bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of isotactic poly(propylene) by oxygen and helium plasma with reference to thermo‐oxidative stability
Authors: Bauer Michael , Rembold Manfred , Marti Erwin , Schneider Hans Adam , Mülhaupt Rolf
Published: April 2003

The modification of isotactic poly(propylene) (PP) foils by reactive (O2) and inert (He) gas plasma treatment was studied with relevance to surface structure and thermo‐oxidative stability for different treatment times. The following effects were investigated: change of non‐helical (atactic or amorphous) content in the surface region and formation of vinyl and vinylidene groups by frustrated multiple internal reflection Fourier transform infrared spectroscopy (FMIR‐FTIR), formation of peroxyl redicals by electron spin resonance spectroscopy (ESR) and change of the invariant activation energy of degradation by thermogravimetric analysis (TGA). For the latter a new kinetic evaluation method was used based on a selection of multiple step model to determine the invariant Arrhenius constants, e.g., activation energy and preexponential factor, for the weight loss during thermoxidative degradation of untreated and, for the first time, of plasma‐treated PP. Several thermogravimetric curves under different temperature scanning conditions have been evaluated with different solid state models as well as with a selection of different multiple step reaction pathways. With a limitation to total weight loss of 60% of the mass for an untreated PP and applying a most probable kinetic model consisting of one consecutive and one parallel reaction step, the activation energies were found to be 84.2 ± 1.0 and 73.2 ± 1.0 kJ/mol for the initial and the consecutive reaction and 137.8 ± 3.0 kJ/mol for the parallel reaction. The corresponding data of the plasma‐treated samples are 80 ± 1.0 and 71.0 ± 1.0 kJ/mol for the initial and the consecutive reaction, while the activation energy for the parallel reaction remained almost unchanged. Unexpectedly, we found the He plasma treatment to decrease the activation energies of the first and consecutive reaction nonlinearly and within the first 600 s to a larger extent than O2 plasma treatment. Based on this kinetic model, a modified mechanism for the thermo‐oxidative degradation of PP is proposed in terms of elementary degradation reactions and will be discussed with reference to literature data.
Polymerization of 5‐vinyl‐2‐norbornene with TiCl3 and alkylaluminium catalysts
Authors: Endo Kiyoshi , Fujii Kazuyoshi , Otsu Takayuki
Published: April 2003

The polymerization of 5‐vinyl‐2‐norbornene (VNB) with TiCl3‐alkylaluminium catalysts proceeded selectively via the vinyl group; the vinylene group in the bicyclic ring did not participate in the polymerization. The rate of polymerization of VNB was slow due to the steric effect of the side chain, but effects of the types of TiCl3 and alkylaluminiums on the polymerization were observed. Hydrogen‐activated TiCl3 plus Al(C2H5)3 revealed the highest catalytic activities among the catalysts examined. The monomer‐isomerization copolymerization of VNB and trans‐2‐butene with TiCl3/Al(i‐C4H9)3 afforded a copolymer consisting of VNB and 1‐butene units. The rate of copolymerization of VNB and 1‐butene was larger than the monomer‐isomerization copolymerization of VNB and trans‐2‐butene. Copolymers rich in VNB units were produced easily by monomerisomerization copolymerization of VNB and trans‐2‐butene.
Phase separation state in hemicellulose and lignin blends analyzed by contact angle measurements
Authors: Shigematsu Mikiji , Morita Mitsuhiro , Sakata Isao , Sugihara Gohsuke
Published: April 2003

The phase separation states of hemicellulose and lignin in their blends were investigated by means of contact angle measurements. The hysteresis behavior in dynamic contact angles suggested that a phase separation of cluster‐state type (not of random dispersion type) took place at hemicellulose‐rich and lignin‐rich mixing ratios. It may be caused by the low cohesive force between hemicellulose and lignin molecules. Further, the total surface tension, and the balance between dispersion and polar forces in the total surface tension were evaluated from the equation of Wu. It was found that in the region of a hemicellulose‐rich mixing ratio, the polar and dispersion forces of the surface tension of the solid were reduced and raised, respectively, and in contrary to this, in the lignin‐rich region, the former were raised and the latter were reduced. The polymer‐polymer interaction parameter of Flory between hemicellulose and lignin depends on the mixing ratio as reported previously; this may be ascribed to a difference of the balancing of polar‐dispersion forces.
Thermal degradation of polymers in the melt, 2. Kinetic approach to the formation of volatile oligomers by thermal degradation of polyisobutylene
Authors: Sawaguchi Takashi , Ikemura Tadashi , Seno Manabu
Published: April 2003

