bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoplastic graft copolymer elastomers with chain‐folding or bifurcated side chains
Authors: Eisenbach Claus D. , Heinemann Torsten
Published: April 2003

Graft copolymers with a poly(oxytetramethylene) main chain and molecularly uniform oligourethane grafts were synthesized by substitution polycondensation of a telechelic polyether and the corresponding α,α′‐bifunctional oligourethane macromonomer. The side chains were either characterized by a built‐in constitutional unit allowing a symmetrical chain fold or by bifurcation with two equally long oligourethane branches. Differential scanning calorimetry, small‐angle X‐ray scattering and dynamic mechanical analysis proved a microphase‐separated system with semicrystalline oligourethane hard domains, and the materials were thermoplastic elastomers. These data and the comparative study of model compounds for the specially structured grafts and of poly(ether‐urethane)s with symmetrically chain‐folded segments illustrated that the morphology and properties of these polyurethane elastomers could be perfectly mimicked by a graft copolymer with bifurcated side chains.
Cationic polymerization of hexamethylcyclotrisiloxane by trifluoromethanesulfonic acid and its derivatives, 2. Reaction involving activated trifluoromethylsulfonates
Authors: Toskas Georgios , Besztercey Gyula , Moreau Michel , Masure Michèle , Sigwalt Pierre
Published: April 2003

Silyl trifluoromethanesulfonates are inactive for the polymerization of cyclosiloxanes in the complete absence of trifluoromethanesulfonic (triflic) acid, but polymerization occurs in its presence. Using a triflic ester as tagged silyl triflate (benzyldimethylsilyl triflate) the degree of polymerization (DPn) of the linear polymer formed with hexamethylcyclotrisiloxane (D3) in CH2Cl2 at 20°C is inversely proportional to the ester concentration and near to the theoretical value. The polymer contains one PhCH2(CH3)2 Si group per macromolecule, in agreement with a propagation occurring on the monoester PhCH2(CH3)2 SiD3x OTf. By comparison with experiments using the acid alone, polymerizations made in the presence of this ester lead to the suppression of the formation of macrocycles and to a strong decrease of that of D9 and D12. But the amount of D6 is only slightly reduced, which agrees with the hypothesis of its main direct formation on the active sites and not by ring closure of a silanol ester. The rate of D3 polymerization is internally 1st order in [D3] and externally proportional to both acid and ester initial concentrations, in agreement with a propagation involving silyl triflates activated by the acid, interconverting with transitory siloxonium ions leading to D6 formation by a ring expansion involving the polymer chain.
Main chain modification of aromatic polyamides by incorporation of kinked, flexible monomers
Authors: Maglio Giovanni , Palumba Rosario , Vignola Maria Carmela
Published: April 2003

Multiring diamines and diacids containing ether and isopropylidene or hexafluoroisopropylidene bridges between phenyl groups were used alone or together with 1,4‐phenylenediamine and terephthalic acid to prepare flexible or semirigid aromatic polyamides by direct polycondensation using triphenyl phosphite and pyridine as condensing agents. All the polyamides are readily soluble in N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone and N,N‐dimethylformamide. The wholly flexible polyamides are completely amorphous whereas those prepared from 1,4‐phenylenediamine or terephthalic acid are partially crystalline and melt in the temperature range from 276 to 330°C. Thermal analysis shows Tg's in the range from 204 to 216°C for the wholly flexible polyamides and in the range from 239 to 257°C for the semirigid ones. Both classes of aromatic polyamides show excellent thermal resistance which is comparable with that of rigid‐rod aramides.
Conformational properties of the amphipathic lytic polypeptide bombolitin II. A circular dichroism, NMR and computer simulation study
Authors: Battistutta Roberto , Pastore Annalisa , Mammi Stefano , Peggion Evaristo
Published: April 2003

Bombolitin II is a member of a family of five structurally related heptadecapeptides, originally isolated from the venom of a bumblebee, acting at the membrane level and able to increase the activity of phospholipase A2. The biological activity of bombolitins seems to be related to their ability to form amphipathic helical structures. To complete our systematic studies on this class of peptides, in the present work we synthesized bombolitin II by solid phase methodology. The secondary structure of this peptide was fully characterized by circular dichroism, 1H NMR, distance geometry and molecular dynamics simulation. The peptide tends to aggregate in aqueous solution at millimolar concentrations, with formation of bundles of amphiphilic helices. In dilute aqueous solution (10−5 mol/L) bombolitin II adopts an amphipathic helical structure in the presence of sodium dodecyl sulfate. The helical segment spans the sequence from residue 2 to residue 16. The results are in line with the hypothesis that this class of peptides modulate the acitivity of phospholipase A2 by altering the physical state of the aggregated substrate.
Synthesis of new polymers containing α‐(trifluoromethyl)‐acrylate units
Authors: Aglietto Mauro , Passaglia Elisa , di Mirabello Lorenzo Montagnini , Botteghi Carlo , Paganelli Stefano , Matteoli Ugo , Menchi Gloria
Published: April 2003

Free radical polymerization of both α‐(trifluoromethyl)acrylic acid (TFMAA) and its methyl ester MTFMA is shown to be possible in the presence of bis(4‐tert‐butylcyclohexyl) peroxycarbonate (Percadox) as initiator and dioxane or THF as solvent. Also it is shown that copolymers of TFMAA with α‐olefins (1‐decene, 2‐methyl‐1‐hexene) and of methyl α‐(trifluoromethyl)acrylate (MTFMA) with vinyl ethers (butyl, 2‐ethylhexyl, and menthyl vinyl ether) can be simply obtained with AIBN as initiator; these copolymers have a predominantly alternating structure.
Novel types of polysaccharidic assemblies
Authors: Crescenzi Vittorio , Imbriaco David , Velàsquez Cristòbal Làrez , Dentini Mariella , Ciferri Alberto
Published: April 2003

