N,N-dimethylacetamide, dimethyl sulfoxide and tetrahydrofuran. Their Langmuir monolayers were studied at the air/water interface. The monolayers were generally stable at the water surface and could be reproducibly transferred onto solid substrates to build up Langmuir-Blodgett (LB) multilayers. The LB mono- and multilayers were characterized by ultra-violet/visible spectroscopy (UV-Vis), surface plasmon resonance, atomic force microscopy.     

Potentiometric saccharide detection based on the pK(a) changes of poly(aniline boronic acid)

A novel approach for the potentiometric detection of saccharides using poly(aniline boronic acid) is presented. A model is described in which the electrochemical potential is sensitive to the change in the pK(a) of the conducting polymer as a result of boronic acid-diol complexation. In this system, boronic acid complexation is the mode of transduction and it is manifested as changes in the electrochemical potential of the polymer with remarkable selectivity. Characteristics of both transient and steady-state response associated with the complexation are discussed. The presence of Nafion and fluoride during the electrochemical polymerization of 3-aminophenylboronic acid are shown to impact the sensitivity and the stability of the electrode response. The sensor sensitivity is improved significantly by increasing the concentration of sodium fluoride during the polymerization. Finally, the nature of the selectivity of the boronic acid-diol reaction under these conditions is explored by using molecular orbital calculations.     

Synthesis of hydrogen-terminated aliphatic bis(ethynyl ketone)s and aliphatic poly(enamine-ketone)s and poly(enonesulfide)s

Hydrogen-terminated aliphatic bis(ethynyl ketone)s (H-ABEKs): 1,9-decadiyne-3,8-dione ( 3a ) and 1,13-tetradecadiyne-3,12-dione ( 3b ) were prepared by the Friedel-Crafts reaction of bis(trimethylsilyl) acetylene (BTMSA) with adipoyl chloride and sebacoyl chloride, followed by desilylation with an aqueous buffer solution. Aliphatic poly(enamine-ketone)s (APEKs) and aliphatic poly(enonesulfide)s (APESs) were prepared in nearly quantitative yield by the nucleophilic addition polymerization of 3a,b with various diamines and dithiols in N,N-dimethylformamide (DMF) and m-cresol at room temperature during 14-22 h. Aromatic diamines and dithiols gave polymers that were soluble only in m-cresol. Primary diamines gave exclusively APEKs with the cis (Z) configuration. Dithiols gave APESs which contained more cis (Z) than trans (E) configurations. The inherent viscosities (η_inh) of the APEKs ranged from 0.05 to 0.73 dL/g. The APESs gave η_inh ranging from 0.36 to 2.21 dL/g.