The use of volume fractions in the empirical mixing laws to predict the glass transition temperatures (Tg) of polymer blends provides good agreement with experimental values, even for polymer systems with different densities. No adjustment parameter is therefore required whereas Gordon-Taylor and Kwei equations based on weight fractions need the use of a fitting parameter which has to be determined from experimental data. This assumption was validated from Tg measurements through DSC experiments conducted on PMMA /PVDF blends which have significantly different densities.

The mixing of dry starch with 40 or 99% (v/v) formic acid (FA) produces an O-formylation reaction which causes a combination of acid hydrolysis and starch destructuration. Moreover, this esterification reaction is highly exothermic in the presence of pure FA. When O-formylation is performed at temperatures higher than 20degreesC, starch formate content is high (degree of substitution, DS, of 2.15 after 60 min at 105degreesC) but then molecular weight decreases (eta(red) < 10 mL/g). Under thermally-controlled conditions at 20 degrees C in formic acid, degrees of substitution reach 1.5-1.6 after 6 h reaction times and polymer degradation seems to be limited (eta(red) = 110 to 140 mL/g). The degrees of substitution obtained in water/formic acid mixtures are below those in formic acid alone. The level of destructuration of starch in formic acid and water/formic acid mixtures was also evidenced by dynamic rheological measurements and optical microscopy. Plots of storage modulus (G') versus frequency (omega) was used to characterize both the gelatinization and the gel destruction processes as a function of reaction temperature (T-r) and FA concentration.

From a long time, the traditional source of collagen has been mammals wastes, mainly bovine and porcine skins and bones. This study undertakes a comparative analysis of the viscoelastic behaviour and the structural properties of gelatin gels from both mammalian and fish origins.All the rheological measurements were carried out within the linear viscoelastic region for gelatin gels and tentatively related to structural characteristics. At a given concentration the pig gelatine exhibits a high storage modulus, G', which indicates that the gel is stiffer than the fish one. The helical structures content measured by the specific rotation, [alpha], is also higher for the pig gelatin. Moreover, the gel is denatured in the same range of temperature, namely, around 30degreesC but the transition is sharper for fish gelatine. These differences between the gelatins lie in the amino-acid composition and molecular weight distribution which may influence the nature of the interchain junctions yielding to various gel mesostruture.

The influence of pigments and mineral fillers on the crystallization kinetics of poly(vinylidene fluoride) (PVDF) in its blends with poly(methyl methacrylate) (PMMA) was studied by Differential Scanning Calorimetry and Optical Microscopy. The introduction of organic pigments or mineral fillers into FVDF results in a more or less significant increase in non-isothermal crystallization temperatures, depending on the additives used. In FVDF, the pigment nucleation activity is quite different from that previously found in poly(butylene terephthalate) (PBT). Attractive interactions between PVDF and additive surfaces are particularly important parameters. The competition between pigments and talc lead to the observation that some pigments are able to inhibit the nucleating power of this mineral in PVDF, probably through specific attractive interactions. In PVDF-PMMA blends, selective interactions between polymers and additives were observed, depending on their chemical structures. Highly chlorinated pigments present a strong attraction for PMMA and then lose an important part of their nucleating power towards FVDF. On the other hand, a pigment containing carbonyl groups becomes the most active nucleating agent, illustrating the presence of strong interactions between such compounds and the PVDF C-H bonds.