New types of polysaccharidic assemblies based on chitosan and uncharged or charged derivatives of scleroglucan are presented. Macroscopic assemblies having a spherical skinlike shape were prepared by controlled mixing of two polyelectrolyte solutions. Hydrogels based exclusively on the above natural derivatized polysaccharides crosslinked via simple chemical processes, avoiding the use of extraneous reticulating agents and organic solvents, are also described. These biocompatible materials may, eventually, be used in drug release formulations or for the incapsulation of bioactive macromolecules. The interesting possibility exists to study the micelle formation of amphiphiles within the spherical skins.
A study for distinguishing mono‐ and bimetallic mechanisms in heterogeneous Ziegler‐Natta catalysis
Authors: Sacchi Maria Carmela , Forlini Fabrizio , Tritto Incoronata , Locatelli Paolo , Morini Giampiero
Published: April 2003

The results of 13C NMR analysis of chain end groups of poly(propylene) samples prepared with traditional δ‐TiCl3 and high yield TiCl4/MgCl2 catalysts in the presence of different 13C enriched alkylaluminium cocatalysts — Al(13CH2CH3)3, Al(13CH2CH3) (is‐o‐C4H9)2 and Al(13CH2CH3)(CH3)2 — have been compared. The data show that, while molecular weights and fraction distribution change from one cocatalyst to another, the mechanism of steric control is the same independent of the cocatalyst used. This supports the hypothesis that the role of the metal alkyls is that of activating the solid catalyst by alkylation of the titanium surface complexes, but they do not participate directly in the structure of the active center.
Synthesis and thermal properties of side‐chain liquid‐crystalline poly(glycidyl ethers) with racemic and chiral backbone
Authors: Taton Daniel , Le Borgne Alain , Spassky Nicolas , Noël Claudine
Published: April 2003

Oxiranes bearing a 4‐cyanobiphenyl‐4′‐oxy mesogenic group with spacers of different length have been synthesized from glycidyl p‐toluenesulfonate or epichlorohydrin (racemic or optically active). These monomers were polymerized with anionic initiators (CsOH, tBuOK

tBu: tert‐butyl, Et: ethyl.

) or a chelate initiator (AlEt3/H2O/acetylacetone). A transfer of chirality from the polymer backbone to the mesophase is observed for polyethers with a short spacer. A cholesteric phase is observed for the optically active polymer while the racemic polymer is nematic. Increasing the length of the spacer leads to a smectic mesophase. However, in that case, the effect of the chiral centre of the polymer backbone on the mesomorphous properties is not detected.
Syndiotactic specific polymerization of styrene: driving energy of the steric control and reaction mechanism
Authors: Longo Pasquale , Proto Antonio , Zambelli Adolfo
Published: April 2003

The stereoregularity of polystyrenes prepared in the presence of different syndiotactic specific homogeneous catalysts, at different temperatures and monomer concentrations, has been evaluated by 13C NMR. It is confirmed that the statistical model of the stereospecific propagation is first‐order Markovian. The stereoregularity of the polymers decreases while increasing the polymerization temperature and is affected by the concentration of the monomer, by the ligands of the transition metal precursor of the catalyst, and is higher in the presence of titanium based catalysts. Polymerization of substituted styrenes is increasingly stereospecific in the order p‐chlorostyrene < styrene < p‐methylstyrene. The results strongly support the polyinsertion mechanism proposed in a previous paper by some of us.
Synthesis of polyurethanes by polycondensation of active biscarbonates of diols with hexamethylenediamine and its derivatives
Authors: Katsarava Ramaz , Kartvelishvili Tamara , Khosruashvili Tamara , Beridze Vakhtang
Published: April 2003

A new synthesis pathway to polyurethanes (PURs) by polycondensation of active carbonates of diols with hexamethylenediamine was investigated in detail including model studies. It has been shown that high‐molecular‐weight PURs (ηred ≤ 3,8 dL/g) can be obtained under optimum reaction conditions. Salts of the diamine and its N,N′‐trimethyl‐silylated derivative were also used for the synthesis of film‐ and fiber‐forming PURs.
Linear non‐conjugated dienes from biomass as termonomers in EPDM synthesis, 1. Study of their reactivity in homo‐, co‐ and terpolymerizations
Authors: Dolatkhani Mohamad , Cramail Henri , Deffieux Alain
Published: April 2003

This paper deals with the use of 3,7‐dimethylocta‐1,6‐diene (3,7‐DMO) and 5,7‐dimethylocta‐1,6‐diene (5,7‐DMO), issued from terpene feedstock, as termonomers for the synthesis of ethylene‐propylene‐diene terpolymers (EPDM). Their reactivity is first compared to 7‐methylocta‐1,6‐diene (MOCD), an industrial linear diene, in homopolymerization and cross‐copolymerization. Two catalytic systems are used: TiCl3, 1/3AlCl3, 14 MgCl2 associated with Al(C2H5)3, and VOCl3 or VCl4 associated with Al(C2H5)2Cl. The influence of the diene structure on the observed order of reactivity is discussed. In a second part, the copolymerization and the terpolymerization of the different dienes with ethylene and propene are implemented. A drastic influence of the diene structure and concentration on the productivity (and activity) is observed. Potentiometric titrations of the vanadium, performed both in the absence and in the presence of dienes (and of other substituted olefins), indicate that the productivity loss mainly results from a reduction process of the vanadium, involving the di‐ or trisubstituted olefins
Dynamic viscoelastic properties of blends of poly(ethylene‐co‐vinyl acetate) and a modified starch
Authors: Jauregui Belén , Muñoz María Eugenia , Santamaria Anton
Published: April 2003

