bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid‐crystalline polyurethanes, 6. Amphiphilic polyurethanes containing long alkyl chains in the side chains and amino or quaternary ammonium groups in the main chains
Authors: Tanaka Mamoru , Nakaya Tadao
Published: April 2003

Amphiphilic polyurethanes5a–c,6a–c,10a–cand11a–ccontaining hydrophilic amino or quaternary ammonium groups in the main chain, and hydrophobic ocatadecyl or docosyl groups in the side chain, were synthesized by polycondensation of 2,2′‐octadecyliminodiethanol (3a), 2,2′‐docosyliminodiethanol (3b), bis(2‐hydroxyethyl)methyloctadecylammonium bromide (8) and bis(2‐hydroxyethyl)docosylmethylammonium bromide (9) with a diisocyanate such a hexamethylene diisocyanate (4a), 2,4‐toluylene diisocyanate (4b) and 4,4′‐methylenediphenyl isocyanate (4c). Some of them show a thermotropic liquid‐crystalline state, as determined by DSC and polarizing microscopy.
Excimer laser‐induced free‐radical copolymerization of ethylene and acrylonitrile
Authors: Brackemann Holger , Buback Michael
Published: April 2003

The free‐radical copolymerization of ethylene (E) and acrylonitrile (A) was studied up to 275°C and 2900 bar in continuously and in discontinuously operated devices. Polymerization is induced by KrF excimer laser light at 248 nm. In addition, results for copolymerizations with thermal and with chemical (oxygen) initiation are presented. The ethylene reactivity ratio, rE, is derived as a function of temperature. At 2450 bar, rE increases from 0,016 ± 0,003 at 150°C up to 0,055 ± 0,009 at 275°C. rE measured as a function of pressure, yields an activation volume of ΔV# (rE) = (−5,2 ± 3,5) cm3·mol−1. The kinetic information from the laser‐induced experiments is used to describe the measured overall quantum yield, ϕ0, which is found to be a few thousand monomer molecules polymerized by one absorbed laser photon. ϕ0 decreases toward higher acrylonitrile content. The kinetic parameters are also used to predict overall and acrylonitrile conversion in continuous free‐radical E/A copolymerizations with various chemical initiators.
On the relationship between room‐temperature conductivity and morphology of polyacetylene
Authors: Gläser Daniel , Schimmel Thomas , Schwoerer Markus , Naarmann Herbert
Published: April 2003

Several sets of samples of elongated Naarmann‐type polyacetylene were investigated by conductivity measurements and scanning electron microscopy. For the latter investigations, a special kind of sample preparation was developed to ensure authentic information about the internal morphology of polyacetylene. We found two different types of fibrillar morphologies, one exhibiting thick bundels or strings along the elongation direction and an intermediate tissue of nonaligned fibrils, the other showing only individual, well aligned fibrils. The first type of structure has low conductivities after oxidation with iodine, whereas the second one tends to have significantly higher values. A comparison of the geometrical and electrical anisotropy shows that charge transport takes place mainly in highly aligned regions, the conductivity being a weighted average over all possible conducting paths.
Electron‐ion recombination luminescence from UV irradiation of glassy epoxy resins
Authors: Billingham Norman C. , Burdon Jeremy W. , Kozielski Karen A. , George Graeme A.
Published: April 2003

Brief irradiation of an epoxy resin is shown to induce a chemiluminescence emission which decays over a period of minutes. At cure temperatures, the intensity of this emission passes through a minimum with cure time, correlating with the vitrification of the resin. Photo‐induced chemiluminescence can also be observed at room temperature in glassy resins. Studies of emission and excitation wavelengths, atmosphere dependence, electric field effects and thermoluminescence from irradiated resin suggest that two phenomena are responsible. For fluid resins curing in air, the emission is due to the recombination of radicals participating in the oxidation of the resin. As the resin vitrifies, the luminescence is increasingly due to recombination of photo‐induced electron‐cation pairs and is sensitive to the vitrification. This phenomenon could provide a new method for monitoring cure in thermosetting resins.
Graft copolymers of polytetrahydrofuran and butyl rubber, 1. Cationic copolymerisation of tetrahydrofuran with bromobutyl rubber
Authors: Cameron G. Gordon , Sarmouk Khiredine
Published: April 2003

Graft copolymers of butyl rubber (BR) with polytetrahydrofuran (PTHF) were prepared from bromobutyl rubber by a cationic “grafting‐from” reaction initiated by silver perchlorate at allylic bromine sites on the rubber. By studying the influence of variables, such as temperature etc., it was shown that initiation at −20°C for 30 min, followed by polymerisation at 0°C with a [AgClO4]/[Br] ratio of ca. unity, produced near optimum reaction conditions with grafting efficiencies >90%. Copolymers containing upto 40% of grafted PTHF were obtained by this means. The BR‐g‐PTHF copolymers have a two‐phase morphology comprising amorphous BR with crystalline domains of PTHF which function as points of reinforcement in the rubber upto ca. 300 K.
Liquid‐crystalline polyethers and copolyethers based on conformational isomerism, 4. Thermotropic polyethers and copolyethers based on 1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane and flexible spacers containing an even number of methylene units
Authors: Percec Virgil , Yourd Raymond
Published: April 2003