We have studied the influence of the addition of poly(butylene terephthalate) (PBT) to poly(ethylene-co- ethyl acrylate)-carbon black (EEA-CB) on the electrical properties of the blends, namely the resistivity and power dissipation of the monophasic and diphasic systems. The morphology of the latter blend is characterized by two interpenetrated immiscible phases which provide a good thermal stability to the composite up to at least 170degreesC. Power can be regularly delivered without a negative temperature coefficient (NTC) effect at 100degreesC where poly(ethylene-co-ethyl acrylate) melts. However, the significant decrease of positive temperature coefficient (PTC) amplitude compared to the monophasic systems reduces the self-regulating heating ability. The PTC effect amplitude decrease was studied by some of its known origins (thermal expansion, melting of crystalline phase, carbon black localization). Correlation of the composites resistivity with linear expansion, the melting process of EEA, and the volume expansion of PBT, show that none of these parameters can alone explain the electrical properties' evolution with temperature. Our interpretation of the PTC effect amplitude decrease is based on the PBT matrix lower thermal expansion and on the increased carbon black content located at the interface. Copyright (C) 2003 John Wiley Sons, Ltd.

New organic-inorganic hybrid materials, prepared via in situ intercalative polymerization of cyclosiloxanes in the presence of (R4N)(x)H1-xTiNbO5, are described. The polysiloxane-g-TiNbO5 nanocomposites were identified mainly by Fourier transform infrared absorption spectroscopy, X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. All of these techniques confirm the proposed structure and show exfoliation of the initial mineral sheets in the polymer matrix is largely achieved. Elemental analysis indicates that grafting yields lie in the range 100-200% (w/w), corresponding to nanocomposites in which the mineral phase occupies between 50 and 25% of the total volume.

The miscibility of poly(methylmethacrylate) (PMMA) and (trifluoroethyl methacrylic ester–MMA) copolymers (MMA–MATRIFE) with poly(vinylidene fluoride) (PVDF) and VDF copolymers was studied by differential scanning calorimetry (DSC) as a function of the fluorinated copolymer crystallinity and fluoroalkyl methacrylic ester content in the methacrylic copolymer. Miscibility limits were found identical whatever be the blend preparation technique, although solution mixing induced some polymer fractionation, thus giving slightly higher blend glass transition temperature. The miscibility domain widths are reduced when using MMA–MATRIFE copolymers as compared to PMMA-containing blends and miscibility limits are dependent on the MATRIFE content in the methacrylic copolymer. Moreover, PVDF or VDF copolymer melting enthalpy decrease is associated to a partial dissolution of the semi-crystalline polymer in PMMA or MMA–MATRIFE copolymer above the total miscibility limit. The evolution of dynamic moduli as a function of blends composition confirms the miscibility limits determined by DSC. The Flory–Huggins interaction parameters were determined through the melting point depression analysis and compared to correlate the intensity of inter- or intra-molecular interactions between the polymers to the postulated ‘acidity’ of hydrogen atoms in various VDF-containing polymers. The interaction parameter χ12 increases with the fluoroalkyl methacrylic ester content, corresponding to a prevalence of intra-molecular on inter-molecular interactions in these blends. Similarly, PVDF offers higher χ12 values as compared to VDF–TFE or particularly to VDF–TrFE copolymers. These results highlight the importance of the nature of fluorinated polymers and of the inter- or intra-molecular character of dipolar interactions on both, copolymer miscibility and interaction parameter values.

Ultrafiltration (UF) of gelatin liquor from marine source (tuna skins) has been performed on a tubular mineral membrane of cut-off 10,000 Da. An attempt was made to concentrate the fish gelatin as well as to purify it by means of the diafiltration technique (DF). Primary experiments were devoted to optimise the UF performances as a function of the main adjustable parameters. The influence of pH, transmembrane pressure, recirculating velocity, and working temperature on both volumetric permeate fluxes and protein retention rates was successively examined. Under the appropriate operating conditions, it was shown that the used membrane can achieve the initial concentration step of the gelatin solutions up to 12 wt% with a protein yield as high as 0.98. In addition, continuous DF proved useful to reduce the salt content of the solutions at an average desalting speed of 185 g/h.m2 with a few loss of protein in the permeate side.

