Facile syntheses and characterization of hyperbranched poly(ester-amide)s from commercially available aliphatic carboxylic anhydride and multihydroxyl primary amine

A new method for synthesis of novel hyperbranched poly(ester-amide)s from commercially available AA' and CBx type monomers has been developed on the basis of a series of model reactions. The hyperbranched poly(ester-amide)s with multihydroxyl end groups are prepared by thermal polycondensation of carboxyl anhydrides (AA') and multihydroxyl primary amine (CBx) without any catalyst and solvent. The reaction mechanism in the initial stage of polymerization was investigated with in situ H-1 NMR. In the initial stage of the reaction, primary amino groups of 2-amino-2-ethyl-1,3-propanediol (AEPO) or tris(hydroxymethyl)aminomethane (THAM) react rapidly with anhydride, forming an intermediate which can be considered as a new AB(x) type monomer. Further self-polycondensation reactions of the AB. molecules produce hyperbranched polymers. Analysis using H-1 and C-13 NMR spectroscopy revealed the degree of branching of the resulting polymers ranging from 0.36 to 0.55. These hyperbranched poly(ester-amide)s contain configurational isomers observed by C-13 and DEPT C-13 NMR spectroscopy, possess high molecular weights with broad distributions and display glass-transition temperatures (T(g)s) between 7 and 96 degreesC.

Study on polymer micelles of hydrophobically modified ethyl hydroxyethyl cellulose using single-molecule force spectroscopy

Individual hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC) molecules under different conditions were elongated using a new atomic force microscope (AFM) based technique-single-molecule force spectroscopy (SMFS). The critical concentration of HM-EHEC for micelle-like clusters at a solid/liquid interface was around 0.8 wt %, which is lower than that in solution. The different mechanical properties of HM-EHEC below and above the critical concentration were displayed on force-extension curves. Through a comparison with unmodified hydroxyethyl cellulose, substituent-induced effects on nanomechanical features of HM-EHEC were investigated. Because of hydrophobic interactions and cooperative binding with the polymer, surfactants such as sodium dodecyl sulfate (SDS) dramatically influence the elastic properties of HM-EHEC below the critical concentration, and further addition of SDS reduces the interactions between the hydrophobic groups and the surfactant.

Use of SAXS to characterize the morphology of poly(polyethylene glycol diacrylate)/epoxy resin interpenetrating networks

Interpenetrating polymer networks (IPNs) have been synthesized from prepolymers that form miscible blends. All IPNs made from polyacrylate ((polyethylene glycol diacrylate), PEGDA) and epoxy (diglycidyl ether of bisphenol A, DGEBA) can be made in phase separated states by incorporating crosslinks. However, blends of these prepolymers, having a negative Flory-Huggins interaction parameter, are highly miscible. This indicates that formation of IPNs favours phase separation relative to blends. The microphase separation characteristics in the PEGDA/DGEBA IPNs were determined using smalt-angle X-ray scattering (SAXS). The Debye-Bueche and Guinier methods were used to calculate the correlation lengths of the segregated phases existing in the PEGDA/DGEBA IPNs. The results from SAXS showed that the size of the phase segregation zones changed with composition from about 50 to 100 Angstrom.

Reversibly collapsible macroporous poly(styrene-divinylbenzene) resins

A series of poly(styrene-divinylbenzene) (poly(PS-DVB)) resins have been prepared by suspension polymerisation of styrene-DVB mixtures with DVB contents of 1-12 mol%. In each case 2-ethyl-hexan-1-ol was used as a porogen. Those resins prepared with

UV VIS AND RESONANCE RAMAN SPECTROELECTROCHEMICAL PROPERTIES OF TRANSITION-METAL CENTERS IMMOBILIZED WITHIN A POLY(AMINO ACID) MATRIX - ILLUSTRATED WITH AN IRON PORPHYRIN

An iron prophyrin complex has been immobilized on the surfaces of platinum, silver, and indium doped-tin oxide coated glass by using the poly(gamma-ethyl L-glutamate)-N-(3-aminopropyl)imidazole derivative 1 as a linking agent, thus allowing-the surface-enhanced resonance Raman and UV-VIS absorption spectra and electrochemical properties of the porphyrin to be studied in solvents in which it is not normally soluble.