The synthesis and characterization of thermotropic main‐chain liquid‐crystalline polyethers MBPE‐X and copolyethers MBPE‐X/Y based on 3‐methyl‐4,4′‐ethylenediphenol [1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane (MBPE)], which is flexible rod‐like mesogenic unit or a rod‐like mesogenic unit based on conformational isomerism, and flexible spacers containing an even number of methylene units, X, Y, are described. The particular examples presented in this paper refer to polyethers MBPE‐4, MBPE‐6, MBPE‐8, MBPE‐10, and MBPE‐12, and copolyethers MBPE‐X/Y; where X,Y = 4, 6, 8, 10, 12. MBPE‐4, MBPE‐6, MBPE‐10 and MBPE‐12 are crystalline. MBPE‐8 displays an enantiotropic nematic mesophase. Copolymerization of MBPE with different pairs of spacers containing even numbers of methylene units leads to MBPE‐X/Y copolymers displaying monotropic or enantiotropic nematic mesophases. Both liquid‐crystalline transition temperatures and the corresponding enthalpy changes of the copolymers represent weight‐averaged values of the similar parameters of the parent homopolymers. Extrapolation of the isotropic‐nematic and nematic‐isotropic transition temperatures and their corresponding enthalpy changes demonstrated that all homopolymers containing an even number of methylene units in the flexible spacer exhibit virtual nematic mesophases. The virtual isotropic‐nematic transition temperatures and the corresponding enthalpy changes were determined for MBPE‐4, MBPE‐6, MBPE‐10 and MBPE‐12. The virtual nematic‐isotropic transition and the corresponding enthalpy changes could be determined only for MBPE‐10 and MBPE‐12.
Synthese und Reduktion des Tetra‐tert‐butyltetraoxocalix[4]arens
Authors: Görmar Gerhard , Seiffarth Klaus , Schulz Manfred , Zimmermann Jochen , Flämig Gesina
Published: April 2003

5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxy‐2,8,14,20‐tetraoxocalix[4]arene (4) was synthesized by oxidation of the tetraacetate of 5,11,17,23‐tetra‐tert‐butyl‐25,26,27,28‐tetrahydroxycalix[4]arene (1). Compound 4 was characterized by chemical and spectroscopic methods. Reduction of 4 with hydrazine forms the starting material 1. 4 reacts with sodium borohydride to give 5,11,17,23‐tetra‐tert‐butyl‐2,8,14,20,25,26,27,28‐octahydroxycalix[4]arene (6).
Preparation of poly(amide‐imide)s by direct polycondensation with triphenyl phosphite, 3. Poly(amide‐imide)s based on bis(trimellitimide)s
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping
Published: April 2003

Six dicarboxylic acids (1a–f) were prepared from trimellitic anhydride and 4,4′‐oxydianiline, 4,4′‐methylenedianiline, 4,4′‐sulfonyldianiline, benzidine, 1,6‐hexamethylenediamine, and 4,4′‐methylenedicyclohexylamine. These diacids were condensed directly with various aromatic diamines using triphenyl phosphite in 1‐methyl‐2‐pyrrolidone/pyridine solution in the presence of calcium chloride. The inherent viscosity of the polymers is affected by the nature of the diamine and the solubility of the resulting polymers in the reaction media. The highest ηinh‐value of a poly(amide‐imide) obtained was 1,41 dl/g (in N,N‐dimethylacetamide/5% LiCl at 30°C). Among the polymers, the wholly aromatic ones show better solubility, higher glass transition temperatures, and higher thermostability than the aliphatic‐aromatic ones. Well‐defined melting points (Tm) of most wholly aromatic poly(amide‐imide)s were not obtained by differential scanning calorimetry (DSC); however, some poly(amide‐imide)s containing aliphatic chains showed clear Tm in the first DSC heating traces. Measurements of wide‐angle X‐ray diffraction revealed that those polymers containing biphenyl or linear hexamethylene groups are partially crystalline. Flexible films with excellent tensile properties were cast from N,N‐dimethylacetamide solutions of most of the wholly aromatic poly(amide‐imide)s.
Investigations of poly(vinyl alcohol)/poly(N‐vinyl‐2‐pyrrolidone) blends, 2. Influence of the molecular weights of the polymer components on crystallization
Authors: Ping Zheng‐Hua , Nguyen Quang Trong , Néel Jean
Published: April 2003

Blends of crystallizable poly(vinyl alcohol) (PVA) and poly‐(N‐vinyl‐2‐pyrrolidone) (PVP) of different molecular weights were prepared from aqueous solutions by evaporation and studied by Fourier‐transform IR spectroscopy. When the molecular weight of one of the polymer components increases, the PVP content at which crystallinity in PVA is no longer observed decreases. The wide band representing hydroxyl stretching splits into four components at welldefined frequencies which are assigned to (1) multiple hydroxyl‐hydroxyl bonding in organized PVA regions, (2) hydroxyls which are simply bonded to carboxyl, (3) hydroxyls doubly bonded to two carbonyls or to one carbonyl and one hydroxyl, and (4) simple hydrogen‐hydrogen bonding in amorphous PVA regions. When the PVP content increases, the relative intensity of the bond of di‐hydrogen‐bonded hydroxyls remains quasi‐invariant, while that of multiple hydrogen bonds in PVA decreases, and that of simple hydroxyl‐carbonyl bonds increases correspondingly. It appears that the higher the molecular weight, the more effective the hindrance of PVP crystallization. An explanation of the mechanism leading to the formation of different structures in the blends is proposed on the basis of these results. It stresses the importance of the role of chain dynamics in an entangled chain network, which greatly affects the kinetics of crystallization of PVA during the drying step.
Polyesters prepared by polycondensation in the presence of carbodiimides, 2. On the reaction of methyl α‐(S)‐malate with N,N′‐dicyclohexylcarbodiimide under mild conditions
Authors: Belcheva Nadya , Tsvetanov Christo , Panayotov Ivan M. , Lazarova Stoyanka
Published: April 2003

The reaction of methyl α‐(S)‐malate with N,N′‐dicyclohexylcarbodiimide in the presence of amines under mild conditions was studied. It was established that in solvents with weak donor properties, N‐acyl derivatives are preferentially formed instead of ester condensation products. An optically active polymer fraction was separated by precipitation in diethyl ether (yield up to 30%) with M̄n,GPC 1 000 to 4 000 and of low polydispersity M̄w/M̄n = 1,1–1,4. The method permits the preparation of optically active biodegradable condensation products with controlled molecular structure.
Some 13C NMR evidence on isotactic polymerization of styrene
Authors: Longo Pasquale , Grassi Alfonso , Oliva Leone , Ammendola Paolo
Published: April 2003