Co-continuous extruded polyester-carbon black filled polyalkene blends exhibit a slightly positive temperature coefficient, which depends on the nature of the polyester. From studies on various polyesters (poly(butylene terephthalate), poly(ethylene terephthalate), and some of their blends), it appears that the positive temperature coefficient becomes higher when the blends are heated above the glass transition temperature of the polyester. Polyalkene melting induces a hysteresis effect between heating and cooling steps. Attempts to catalyse grafting through enhanced transesterification also promote polyester degradation and alter the morphologies of the blends.

New organic−inorganic hybrid materials, prepared via in situ intercalative polymerization of cyclosiloxanes in the presence of (R4N)xH1-xTiNbO5, are described. The polysiloxane-g-TiNbO5 nanocomposites were identified mainly by Fourier transform infrared absorption spectroscopy, X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. All of these techniques confirm the proposed structure and show exfoliation of the initial mineral sheets in the polymer matrix is largely achieved. Elemental analysis indicates that grafting yields lie in the range 100−200% (w/w), corresponding to nanocomposites in which the mineral phase occupies between 50 and 25% of the total volume.

Star-shaped poly(methylthiirane)s were prepared by ring-opening polymerization of methylthiirane with thiolate ions as initiators. As expected, the "arm first method" using 1,2,4,5-tetrakis(bromomethyl) benzene as a linking agent gave mixtures of tetra-, (tri) and di-armed polymers. The "core first method" with tri- and tetrathiols as core components seemed to be a better method and gave polymers of different molar masses, varying from 800 to 60 000 g. mol(-1) with narrow polymolecularity indices, but the presence of macromolecular disulfides - formed by oxidation of the thiolate ions - broaden the molar distribution. These disulfides could be reduced with lithium aluminium hydride. The star polymers could be end-capped with various functional groups through reaction of the thiolate end groups, either at the end of the polymerization or after acid regeneration from the thiol polymers.

Chain transfer to ethylene bis(mercaptoacetate) in the free radical polymerisation of styrene and methyl methacrylate leads to ester and sulfide-containing polymers functionalized both in chain ends as well as in the chains. The functionalized polystyrene can be (bio)degraded from ester functions as well as from sulfide functions. Attempts to chemically degrade functionalized poly(methyl methacrylate) from sulphur functions was less successful.

Poly(butylene terephthalate)/poly(ethylene-co-alkyl-acrylate)/carbon black (PBT-EXA-CB) blends, prepared through extrusion, were characterized as electrical conductive materials. In the composition range studied (55 less than or equal to PBT % less than or equal to 75 w/w; 5.5 less than or equal to CB % less than or equal to 11.1 w/w), various conductive behaviors were observed depending mainly on composition and poly(olefin) crystallinity. The observed positive temperature coefficient (PTC) is quite small compared to poly(olefin)-CB systems, and our blends do not present a negative temperature coefficient (NTC) on complete melting of the CB-containing phase, thus offering new possibilities for a regular electric power control. Volume expansion of both PBT and EXA was postulated to be the main parameter responsible for the thermal resistivity evolution through the range +20 to +170 degreesC. A double-percolation system between both the co-continuous polymer phases and CB-particles included in the poly(olefin) phase is postulated to explain these results.