We report dynamic viscoelastic measurements of a series of binary blends of hydroxyethyl ether of starch and ethylene‐vinyl acetate copolymer (EVA), which are correlated with the granular arrangement of the starch derivative within the EVA matrix and the adhesion between both phases, studied by scanning electron microscopy. The rheological properties are similar to those of polymers filled with solid spheres, although we found a minimum in the Newtonian viscosity and a maximum in the elasticity at low starch derivative concentrations, which have been attributed to a change in the density of chain entanglements.
Synthesis and photobehaviour of hydrophilic acrylic polymers containing azobenzene groups
Authors: Altomare Angelina , Ciardelli Francesco , Solaro Roberto , Tirelli Nicola
Published: April 2003

New hydrophilic photochromic polymeric systems containing side‐chain azobenzene groups were synthesized by radical copolymerization of 4‐acryloyloxyazobenzene with hydrophilic acrylic comonomers containing in the side chain either amide or quaternary onium groups. In all cases copolymerization products characterized by an almost random distribution of monomeric units were obtained. On irradiation at 366 nm, azobenzene‐ containing copolymers underwent trans‐to‐cis photoisomerization of the side‐chain azo groups and in all cases monoexponential decay of the 320 nm absorbance was observed. Copolymer properties were investigated by DSC analysis, solubility measurements, UV spectroscopy and photoisomerization kinetics. The results obtained are discussed in terms of nature and content of hydrophilic comonomer and water content of the solvent used. The possibility of photomodulating copolymer solubility is also suggested.
A novel ferroelectric side‐chain liquid crystalline polysiloxane and its monomer with low transition temperature at the air/water interface
Authors: Xue Qing‐Bin , Chen Xiao , Yang Kong‐Zhang , Zhang Qi‐Zhen
Published: April 2003

Stable monolayers of a novel side‐chain liquid crystalline polysiloxane (PI) and its monomer (MI), both having low transition temperatures, are formed at the air/water interface at 20°C. In monolayer films mesogens are packed closely and their long axes are titled slightly to the water surface. Monomer molecules are thought to lie flat on the water surface when they are initially spread, and a possible model is presented to describe the conformational changes after compressing. Multilayer formations have been observed during isothermal compression of both the polymer and the monomer. Monomer monolayers cannot be deposited onto hydrophobic substrates, whereas polymer monolayers can be deposited at various surface pressures with Y‐type or Z‐type. UV‐Vis spectra of PI Langmuir‐Blodgett films indicate that H‐aggregates are formed during film formation. The absorption of Langmuir‐Blodgett films and cast films shows a distinct hypsochromic shift compared with that of PI chloroform solution.
The fast activation of ε‐caprolactam polymerization in quasi‐adiabatic conditions
Authors: Russo Saverio , Imperato Amalia , Mariani Alberto , Parodi Fabrizio
Published: April 2003

Two carbamoyl‐type activators of ε‐caprolactam (CL) anionic polymerization have been used in quasi‐adiabatic conditions with sodium caprolactamate as initiator, at different concentrations and relative ratios. The reaction products have been characterized in terms of high‐polymer content and extent of crosslinking. Correlations between the various polymerization parameters on one side, and amount of crosslinked fraction and resultant polymer properties on the other side, have been found. Potential implications on a fine control of PCL properties, exerted by the experimental conditions chosen for the anionic synthesis, are envisaged.
Synthesis and polymerization of 2‐cyano‐2‐methyltrimethylene carbonate
Authors: Kalbe Michael , Keul Helmut , Höcker Hartwig
Published: April 2003

2‐Cyano ‐methyltrimethylene carbonate (CMTC, 2) was synthesized starting from 2‐methylacrolein (6), propionaldehyde (8) or 2‐hydroxymethyl‐2‐methyl‐1,3‐propanediol (9). A key position in this synthesis is held by 2,2‐bis(hydroxymethyl)propionitrile (3), which in a first step, is reacted — in conjunction with 2,2‐dimethyl‐1,3‐propanediol (200) — with diphenyl carbonate (17) to result in a statistical copolycarbonate. Ring‐closing depolymerization of this polymer, with a catalyst based on tin, yields in a second step the title monomer, CMTC (2), along with 2,2‐dimethyltrimethylene carbonate (DTC, 1b). Separation of the two monomers can be achieved by selective solubilization of the latter in toluene. Polymerization of CMTC is performed preferentially by using weak nucleophiles as initiators, such as Et2AlOEt, Al(O‐secBu)3 or MgBu2, since strong nucleophiles such as BuLi or ZnEt2 tend to give side reactions with the cyano group. Copolymerization of CMTC with DTC results in statistical copolymers. With Et2AlOEt as initiator copolymers with Bernoulli statistics are obtained, with a ratio of diads DTC/DTC : (DTC/CMTC + CMTC/DTC) : CMTC/CMTC equal to 1:2:1 for equimolar feed composition. With MgBu2 as initiator and the same feed composition, a copolymer with the diad ratio 1:5:1 is obtained. Poly(CMTC) is a crystalline polymer with a melting point of 132.9°C and a glass transition temperature of 68.8 °C.
Liquid crystalline polyfumarates, 2 Polymerization of fumarates with two mesogenic groups per unit
Authors: Jähnichen Klaus , Voigt Dieter , Jehnichen Dieter , Rätzsch Manfred
Published: April 2003