13C NMR analysis of isotactic polystyrene prepared in the presence of different catalysts reveals that isotactic polyinsertion can arise from mechanisms involving different regiospecificity and possibly different steric control.
Influence des traitements thermiques à l'état fondu sur les cinétiques de cristallisation du poly(oxyméthylène)
Authors: Franbourg Alain , Rietsch François
Published: April 2003

The influence of the temperature of the melt T1 on the kinetics and the morphology of a semicrystalline polymer (poly(oxymethylene)) was investigated using thermal analysis and optical microscopy. The thermodynamic melting point T and the enthalpy of melting at thermodynamical equilibrium ΔH were determined by extrapolation of the graphs Tf = f(Tc) and ΔHf = f(Tc); (T = 198°C, ΔH = 251 J/g). For different temperatures of the melt (T1 = 185°C, 195°C, 205°C), isothermal and non‐isothermal crystallizations were analysed using the Avrami and Ozawa equations. Nucleation and spherulitic growth in this polymer were studied by using optical microscopy at elevated temperatures. Using different analyses, we observed initial nucleation followed by spherulite growth with the following influence of the temperature of the melt on the distribution and the number of spherulites: T1 < T produces many small spherulites; T1 > T gives rise to few large spherulites.
Theoretical approach to cationic polymerization of alkenylfuranes
Authors: Alvarez J. Raul , Montero Luis , Martinez Ricardo
Published: April 2003

The molecular species proposed for the initial steps in the cationic polymerization of alkenylfurans were modeled by MNDO theoretically fully optimized structures. It was confirmed that the anomalous reactivity of ring C‐5 of the monomers is determined by HOMO electron densitites, whereas calculated proton affinities from the semiempirical heats of formation fail to explain the low temperature experimental behavior of 2‐vinylfuran (1c) from the point of view of stability of intermediate species. However, ab initio 4‐31G calculations of proton affinities agree with the experimental facts and allow further explanations of the reactivity of furan derivatives in electrophilic media.
Observations on the swelling behaviour of copolymeric hydrogels containing N‐vinyl‐2‐pyrrolidone
Authors: Al‐Issa Mahmoud A. , Davis Thomas P. , Huglin Malcolm B. , Rego Jose M. , Rehab Mahmoud M. A.‐M. , Yip Daniel C. F. , Zakaria Mat B.
Published: April 2003

Polymer‐water interaction parameters, sequence length distributions and contents of total, freezing and non‐freezing water have been discussed for a family of hydrogels. The xerogel precursors contained N‐vinyl‐2‐pyrrolidone (VP) with several co‐monomers of different levels of hydrophobicity present in the xerogel over a wide range of composition. Common trends in the behaviour of these systems have been noted and rationalised. In particular the findings indicate that (i) in the poly‐VP hydrogel ther are ca. 8–10 molecules of non‐freezing water per VP unit and (ii) in the copolymeric hydrogels the maximum occurring in the variation of mole fraction of VP versus mole fraction of water is due substantially to the sharp increase in uptake of freezing (or bulk) water by copolymers rich in VP.
Energy calculations on chain conformation and mode of packing of crystalline isotactic cis‐1,4‐poly(1,3‐pentadiene)
Authors: Napolitano Roberto
Published: April 2003

Conformational and packing energy calculations were performed on crystalline isotactic cis‐1,4‐poly(1,3‐pentadiene). Internal parameters corresponding to a chain conformation similar to that of other polydienes were found by conformational energy calculations. The packing energy calculations indicate that the most stable mode of packing is obtained in the P212121 space group. A possible structure of the polymer is also suggested.
Small‐angle X‐ray scattering studies on poly(vinyl alcohol)/poly(N‐vinyl‐2‐pyrrolidone) blends
Authors: Zhang Hongfang , Yin Jinghua
Published: April 2003

The structures of unannealed and annealed poly(vinyl alcohol) (PVAl)/poly(N‐vinyl‐2‐pyrro‐lidone) (PVP) blends were investigated by means of small‐angle X‐ray scattering (SAXS). The results indicate that the structural parameters are strongly dependent upon both composition and crystallization conditions. The amorphous region, the long period and the thickness of the lamellae increase with increasing content of PVP in the blends. Annealing increases the crystallinity significantly. The degree of crystallinity and the specific inner surface are reduced with decreasing content of PVAl. A crystal‐amorphous interface exists within the lamellae; the size of the interface is of the order of 20–25 Å.
Synthesis of polystyrene‐polycarbonate block copolymers: A reappraisal of the reaction between polystyryllithium and bisphenol‐A polycarbonate
Authors: Berti Corrado , Bonora Virna , Pilati Francesco , Chiantore Oscar
Published: April 2003

Polystyrene (PS)/bisphenol‐A polycarbonate block copolymers were prepared by direct reaction of polystyryllithium with bisphenol‐A polycarbonate. Contrary to what was previously reported by Polowinski et al., the yields of block copolymers were low owing to side reactions. These are due to consecutive attacks of the polystyryl anions and lead to a dimeric ketone (dipolystyryl ketone, PSCOPS) and a trimeric tertiary alcohol (tripolystyryl carbinol, (PS)3COH). The block copolymers were separated from the reaction mixture and characterized.
Synthesis and properties of polymeric iron(II)‐complexes containing terpyridinyl groups
Authors: Hanabusa Kenji , Nakano Kunihiro , Koyama Toshiki , Shirai Hirofusa , Hojo Nobumasa , Kurose Akio
Published: April 2003