Poly(ethylene-co-acrylic acid) random copolymers : amphiphilic properties and self-assembly in aqueous medium

Les travaux de recherche présentés ici avaient pour objectif principal la synthèse de copolymères statistiques à base d’éthylène et d’acide acrylique (AA). Pour cela, la déprotection des groupements esters d’un copolymère statistique précurseur, le poly(éthylène-co-(tert-butyl)acrylate), a été effectuée par hydrolyse à l’aide d’iodure de triméthylsilyle. La synthèse de ce précurseur est réalisée par polymérisation catalytique en présence d’un système à base de Palladium (Pd). Le deuxième objectif a été d’étudier et de caractériser des polymères synthétisés à l’état solide et en suspension colloïdale. Plusieurs copolymères précurseurs comprenant différents pourcentages molaires en tert-butyl acrylate (4 à 12% molaires) ont été synthétisés avec succès, puis déprotégés par hydrolyse pour obtenir des poly(éthylène-coacide acrylique) (pE-co-AA) avec différentes compositions. Seuls les copolymères comprenant 10% molaire ou plus de AA sont solubles dans le Tétrahydrofurane (THF) et uniquement dans ce solvant. De telles solutions peuvent être dialysées dans l’eau, ce qui conduit à un échange lent entre cette dernière et le THF, et l’autoassemblage du copolymère dans l’eau peut ensuite être étudié. C’est ainsi qu’ont pu être observées des nanoparticules stables dans le temps dont le comportement est sensible au pH et à la température. Les polymères synthétisés ont été caractérisés par Résonance Magnétique Nucléaire (RMN) ainsi que par spectroscopie Infra-Rouge (IR), avant et après déprotection. Les pourcentages molaires d’AA ont été déterminés par combinaison des résultats de RMN et ii de titrages conductimètriques. A l’état solide, les échantillons ont été analysés par Calorimétrie différentielle à balayage (DSC) et par Diffraction des rayons X. Les solutions colloïdales des polymères pE-co-AA ont été caractérisées par Diffusion dynamique de la lumière et par la DSC-haute sensibilité. De la microscopie électronique à transmission (TEM) a permis de visualiser la forme et la taille des nanoparticules.

Étude des poly(2-alkyl-2-oxazoline)s munis d'extrémités hydrophobes en solution aqueuse et à linterface eau/air

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Temperature-responsive water-soluble copolymers based on 2-hydroxyethyl acrylate and butyl acrylate

Amphiphilic copolymers have been synthesised by free radical copolymerisation of 2-hydroxyethyl acrylate with butyl acrylate, the reactivity ratios of which indicate practically equal reactivity. The copolymers containing less than 30 mol-% of BA were soluble in water and exhibited a LCST in aqueous solutions. It was found that the interaction between these copolymers and poly(acrylic acid) in aqueous solutions resulted in the formation of interpolymer complexes stabilised by hydrogen bonds and hydrophobic interactions. This interaction was significantly affected by solution I pH and led to modification of the temperature-responsive behaviour of the copolymers.

