Thermal Stability of Succinate Groups in the Exopolysaccharide Marginalan 1

Abstract

An investigation on the possible effect of temperature on the conformation of the exocellular polysaccharide marginalan, produced by Pseudomonas marginalis strain HT041B, in aqueous solutions led to the observation that 30 % of the succinate groups were peeled off from the polymeric backbone when polymeric solutions were heated at 70 °C. This desuccinylation effect was investigated by means of NMR, circular dichroism and viscosity measurements. The experimental findings were compared with those obtained for a sample of chemically desuccinylated marginalan. A possible mechanism for the temperature-induced hydrolysis of succinate groups is discussed.

     

The Structural Features of Low Molecular Weight Ionic Diblock Polymers Based on Group Transfer Polymerized Methacrylates

Abstract

The solid-state ordered structures formed by low M _a ionic diblock copolymers of less than 10,000 g/mol, made by group-transfer polymerization of methacrylates, were studied. The unquaternized diblocks exhibit no structure via small-angle x-ray scattering (SAXS) and are apparently below their critical value of XN in a disordered melt state at room temperature. However, the amine salt ionomers exhibit morphologies ranging from dispersed spheres to lamellae which were investigated by SAXS and transmission electron microscopy (TEM). The morphology depends strongly on the size and proportion of the blocks, the extent of quaternization, and the concentration of the blocks in the casting solution.     

THE FORMATION AND STABILITY OF MICROSCOPIC EMULSION FILMS OF AQUEOUS SOLUTIONS OF POLY (ACRYLIC ACID) AND ACRYLIC ACTD-VINYLACETATE COPOLYMERS

ABSTRACT

The effect of polymer volume concentration C, pH and ionic strength (NaCl concentration, CNal) of solution, polymer molecular mass, acetate groups' content in a polymer chain, and ethanol concentration on the stability of microscopic emulsion films (MEF) stabilized with the adsorption layers of poly(acrylic acid) (PAA) and acrylic acid-vinylacetate copolymers (PAA-VA) has been studied.

The kinetics of MEF thinning under the conditions when two heptane drops in a polymer solution are brought into contact and pressed with a permanent force has been studied.

The free energy ? F of interaction in the film has been evaluated on the basis of measuring the film thickness Hf by photometry and determining the film profile in the Plateau region.     

Polymerlzatlon of 1-Ethynyl-1-Cyclohexanol by Radiation,Electroinitiation, and Chemical Catalysts

Abstract

Solid-state polymerization of 1-ethynyl-1-cyclohexanol was carried out by irradiation in vacuum and in open air at 20°C. Radiation-induced polymerization was also done in a benzene solution. The products were mixtures of oligomers and polymers. IR, NMR, U V, and x-ray investigations showed the initial formation of trimer, oligomer, and polymer. The polymer fraction increased with an increase of conversion. Electro-initiated polymerization gave soluble and insoluble fractions. The soluble fraction was an ether. However, the results were not reproducible. No polymers were obtained with n-butyllithium and borontrifluoride etherate as chemical catalysts.     

Supramolecular polymer networks based on calix[5]arene chained poly(p-phenyleneethynylene) and C60 fulleropyrrolidine

Abstract

A poly(p-phenyleneethynylene) polymer (PCF[5]), bearing two π-rich cone-like calix[5]arene cavities (assembling cores) attached to a rigid p-phenyleneethynylene spacer, was synthesised by a Pd-catalysed cross-coupling reaction. UV–vis absorption and fluorescence spectroscopies combined with dynamic light scattering measurements provide evidence for the self-assembly of PCF[5] (homopolytopic host molecule) with a complementary C₆₀ fulleropyrrolidine (C₆₀-Pyr) guest in solution, in the construction of a supramolecular polymer network. Atomic force microscopy analysis of PCF[5]/C₆₀-Pyr highlights the formation of a bicontinuous network consisting of a uniform distribution of prominent structures, within a polymeric background forming a biphasic structure.     

