bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative study of the thermal discharge behaviour of cellulose diacetate and cellulose triacetate films
Authors: Naidu Y. R. Vidyadhar , Sagar D. S. , Sharma A. K.
Published: April 2003

The thermal discharge behaviour of cellulose diacetate (CA2) (39% acetyl content) and cellulose triacetate (CA3) (44% acetyl content) films was studied at different polarizing temperatures and fields. Cellulose diacetate exhibited two peaks, one at low temperatures and the other at high temperatures, whereas cellulose triacetate exhibited only one peak. The origin of these peaks in CA2 is attributed to dipolar orientation and space charge polarization respectively, while the only peak in CA3 is due to space charge polarization. The difference in thermal discharge behaviour of CA2 and CA3 is attributed to the difference in acetyl contents of the two acetates.
Interpolymer complexes. Properties and characterization
Authors: Leiva A. , Gargallo L. , Radić D.
Published: April 2003

Interpolymer complex formation between poly(N‐vinyl‐2‐pyrrolidone) (PVP) and poly(monomethyl itaconate) (PMMel) has been studied. Data from Dynamic Light Scattering show at least two different size distributions of polymer complex (PC). The PC size distributions increase when the temperature increases. Viscosity measurements were also performed in order to estimate the polycomplex segmental density. From these results it can be concluded that PVP and PMMel give rise to a polycomplex formation and the driving force for this association is hydrogen bonding as much as hydrophobic interactions.
Effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile using dialkylmagnesium as catalyst
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji
Published: April 2003

An attempt was made to clarify the effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile (AN) initiated by dialkylmagnesium (R2Mg) above 100°C. The triad isotacticity (i.e. the content of mm (m: meso)) as well as the viscosity‐average molecular weight (M̄v) of polyacrylonitrile (PAN) increased when trialkylaluminum (R3Al) and trialkylboron (R3B) were used as additives. Diisobutylaluminum hydride [(i‐C4H9)2AlH] was found to be the best additive. in the stereospecific polymerization of AN, giving PAN with higher (mm) content (0.63), higher M̄v value (5.2 × 104), and a yield approximately double that obtained using (n‐C6H13)2Mg alone. When the (n‐C6H13)2Mg/(i‐C4H9)2AlH system was used, the yield, (mm), and M̄v of PAN increased with polymerization temperature (Tp); maximum values of yield, (mm), and M̄v were obtained at c. 130°C. The optimum amount of additives was approximately equimolar to R2Mg as initiator. The 13C chemical shift of α‐carbon in R2Mg at 90°C shifted by mixing with R3Al and R3B, respectively, indicating the existence of interaction between R2Mg and the additives. The main role of the additives is considered to be suppression of the self‐association of R2Mg by strong interaction with R2Mg.
Dielectric behaviour of cyanoethylated cellulose
Authors: Saad Gamal R.
Published: April 2003

The dielectric characteristics of cyanoethylated cellulose samples having different degrees of substitution have been investigated at different frequencies from 0.1 to 10 KHz and at temperatures from −40°C to 180°C. Two relaxation processes, designated as α and β in order of decreasing temperature, were recognised. The low temperature β‐relaxation is expected to be due to local motion of anhydroglucose rings, while the α‐relaxation is related to the side group motion. The data obtained are discussed in terms of the progressive destruction of the fibre structure, together with the increase of side group polarity due to cyanoethylation.
Surface modification of kaolin. 1. Covalent attachment of polyethylene glycol using a urethane linker
Authors: Molphy Marylou , Laslett Robert L. , Gunatillake Pathiraja A. , Rizzardo Ezio , Mainwaring David E.
Published: April 2003

The kaolin surface was modified through surface reaction in order to tailor the colloidal behaviour of the particles. A molecular weight series of polyethylene glycols was attached to the surface hydroxyls, using a urethane linker, by reaction with toluene 2,4‐diisocyanate. The change in the surface was monitored and the surface products identified using Diffuse Reflectance Infrared Fourier Transform Spectroscoy (DRIFTS) and solid‐state carbon‐13 NMR spectroscopy. The strength of attachment was evaluated by extraction with solvents for urethanes and poly(ethylene oxides). The surface coverage of polymer chains was quantified using a combination of two methods. Potentiometric titration was used to determine the amount of urethane formed on the surface and the number of terminal isocyanate groups available for subsequent reaction with the hydroxy‐terminated polymer. The grafting density of poly(ethylene oxide) on to the kaolin surface was determined through elemental analysis.
The effect of polymers on the crystallisation of n‐alkanes from solution, part 1. Preparation and investigation of spin‐labelled fumarate–vinyl acetate copolymers
Authors: Davidson Iain G. , Cameron G. Gordon
Published: April 2003

Spin‐labelled fumarate‐vinyl acetate (FVA) copolymers with octyl (C8) and octadecyl (C18) ester groups were prepared and characterised. An interaction between the C18FVA and the developing crystals of n‐dotriacontane growing from dodecane solution was observed as a slow‐motion component in the electron spin resonace (ESR) spectrum of the system. The C8FVA showed no such behaviour, the spectrum being entirely of the motionally narrowed type through out the crystallisation process. Above the cloud point of the system, no interaction between the polymer and alkane could be detected either in the ESR spectra or from measurements of the rotational correlation times of the spinlabel nitroxide.
Unified approach to living and non‐living cationic polymerization of alkenes
Authors: Matyjaszewski Krzysztof , Sigwalt Pierre
Published: April 2003

The observation of various features of living polymerizations (‘theoretical’ molecular weights, narrow molecular weight distribution) in a large number of carbocationic polyerizations has led to the conclusion that termination and transfer were suppressed in these ‘living’ systems, while they played a predominant role in the ‘classic’ carbocationic polymerizations. This suppression has been attributed to the presence of new types of active sites, such as ‘stretched’ covalent bonds or ‘stabilized’ carbocations.