A new vinyl monomer (4) containing a terpyridinyl group was prepared and radically copolymerized with styrene or methyl methacrylate. The terpyridinyl groups in the resulting copolymers (5 and 6) coordinate almost quantitatively to the Fe(II) ion and form a complex. The decrease of ηinh, accompained by the coordination to the Fe(II) ion, suggests that the formation of the Fe(II)‐complex occurs in each polymer chain with shrinking. A cyclic voltammogram of the Fe(II)‐complex of polymer 6 showed characteristic Fe2+/Fe3+ redox couples at +1,12 V vs. SCE, which was followed by a color change from purple to colorless.
Alkylumlagerungen und acidolyse der ethylidenbrücken bei der synthese von ethylidendiphenolen
Authors: Kämmerer Hermann , Kiegel Einhart
Published: April 2003

For the synthesis of symmetrical and unsymmetrical ethylidenediphenols the corresponding hydroxyphenylethanols (1a–c) were prepared by hydrogenation of hydroxyphenyl methyl ketones with hydrogen/Raney nickle or with lithium aluminium hydride. Condensations of the hydroxyphenylethanols with different phenols under the usual acidic conditions gave products formally resulting form transalkylations. Only the reaction of 1‐(3‐bromo‐2‐hydroxy‐5‐methylphenyl)ethanol (1c) with p‐cresol gave the expected product 2d with 82% yield. Experiments with ethylidenediphenols showed that with acids in presence or absence of phenols cleavage and recondensations take place leading to products of formal transalkylation. Based on these results a method of synthesis was developed (the so‐called “gaseous HCl‐method”) leading to the desired ethylidenediphenols, as shown in the case of 4,4′,6‐trimethyl‐2,2′‐ethylidenediphenol (2b).
A novel, facile technique for deacetylating chitin
Authors: Batista Irineu , Roberts George A. F.
Published: April 2003

The use of water‐miscible organic solvents such as 2‐propanol, 2‐methyl‐2‐propanol and acetone in the alkaline deacetylation of chitin was examined. Using such diluents enables adequate deacetylation to be obtained with much smaller volumes of alkali, typically 1,5 cm3 50 wt.‐% aq. NaOH per 1 g of chitin, although in general the extent of deacetylation is less than that obtained using alkali alone under the same conditions of time and temperature. Sufficient deacetylation to render the product acid‐soluble may be obtained at temperatures as low as 56°C, but temperatures of 75–80°C are preferred. The extent of chain cleavage may be reduced by addition of thiophenol or sodium borohydride to the reaction mixture, or by carrying out the deacetylation in an inert atmosphere, and chitosan having M̄v > 1 · 106 and ca. 70% deacetylated sugar units was obtained using the latter technique.
Synthèses de diols téléchéliques isomoléculaires par télomérisation
Authors: Boutevin Bernard , El Idrissi A. , Parisi J. P.
Published: April 2003

Telechelic diols(10–13 and 15–18) were synthesized by addition of 2‐mercaptoethanol(2) and dithiols (3 and 4) to 9‐undecen‐1‐ol (9), ω‐hydroxyalkyl esters of 10‐undenoic acids (8a–c) or N‐(2‐hydroxyethyl)‐10‐undecenamide (5) in the presence of benzoyl peroxide in quantitative yields. The resulting diols have a length in the range of 15 to 50 carbon atoms. They show, however, properties of isomolecular substances.
Polystyrènes à motifs bifonctionnels: synthèses, caractérisations et modifications chimiques
Authors: Monthéard Jean‐Pierre , Boinon Bernard , Benayad Belabbas , Brigui Jamal , Camps Marcel
Published: April 2003

Four enol esters with a styrene skeleton (3a–d) were synthesized in two steps from commercial products and polymerized or copolymerized with styrene as a comonomer. The polymers and copolymers (7 and 8) were characterized. They are stable up to 140°C and lose acetic acid upon heating. Chemical modifications, such as nucleophilic substitutions with cyanide ions or nucleophilic addition of butyllithium, were studied.
Poly(vinylsaccharide)s, 7 New surfactant polymers based on carbohydrates
Authors: Klein Joachim , Kunz Markwart , Kowalczyk Jörg
Published: April 2003

New amphiphilic poly(vinylsaccharide)s (poly(7) and poly(8)) were synthesized. Various alkylamino substituted mono‐ and disaccharides 3 and 5 were obtained by reductive amination of reducing mono‐ and disaccharides with alkylamines. The reaction of these monofunctionalized sugar derivates with 2‐isocyanatoethyl methacrylate (2) leads to well‐defined monomers (7 and 8) of the urea type. The monomers were polymerized in aqueous solution to high‐molecular‐weight polymers, using the redox initiator system (NH4)2S2O8/Na2S2O5. The influence of structural variations by changing the hydrophilic sugar moiety or the lipophilic alkyl part was studied by viscometry, light scattering and measurements of the surface tension.
Synthese und polymerisationsverhalten neuer spirocyclischer methacrylate
Authors: Haase Ludwig , Klemm Elisabeth
Published: April 2003

Novel 2‐substituted 9‐methacryloyloxy‐8,8‐dimethyl‐1,4,6‐trioxaspiro[4,4]nonanes 3a–e were synthesized by O‐acylation of the corresponding 9‐hydroxyspiroorthoesters 2a–e with methacrylic acid. Its radical homopolymerization in solution results in film‐forming, soluble polymers with intact spiroorthoester groups, which can be crosslinked by cationic ring‐opening reaction. On the other hand, insoluble polymers are formed by radical polymerization of these methacrylic spiroorthoesters 3a–e in bulk. Crosslinking is traced back to a radical ring‐opening reaction as a consequence of a chain transfer reaction at the spirocyclic part of the molecule.
Methyl rotation of pendant trimethyl moieties in polymethacrylates
Authors: Zhan Yongjian , Jin Xigao , Qian Renyuan , Cao Qijuan , Meng Qing'an
Published: April 2003