Synthesis and Study of a Sulfur Heterocycle Fused p-Phenylene Vinylene Conducting Polymer

Abstract

Poly(benzo[1,2-b:4,5-b′]dithiophene-4,8-diyl vinylene) (1) has been prepared by the pyrolysis of the precursor polymer 2 and studied. Quantum mechanical calculations on the aromatic and quinoid monomers, oligomers and polymers indicate that 1 is a planar aromatic polymer.     

Evaluation of Huggins' Constant,Kraemer's Constant and Viscosity Concentration Coefficient of Polymer Dextran in Urea,Glycine and Glucose

Abstract

Reduced viscosity (η_sp/c) and Inherent viscosity (In η_rel/c) of dilute solution of water soluble polysaccharide polymer “Dextran” has been calculated by measuring the flow time of the polymer solution in solvents like 6(M) Urea, 2(M) Glycine and 50% Glucosc at three different temperatures ? 25°C, 30°C and 35°C. From extrapolation of curve (η_sp/c) versus (c) and (In η_rel/c) versus (c), thermo viscosity parameters like Huggins' constant (k′_H) Kraemer's constant (k″_H) and viscosity concentration coefficient (a ₂) have been estimated which enable us to know the fate of the polymer molecules in these solvents.     

Surface Initiated Polymerization from Nanoparticle Surfaces

Abstract

The synthesis, characterization, and development of new nanoparticle materials have both scientific and technological significance. Surface initiated polymerization (SIP) from nanoparticle surfaces involves the growth of end‐tethered polymer brushes where the length or thickness can be more than twice the radius of gyration (Rg) compared to a free polymer in solution. Different mechanisms are possible on a variety of initiators, reaction conditions, monomers, and nanoparticles. Important differences to solution and bulk polymerization can be observed where the nanoparticles with grafted initiators behave as macroinitiators. In turn, the development of these materials will allow the preparation of thermodynamically and kinetically stable nanocomposites and colloids. Through the careful use of surface sensitive spectroscopic and microscopic techniques, much has been gained from the direct and in‐situ analysis of grafted polymers on the nanoparticles with regards to the kinetics and mechanism of the polymerization process. Parallels can be drawn to SIP on flat surfaces where surface sensitive spectroscopic and microscopic measurements are complementary to analysis methods for colloidal particles. Thus, this review surveys the different polymerization mechanisms and procedures towards forming core‐shell types of hybrid inorganic–organic polymer nanoscale materials.     

[Hydroxy(tosyloxy)iodo]benzene as Thermal initiator for the Radical Polymerization of Methyl Methacrylate

Abstract

The thermal polymerization of methyl methacrylate in a solution of N,N-dimethylacetamide has been studied using [hydroxy(tosyloxy)- iodo]benzene (HTIB) as the initiator. The rate of polymerization was a direct function of the monomer and initiator concentrations. The initiator and monomer exponent values expressing this dependence were found to be 1.0 and 0.8, respectively. The overall activation energy of polymerization was estimated to be 45 kJ·mol^?-1. The polymerization was inhibited in the presence of hydroquinone. The effect of various solvents on the polymerization rate was studied. The polymer prepared with HTIB (0.47 × 10^?3 mol·L^?-1) had a number-average molecular weight of 138,000 and a glass transition temperature of 106°C. The polymer showed good thermal stability as determined by thermogravimetric analysis.     

Living Radical Polymerization of Styrene with Diphenyl Diselenide as a Photoiniferter. Synthesis of Polystyrene with Carbon-Carbon Double Bonds at Both Chain Ends

Abstract

Photopolymerization of styrene in the presence of diphenyl diselenide proceeded smoothly. The polymer yields and the number average molecular weight (Mn) of the polymers increased with reaction time. Further, a linear relationship was found for a plot of Mn for polystyrene versus polymer yield. These results indicate that this polymerization proceeds through a living radical mechanism. Photopolymerization of styrene with bis(p-tertbutylphenyl) diselenide afforded a telechelic polystyrene with terminal arylseleno groups. The resulting polymer underwent the reductive elimination of terminal seleno groups by the reaction with tri-n-butyltin hydride. Moreover, this telechelic polymer was treated with hydrogen peroxide to afford polystyrene with carbon-carbon double bonds at both chain ends.     