Mucoadhesive interactions of amphiphilic cationic copolymers based on [2-(methacryloyloxy)ethyl]trimethylammonium chloride

Three series of water-soluble cationic copolymers have been synthesised by free-radical copolymerisation of [2-(methacryloyloxy)ethyl]-trimethylammonium chloride (MADQUAT) with methyl acrylate (MA), butyl acrylate (BA) and butyl methacrylate (BMA). The interactions between these copolymers and porcine stomach mucin have been studied in aqueous solutions using dynamic light scattering, zeta-potential measurements, turbidimetric titration and transmission electron microscopy (TEM). It was demonstrated that mixing aqueous dispersions of mucin with solutions of the cationic copolymers results in significant changes in size distribution and zeta-potential of its particles. It was found that an increase in the content of hydrophobic groups in copolymers leads to more efficient adsorption of macromolecules on the surface of mucin particles, which evidences the importance of hydrophobic effects in mucoadhesion. The efficiency of mucoadhesive interactions was found to be significantly dependent on pH, which affects the surface charge and aggregation stability of mucin. (C) 2007 Elsevier B.V. All rights reserved.

De-aggregation of polyfluorene derivative by blending with a series of poly(alkyl methacrylate)s with varying sidegroup sizes

A polyfluorene derivative of the PPV, poly(9,9`-n-dihexyl-2,7-fluorenedilvinylene-alt-1,4-phenylenevinylene), with a strong tendency to aggregation was blended with several members of a series composed by poly(alkyl methacrylate)s with the following substituents in the ester position: methyl, ethyl, isopropyl, isobutyl, n-butyl, and cyclohexyl. The de-aggregation effect in blends was studied by steady-state photoluminescence spectroscopy using several blend compositions. The efficiency of each dispersing phase was discussed in terms of the polymer miscibility, controlled by interaction parameters between the polyfluorene and every poly(alkyl methacrylate)s, here described using Hilde-brand solubility parameters. (c) 2009 Elsevier Ltd. All rights reserved.

Thioxanthone Sensitized Photodegradation of Poly(alkyl methacrylate) Films

The thioxanthone-sensitized photodegradation of poly(alkyl methacrylate) films [alkyl = methyl, ethyl, butyl, and hexyl] was studied using near UV-vis light. The photooxidation process continued even after the total consumption of the sensitizer, possibly due to the excitation of the ketyl groups formed during the first stages of the process. The rate of oxidation, as well as the formation of hydroxy, peroxy, and ketyl groups was faster for polymers with larger ester groups. The decrease of the molecular weight of the degradated polymers was also larger for the hexyl substituted polymer. The side-chain size effect was attributed to the larger amount of secondary hydrogens available for abstraction by the triplet state of thioxanthone, present in the larger ester groups. The lower glass transition temperature of the hexyl substituted polymer allows a better diffusion of oxygen to the deeper layers of the films that also contributes to the faster photodegradation rate. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1283-1288, 2010

Cycling performance of lithium metal polymer cells assembled with ionic liquid and poly(3-methyl thiophene)/carbon nanotube composite cathode

A poly(3-methylthiophene) (PMT)/multi-walled carbon nanotube (CNT) composite is synthesized by in situ chemical polymerization. The PMT/CNT composite is used as an active cathode material in lithium metal polymer cells assembled with ionic liquid (IL) electrolytes. The IL electrolyte consists of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and LiBF4. A small amount of vinylene carbonate is added to the IL electrolyte to prevent the reductive decomposition of the imidazolium cation in EMIBF4. A porous poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) film is used as a polymer membrane for assembling the cells. Electrochemical properties of the PMT/CNT composite electrode in the IL electrolyte are evaluated and the effect of vinylene carbonate on the cycling performance of the lithium metal polymer cells is investigated. The cells assembled with a non-flammable IL electrolyte and a PMT/CNT composite cathode are promising candidates for high-voltage–power sources with enhanced safety.