In the present article, a comparison of the data observed with the ‘classic’ and the ‘living’ systems shows that the active sites are similar, with only a change in the relative proportion of carbocationic species, which reduces the rate and favors complete initiation. This means that these ‘living’ systems are generally only apparently living, since termination and transfer reactions also occur and are hidden because the molecular weights of the ‘living’ polymers are typically low. Transfer and termination may, however, be considerably reduced or even suppressed by working at very low temperatures, as is also the case for ‘classic’ systems.
Metal chelates with some cellulose derivatives. Part I. Preparation and characterization of chromium (III)–carboxymethyl cellulose complexes
Authors: El‐Saied Houssni , Basta Altaf H. , Abdel‐Hadi Afkar K. , Hosny Wafaa M.
Published: April 2003

A systematic spectrophotometric study on the complexation of chromium (III) ion with sodium carboxymethyl cellulose (CMC) was carried out. The effects of the degree of substitution (DS) of the polymer, the concentrations of Cr(III) and CMC solutions, the pH and temperature on the complex formation were studied in the aqueous state. CMC complexes with Cr(III) were characterized by elemental analysis, magnetic moment and spectral (Vis and IR) data. The results showed that CMC (L) chelated to the metal ion according to the formula CrL2 · 2H2O. The ligand field parameters, namely Dq, B and β were calculated; the β‐values indicate strong covalency in the ligand σ bond. The IR spectra revealed that the chelating sites of CMC are not only the carboxymethyl groups, via the ether‐ and the carboxyl‐oxygen atoms, but also the secondary hydroxyl groups.
Asymmetric induction in forming poly(olefin sulphone)s
Authors: Fawcett Allan H. , Malcolm R. Karl
Published: April 2003

Poly(1‐olefin sulphone)s have been prepared from olefins with a chiral centre at the carbon atom adjacent to the double bond. In 13C and 1H NMR studies on the polymers obtained by free radical copolymerisation it has been found that the chirality of a main chain methine carbon that forms part of the backbone depends upon the chirality of the carbon initially present within the same hydrocarbon residue. The introduction of bulky groups into the chiral group of the monomeric olefin increased the ratio of diastereoisomers formed within the residue. In the most favoured case 69% of the backbone chiral centres were fixed with reference to the side chain structures. By employing a simple theory based upon an enumeration of steric interactions and upon the γ‐gauche effect on carbon chemical shifts, it was deduced that the main chain chiral centre preferred to adopt the opposite stereochemistry to that of the side chain when that carries an ethyl group, a methyl group and a hydrogen atom. A bias was also found at the backbone when the monomer chiral centre contained polar acid or ester groups.
The self‐condensation of 4‐bromopyridine
Authors: Feast W. J. , Tsibouklis J.
Published: April 2003

The easily accessible, water soluble, conjugated polymer poly(4‐bromopyridine), has been synthesised by the self‐condensation of 4‐bromopyridine at various temperatures and also in the presence of methyl iodide. The structure of the material is complex with a variety of sub‐units; possible structures are discussed in the light of a detailed spectroscopic analysis.
Radiation assisted compatibilisation of blends of vinylidenefluoride polymers with fluorosilicone elastomers by means of crosslinking coagents
Authors: Mascia L. , Pak S. H. , Caporiccio G.
Published: April 2003

An experimental study was carried out to demonstrate the possibility of compatibilising blends of polyvinylidenefluride with minor amounts of fluorosilicone elastomer, thereby achieving better low temperature ductility without excessively reducing the melting point and degree of crystallinity of the fluoropolymer.

The principle that has been explored is the use of multifunctional crosslinking agents acting as a common solvent for the two polymers during mixing, and providing interpenetrating networks through the two polymer phases by means of peroxide‐induced crosslinking reactions.

It has been found that mixtures of triallyl isocyanurate with diallyl phthalate are particularly effective in compatibilising the combination of polymers in question, giving the best overall balance of properties. Compatibilisation was enhanced by grafting part of the coagent on to the chains of the fluoropolymer prior to being blended with the fluorosilicone gum. Further evidence for enhanced compatibilisation by such a procedure was obtained from dynamic mechanical tests, which revealed an increase in glass transition temperature for the fluorosilicone phase and a suppression of α‐relaxations in the fluoropolymer component.
Synthesis of polyaniline/polytoluidine block copolymer via the pernigraniline oxidation state
Authors: Mattoso Luiz H. C. , Oliveira Osvaldo N. , Faria Roberto M. , Manohar Sanjeev K. , Epstein Arthur J. , Macdiarmid Alan G.
Published: April 2003

Polyaniline was electrochemically synthesized in the emeraldine oxidation state and then converted to the pernigraniline oxidation state by applying an electric potential under optimized conditions. The stability/reactivity of polyaniline in the pernigraniline oxidation state was evaluated in various aqueous media. The products of the reduction of the pernigraniline oxidation state by o‐toluidine were analyzed by gel permeation chromatography, ultraviolet–visible and infrared spectroscopies, and cyclic voltammetry. The results are consistent with the synthesis of a diblock copolymer of polyaniline/poly(o‐toluidine) and also of some poly(o‐toluidine) homopolymer in the emeraldine oxidation state as a side product.
Blood compatibility of poly(ether urethane)–nylon 6 block copolymer
Authors: Seo Seung Won , Ha Wan Shik
Published: April 2003