The paper describes synthesis and characterization of some new side‐chain liquid crystalline polymers (SCLCP) obtained by homo‐ and copolymerization of fumarates with two mesogenic groups per unit. The homopolymerization of spacerless bis[4‐(4‐butoxy‐benzoyloxy)phenyl] fumarate (1) did not take place due to steric hindrance of the propagation reaction by the bulky phenyl benzoate groups. The radically induced polymerization of the fumarates with spacer between fumaric unit and the mesogenic groups was performed in bulk. At the polymerization temperature the monomers were isotropic. During polymerization the mixtures became turbid due to phase separation of the isotropic monomer and the resulting polymerization products which formed a liquid crystalline (lc) phase. The molecular weights of the obtained homopolymers were relatively low and depended on spacer length. Transfer reactions to the monomer occurred to a considerable extent. The homopolymers showed an enantiotropic SA phase. This was confirmed by X‐ray measurements. A model for the arrangement of the polymer backbones in the smectic phase is given. Copolymerization of bis{6‐[4‐(4‐butoxybenzoyloxy)benzoyloxy]hexyl} fumarate (4) with styrene yielded copolymers 6 with different percentages of styrene. All copolymers formed an enantiotropic SA phase. With increasing percentage of styrene the transition to the isotropic state was shifted toward lower temperatures.
Terpolymerization of propene, ethylene and 1‐dodecene with highly efficient supported catalyst
Authors: Wen Yufeng , Han Shimin , Hu Youliang
Published: April 2003

The terpolymerization of propene, ethylene and 1‐dodecene (PED) with a highly efficient supported Ziegler‐Natta catalyst and the main physical and mechanical properties of PED terpolymers were investigated. It was found that, under equal polymerization conditions, the polymerization activities followed the order: PED terpolymerization > PE, PD copolymerizations > E, D homopolymerizations. The 13C NMR spectra of PED terpolymers indicated the existence of long propylene chain sequences. The content of ethylene and 1‐dodecene in PED terpolymers increased with the enhancement of the mole ratio of ethylene in the gas feed, whereas the effect of the concentration of 1‐dodecene in the reactor is much smaller. The intrinsic viscosity, density, melting temperature and crystallinity of the terpolymers decrease when the amount of comonomers in the feed increases. Compared with polypropene, the tensile and bending strenghts of PED terpolymers are reduced, but the elongation at break is over 700%, and the Izod impact is enhanced both at ambient and low temperatures.
Investigation of γ‐irradiated syndiotactic poly(2‐methylheptyl methacrylate) using NMR spectroscopy
Authors: Dong Limin , Hill David J. T. , O'Donnell James H. , Pomery Peter J. , Brereton Ian M.
Published: April 2003

Syndiotactic poly(2‐methylheptyl methacrylate) which was γ‐irradiated at room temperature to a dose of 1600 kGy was investigated by NMR spectroscopy. The 1H and 13C resonances for the macromolecular chain were assigned by using the 2D and the DEPT (distortionless enhancement by polarization transfer) technique. The spin‐echo modified 2D NMR pulse sequence was used to investigate the small molecules and new structures which were formed during γ‐irradiation. The radiation mechanisms for cleavage of the side chain from the main chain and formation of double bonds from both the main chain and the side chain have been formulated based upon the NMR analysis.
Molecular design of biodegradable functional polymers, 4 Poly(vinyl alcohol) block as biodegradable segment
Authors: Matsumura Shuichi , Shimura Yukimasa , Toshima Kazunobu , Tsuji Masao , Hatanaka Tadashi
Published: April 2003

The minimum structure of a poly(vinyl alcohol) block as a biodegradable segment in the polymer chain was estimated with respect to block length and its stereochemical configuration. It was found that poly(vinyl alcohol) block with a chain length of more than 3 monomeric units and having an isotactic structure is quickly biodegraded, in contrast to an atactic block having the same chain length, by poly(vinyl alcohol) (PVA) assimilating microbes and PVA‐dehydrogenase. It was also found that the substrate specificity of PVA‐dehydrogenase obtained from both Alcaligenes faecalis KK314 and Pseudomonas sp. 113 P3 is quite similar.
Liquid‐crystalline polyimides, 23. Photoreactive, cholesteric copoly(ester‐imide)s derived from 1,4‐phenylenediacrylic acid and 4‐aminobenzoic trimellitimide
Authors: Kricheldorf Hans R. , Probst Nicolas
Published: April 2003

The dichlorides of commercial 1,4‐phenylenediacrylic acid

3,3′‐(1,4‐Phenylene)di‐2‐propenoic acid.

and N‐(4‐carboxyphenyl)‐trimellitimide were polycondensed with a chiral spacer prepared from (S)‐3‐bromo‐2‐methylpropanol and 4‐mercaptophenol. Optical microscopy revealed that all the resulting copoly(ester‐imide)s form an enantiotropic cholesteric melt and adopt a Grandjean texture upon slight shearing. The WAXD powder patterns indicate the formation of a layered structure in the solid state. Irradiation with UV light of wavelength ⩽ 360 nm allows crosslinking at any temperature above 25°C.
Graft copolymers of poly(methyl methacrylate) and polythiophene
Authors: Hallensleben Manfred L. , Hollwedel Fred , Stanke Dietmar
Published: April 2003

2‐(2‐Thienyl)ethyl methacrylate (2TEMA, 1), 2‐(3‐thienyl)ethyl methacrylate (3TEMA,2) and 2‐(N‐pyrrolyl)ethyl methacrylate (PEMA, 3) were synthesized and copolymerized with methyl methacrylate (MMA) by radical initiation with AIBN. The reactivity ratios for the system MMA/2TEMA were determined to be rMMA = 0,57 ± 0,09 and r2TEMA = 0,90 ± 0,03. Thiophen was grafted into the copolymers from 1–3 via oxidative polymerization in nitromethane. The graft copolymers were soluble as aggregates, and films cast from these solutions reached conductivities in the range of 0,2 to 0,4 S/cm.
A small‐ and wide‐ angle X‐ray scattering study on the smectic‐α‐monoclinic phase transition and on the melting behaviour of isotactic poly(propylene) cast films
Authors: Marigo Antonio , Marega Carla , Zannetti Roberto , Fichera Annamaria , Ferrari Paolo
Published: April 2003