Synthesis of ethyl oleate employing synthetic hydrogel-immobilized lipase of Bacillus coagulans MTCC-6375

Ten polymeric hydrogels were chemically synthesized by varying the concentrations of copolymer (DMA) and cross-linker (MBAm) molecules. An alkaline lipase of Bacillus coagulans MTCC-6375 was immobilized onto a poly (MAc-co-DMA-cl-MBAm)-hydrogel support at pH 8.5 and temperature 55ºC in 16 h. The bound lipase possessed 7.6 U.g⁻¹ (matrix) lipase activity with a specific activity of 18 U.mg⁻¹ protein. Hydrogel bound-lipase catalyzed esterification of oleic acid and ethanol to synthesize ethyl oleate in n-nonane. Various kinetic parameters were optimized to produce ethyl oleate using immobilized lipase. The optimal parameters were bound enzyme/substrate (E/S) ratio 0.62 mg/mM, ethanol/oleic acid 100 mM:75 mM or 100 mM:100 mM, incubation time 18 h and reaction temperature 55ºC that resulted in approximately 53% conversion of reactants into ethyl oleate in n-nonane. However, addition of a molecular sieve to the reaction mixture promoted the conversion to 58% in 18 h in n-nonane, which was equivalent to 55 mM of ethyl oleate produced.

Synthesis of ethyl laurate by hydrogel immobilized lipase of Bacillus coagulans MTCC-6375

An alkaline thermo-tolerant lipase from Bacillus coagulans MTCC-6375 was purified and efficiently immobilized onto a synthetic hydrophobic poly (MAc-co-DMA-cl-MBAm)-hydrogel at pH 8.5 and temperature 55°C in 16 h. The hydrogel bound matrix possessed 7.6 IU g -1 matrix lipase activity with a specific activity of 18 IU mg -1 protein. Immobilized lipase was used to catalyze the esterification of lauric acid and ethanol to produce ethyl laurate in n-nonane. The reaction conditions that were optimized to produce ethyl laurate in n-nonane included enzyme/substrate (E/S) ratio, substrate concentration, reaction time and reaction temperature. The optimized parameters were E/S ratio of 0.5 mg mM -1, ethanol:lauric acid in ratio of 100 mM:100 mM and reaction time of 15 h at 65°C under continuous shaking (200 rpm). Optimized conditions resulted in 66% conversion of reactants into ethyl laurate in n-nonane in the presence of 300 mg molecular sieve mL -1 reaction mixture.

Comparative study of the whisky aroma profile based on headspace solid phase microextraction using different fibre coatings

A dynamic headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to ion trap mass spectrometry (GC–ITMS) method was developed and applied for the qualitative determination of the volatile compounds present in commercial whisky samples which alcoholic content was previously adjusted to 13% (v/v). Headspace SPME experimental conditions, such as fibre coating, extraction temperature and extraction time, were optimized in order to improve the extraction process. Five different SPME fibres were used in this study, namely, poly(dimethylsiloxane)(PDMS),poly(acrylate)(PA),Carboxen-poly(dimethylsiloxane)(CAR/PDMS),Carbowax-divinylbenzene(CW/DVB)and Carboxen-poly(dimethylsiloxane)-divinylbenzene (CAR/PDMS/DVB). The best results were obtained using a 75 m CAR/PDMS fibre during headspace extraction at 40◦C with stirring at 750rpm for 60min, after saturating the samples with salt. The optimised methodology was then appliedtoinvestigatethevolatilecompositionprofileofthreeScotchwhiskysamples—BlackLabel,BallantinesandHighlandClan.Approximately seventy volatile compounds were identified in the these samples, pertaining at several chemical groups, mainly fatty acids ethyl esters, higher alcohols, fatty acids, carbonyl compounds, monoterpenols, C13 norisoprenoids and some volatile phenols. The ethyl esters form an essential group of aroma components in whisky, to which they confer a pleasant aroma, with “fruity” odours. Qualitatively, the isoamyl acetate, with “banana” aroma,wasthemostinteresting.Quantitatively,significantcomponentsareethylestersofcaprilic,capricandlauricacids.Thehighestconcentration of fatty acids, were observed for caprilic and capric acids. From the higher alcohols the fusel oils (3-methylbutan-1-ol and 2.phenyletanol) are the most important ones.