Poly(ether urethane) (PEU)–nylon 6 A–B–A triblock copolymer was synthesised. Correlation of blood compatibility with morphological and surface energetic properties of the block copolymer film was investigated. The block copolymer film exhibited a suppressing effect on thrombus formation and it is suggested that controlling the crystallite size of the nylon 6 block in the block copolymer by regulating the copolymer composition is an important factor in the antithrombogenicity.
Anionic polymerization of octamethylcyclotetrasiloxane in aqueous emulsion I: Preliminary results and kinetic study
Authors: De Gunzbourg Anémone , Favier Jean‐Claude , Hémery Patrick
Published: April 2003

The synthesis of poly(dimethylsiloxane) (PDMS) by anionic polymerization of octamethylcyclotetrasiloxane (D4) in aqueous emulsion using an emulsifying agent acting also as initiator (benzyldimethyldodecylammonium hydroxide) is described. Stable emulsions of α,ω‐dihydroxy PDMS with an easily controlled molar mass (up to 15 000), a low polydispersity index and high yields were obtained. The amount of cyclics formed (essentially D4 to D7) is lower than that observed in bulk. Kinetics analysis and computerized simulations are in good agreement with a reaction scheme involving simultaneous polyaddition/polycondensation processes. At high monomer consumption, polycondensation predominates leading to a broadening of the molecular weight distribution (MWD). The apparent rate constants of initiation, propagation and condensation at various temperatures and the corresponding activation energies were determined.
Characterising the chemical interactions that occur on polyaniline with inverse thin layer chromatography
Authors: Teasdale P. R. , Wallace G. G.
Published: April 2003

Inverse thin layer chromatography is used to characterise the chemical interactions that occur on polyaniline that has been electrochemically deposited on to a support. Amino acids are used as the molecular probe species by which the retention behaviour can be related to particular chemical interactions. The mobile phase is also varied, with respect to its polarity and pH, in order to add a further dimension to the qualitative information that is obtained. Anion exchange interactions are found to be the dominant interaction type. However, the behaviour seems to be different to that which occurs on conventional anion exchange materials. The behaviour was dependent upon the number of negative sites and also their spatial arrangement. A configurational‐selective ionic interaction with the polaron lattice of the polyaniline is proposed. The response of the anion exchange behaviour to a change of pH suggested that protonated sites remained within the polymer, even at high pH values (c 9).
Synthesis of highly isotactic (mm > 0.70) polyacrylonitrile by anionic polymerization using diethylberyllium as a main initiator
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji
Published: April 2003

An attempt was made to synthesize steroregular polyacrylonitrile (PAN) with a high triad isotacticity (i.e. the content of mm (m, meso)) exceeding 0.70 by the anionic polymerization method. In the stereospecific polymerization of acrylonitrile (AN) initiated by diethylberyllium (Et2Be) in xylene at 130°C, the (mm) content as well as the viscosity‐average molecular weight (MÞv) of PAN increased by addition of diisobutylaluminum hydride (i‐C4H9)2AlH) as an additive to the polymerization system. Maximum (mm) content, attained in the molar ratio region of (i‐C4H9)2AlH/Et2Be > 1.0, was about 0.73. The stereospecific polymerization of AN was also initiated using a mixture of Et2Be and di‐n‐hexylamagnesium ((Et2Be/(n‐C6H13)2 Mg system), where both Et2Be and (n‐C6H13)2 Mg can induce the stereospecific polymerization of AN at 130°C. The (mm) content of the PAN sample prepared using the Et2Be/(n‐C6H13)2 Mg system ((mm) = 0.64) was higher than that of PAN samples synthesized using Et2Be alone ((mm) = 0.56) and (n‐C6H13)2Mg alone ((mm) = 0.51) under the same conditions except initiator. A significant difference in 13C chemical shifts of α‐carbons between Et2Be (1.35 ppm) and (n‐C6H13)2Mg (10.72 ppm) dissolved in hydrocarbon solvent at 110°C leads us to the conclusion that when Et2Be induces the stereospecific polymerization in the Et2Be/(n‐C6H13)2Mg system as initiator, the main role of (n‐C6H13)2Mg is considered to be the suppression of the association of Et2Be (active site) itself.
Electropolymerization and characterization of terpyridinyl iron (II) and ruthenium (II) complexes
Authors: Hanabusa Kenji , Nakamura Atsushi , Koyama Toshiki , Shirai Hirofusa
Published: April 2003

Electroactive 2,2′: 6,2″‐terpyridinyl ligands (3, 5, 6) and their iron(II) (7a–9a) and ruthenium(II) complexes (7b–9b) were synthesized. Bis[3‐(aminophenyl)‐2,2′ :6,2″‐terpyridinyl]metal(II) complexes (7a, 7b) and bis[2‐(hydroxyphenyl)‐2,2′ :6,2″‐terpyridinyl]metal(II) complexes (8a, 8b) were electropolymerized on to the surface of Pt or In‐SnO2 (ITO) electrodes in acetonitrile containing Bu4NCIO4 by scanning the potential between O and + 1.6V (for 7a and 7b), and −0.8 and +1.6V (for 8a and 8b) versus saturated calomel electrode. The electrodes obtained by electropolymerization exhibited reversible electrochromism based on Fe(II)/Fe(III) or Ru(II)/Ru(III) redox couple. Photoresponses to visible light were found in the modified electrode obtained by electropolymerization of ruthenium complex 7b in an aqueous LiClO4 solution containing methylviologen (cation MV2+) under an O2 atmosphere. The mechanism for the photoresponded cathodic current was explained in terms of an excitation of bis(terpyridinyl)ruthenium(II) complex [Ru(terpy)22+] by visible light, an electron transfer from the excited state [Ru(terpy)2+*2] to MV2+, reduction of Ru(terpy)3+2 at an electrode, and oxidation of MV+* with O2.
Carbon membranes from precursors containing low‐carbon residual polymers
Authors: Linkov Vladimir M. , Sanderson Ron D. , Jacobs Ed P.
Published: April 2003