The morphological changes of isotactic poly(propylene) cast films have been investigated during the smectic–α‐monoclinic phase transition and the following melting. The small‐and wide‐angle X‐ray scattering techniques allow to point out the different behaviour of a homopolymer sample and of two propylene‐ethylene copolymer samples as a function of the presence and concentration of the ethylene comonomer. During the smectic–α‐monoclinic phase transition the crystallinity increase appears to be directly connected to the lamellar thickening and/or to the formation of new lamellar stacks.
Compatibilization of high density polyethylene/polyisoprene blends with polyethylene/polyisoprene “thread‐through” copolymers
Authors: Zhang Xuequan , Chen Hui , Tang Tao , Huang Baotong
Published: April 2003

The compatibilization of high density polyethylene (HDPE)/polyisoprene (PI) blends with polyethylene/polyisoprene (PE/PI) “thread‐through” copolymers was investigated. The proliferating structure of PE/PI with segments chemically identical to HDPE and PI, respectively, is different from that of graft copolymers. Studies showed that the dispersed domain size in the blends was significantly reduced and interfacial adhesion was improved by the compatibilization action of the copolymer. In the differential scanning calorimetry (DSC) analysis, the crystallization peak of HDPE in the blends became broad with adding the copolymer and fractionated crystallization appeared in the HDPE/PI blend compatibilized with the copolymer at a weight ratio of 30/70 while it appeared in the blend without copolymer at a weight ratio of 20/80. DMA results showed that by adding the copolymer, both the glass transition temperature (Tg) of the PI component and the a‐ relaxation of HDPE shifted to lower temperature, demonstrating the enhanced penetration of the two components. Mechanical properties of the blends were improved, especially the elongation at break, by the presence of the copolymers. The characteristic yielding at the fractured surface of the blends compatibilized with the copolymer indicates the fractural behavior of the material changed from brittle to tough.
Interaction of N‐tert‐butylaziridine with π‐electron acceptors, 1. Zwitterion copolymerization with maleic anhydride
Authors: Christova Darina Ch. , Velichkova Rumiana S. , Panayotov Ivan M.
Published: April 2003

Zwitterion copolymerization of N‐tert‐butylaziridine (TBA) with the weak π‐electron acceptor maleic anhydride (MA) was investigated. It was demonstrated that the reaction proceeds by opening of both aziridine and anhydride rings, and copoly(ester‐amide)s of different composition were prepared depending on the polymerization conditions. On the basis of a model reaction it was assumed that charge‐transfer interaction is a stage of the zwitterion mechanism. The structure and the composition of the products obtained were investigated.
Phase‐inversion membranes. Characterisation of patterns of skin holes
Authors: Addad Jean‐Pierre Cohen , Pedro‐Bom Ricardo
Published: April 2003

The statistical structure of the two‐dimensional random pattern of holes which are formed through the skin of phase‐inversion membranes is analysed. Membranes were prepared from a polyetherimide solved in N‐methyl‐2‐pyrrolidone; solutions were quickly immersed in water, at room temperature. The random pattern was observed with videomicroscopy; it is shown that it can be described quantitatively from the analysis of the ensemble of all quadrilaterals drawn from nearest neighbouring holes. Perimeters and areas of quadrilaterals were found to obey a log‐normal probability distribution function. Several features characterize the random pattern of holes. (i) There is a characteristic minimum distance between nearest neighboring holes; its order of magnitude is 5 μm. (ii) This distance is shortened when the polymer concentration in the casting solution is increased. (iii) This distance is lengthened when the solvent concentration in the coagulation bath is increased.
Chain transfer by addition‐fragmentation mechanism, 5 Investigation of the chain transfer activity of several ethyl 2‐(substituted)cinnamates
Authors: Colombani Daniel , Chaumont Philippe
Published: April 2003

A variety of ethyl 2‐(substituted)cinnamates

Systematic name: ethyl 3‐phenyl‐2‐(substituted)propenoate.

were synthesized and added to vinylic monomer polymerizations. These olefins are activated towards free radical addition and contain a homolytic leaving group in the allylic position. Thus, they exhibit chemical transfer properties in free radical polymerization. The compounds studied include bromide, iodide, sulfone, mercaptan and peroxide derivatives. Cinnamic iodide, however, exhibits degradative chain transfer activity. These compounds have an advantage over simple thiols in that they permit a good control of molar mass by an addition‐fragmentation mechanism involving difunctionalization of the resulting telomers. The methods of synthesis of ethyl 2‐(substituted)cinnamates are discussed through the nucleophilic substitution of various anions toward the allylic bromo derivative prepared from ethyl 2‐(α‐hydroxybenzyl)propenoate.
Curing kinetics of cyanated poly(ether sulfone)s of different molecular weight
Authors: Chang Jer‐Yuan , Hong Jin‐Long
Published: April 2003

Three cyanated poly(ether sulfone)s (CPESs) with number‐average molecular weights of 910, 1550 and 3 240 were synthesized and their polycyclotrimerization kinetics studied by dynamic differential scanning calorimetry (DSC). The resulting apparent activation energies (Ea) are quite close and range from 87.5 to 92.0 kJ/mol. The corresponding curing reactions in relation to conversion (α) can be expressed with an autocatalytic first‐order kinetics dα/dt = A (1+ Bα) (1 – α) exp (–Ea/(RT)). This kind of kinetics can be explained by a mechanism consisting of both a hydroxyl‐catalyzed and an autocatalytic path. The lower pre‐exponential factor (A) and contribution of autocatalytic reaction (B) for high molecular weight CPES are due to the low concentrations of catalytic species in the starting CPES and the resulting sym‐triazine rings, respectively.
Temperature effect of TiCl4 impregnation of a recrystallized MgCl2 support on propene polymerization
Authors: Shin Ho Woo , Chung Jin Suk , Song In Kyu , Lee Wha Young
Published: April 2003