Concentration Dependence of Dispersion of Polymer Solutions Flowing in Capillaries

Abstract

Dispersion of polymer solutions flowing in capillaries is an important phenomenon the knowledge of which is necessary for quantitative evaluation of polymer separations by chromatographic methods. The papers published in this field present a number of contradictory results. At various concentrations and various molecular weights also some other phenomena occur in the case of polymers, such as, e.g., non-Newtonian behaviour, which can affect dispersion.

In the present work influences of polymer molecular weight, specific viscosity of the polymer solution injected as a pulse or as a step into a capillary and influence of the flow-rate were studied. Experimental conditions were selected, so as to avoid possible interfering effects. The results confirmed our theoretical considerations and numerical calculations of other authors.     

水溶性β-环糊精聚合物和疏水改性聚丙烯酰胺的主客体相互作用

主体环糊精聚合物(β-CDE)与客体疏水改性丙烯酰胺共聚物P(AM/POEA)构成超分子结构的高分子识别体系. 这种客体聚合物是含有少量疏水体(x_POEA＜0.01)的水溶性聚合物, NMR测定结果表明β-CDE和P(AM/POEA)的主客体相互作用是通过环糊精空腔和疏水体POEA形成包结络合物进行的. 在P(AM/POEA)聚合物水溶液中加入β-CDE, 由于主客体聚合物相互作用出现粘度的大幅上升, 增粘的幅度可通过改变聚合物浓度和疏水体含量来调节, 同时对盐浓度和温度的影响也进行了研究. 通过透射电镜直观观察的结果表明, 此类缔合聚合物体系的主客体相互作用生成实心球状多分子聚集体.     

Determination of Mescaline in Hallucinogenic Cactaceae by Ion-Interaction HPLC.

Abstract

An ion-interaction HPLC method is developed for the determination of mescaline in some Cactaceae species, namely Gymnocactus beguinii, Echinocactus polycephalus, Coriphanta radians, Coriphanta scolymoides, Coriphanta palmeri, Lophophora williamsii and Trichocereus pachanoi.

Mescaline is characterized by hallucinogenic properties and can be prescribed as a psychodrug.

The method makes use of a C18-reversed-phase as the stationary phase and of a 5.0 mM aqueous solution of octylamine o-phosphate as the mobile phase, with spectrophotometric detection at 230 nm.

The method is sensitive (detection limit of 35 μg/L) and matrix interference-free.

The pretreatment of the sample is performed by grinding the fresh cactus and extracting the jelly pulp obtained either with a methanolic-ammonial solution or an aqueous solution buffered at pH 4.0 (phosphate buffer).

The average amounts of mescaline found in Lophophora williamsii and in Trichocereus pachanoi were respectively 2.55 mg and 3.10 mg/g of fresh cactus.     

Recognition of Sialic Acid Using Molecularly Imprinted Polymer

Abstract

The molecular imprinting technique was applied for the preparation of a polymer selective for sialic acid. To evaluate its binding ability the molecularly imprinted polymer obtained was used as a stationary phase in liquid chromatography. The polymer showed pH-dependent characteristics for binding: an optimum specificity to sialic acid at pH 8.1 and a higher affinity with group selectivity for cis-diol containing sugars at higher pH.     

Chemical-Modified Nylon 4 Membrane for Pervaporation

Abstract

A hydrophilic polymer membrane was synthesized with 2-hydroxyethyl methacrylate (HEMA) onto a Nylon 4 polymer backbone, PHEMA-g-N4. The membranes were water permselective because of the hydrophilicity, and the water permselectivity increased with increasing the degree of grafting. Permseparation of water was investigated with respect to the feed aqueous alcohol concentration, feed temperature, size of the alcohols, and degree of grafting. The separation factors of this PHEMA-g-N4 membrane were higher than those of the unmodified Nylon 4 membrane for pervaporation of aqueous ethanol solution, while the permeation rate was slightly lower. A separation factor of 98 and a 194 g/m²·h permeation rate could be obtained. Compared with an unmodified Nylon 4 membrane, the PHEMA-g-N4 membrane effectively increased the pervaporation separation index for the water-ethanol mixtures on pervaporation separation.     