Asymmetrical hollow‐fibre carbon membranes with increased porosity were obtained by carbonization of polyacrylonitrile based precursors containing high quantities of polymers, such as polyethylene glycol and polyvinylpyrrolidone, which give low‐carbon residue upon pyrolysis. The interaction between molecules of the two polymers, which could serve as evidence of at least partial miscibility of these polymers, occurred only with PVP‐containing precursors. The narrowest pore‐size distribution was inherent in carbon membranes produced from such precursors.
Highly isotactic polyacrylonitriles prepared using dialkylmagnesium/water systems as initiators
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji
Published: April 2003

An attempt was made to synthesize stereoregular polyacrylonitrile (PAN) with high molecular weight (e.g. viscosity‐average molecular weight (M̄v) > 1 × 105) by anionic polymerization. The triad tacticities (i.e. the content of mm, mr and rr (m, meso; r, racemo)) of the polymers obtained were analyzed by 13C NMR and their M̄v was determined by viscometry in dimethylsulfoxide at 25°C using Kamide et al.'s Mark–Houwink–Sakurada equation. Highly isotactic and high molecular weight PAN with M̄v > 2.5 × 105 ((mm) ∼ 0.57) was synthesized in anisole at 130°C when the reaction product of di‐n‐hexylmagnesium with water supplied by heating sulfate hydrates (Na2SO4 10H2O, CuSO4 5H2O, and MgSO4 7H2O) was used as a polymerization catalyst. The M̄v of PAN was increased significantly by using the catalyst combined with triethylaluminum (Et3Al). Maximum M̄v attained was 9.7 × 105 ((mm) = 0.64). The main role of Et3Al added is explained as the reduction of OH groups in the catalyst and of residual H2O in the catalyst solution.
Kinetics of nitroglycerine migration through unsaturated non‐halo and halo polyesters
Authors: Agrawal J. P. , Kulkarni K. S.
Published: April 2003

The diffusion coefficients (D) of nitroglycerine (NG) migration through cured non‐halo and halo polyesters have been calculated with the help of M∞ determined experimentally and Fick's Law. The calculated NG migrations at different time intervals compare very closely with the corresponding NG migrations determined experimentally. The concentration profiles at various locations in thin sheets of non‐halo and halo polyesters have also been calculated.
Hydrocarbon‐soluble difunctional organolithium anionic initiators. A gas–liquid chromatographic study of the reaction of sec‐butyllithium with m‐divinylbenzene
Authors: Sanderson Ronald D. , Roediger Andrew H. A. , Summers Gabriel J.
Published: April 2003

Quantitative gas–liquid chromatography provides an efficient, novel technique for the kinetic study of the reaction between sec‐butyllithium and m‐divinylbenzene. The reaction of stoichiometric amounts of ultra‐high purity sec‐butyllithium with pure m‐divinylbenzene at −23°C produces an anionic initiator, 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene, 2, without traces of monofunctional and polyfunctional impurities. The relative rates of formation of 2 with and without the presence of Lewis base, triethylamine, or Lewis acid, diethylzinc, were studied by gas–liquid chromatography. The presence of diethylzinc reduces the activity of sec‐butyllithium to such an extent that the reaction did not proceed beyond the monofunctional component stage, that is, the formation of m‐1‐lithio‐3‐methylpentylvinylbenzene, 1. The reaction of sec‐butyllithium with m‐divinylbenzene at −79°C with a 10mol% ratio of triethylamine to sec‐butyllithium yielded a homogeneous product with composition of 94% difunctionality and 6% monofunctionality, with the total disappearance of m‐divinylbenzene as observed by GLC. However, precipitation due to agglomeration was observed at 25°C at 100% conversion.

The high purity 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene initiator, 2, is effective for the polymerization of 1,3‐butadiene and allows the synthesis of polybutadienes with predictable molecular weights and narrow molecular weight distributions. Depending on the polymerization solvent, polybutadienes with microstructures ranging from 9 to 13% 1,2‐vinyl content were observed by 1H NMR analysis and FTIR spectroscopy. However, the presence of diethylzinc retards the rate of polymerization of 1,3‐butadiene, without any change in polymer microstructure. Triethylamine enhances the rate of 1,2‐enchainment without significant reduction in the 1,4‐enchainment of polybutadiene.
Monolayer formation of chitin derivatives containing PMMA side‐chains
Authors: Ren Long‐Di , Goto Yasutomo , Kaneko Hiroaki , Shirai Akihiro , Nishi Norio , Nishimura Shin‐Ichiro , Yamagishi Akihiko , Tokura Seiichi
Published: April 2003