The calorimetric characteristics of carbon black (CB)/poly(ethylene-co-alkyl acrylate) composites depend on both the CB and acrylate contents. An increase of the acrylate content in the pure copolymers tends to decrease all the crystalline characteristics: T-c,T-n, the nonisothermal crystallization temperature; T-m, the melting temperature, and DeltaH(m), the melting enthalpy. CB modifies the crystallization kinetics of poly(ethylene-co-ethyl acrylate) (EEA) alone and in blends with poly(ethylene-co-24% w/w methyl acrylate) (24EMA) and poly(ethylene-co-35% w/w methyl acrylate) (35EMA). In the presence of CB, T-c,T-n, the nonisothermal crystallization temperature of EEA, increases and t(1/2), the half-crystallization time, decreases for a given isothermal crystallization temperature, T-c,T-i. The thermograms obtained during the melting of EEA after isothermal crystallization show multiple endotherms, suggesting that crystalline-phase segregation has occurred. The existence of different crystalline species can be explained by the presence of fractions of different acrylate content in the copolymers as shown by SEC. Therefore, CB does not seem to have much effect on the subsequent melting temperature of EEA, T-m,T-s. CB also induces a lower melting enthalpy, Delta H-m, in the blends. This decrease of DeltaH(m) appears to be constant whatever the compound, but when reported to the melting enthalpy of the polymer without CB, delta DeltaH(m)/DeltaH(m) increases with the acrylate content. A slight increase of the amorphous phase stiffness after CB introduction is noticed: The T-g of EEA/24EMA and EEA/35EMA blends increases by several degrees. Therefore, plotting DeltaH(m), versus DeltaC(p) shows that for the same DeltaH(m) the DeltaC(p) is lower in CB-filled samples, suggesting there is some bind of rigid amorphous phase not contributing to the glass transition. We propose to explain the CB activity during the crystallization process by the existence of:molecular interactions between CB and acrylate groups rather than by a pure nucleating effect. Thus, the increase of T-c,T-n and the decrease of DeltaH(m) could be explained by the fact that CB separates acrylate-rich chains from the crystallization medium, accelerating the crystallization of the acrylate-poor chains; During such a crystallization process, CB may be preferentially localized in the more polar amorphous phase and scattered between the two crystalline phases of EEA and EXA. These blends of poly(ethylene-co-alkyl acrylate) copolymers with CB provide interesting materials with adjustable properties depending on the acrylate and CB contents and on the thermomechanical treatments. (C) 2000 John Wiley & Sons, Inc.

Degradation of poly(butylene terephthalate) (PBT) induced by blending time at 260 degreesC leads to an increase of both carboxylic end groups and melt viscosity index and a decrease of the molecular weights. Crystallization kinetics of pure PET and PET blended with an epoxide, which was used to reduce the free carboxylic acid concentration, were compared. Lower carboxylic acid concentrations were obtained, but the molecular weights still decreased. The crystallization kinetics of PET blended with pigments and/or mineral fillers were also studied. Dyes, some of which are known for their nucleation activity, were used for differentiating extruded PET tubes in optical fiber loose cables. Post-shrinkage appeared to depend on the type of pigment used. Pigments concentration, particle size and chemical nature have been correlated to the PET crystallization kinetics. An increase of the nonisothermal crystallization temperature was observed, more or less important according to the pigment used. Talc and mica were also tested in PET blends, with and without pigments. Their nucleation activity parameters were measured and compared with those for the pigments. An average value of the crystallization temperature, nearly constant and independent of the pigment, was obtained with the addition of 0.15% (w/w) talc in the blends. This may be a way to obtain controlled shrinkage on industrial products with strict dimension requirements.

ADVERTISEMENT RETURN TO BOOKPREVChapterNEXTFluorinated Polymer Blends as Plastic Optical Fibers Cladding MaterialsS. PimbertS. Pimbert Corresponding author: email: [email protected]More by S. Pimbert, L. Avignon-PoquillonL. Avignon-PoquillonLaboratoire Polymeres et Procedes, Université de Bretagne-Sud, Rue St. Mandé, 56325 Lorient, France Corresponding author: email: [email protected]More by L. Avignon-Poquillon, and G. LevesqueG. LevesqueLaboratoire Polymeres et Procedes, Université de Bretagne-Sud, Rue St. Mandé, 56325 Lorient, France Corresponding author: email: [email protected]More by G. LevesqueDOI: 10.1021/bk-2001-0795.ch008Publication Date (Print):September 13, 2001Publication History Published online23 July 2009Published inprint 13 September 2001RIGHTS & PERMISSIONSOptical PolymersChapter 8pp 113-128ACS Symposium SeriesVol. 795ISBN13: 9780841237063eISBN: 9780841218734 Copyright © 2001 American Chemical SocietyChapter Views109Citations-LEARN ABOUT THESE METRICSChapter Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) SUBJECTS:Fibers,Copolymers Get e-Alerts