The methyl rotation of a series of polymethacrylates \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 \hbox{---} {\rm C}({\rm CH}_3){\rm COOX}({\rm CH}_3)_3 \rlap{--}]_n $\end{document} 1 a – c where XC, Si and Sn, was studied by observing the solid‐state 1H NMR spin‐lattice relaxation. Minima of the spin‐lattice relaxation times for methyl group rotation in the OX(CH3)3 pendant groups, T1, min, were found at 165, 75 and 55 K for polymers 1a (XC), 1b (XSi) and 1c (XSn), respectively, at a resonance frequency of 30 MHz. The data indicate that methyl rotation is less restricted when it is bonded to an atom with larger covalent radius.
Determination of the number of active centers in Ziegler‐Natta polymerization of propene using sulfur‐containing terminating agents 2. Tagging of growing chains during retardation of polymerization by carbon disulfide
Authors: Vozka Pavel , Mejzlík Jiří
Published: April 2003

The CS2‐induced retardation of propene polymerization catalyzed by TiCl3/AiEt2Cl and TiCl3/AlEt3 systems was investigated. From the two systems, the latter was much more active in polymerization and also exceedingly more susceptible to retardation by CS2. At least for the TiCl3/AlEt2Cl‐catalyzed polymerization, there is no diffusion limitation imposed on the reaction of growing chain with CS2. It was found that the number of sulfur tags introduced by the above CS2 treatment is dominantly related to the ratio of polymerization rates before and after CS2 addition. Monomer plays a dual role during the CS2 treatment: on one hand it enhances the CS2 insertion into the growing metal‐polymer bond, on the other hand it competes with CS2 in the same reaction. CS2 reacts preferentially with centers of highest reactivity. It allows, in principle, the determination of the reactivity distribution of active centers. Several potential side reactions which might lead to an increase of the number of tags in polymer were considered. None of the side reactions play an important role except for a reaction of CS2 with chains formed via transfer with the organometal compound in AlEt3‐cocatalyzed polymerization.
Poly(ether/ester)s based on poly(butylene terephthalate) and poly(ethylene glycol), 1. Poly(ether/ester)s with various polyether: polyester ratios
Authors: Fakirov Stoyko , Gogeva Tanya
Published: April 2003

A series of poly(ether/ester)s 1 based on poly(butylene terephthalate)

Systematic IUPAC nomenclature: poly(oxytetramethyleneoxyterephthaloyl).

and poly(ethylene glycol) is synthesized. 1H and 13C nuclear magnetic resonance, infrared and differential scanning calorimetry (DSC) measurements prove a block structure of the prepared copolymers. The DSC curves suggest the existence of a three‐phase morphology — two amorphous phases for both polyether and polyester segments, and a crystalline phase for the polyester segments. Small angle X‐ray scattering (SAXS) measurements lead to the same conclusion. The degree of crystallinity assigned to the polyester fraction differs insignificantly and is similar to that of the homopolymer. SAXS data show approximately the same long spacing for all crystallizable copolymers. The tensile parameters of the studied polymers are similar to those of available commercial products based on poly(butylene terephthalate) and poly(tetrahydrofuran).
Poly(ether/ester)s based on poly(butylene terephthalate) and poly(ethylene glycol), 2. Effect of polyether segment length
Authors: Fakirov Stoyko , Gogeva Tanya
Published: April 2003

Structure‐properties relationships of poly(ether/ester)s (PEEs) 1 based on poly(butylene terephthalate) (PBT) and poly(ethylene glycol) (PEG) are studied. By varying the length of the soft segments (PEG) of molecular weights 600, 1000 and 2000) two series of PEEs are obtained, (i) with constant mole ratio PBT:PEG (the PBT block length being approximately the same) and (ii) with constant weight ratio PBT:PEG (different PBT segment length). The block structure is proved by 1H nuclear magnetic resonance and differential scanning calorimetry studies. A three‐phase morphology is established, i.e. two amorphous phases (polyether and polyester) and a crystalline phase (PBT), each one distinguished by its own transition temperature. At low temperatures (between −60 and 20°C) a fourth phase (crystalline PEG) appears. Small angle X‐ray scattering intensity and long spacing increase abruptly for the compositions with PEG 2000. The mechanical characteristics of the studied PEEs depend on the weight ratio of the two types of blocks.
Fluorinated polyurethanes, 1. Synthesis and characterization of fluorine‐containing segmented poly(urethane‐urea)s
Authors: Takakura Teruo , Kato Masao , Yamabe Masaaki
Published: April 2003

To produce high performance antithrombus elastomers, a series of new fluorine‐containing segmented poly(urethane‐urea)s was synthesized from 2,2,3,3,4,4,5,5‐octafluorohexamethylene diisocyanate (1) and α‐hydro‐ω‐hydroxypoly(oxyalkylene)s (5a, b and 6) or fluorinated dioxa‐1,10‐decanediols (3 and 4) (as the soft segments) via the prepolymers (7) which subsequently were reacted with various diamines including a fluorinated aliphatic diamine (2) as chain‐extenders. High‐molecular‐weight polymers were obtained in high yields with 5a and nonfluorinated diamines. Spectroscopic analysis of the prepolymers and the chain‐extended polymers indicated their structures to be highly ordered. Stress‐strain curves of films cast from a DMF solution indicated the polymers to be typical elastomers with tensile strength as much as 600–700 kg/cm2.
Dielectric relaxation properties of linear polythioethers
Authors: Díaz‐Calleja Ricardo , Riande Evaristo , Guzmán Julio
Published: April 2003

Values of the dielectric loss tangent were obtained as a function of temperature for poly(pentamethylene sulfide) (P5MS) and poly(1,3‐dithiocane) (PDTC). Both P5MS and PDTC exhibit a β absorption, located in the vicinity of their respective glass transition temperatures, −105°C and −73°C, which is believed to be associated with micro‐Brownian motions in the amorphous phase of the crystalline polymers. The glass‐rubber transitions of the polymers are discussed in terms of the flexibility of the chains, as expressed by their conformational partition functions and entropies.
Ion aggregation in magnesium‐neutralized polyester resins — Small angle X‐ray scattering study
Authors: Habassi Chefik , Brigodiot Maryvonne , Fradet Alain , Williams Claudine E.
Published: April 2003