The monolayer behaviour of poly(methyl methacrylate) (PMMA)‐grafted chitin derivatives was studied on an air–water interface by measuring surface pressure–area isotherms. The formation of a stable monolayer indicates the well‐defined packing and orientation of the chitin derivative, which can be regulated by the main‐chain length under appropriate experimental conditions. The isotherms exhibit a transition point from a liquid expanded phase to a condensed phase at a surface pressure of approximately 15mN/m for almost all monolayers examined. The transition pressure decreases with increase of temperature from 10 to 20°C. The properties of the sub‐phase affected the formation of a monolayer greatly. The collapse of a surface film takes place at lower pressure on the sub‐phase of a 0.1 M NaCI solution. After introducing lysozyme at a concentration at 2.4 × 10−8M to the sub‐phase, the monolayer showed an extensively expanded phase with a longer transition region. This indicates that the monolayer was degraded by the lysozyme, resulting in a disordered structure. The results are contrasted with those of an aqueous phase where N‐acetylglucosamine residues may be inaccessible to lysozyme so that the degradation of the chitin derivative occurs at a very slow rate.
DC electrical conduction in solution‐grown pure and iodine‐doped poly(butylene terephthalate) films
Authors: Dasaradhudu Y. , Rao V. V. R. Narasimha
Published: April 2003

DC electrical conduction in poly(butylene terephthalate) films sandwiched between planar aluminium electrodes was investigated. The films were grown by the isothermal immersion technique. The conduction process was studied in the temperature range 300–450K, with an applied electric field of 0.22 × 107−6.66 × 107 Vm−1. It was found that the Richardson‐Schottky type of conduction mechanism was dominant throughout the temperature range of study. The values of the Schottky field lowering constant β, the effective metalinsulator potential barrier and the activation energy were evaluated. The value of the activation energy (U = 0.7 eV) indicates the predominance of electronic conduction. The effect of impurities like iodine on electrical conduction was also investigated.
Gamma‐radiation damage to polyamide‐1010 crystal structure
Authors: Zhang Lihua , Zhang Hongfang , Yu Li , Zhang Wende , Mo Zhishen , Chen Donglin
Published: April 2003

Radiation effects on polyamide‐1010 specimens having various states of aggregation were studied using wide angle X‐ray diffraction, electron spin resonance, calorific and sol measurement techniques. Experimental results indicated that chain crosslinking and scission of the irradiated polyamide‐1010 occurred mainly in the amorphous region and on the crystal surface. The radiation‐induced crystal damage and amorphotization started from the crystal surface (or interface) and extended into the inner portion of the crystal with increasing radiation dose. It is believed that the interface between crystalline and amorphous regions was the main region wherein free radicals were trapped.
β‐relaxation of drawn isotactic polypropylene in terms of a simplified two phase model
Authors: Jawad S. A. , Alhaj‐Mohammad M. H.
Published: April 2003

β‐Relaxation in die‐drawn isotactic polypropylene (i‐pp) is associated with a glass transition temperature and depends on the mobility of the molecules in the amorphous regions. A simplified two phase model was employed to explain the decrease in the intensity of the β‐process peak upon drawing. The model predicts that the decrease in the loss factor (tan δ) upon drawing is associated with a change in continuity from a series to a parallel situation.
Free radical two step synthesis of styrene and acrylate block copolymers with disulphide initiators
Authors: Opresnik Marko , Šebenik Anton
Published: April 2003

Controlled two step block copolymerization of styrene, methyl methacrylate and ethyl acrylate with aliphatic and aromatic disulphides under UV irradiation took place in bulk and in THF solution. In the first step of the polymerization, the most reactive system was ethyl acrylate with aromatic disulphides.

The molecular weights and yields of polymerizations increased with reaction time. The macromolecules were terminated by primary. SR radicals and by combination of two macroadicals which was observed by NMR spectroscopy. Aninsignificant portion of uninitiated photopolymerization was detected only for MMA. In the second step of polymerization, the purified macroinitiators from the first step reacted with additional monomers to form block copolymers with a small quantity of unreacted macroinitiator. The molecular weights of copolymers increased, the bonding segments between the blocks being detected by 1H NMR. The overall reaction is an insertion of monomers between two thiyl groups.
Polymerization of ethylene oxide by the activated monomer mechanism
Authors: Manolova Nevena , Libiszowski Jan , Szymanski Ryszard , Penczek Stanislaw
Published: April 2003

The Polymerization of ethylene oxide catalysed by protonic acids and proceeding via the activated monomer mechanism differs from the polymerizations of substituted epoxides like propylene oxide and epichlorohydrin. The kinetics of ethylene oxide polymerization were investigated and compared with the kinetics of model reactions, namely addition of oligomers of ethylene oxide to ethylene oxide. The mechanism of polymerization involves, besides the addition of monomer to the terminal hydroxyl groups, the addition to the polymer ether groups. This reaction does not take place for substituted oxiranes, most probably because of steric hindrance.
Polymerization of t‐butylacetylene initiated by tungsten carbene complex
Authors: Liaw Der‐Jang , Lin Cheng‐Len
Published: April 2003

Polymerization of t‐butylacetylene initiated by a tungsten carbene complex (I) was investigated under various conditions. t‐Butylacetylene was polymerized in high yield in chlorinated hydrocarbons such as CHCI3 and CCI4 and in the presence of AICI3. The molar mass of the polymers formed was as high as 8.2 ×104 ∼ 3.2 × 105. Moreover, when the solution of tungsten carbene complex in CCI4 was irradiated with UV light, the molar mass was remarkably enhanced. This phenomenon may occur because tungsten dichlorocarbene immediately forms. Apparent rate constants were determined by gas chromatography. NMR spectra show a predominant characteristic of high cis content in the structure of poly(t‐butylacetylene) in contrast to poly(phenylacetylene). The cis content increased ca. 11% when poly(t‐butylacetylene) was heated in decalin at 110°C. X‐Ray diffraction diagrams show that poly(t‐butylacetylene) has an amorphous structure.
Macromonomers by activated polymerization of oxiranes. Synthesis and polymerization
Authors: Biedron Tadeusz , Brzezinska Krystyna , Kubisa Przemyslaw , Stanislaw Penczek
Published: April 2003