IN AQUA SYNTHESIS OF A HIGH MOLECULAR WEIGHT ARYLETHYNYLENE POLYMER EXHIBITING REVERSIBLE HYDROGEL PROPERTIES

ABSTRACT

A high molecular weight poly(aryleneethynylene) (M_w ～ 60,000) is prepared by the palladium catalyzed copolymerization of 3,5-diiodobenzoic acid and acetylene gas in a basic aqueous medium. The polymer has a “zig-zag”, fully conjugated backbone. The polymer has been characterized by a variety of methods and exhibits high thermal stability. Furthermore, the polymer is readily soluble in aqueous base and is reversibly switchable from the solution state to a hydrogel state, in water, by changing the pH of the solvent.     

Synthesis and Polymerization of Carbamate-Linked Cyclodextrin Methacrylate Monomers

Abstract

A one-step synthesis for cyclodextrin methacrylate monomers was examined starting from α-, β- and γ-cyclodextrin. The reaction of 2-isocyanatoethyl methacrylate as well as allylisocyanate with the corresponding cyclodextrin gave the monofunctionalized carbamate-linked cyclodextrin methacrylates 2, 6 and 9 and allylcarbamates 11 and 14 in moderate yields. By NMR spectroscopic means, it could be proven that in all cases only the primary 6-hydroxyl groups of the cyclodextrins reacted with the isocyanate group. For the synthesis of a β-cyclodextrin monoallyl compound, a substitution reaction of purchasable 6-O-monotoluenesulfonyl-β-cyclodextrin with allylamine gave 6-N-allylamino-6-deoxy-β-cyclodextrin 18 in high yield. The reaction of 2-isocyanatoethyl methacrylate with α-cyclodextrin to the 6-O-carbamoyl-2-methylpropenoylethyl-α-cyclodextrin (2) was optimized so that the monomer 2 could be prepared on a larger scale without chromatographic separation. The aqueous radical homopolymerization of 2 with the peroxodisulfate/bisulfite redox initiator gave the water soluble cyclodextrin polymer 19 in good yield. Its molecular weight was determined by gel permeation chromatography to be M_n = 101,800 corresponding to an average degree of polymerization P_n = 90.     

Viscosity Molecular Weight Determination of Polyadenylic Acid

Abstract

In this study viscosity measurements of polyadenylic acid (PolyA) in aqueous solution were carried out under different conditions. In the absence of any additives, the polymer degraded during flow through the capillary of a viscometer or when standing still. Degradation during the former was more severe. The degradation of polyadenylic acid can be prevented by addition of an electrolyte such as KCl to increase the ionic strength. However, in this case the deviation from linearity was still considerable at most ionic strength values. The best fit to the Huggins and Kraemer equations was obtained using a Tris–EDTA buffer solution with a final pH of 7.65. Estimation from intrinsic viscosity and weight-average molecular weight values gave k and α as 2.04 × 10^?5 and 0.89 from the equation η = kM ^α. The difference between Huggins (k ₁) and Kraemer (k ₁′) constants was close to 0.50 for all measurements.     

The Kinetics of Donor-Acceptor Complex Polymerization. I. Introduction and Theory

ABSTRACT

A general reaction pattern is proposed for donor-acceptor complex polymerization. The explicit solution of polymer yield as a function of time is obtained for three limiting cases of reactant concentration.     

High-resolution NMR spectra and phase equilibria in poly(phenylacetylene)-diluent mixtures

The C-13 NMR spectra of partly crystalline poly(phenylacetylene) (PPA) in CDCl₃ CCl₄ are rather well resolved and the peaks can be matched with those of 1, 3,5-triphenylbenzene. A different, less-well-resolved C-13 spectrum is characteristic of a disordered PPA obtained by heating. We conclude that crystalline PPA has the chain conformation of a cis-cis-oid helix. This interpretation is consistent with the proton NMR spectra and is supported by the fluorescence spectra, which can display two bands, one concluded to be characteristic of the cis-cis-oid conformation, the other of chain conjugation in the disordered polymer. Phase equilibria of PPA in the presence of chloroform were determined and are represented as those of the quasiternary mixture cis-cis-oid helix, disordered polymer, and chloroform.