The MgCl2 support for a propene polymerization catalyst was prepared by the recrystallization method using ethanol as a solvent and ethyl benzoate as an internal electron donor. The recrystallized MgCl2 was impregnated with TiCl4 at various temperatures, and the effect of impregnation temperature on the catalytic activity and isotactic index (I. I.) of polypropene (PP) was investigated. It was found that ethanol and titanium chloride ethoxide (TCE) in the catalyst play an important role in the catalytic activity and I. I. The support treated with TiCl4 at high temperatures showed good performance but large activity reduction during polymerization. The enhanced performance is mainly due to activity Ti species containing small amounts of TCE. The large activity reduction is also mainly due to small amounts of ethanol and TCE, yielding small amounts of atactic sites with low Lewis acidity.
Thermal effects on the structure and relaxation properties of poly(monocyclopentyl itaconate)
Authors: Calleja Ricardo Díaz , Sanchis Maria‐Jesus , Gargallo Ligia , Radíc Deodato
Published: April 2003

The effect of thermal treatment and subsequent chemical structural modifications on the viscoelastic and dielectric properties of PMCPI (poly(monocyclopentyl itaconate)) was studied. The low temperature relaxation (γ‐relaxation) is unaffected by the thermal history or chemical modifications. The intermediate relaxation (β‐relaxation) is shifted by about 40°C to higher temperature after thermal treatment. The α‐relaxation (related to the glass transition temperature Tg) suffers more striking changes when moving to higher temperatures.
Characterization of strictly alternating hydrogenated poly[butadiene‐alt‐(1‐olefin)] copolymers
Authors: Gerum Werner , Höhne Günther W. H. , Wilke Wolfgang , Arnold Manfred , Wegner Tino
Published: April 2003

The crystallization behaviour of the series of hydrogenated poly(butadiene‐alt‐ethene) to poly[butadiene‐alt‐(1‐hexadecene)] copolymers was investigated with the aid of differential scanning calorimetry (DSC) and X‐ray measurements. Hydrogenated poly(butadiene‐alt‐ethene) corresponds to polyethylene and crystallizes in the same way. Hydrogenated copolymers poly(butadiene‐alt‐propene) through poly[butadiene‐alt‐(1‐decene)] are completely amorphous. In these cases the large branching degree prevents crystallization of the main chains, whereas the side chains are too short to be able to crystallize above the glass transition temperature. The critical length is obviously reached in case of hydrogenated poly[butadiene‐alt‐(1‐dodecene)]. The part of the series with large side chains (hydrogenated poly[butadiene‐alt‐(1‐dodecene)] through poly[butadiene‐alt‐(1‐hexadecene)], shows the most interesting effects, especially hydrogenated poly[butadiene‐alt‐(1‐dodecene)], which shows crystallization depending on thermal history. In these substances the side chains are long enough to cause side‐chain crystallization, which becomes more pronounced with increasing length of the side chains. The crystal structure is not excactly to be determined, but some data indicate a model, in which the side chains are packed in a manner as in unbranched alkanes, but are also possible orthorhombic. However, the quality of the crystals formed is not very good, so these regions are better described as ordered domains rather than as crystallites.
Temperature‐dependent Cu2+‐Cu2+ paired structure in ethylene/methacrylic acid copolymer neutralized with Cu(II). Ionic crystallite disordering and polyethylene crystallite melting
Authors: Yamauchi Jun , Narita Hidehiro , Kutsumizu Shoichi , Yano Shinichi
Published: April 2003

Temperature‐dependent ESR spectra of Cu2+‐Cu2+ pairs in ethylene/methacrylic acid copolymer neutralized with Cu(II) were reexamined in detail. The resonance positions and the linewidths of one of the ESR fine‐structure lines showed thermal distension of the Cu2+‐Cu2+ distance, and the slopes in the temperature variations changed at the temperature associated with melting of the polymer crystallites. No meaningful anomalies were observed around the temperature at which the preceding endothermic transition takes place. In this transition, the Cu2+‐Cu2+ pairs seems to enter a disordered state, keeping almost the same paired structure. In contrast to this irreversible order‐disorder transition, the melting process in the most part of the polyethylene crystallite phases starts to impose stress upon the Cu2+‐Cu2+ pairs, accompanying the slope changes of the ESR parameters. These reversible variations with remarkable thermal hysteresis are compatible with the DSC analyses.
Homo and copolymerization of ethylene: improvement of supported vanadium catalysts performance by halocarbons
Authors: Ribeiro M. Rośario , Deffieux Alain , Fontanille Michel , Portela Manuel F.
Published: April 2003

The effect and the role of halogenated molecules as additives for supported vanadium catalytic systems has been investigated both in high temperature ethylene homopolymerization and in its copolymerization with 1‐hexene. Addition of CH3CCI3 to the {VCl3, xAICI3} or {VCl3, xCrCI3} system, leads to a strong productivity improvement. The intensity of the activating effect depends on the nature of the support. Results suggest that the activation involves both oxidation of V(II) deactivated species into potentially active trivalent ones, and generation of new active sites. Studies on the structure of ethylene/1‐hexene copolymers show that the addition of halocarbons leads to copolymers with a higher comonomer content (SCB) and a better homogeneity in composition.
Synthesis and structural characterization of chiral smectic C and smectic A poly(vinyl ether)s
Authors: Chiellini Emo , Dossi Eleftheria , Galli Giancarlo , Solaro Roberto , Gallot Bernard
Published: April 2003