Macromonomers were obtained by cationic polymerization of propylene oxide and epichlorohydrin proceeding by the activated monomer mechanism with hydroxyethyl acrylate as initiator. Up to DPn ∼ 15 for propylene oxide and DPn ∼ 20 for epichlorohydrin, polymerization proceeds as a living process, giving with quantitative yields macromonomers with functionality equal to one, controlled molecular weight and narrow molecular weight distribution (MwMn<1.2) free of side products. In the higer molecular weight region, side reactions become increasingly noticeable. Propylene oxide macromonomers undergo radical homopolymerization. Homopolymerization of macromonomer with Mn = 8×102 gives graft copolymers with Mn up to 7.2×103 in copolymerization with styrene, completely soluble graft copolymers with Mn ∼ 2×104 were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with Mn ∼ 6×104 were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with Mn∼ 6×104, which are converted in the later stages into insoluble gels, apparently due to the chain transfer to chloromethly groups of the polyepichlorohydrin chains.
Photopolymerization of carbazolyloxiranes
Authors: Gražulevičius Juozas V. , Kavaliūnas Rimtautus , Lazauskaitė Rūta
Published: April 2003

Photopolymerizations of 1‐allyloxy‐3‐(carbazol‐9‐yl)‐2‐propanol glycidyl ether and 1‐(carbazol‐9‐yl)‐4‐oxa‐2‐pentanol glycidyl ether with diaryliodonium salts in solution and in bulk are reported. These reactions give oligomers of degree of polymerization 4–6. The influence of the functional groups of the monomers on the rate of polymerization, conversion limit and molecular weight is discussed. The effects of photoinitiator and reaction media on these factors have also been studied.
Molecular dynamics simulations of macroscopic vibrations on cooling of superheated polyethylene crystals
Authors: Kreitmeier Stefan N. , Liang Guanghe L. , Noid Donald W. , Wunderlich Bernhard
Published: April 2003

In this paper a discussion is given of the change of density with time and temperature within a crystal of 192 (CH2)50 chains, simulated by molecular dynamics computations at temperatures from 65 to 425 K. The highest temperatures exceed the melting temperature (about 365K). On simulation for times of up to 100 ps the temperature dropped through the melting temperature, permitting the study of the behavior of the crystal during initial melting, followed by limited recrystallization. In these short times only a limited number of chains on the surface can begin to coil and melt conformationally, but there is an indication of a disordering transition. A better comparison with experimental data on density, expansivity and speed of sound is possible.
Organo‐soluble aromatic polyamide films
Authors: Lee Chul Joo , Park Seung Koo , Kim Sang Yup , Lee Yun Joo , Min Byung Ghyl , Son Tae Won , Kim Byong Chul
Published: April 2003

To make stable isotropic aramid solutions and films, 6‐amino‐2‐(4‐aminopheyl)‐4‐phenyl quinoline (QDA) was used as base diamine, and copolymerized using terephthaloyl chloride (TPC) with p‐phenylene diamine (PPD), 2,2′‐bis(trifluoromethyl)benzidine (PFMB), and oxydianiline (ODA) as second diamine, respectively. Homogeneous viscous polymerization solutions based on QDA were obtained, and films prepared from them were transparent and amorphous. The reactivity of QDA with TPC was almost equal to that of PPD; the reactivity of PFMB was low due to the electron withdrawing groups (CF3) attached to the ortho positions of the benzene rings. Bulkiness and flexibility of the monomer structure widened the of stable conditions in polymer solution. A rod‐like structure of the monomer caused drawbility to decrease. QDA/ODA copolymer films could be drawn well, probably as a result of the flexible linkage of ODA, and had high tensile strength (86 kg/mm2). High modulus, 3.1 × 103 kg/mm2, was obtained in QDA/PPD copolymer films. Tensile strength and modulus increased with draw ratio. Tg and Tm were not seen by DSC and Td of the polymers was as high as c. 500°C. Excess drawing caused the films to be fibrillated, affecting their tensile properties.
Formation and relative reactivity of comonomer H‐complexes in the radical copolymerization of acrylic acid with 1‐vinyl‐2‐pyrrolidone
Authors: Georgiev George S. , Koseva Nely S. , Christov Latchezar K.
Published: April 2003

The dimerization constant (Kg) of acrylic acid and the association constant of the comonomer complex between acrylic acid and 1‐vinyl‐2‐pyrrolidone (K1) have been determined in chloroform by means of IR and 1H NMR spectroscopy: Kd=(2.0±0.2) × 103litre mol−1 and K1=68.5±0.5 litre mol−1. A detailed equation for the copolymer composition considering the participation of the intermolecular complexes in the chain propagation has been derived with the help of a specific regular three addition states Markov chain. Applying a numerical procedure for fitting the experimental curve for the comonomer composition, this equation has been used in the estimation of the dimer and the comonomer complex relative reactivities. The considerably higher reactivities of the two complexes compared with that of the monomers are accounted for by the π‐electrons' greater delocalization in the transition states involving the complexes species.
Thermal and mechanical properties of poly(esterurethane) modified by copolyamide segments of various molecular weight
Authors: Ahn Tae Oan , Oh Myung‐Hwan , Yoo Kwang Sik , Jeong Han Mo
Published: April 2003