Evidence for ion aggregation was found in SAXS studies of models of unsaturated polyester resins: magnesium icosanoate, magnesium α,ω‐dicarboxylatopoly(ethylene adipate), ‐poly(1‐hexylethylene adipate), ‐poly(propylene succinate), and ‐poly(propylene maleate‐co‐fumarate), swollen by various solvents or in the dry state. The results were compared with those obtained for commercial unsaturated polyester resins after neutralization with MgO, leading to the conclusion that the formation of aggregates is the key phenomenon of the so‐called thickening reaction of polyester resins. The existence of high amounts of branched units in the polyester chain does not appear to hinder ion aggregation. The aggregates are small (Guinier radius RG = 4 to 9 Å) and their average distance increases with chain length and swelling.
Quelques avantages de la polymérisation induite par un plasma froid microonde
Authors: Poncin‐Epaillard Fabienne , Brosse Jean‐Claude
Published: April 2003

Plasma induced polymerizations using an RF (13,56 MHz) or a microwave (433 MHz) generator were compared. The microwave plasma induced polymerization of a multifunctional acrylate (3‐ylomethylpentamethylene triacrylate) (trimethylolpropane triacrylate) (1) was studied as a function of different macroscopic parameters (chemical nature of gas, time, discharge power, distance between the surfatron and the substrate etc.). The involved mechanisms were found to be similar to those in the RF plasma. One of the advantages of the microwave apparatus is the possibility of working in the post‐discharge regime with selected reactive species. Evidence of the chemical structure of the polymer at its surface is given by ATR‐FTIR spectroscopy.
Amphiphilic block copolymers as phase transfer agents in toluene‐water two‐phase systems
Authors: Berlinova Iliyana V.
Published: April 2003

Amphiphilic block and star‐shaped copolymers based on polystyrene and poly(ethylene oxide) were used as phase transfer catalysts in the reaction of aqueous potassium iodide with 1‐bromooctane in toluene. The effects of composition and molecular architecture on observed reaction rates were examined. At constant copolymer composition, reaction rates increased with decrease of molecular weight of the copolymer. The catalytic activity of the amphiphilic block copolymers was correlated with their ability to extract potassium picrate from water into toluene. The results are discussed on the basis of the concept of one ion, one ligand transport.
Presence of fragmentation products in the cationic oligomerization of 1‐butene
Authors: Priola Aldo , Audisio Guido
Published: April 2003

In the cationic oligomerization of 1‐butene in the presence of BF3‐proton donor complexes a mixture of hydrocarbons was obtained. By means of GC‐MS analysis, beside the peaks corresponding to (C4)n products, the presence of significant amounts of products with different carbon atom numbers was revealed, indicating that fragmentation processes are operative in these systems. Moreover, in the different oligomer fractions, saturated and unsaturated hydrocarbons were found. Experiments of propene oligomerization, performed under similar conditions, yield a lower amount of fragmentation products and almost exclusively unsaturated products. Possible reaction mechanisms are presented.
Copolymerization of styrene and methyl α‐cyanocinnamate, 1. Synthesis, NMR‐assignment, reactivity ratios
Authors: Bednarski Ralf , Braun Dietrich , Borbély János , Kelen Tibor
Published: April 2003

The free‐radical copolymerization of styrene and methyl α‐cyanocinnamate was studied. The copolymers were investigated by means of NMR spectroscopy. From the assignment of the signals both in 1H and 13C NMR spectra it follows that not only head‐to‐tail but also head‐to‐head coupling of styrene and methyl α‐cyanocinnamate monomeric units occurs in the copolymers. The composition data of the copolymers can be described by the penultimate model as seen from the linear distribution of the data points in a modified Kelen‐Tüdös representation.
Telechelic poly(thio‐1,4‐phenylene)s and poly(thio‐1,4‐phenylene)‐block‐polyamides
Authors: Freund Lothar , Heitz Walter
Published: April 2003

Poly(thio‐1,4‐phenylene)s (PPS) 5a–d with reactive end groups like carboxyl, nitro, cyano and aldehyde groups were synthesized under high as well as atmospheric pressure. Carboxyl terminated telechelics 5a were used as starting materials for the synthesis of poly(thio‐1,4‐phenylene)‐block‐polyamides. Semicrystalline and amorphous polyamides like Nylon 6 and Trogamide® served as coblocks. The formation of block copolymers was approved by the solubility behavior, the NMR and IR spectra as well as high temperature GPC. The thermal stability increases with the fraction of PPS. By DSC, phase separation of the block copolymers was observed at certain compositions and molecular weights.
Scanning electron microscopy and ultrasonic investigations of the morphology of polypropylene (PP) films
Authors: Sadiku Emmanuel Rotimi
Published: April 2003

Ultrasound measurements (at four different frequencies) in the range 15 MHz–75 MHz corresponding to a low frequency pulse technique were made on polypropylene (PP) films of different draw ratios, λa = 1,0, 2,8, 4,9 and 5,8. Process‐dependent properties such as draw ratio (and/or thickness), quenching and annealing are functions on which attenuation depends. The logarithm of attenuation for all the samples increases almost linearly with frequency (an instrumental parameter). Such linearity is not observed when looking into the dependence of attenuation on draw ratio or thickness. This is explained in terms of the structural and morphological nature of the samples. The variation of attenuation with draw ratio indicates an exponential increase at frequencies greater than 17 MHz. The increase is very sharp at frequencies of 60,11 and 71,00 MHz. At a frequency of 16,58 MHz, a gradual linear increase in attenuation is observed with draw ratio. On the other hand, as expected, the converse situation of these observations is noted in the dependence of attenuation on film thickness.
Magnesium and calcium ions transport by synthetic analogues of teichoic acids with 1,2‐ and 1,3‐linked phosphodiester units
Authors: Wódzki Romuald , Kłosiński Paweł
Published: April 2003