A new series of chiral liquid‐crystalline poly(vinyl ether)s was synthesized by cationic polymerization of the corresponding vinyl ether monomers. They consisted of a biphenyl mesogenic unit bearing an (S)‐2‐methylbutyl chiral substituent and spaced via an alkyl segment of varying number x of methylene groups. Different initiators and experimental conditions were used for the polymerization reactions. All the samples were semicrystalline, and smectic C and A sequential mesophases were formed in polymers comprising a sufficiently long spacer segment (x > 8). X‐ray diffraction measurements were performed on unoriented specimens. In the smectic C phase, the occurrence of different orders of X‐ray reflection on the smectic layers enabled drawing of the electron density profiles along the layer normal. By simple model considerations it was possible to choose the most physically acceptable one and to identify the low temperature mesophase as double layer smectic C.
Amino‐termined poly(L‐lactide)s as initiators for the polymerization of N‐carboxyanhydrides: synthesis of poly(L‐lactide)‐block‐poly(α‐amino acid)s
Authors: Gotsche Michael , Keul Helmut , Höcker Hartwig
Published: April 2003

Poly(L‐lactide)‐block‐poly(L‐amino acids) block copolymers were prepared via polymerization of α‐amino acid N‐carboxyanhydrides with amino‐terminated poly(L‐lactide)s as macroinitiators. Two types of macroinitiators were used, one with an aminopropoxy head group (number‐average molecular weight Mn = 22000) and the other one with a phenylalanine end group (Mn = 18000). The first macroinitiator was obtained by polymerization of (L,L)‐lactide with an initiator prepared in situ from diethylzinc Et2Zn and N‐tert‐butoxycarbonyl‐1‐amino‐3‐propanol, followed by deprotection of the amino group. The second macroinitiator was obtained by endcapping of poly(L‐lactide) with N‐tert‐butoxycarbonylphenylalanine and deprotection of the amino group. 1H‐ and 13C NMR spectroscopies confirm the block structure of the copolymers obtained. In differential scanning calorimetry curves only one melting transition characteristic of the poly(L‐lactide) block is observed, on further heating decomposition occurs. By thermogravimetry two steps of decomposition are observed, the first one being assigned to the decomposition of the poly(L‐lactide) block, and the second one to that of the poly(amino acid) block, by comparison with the thermal behaviour of the corresponding homopolymers.
MALDI‐TOF mass spectrometry in polymer analytics, 1. Monitoring the polymer‐analogous sulfonation reaction of polystyrene
Authors: Räder Hans Joachim , Spickermann Jochen , Müllen Klaus
Published: April 2003

In the present paper, homologous series of polystyrenes, poly(styrenesulfonic acid)s and their corresponding sodium salts in a mass range between 2000 and 100000 Dalton were used as model systems, to check for the significance of matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF MS) in the analysis of synthetic polymers. These three different types of polymers were specially selected, because they are related to each other by polymer‐analogous reactions. The difference in molecular weight between the parent polystyrenes and the poly(styrenesulfonic acid)s or their sodium salts, respectively — prepared from the same sample — provides information on the sulfonation efficiency. It thereby appears that the mass spectrometric monitoring of a polymer analogous reaction proceeds with much greater accuracy than other methods, such as gel permeation chromatography. The measured polymer distributions supply exact values of peak molecular weight (Mp), number‐average molecular weight (Mn), weight‐average molecular weight (Mw) and polydispersity (D = Mw/Mn) which turn out to be close to those values calculated for a complete (100%) transformation in the given polymeranalogous reaction. Additional information is available in the mass range below 10000 Dalton, where single chains of the polymers are resolved. Based on the identified polymer ions, the ionization mechanism for poly(styrenesulfonic acid)s and their sodium salts seems to deviate from the mechanism proposed for the ionization of biomolecules. The exact assignment of all signals shows that there is virtually no fragmentation of the polymer ions during measurement. Even the polyionic sodium salt is analyzed together with the counterions.
Synthesis and thermal properties of poly(enaminonitriles) containing flexible ether units
Authors: Ha Jeong‐Hyup , Lee Seung‐Jae , Gong Myoung‐Seon
Published: April 2003

Poly(enaminonitriles) containing flexible alkyl ether units were prepared by reacting p‐bis(1‐chloro‐2,2‐dicyanovinyl)benzene with various α,ω‐bis(4‐aminophenoxy)alkanes in N‐methyl‐2‐pyrrolidone (NMP). All the polymers are soluble in polar aprotic solvents such as N,N‐dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N‐dimethylacetamide (DMAc) and NMP as well as in common organic solvents such as tetrahydrofuran and acetone. High molecular weight polymers possessing inherent viscosities in the range of 0.82–1.20 dL/g were obtained and tough films were cast from a DMF solution. They showed a large exotherm around 340°C attributable to the chemical changes of the dicyanovinyl group. Thermogravimetric analyses exhibited a good thermal stability with a 10% weight loss around 450°C and 73–88% residual weight at 500°C under nitrogen.
Phase transition from a C‐centered to a B‐centered orthorhombic crystalline form of syndiotactic poly(propylene)
Authors: Auriemma Finizia , Lewis Russell H. , Spiess Hans Wolfgang , De Rosa Claudio
Published: April 2003