Thermoplastic polyurethane elastomers (TPUs) from diol‐terminated poly(ethylene adipate) (PEA), 1,4‐butanediol (BD) and 4,4′‐diphenylmethane‐diisocyanate (MDI) were modified by copolymerizing with diamine‐terminated nylon‐6/6,6 copolyamide (CPA) oligomers. The effects of content and molecular weight of CPA segments on the thermal and mechanical properties of TPU were studied. PEA segments showed enhanced crystallization when some of the hard segments were replaced by CPA segments, showing weaker CPA–PEA interaction. The crystallinity of the hard segments was reduced, probably due to some interaction and phase mixing between hard and CPA segments. The modulus of TPU also decreased, more markedly with CPA segments of higher molecular weight.
Poly(2‐hydroxyethyl methacrylate) (PHEMA)/poly(styrene‐co‐acrylamide) (PSAm) blends: miscibility and hydrogel properties
Authors: Zhu K. J. , Wang Liqun , Yang Shilin
Published: April 2003

The blend miscibility of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(styrene‐co‐acrylamide) (PSAm) was studied by DSC. A ‘miscible window’ was found in the range 47–57 mol% of acrylamide in blending PSAm with PHEMA (1:1 w/w) and was analysed by the mean‐field theory. The water content and permeability coefficients of proteins were measured. The results show that the water content of the blends depends on the composition of PSAm and the blends, and the behaviour of blends swollen in water in Fickian type. However, the permeability of the solutes not only related to water content, but was also affected by phase behaviour. Controlled release of somatotropin from a cylindrical device coated with PHEMA/PSAm was achieved.
Miscibility of poly(vinylidene fluoride) and potassium salt of poly(methyl methacrylate‐ran‐methacrylic acid)
Authors: Leung Louis M. , Lo Kenneth K. C.
Published: April 2003

The crystalline–amorphous polymer pair of poly(vinylidene fluoride) and poly(methyl methacrylate) is known to be miscible over a wide composition range. The effects of ionic moieties on the miscibility were studied by replacing the poly(methyl methacrylate) with a series of random copolymers of methyl methacrylate and potassium salt of methacrylic acid. The interaction parameter (χ) for the miscible blends in their molten state was obtained by thermal analysis using a melting‐point depression calculation. The parameter decreased to a minimum at c.2% ion content (χ=minus;0.514) and approached a positive value at above 10% ion concentration.
Water sorption and water binding properties of crosslinked polyacrylamides: effect of macromolecular structure and crosslinking
Authors: Chandy Mathew C. , Pillai V. N. Rajasekharan
Published: April 2003

The water binding properties of crosslinked copolymers of acrylamide with tetraethyleneglycol diacrylate triethyleneglycol dimethacrylate, N,N′‐methylene bisacrylamide and divinylbenzene were investigated. It was observed that the freezing water contents of these copolymers depend on nature of the monomers and crosslinkers, as well as on the extent of crosslinking.
Surface modification of kaolin. 2. Enhanced steric stabilisation of polymer‐modified kaolin
Authors: Molphy Marylou , Mainwaring David E. , Rizzardo Ezio , Gunatillake Pathiraja A. , Laslett Robert L.
Published: April 2003

The polymer‐modified surface of kaolin was studied to determine the effect of changing the molecular weight of the polymer chain grafted on the surface. The particle was modified by attaching poly(ethylene oxide) to the surface using a urethane linkage.

Upper critical flocculation temperature and contact angle measurements were conducted to quantify the changes in surface characteristics and stability in an aqueous dispersion. The effect of pH on stability and grafted density of polymer chains showed the mechanism of stabilisation to be that of enhanced steric stabilisation.

The kaolin particle was also modified with the more hydrophobic poly(propylene oxide). The behaviour was characterised as for poly(ethylene oxide) and interesting differences in extent and mechanism for stabilisation were observed.
Thermal degradation of polymethacrylic ester containing bisphenol‐S
Authors: Liaw Der‐Jang , Teng Kuei‐Fei
Published: April 2003

Thermal degradation of polymethacrylic ester containing bisphenol‐S, poly(BPS‐M), was investigated under nitrogen and air atmosphere at various heating rates. Ozawa's method was used to calculate the kinetic parameters, activation energy, preexponential factor and reaction order. Thermodegradation of the polymer occurs in one or two stages in nitrogen and air, respectively. The temperature at the start of intense degradation (Tstart) and the temperature corresponding to a 50% mass loss (T50%) were found to be 300 and 402°C, respectively, at a heating rate of 10°C min−1 in nitrogen. Larger sample masses have a larger temperature interval (ΔT) and a greater mass loss (ΔW). The kinetic order of degradation is unity both in nitrogen and air. The direct pyrolysis mass spectrum of the polymer shows one degradation peak. The most important degradation process under inert atmosphere is the loss of carbon dioxide, phenol and sulphur dioxide. A possible mechanism for thermal decomposition of poly(BPS‐M) is proposed based on the product analyses.
Filled interpenetrating networks: their formation and viscoelastic properties
Authors: Lipatov Yu. S. , Alekseeva T. T. , Rosovitsky V. F. , Babkina N. V.
Published: April 2003

The kinetics of curing, the microphase separation process (MPS) and the viscoelastic properties of interpenetrating polymer networks (IPNs) based on crosslinked polyurethane and linear poly(butyl methacrylate) were studied in the presence of two fillers—talc and polymeric fine‐disperse triethylene glycol dimethacrylate. It was found that introducing filler into the reaction mixture changes the reaction kinetics and degree of microphase separation, which in turn affects the viscoelastic properties of the IPNs. The data obtained by dynamic mechanical spectroscopy and differential scanning calorimetry for filled semi‐IPNs and calculations of the degree of segregation of the components show that filler introduction results in MPS inhibition on account of a local increase in viscosity near the solid interface, i.e. compatibility is increased.
Effects of interfacial adhesion on microdamage and rheological behaviour of glass bead filled nylon 6
Authors: Ou Yu‐Chun , Yu Zhong‐Zhen
Published: April 2003