2‐Ethylhexylpoly(trimethylene 1,3‐phosphate) (3), poly(1,2‐glycerol phosphate) (1) and poly‐(1‐acetoxy‐2,3‐glycerol phosphate) (2) were synthesized and used as synthetic analogues of teichoic acids. Their properties as a carrier of magnesium and calcium ions were examined in the competitive exchange diffusion process with the countertransport of hydrogen or sodium ions. It turned out that polymers with 1,2‐glycerol phosphate units (1,2) exhibit lower ability to transport preferentially magnesium ions than poly(1,3‐alkylene phosphate)s (3). In all cases the efficiency of polyphosphates in preferential transport of magnesium ions is higher when transport is coupled with proton counterflow.
Use of constants from Mark‐Houwink‐Sakurada equation for estimating the characteristic ratio of a polymer chain
Authors: Kas̆tánek Alois
Published: April 2003

A new procedure for the estimation of the characteristic ratio of flexible chain polymers is proposed. It is based on a combination of the parameters of the Mark‐Houwink‐Sakurada equation with a theoretical relationship of Kurata and Stockmayer. It is checked against data obtained under “theta” conditions. Good results are provided with systems where the Mark‐Houwink‐Sakurada exponent is lower than 0,65.
Kinetic investigation of photopolymerizations induced by laser beams
Authors: Decker Christian , Moussa Khalil
Published: April 2003

Real time infrared (RTIR) spectroscopy was used to study the kinetics of the polymerization of acrylic monomers exposed to the 337,4 nm continuous emission of a Kr+ laser. Conversion versus time curves were directly recorded in the millisecond timescale, thus allowing a precise evaluation of the polymerization rate and of the induction period due to O2 inhibition. The influence of the type and concentration of photoinitiator and of the laser beam intensity on the polymerization profile was examined for a 20 μm thick polyurethane‐acrylate (Actilane 20) coating. The growth of the radical concentration and its dependence on the initiation rate was determined from the kinetics of the dark polymerization which develops just after the laser exposure. Pulsed laser irradiation proved to be very effective in initiating the polymerization, the overall quantum yield reaching values up to 2500 mol · photon−1.
Isotactic polystyrene: An unusually large lamellar thickness as an effect of a thermodynamically good solvent
Authors: Allegra Giuseppe , Ganazzoli Fabio , Meille Stefano V. , Giunchi Giovanni , Heenan Richard K. , Higgins Julia S. , Luzzati Silvia , Nyström Bo , Roots Jaan
Published: April 2003

Isotactic polystyrene samples crystallized from concentrated solutions (> 10% by weight) in the thermodynamically good solvent toluene display a lamellar thickness L = (170 ± 15) Å at room temperature, as determined by neutron scattering investigation. This thickness is about twice the value reported for samples crystallized in poor solvents. The results may be interpreted in terms of a substantially smaller melting enthalpy of the polymer in toluene, producing a proportionally inverse increase of the thickness L̄c of the central, crystalline portion of the lamellae. In turn, we suggest that the overall thickness L of the lamellae increases more than proportionally with L̄c, due to the need of accomodating in the amorphous zone increasing amounts of polymer containing steric defects. The decrease of the melting enthalpy is also qualitatively consistent with growth rate results. The half‐peak width of the Bragg diffraction peaks suggests that the crystalline fraction of the lamellar thickness is about 50%, in approximate agreement with results obtained by Overbergh, Berghmans and Reynaers (J. Polym. Sci., Polym. Phys. Ed. 14, 1177 (1976)) from bulk‐crystallized samples showing about the same values of L and L̄c as observed by us.
Crosslinkable liquid‐crystalline main‐chain polymers
Authors: Peter Karin , Rätzsch Manfred
Published: April 2003

Crosslinkable liquid‐crystalline main‐chain polymers were prepared by high temperature polycondensation in solution. The polymers have reactive double bonds in the flexible spacer. Orientation of chains in the liquid‐crystalline state was not changed by crosslinking. Crosslinked polymers exhibit a high increase of the mesophase range and a higher E‐modulus than the uncrosslinked ones.
Photodegradation of poly(tert‐butyl methacrylate) in air and in the presence of sulfur dioxide and nitrogen dioxide
Authors: Dulog Lothar , Huber Adalbert
Published: April 2003

The photodegradation of poly(tert‐butyl methacrylate) films under 100 ppm sulfur dioxide in air or 100 ppm nitrogen dioxide in air and in mixtures of the gases in air, at constant temperature (30°C) and humidity (30%), was studied. In the presence of sulfur dioxide and nitrogen dioxide under irradiation the polymer shows a rapid degradation, while the thermal degradation is very small, as well as the photodegradation in air. The measured effect of photodegradation of thin films was stronger than that of thicker films. An equation was derived to characterize the degradation by an autoacceleration and a linear part. FTIR spectroscopy shows the formation of carboxylic acids.
Side reactions during preparation and handling of oligomers and polymers from 2‐vinylpyridine
Authors: Schmitz F. P. , Hilgers H. , Gemmel B.
Published: April 2003

Side reactions which have been proposed during the last 20 years to occur during the polymerization and oligomerization of vinylpyridine were reviewed, and some of them evidenced by experiments. The occurrence of ring substitution at the pyridine ring was demonstrated by model reactions. In addition, chain rearrangement in solution was observed. From the experimental results conclusions are drawn for the choice of the appropriate conditions for preparation and handling of polymers and oligomers of vinylpyridine.
The flocculation of kaolin suspensions with anionic polyacrylamides of varying molar mass and anionic character, 2. Polarographic study of the adsorption of anionic polyacrylamides onto clay
Authors: Petzold James C. , Herrington Thelma M.
Published: April 2003