Samples of highly syndiotactic poly(propylene) (s‐PP) crystallized in a C‐pseudo‐centered orthorhombic form are here characterized through high resolution solid state 13C NMR sepctroscopy and wide angle X‐ray diffraction. The 13C NMR CP MAS (cross‐polarization, magic angle spinning) spectra of highly disordered quench‐precipitated s‐PP samples (with a structure very close to a C‐pseudo‐centered orthrohombic form) yield additional resonances beside those already reported in the literature for s‐PP samples crystallized with the chains in a fully helical \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} (TTGG\rlap{--} )_n $\end{document} conformation (T: trans; G: gauche). From the correlation of 13C NMR CP MAS spectra with the X‐ray diffraction profiles recorded at the same temperatures, it is possible to establish that at a given temperature (approximately 100°C, for our samples) a phase transition from the C‐ to the B‐pseudo‐centered orthorhombic form starts to occur. Correspondingly, the aforementioned additional resonances in the 13C NMR CP MAS spectra progressively disappear with the onset of the phase transition. These extra resonances are indeed completely absent in the 13C NMR CP MAS spectrum of samles crystallized in the B‐pseudo‐centered structure. NMR and X‐ray diffraction data, according to differential scanning calorimetry, were interpreted with a recrystallization phenomenon; at temperatures below 140°C for our samples, the variously sized C‐pseudo‐centered orthorhombic crystallites melt and readily re‐crystallize in the B‐pseudocentered orthorhombic form.
Initiation of polymerization with substituted ethanes, 14 Free‐radical polymerization of methyl methacrylate and styrene with substituted adiponitriles
Authors: Braun Dietrich , Skrzek Thomas
Published: April 2003

Tetraarylsuccinonitriles 1 show an atypical “stepwise” initiation mechanism in freeradical polymerization, particularly in the case of methyl methacrylate (MMA) as monomer. In the prior phase of the polymerization reaction very high concentrations of primary radicals lead to the formation of short‐chain telechelics with both end groups originating from the initiator. In the further course of polymerization these telechelics are able to from radicals by release of initiator end groups and so to “re‐initiate” free‐radical polymerization (‘resusciatable’ radical polymerization). In this communication a general synthesis method of MMA telechelics with a formal degree of polymerization of one is presented. These 2,2,5,5‐tetraaryl‐3‐methoxycarbonyl‐3‐methyladiponitriles 4 dissociate with Arrhenius activation energies in the range of 150 ± 10 kJ/mol. When using these telechelics as initiators in free‐radical polymerization of MMA and styrene, respectively, above 80°C no repeated telechelic formation phase is observed and polymer formation starts immediately from the beginning. The polymers obtained have weight‐average molecular weights of 200 000 to 950000 (poly(methyl methacrylate)) and 50000 to 400000 (polystyrene), respectively.
Thermal and ferroelectric properties of two series of coloured chiral liquid crystalline side group copolymers
Authors: Niesel Frank Thomas , Rübner Joachim , Springer Jürgen
Published: April 2003

Two series of liquid crystalline side group copolymethacrylates were synthesized and their thermal and ferroelectric properties determined. All copolymers contain the same azobenzene mesogen spaced from the backbone by a heptamethylene sequence but different chiral co‐compounds were used. The samples show either a monolayer or a bilayer smectic C* phase but only four polymers with a low content of the azo‐dye could be switched ferroelectrically. The formation of the smectic C* phase of some samples was found to be hindered. In order to study this phenomenon as a function of the molecular weight one copolymer was fractionated.
Electron paramagnetic resonance (EPR) and electron and nuclear double resonance (ENDOR) characterization of radicals produced during the photopolymerization of multifunctional (meth)acrylate monomers
Authors: Selli Elena , Oliva Cesare
Published: April 2003

The electron paramagnetic resonance (EPR) spectra obtained from radicals produced during the photopolymerization of multifunctional acrylic and methacrylic monomers have been interpreted by taking into account the EPR line‐broadening due to dynamic exchange between two conformations of the β‐methylene groups and a spin‐spin dipolar interaction between radicals trapped in rigid regions of the polymer. From 1H matrix electron and nuclear double resonance (ENDOR) spectra the distance between the radical center and the surrounding shells of protons can be estimated.
Random and block 2‐alkyl‐2‐oxazolines telechelic macromonomers
Authors: Guinot Philippe , Bryant Lonnie , Chow Tak Yuen , Saegusa Takeo
Published: April 2003

Ring‐opening polymerization of 2‐methyl‐2‐oxazoline initiated by 2‐(p‐nitrobenzenesulfonato)ethyl methacrylate follows the so‐called “living mechanism”, i.e. fast initiation compared to slow propagation and no chain transfer. Accordingly, methacryl macromonomers having homopolymers, block or random copolymers of 2‐methyl and 2‐pentyl‐2‐oxazoline backbones with narrow molecular weight distribution were obtained. Termination of the propagating species by ion‐exchange or aminolysis with triethylamine yielded hydroxyl and quaternary ammonium terminated macromonomers, respectively.
Poly(oxyethylene)s terminated at both ends with phosphonium ion end groups, 1. Synthesis and characterization
Authors: Kubisa Przemyslaw , Biedroń Tadeusz
Published: April 2003

The series of poly(oxyethylene)s (poly‐EO) with number‐average degrees of polymerization ranging from ≈6 to ≈80, terminated at both ends with phosphonium ion groups, was prepared by conversion of hydroxyl end groups of α‐hydro‐ω‐hydroxypoly(oxyethylene)s into bromide end groups, followed by the reaction with triphenylphosphine. The functionality of the products (diionic poly‐EO) was determined by elemental analysis, 1H and 31P NMR as well as mass spectroscopy (MS). The observation of the signals corresponding to individual oligomers in 31P NMR spectra of short chain (DPn < 10) diionic poly‐EO was explained by intramolecular aggregation of ionic end groups leading to cyclic structures. The measurements of spin lattice relaxation times and the chemical shifts of phosphorus at different conditions (temperature, solvent, concentration) confirmed, that the aggregation of ionic end groups is clearly manifested in the 31P NMR spectra of diionic poly‐EO.