Model composites consisting of glass beads dispersed in a matrix of nylon 6 with different degrees of interfacial adhesion were prepared. The effects of interfacial adhesion on damage generation in the glass bead filled nylon 6 were studied by acoustic emission monitoring and scanning electron microscopy, and the critical damage stress was measured. Improvement of the interfacial adhesion enhanced the tensile strength of the composite. The melt rheological behaviour of the glass bead filled nylon 6 was also investigated. It was found that the interfacial adhesion strength significantly affected the rheological behaviour of the glass bead filled nylon 6.
Plasma polymerization of some silicon‐ and tin‐containing monomers
Authors: Akovali Güneri , Rzaev Zakir M. O. , Mamedov Dadash H.
Published: April 2003

Plasma polymerization of several selected saturated and unsaturated silicon‐ and tin‐containing monomers, such as vinyltriethoxysilane (VTES), 3‐aminopropyltriethoxysilane (APTS), hexamethyldisiloxane (HMDS), hexabutyldistannoxane (HBDS) and tetraethylstannane (TES), were examined in terms of the following selected plasma operational parameters: discharge time (t), flow rate of monomer (F) and power input (W). For the initial deposition rates (DR), the following empirical equation was proposed: DR = k ta Fb Wc, from which the experimental values of the kinetic power factors (a,b,c and k) were calculated. The value of k calculated for VTES was the highest, indicating the high activity of the monomer in plasma in contrast to HBDS, which was about two orders of magnitude smaller. A modified Arrehnius equation was employed in the form of yield of deposition (DR/F) versus the specific energy (W/F), which showed that silicon‐containing monomers are more active than their organotin analogues in the chosen plasma conditions. Plasma polymers of HMDS, TES and HBDS prepared at low conversions were highly crosslinked and their structures were similar to those of crosslinked poly(dialkylsiloxane) or poly(organostannoxane) while those of VTES and APTS were primarily linear.
The role of disorder in phase transformations in PTFE
Authors: Macturk K. S. , Farmer B. L. , Eby R. K.
Published: April 2003

The transformation of PTFE from phase II to phase IV at 19°C and atmospheric pressure has been investigated using wide angle X‐ray diffraction. Diffraction patterns were taken as a function of temperature. The integrated intensity of an equatorial peak present only in phase II was used to monitor the extent of the transformation. Peaks on the second and fifth layer lines were used to determine the effect of transformation and/or disorder. Integrated intensities on these three layer lines were shown to decrease differently with increasing temperature. The decrease in intensity on the second and fifth layer lines could be described in terms of a model comprising the initial integrated intensity, fraction transformed and the amount of rotational disorder present. Molecular modeling also was used to investigate the transformation. A commercially available force field was modified to represent the equilibrium solid state of PTFE. The modified force field was used to examine aspects of the transformation including the influence of neighboring molecules on the molecular conformation.
Novel anionic polymerization of β‐lactones mediated by alkali metal supramolecular complexes
Authors: Jedliński Zbigniew , Kurcok Piotr , Kowalczuk Marek
Published: April 2003

The anionic polymerization of β‐lactones mediated by supramolecular complexes of alkali metal alkoxides and naphthalenides is demonstrated. The novel chemistry of the initiation and the propagation steps of polymerization is discussed.
A study on the hydrated acrylic polymers
Authors: Kim B. C. , Min B. G. , Son T. W. , Lee C. J.
Published: April 2003

The effect of chemical composition of copolymers of acrylonitrile (AN) and methylacrylate (MA) on the hydration and thermal transition behaviour was investigated. An increase of the MA content considerably depressed both Tm and Tc of the hydrated polymers. A double melting and crystallization transition behaviour was observed when the hydrated polymer was reheated after cooling from the molten state. The separation between primary and secondary peaks was more notable in the second heating scan than in the first heating scan. A novel solid‐state transition was observed in the dried acrylic polymers which had experienced hydration and melting in the wet state, followed by drying in the open state at 200°C.
Functionalization of polyethylene using borane reagents and metallocene catalysts
Authors: Chung T. C. , Lu H. L. , Li C. L.
Published: April 2003

A new method to prepare functionalized polyethylene involving borane intermediates and transition metal catalysts is described. Two processes, direct and post polymerizations, were employed to prepare borane‐containing polyethylene (PE‐B), which can be transformed to functionalized polyethylene (LLDPE‐f) with various functional groups, such as BR2, OH, NH2, OSi(CH3)3. In the direct process, the PE‐B copolymers were prepared in one step by copolymerization of ethylene with a borane monomer (ω‐borane‐α‐olefin). The post polymerization process requires two steps: copolymerization of ethylene and 1,4‐hexadiene, and subsequential hydroboration reaction of unsaturated PE. Three transition metal catalysts, including two homogeneous metallocene (Cp2ZrCl2[bis(cyclopentadienyl) zirconium dichloride] and Et(Ind)2ZrCl2[1,1′‐ethylenedi‐η5‐indenyl‐zirconium dichloride] with MAO (methylaluminoxane)) and one heterogeneous (TiCl3·AA/Et2AlCl) ones, were studied in the copolymerization reactions. The single site Et(Ind)2ZrCl2/MAO homogeneous catalyst, with a strained ligand geometry and opened active site, is by far the most effective system in the incorporation of high olefins into polyethylene structures.