A selective method using polarography was developed for the determination of the degree of adsorption of anionic polyacrylamides onto Kaolinite. Four polymers of the same anionic character but different molar mass were studied. Limiting adsorption of the polyacrylamides onto the clay increased with their molar mass.
Model reactions for the synthesis of poly(1,4‐phenylenevinylene). The palladium‐catalyzed arylation of ethylene with halogenated arenes or benzoyl chlorides
Authors: Brenda Martin , Greiner Andreas , Heitz Walter
Published: April 2003

Poly(1,4‐phenylenevinylene) was obtained by reacting dibromoarenes with ethylene in a palladium‐catalyzed reaction. Defects of the polymer structure were elucidated by model reactions. Side reactions in the reaction of halogenated arenes and ethylene or styrene, catalyzed by Pd, could be minimized by low catalyst concentrations and low reaction temperatures. The Pdcatalyzed reaction of aroyl chlorides with ethylene or styrene was probed by model reactions.
13C NMR study of the reaction of unsymmetrical diacids with 4,4′‐bis(2,3‐epoxypropoxy)biphenyl
Authors: Galiá Marina , Mantecón Ana , Cádiz Virginia , Serra Angels
Published: April 2003

Several polymers were synthesized by reaction of unsymmetrical diacids with 4,4′‐bis(2,3‐epoxypropoxy)biphenyl. The reaction progress was followed, and the structure of the polyesters obtained was evaluated by means of 13C NMR spectroscopy. It appeared to be possible to achieve control in the polymer structure as a function of reactivity of the diacids. To obtain unequivocal assignments and to characterize thoroughly the NMR spectra of the polymers, several model compounds resembling the polymer backbone were synthesized.
Structure and conformation of tetrafluoroethylene‐hexafluoropropene copolymer
Authors: Villani Vincenzo , Pucciariello Rachele , Fusco Roberto , Marega Carla , Marigo Antonio , Zannetti Roberto
Published: April 2003

A conformational analysis was performed on an isolated chain of a tetrafluoroethylene‐hexafluoropropene copolymer. The minimum of the conformational energy corresponds to a helix‐like chain containing planar zig‐zag sequences next to the CF3 group. A disordered structural model based on a hexagonal packing of the chains was tested by comparing the corresponding calculated X‐ray diffraction pattern with the experimental one.
On the behaviour of benzo‐1,3‐dioxolan‐2‐one and benzo‐1,3‐dioxan‐2‐one versus carbanionic species
Authors: Bialas Norbert J. , Kühling Steffen , Keul Helmut , Höcker Hartwig
Published: April 2003

Attempts of anionic ring‐opening polymerization of benzo‐1,3‐dioxolan‐2‐one (1) with sec‐butyllithium or potassium dihydronaphthylide as initiators in different solvents and under a variety of reaction conditions revealed that this monomer cannot be polymerized. Possible reasons for this finding are discussed. Benzo‐1,3‐dioxan‐2‐one (2) was prepared and characterized for the first time. Anionic ring‐opening polymerization of this monomer yields a polymer with a non‐uniform constitution, viz., loss of carbon dioxide occurs during polymerization. The mechanism of formation of this polymer is discussed on the basis of product analysis and analysis of the active species formed during polymerization. Attempts to synthesize 5,6‐benzo‐1,3‐dioxepan‐2‐one (3) failed.
Glass transition temperatures of comb‐like polymers. Poly(ethylene oxide)‐polyacrylates and ‐polymethacrylates
Authors: Yan Feng , Déjardin Philippe , Frère Yves , Gramain Philippe
Published: April 2003

A series of twelve poly(ethylene oxide) (PEO)‐polyacrylates and ‐polymethacrylates with PEO side chains, ranging in molecular weight from 164 to 1000, was studied by differential scanning calorimetry in order to analyse the behaviour of the glass transition temperature. It is shown that the glass transition temperature Tg first decreases with increasing side‐chain length to attain a constant value corresponding to the Tg of linear PEO. Contrary to the n‐alkyl homologous polymers, the influence of the side‐chain crystallization is weak and only appears for long side chains (number‐average molecular weight M̄n > 450). The proposed reason is the higher content of amorphous side‐chain units between the backbone and the crystallites in PEO as compared to alkyl chains. A relation predicting variations of Tg in comb‐like polymers with the length of the side chains is proposed. This relation, based on variation of the Tg of the side chain with its length, fits the experimental results for n‐alkyl and PEO side‐chain polyacrylates and polymethacrylates using only one parameter characterizing the nature of the side chain.
Side‐chain crystallinity in comb‐like polymers. Poly‐(ethylene oxide)‐polyacrylates and ‐polymethacrylates
Authors: Yang Fen , Déjardin Philippe , Frère Yves , Gramain Philippe
Published: April 2003

Melting temperatures, heats of fusion and the derived enthalpies and entropies of fusion were obtained by differential scanning calorimetry for poly(ethylene oxide) (PEO)‐acrylate and ‐methacrylate macromonomers and the corresponding polymers. The side‐chain lengths varied from three to ninety‐three ethylene oxide units. The thermodynamic data for macromonomers and polymers were calculated according to the theory of Flory and Vrij, which has been shown to describe well the melting behavior of linear PEO. It is shown that the melting parameters for macromonomers are identical to those of pure PEO in spite of the presence of the chain ends of different nature. With the PEO comb‐like polyacrylates and polymethacrylates, the melting points are only a few degrees higher than those of the corresponding monomers. Their crystalline content calculated from the molar enthalpies are 83% and 78%, respectively. In contrast to linear PEO, the interfacial free energy is negative for both types of polymers due to a high value of the interfacial entropy. It is suggested that the tighter packing of the chain ends, including the backbone, is responsible for this high value, together with the possible presence between the lamellae of constructed amorphous side chains. The combined results lead to the conclusion that the crystalline organization is quite comparable to that of pure PEO of equal length with, however, one or two fewer crystallized EO units.