Thioacylation is a new way for protein chemical modification. Carboxylic dithioesters and -acids react selectively and rapidly at room temperature with aliphatic amines such as lysine epsilon-amino groups leading to thioamide formation, without any other reagent or catalyst. Various thioacylating reagents were synthesized: monofunctional dithioesters bearing on the acylating end various chemical groups such as: aliphatic chains, phenyl group, mono- and dicarboxylic acids, dialkylphosphonic ester, phosphonic acid, thiol, phenol, or quaternary ammonium group. Bifunctional dithioesters containing either a polymethylene chain or an ethylene oxide oligomer as spacer group as well as some mono- and bis(dithio acids) are described. Applications of thioacylation may be involved either in enzyme chemical modifications or in the obtention of new materials from proteins. Bifunctional reagents might be used as cross-linking or coupling reagents.

Several thioacylating reagents have been tested toward hydrolysis under conditions suitable for protein modifications: 20-35 degrees C and buffered solutions at pH 7.5-8.5. Aliphatic dithioesters are sufficiently stable in aqueous media at room temperature (or below) if protein modification reaction time does not exceed 24 h, whereas at 35 degrees C reaction times must be limited to a few hours. Kinetic data obtained in gelatin thioacylation at room temperature using aliphatic dithioesters and dithio acid are consistent with a second-order reaction rate with respect to amine concentration. The pH dependence of the second-order reaction rate constants indicate that dithioester reacts exclusively with the free amine form of lysine residue, whereas dithiocarboxylate ion reacts with both amine and ammonium ion, probably through a more complex mechanism. Interestingly thioacylation using dithio acids may be obtained in pH near neutrality or in slightly acidic media, thus offering protein modification possibilities at pH 5-9. Thioacylation reaction rates may be expressed as R = -(dAt/dt) = k[H3O+](-b)At2[thioacylating agent] in which At is the amine concentration at time t, constants k and b depending on the reagent nature.

Polymers carrying different organic functional groups (carboxylic acids, tertiary amines, nitriles) were successfully synthesized from poly[(ethylene)-co-(vinyl alcohol)] (EVOH) in two steps. The first step involves acylation of hydroxyl functions of EVOH by phthalic anhydride. Under specific experimental conditions, the substitution may become nearly quantitative. In a second step, alkylation of the so-obtained carboxylic salts is realized in situ using methyliodide, 2-chloroethyl piperidine or chloroacetonitrile, for example. Degrees of substitution (DS) are easily determined by titration of carboxylic functional groups after, respectively, the first and the second steps. Final functional polymers were characterized by IR spectroscopy and 1H and 13C Nuclear Magnetic Resonance. Their thermal properties were determined by differential scanning calorimetry and thermogravimetric analysis. Experimental protocols have been established for the transformation of EVOH into polymers bearing new groups such as carboxylic acids, tertiary amines or nitriles through a one-pot procedure from EVOH.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTA New Initiator System for the Living Thiiranes Ring-Opening Polymerization: A Way toward Star-Shaped PolythiiranesE. Nicol, C. Bonnans-Plaisance, and G. LevesqueView Author Information Laboratoire de Chimie et Physique des Matériaux Polymères, CNRS (UMR 6515), Université du Maine, F-72085 Le Mans Cedex 9, France, and Laboratoire Polymères et Procédés, Université de Bretagne-Sud, F-56325 Lorient, France Cite this: Macromolecules 1999, 32, 13, 4485–4487Publication Date (Web):June 10, 1999Publication History Received12 January 1999Revised29 April 1999Published online10 June 1999Published inissue 1 June 1999https://doi.org/10.1021/ma9900434Copyright © 1999 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views879Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (52 KB) Get e-AlertscloseSUBJECTS:Ions,Polymerization,Ring-opening polymerization,Thiolates,Thiols Get e-Alerts