The thermal degradation of polyisobutylene is characterized by kinetics consisting of four types of intramolecular hydrogen abstraction (back‐biting) of primary (p) and tertiary (t) terminal macroradicals (R and R) and the successive β scission at the inner position of the main chain. This reaction affords four types of terminal monoolefins in the volatile oligomers. Assuming the reaction occurs competitively under a steady state regarding the on‐chain macroradicals, the composition of the monoolefins are represented as the rate ratios of the respective back‐biting processes. The rate ratio between the abstractions of different types of hydrogens (CH2 and CH3) from the same type of macroradicals is expressed only by the rate constant ratio. The (TTD)p/(TVD)p and (TTD)t/(TVD)t ratios remain constant during degradation, independently of the decreases in volume and molecular weight of the reacting polymers and this tendency agrees fairly well with the kinetic expectation. This result suggests that back‐biting depends only on the local motion of the reacting chain ends. The ratios between the abstractions of the same type of hydrogen from different macroradicals are expressed by the product of the rate constant ratio and the integrated macroradical concentration ratio ([R]/[R]). The observed values of (TTD)p/(TTD)t and (TVD)p/(TVD)t decrease with reaction time. This decrease results from the decrease in macroradical concentration.
Preparation and solution properties of microhydrogels from poly(vinyl alcohol)
Authors: Brasch Uwe , Burchard Walther
Published: April 2003

Microgels were synthesized by intramolecular crosslinking of poly(vinyl alcohol) single chains with glutaraldehyde in dilute aqueous solutions (concentration c = 0,1 g/100 mL). The degree of crosslinking was varied from X = 0 to X = 150 (X is the number of crosslinker molecules per chain). The reaction products were characterized by static and dynamic light scattering and viscosity measurements. A clear shrinking of molecular dimensions could be observed with increasing degree of crosslinking, since the radius of gyration Rg, and with that, the p‐parameter (p = Rg/Rh) decrease with the number of intramolecular crosslinks. A similar behavior is seen from viscosity measurements. The intrinsic viscosity [η] decreases with increasing X‐parameter and depends only very weakly on the temperature which is an indication of a loss in flexibility and therefore for a relatively fixed structure.
Study of microgelation of unsaturated polyester resins in the presence of low profile additives by dynamic light scattering
Authors: Sun Ber , Yu Tzyy‐Lung
Published: April 2003

Dynamic light scattering (DLS) experiments were used to study the microgelation of unsaturated polyester (UPE)/styrene resins in the presence of low profile additives (LPA), i. e., poly(vinyl acetate) (PVAC) and poly(methyl methacrylate) (PMMA), during the early stage of the curing reaction. The partially cured resins were mixed with solvents being isorefractive with LPA, thus one “sees” only the primary UPE and the partially cured UPEs in the DLS experiments. The DLS experimental results showed that, during the early stage of curing, the size and structure of the UPE microgels are strongly related to the concentration of LPA and to the compatibility of the components in the curing system. The experimental results of this study revealed the evidence of shrinkage of the microgel particles due to intramolecular crosslinking.
The 1H and 13C NMR spectra of alternating isobutene/maleic anhydride copolymer and the corresponding acid and sodium salt — a stereochemical analysis
Authors: Komber Hartmut
Published: April 2003

The 1H and 13C NMR spectra of an alternating isobutene/maleic anhydride copolymer and the corresponding acid and sodium salt forms were reexamined by 1D and 2D NMR methods. This copolymer contains only threo‐succinyl units. The tacticity is characterized by a 53/47 ratio of threo‐diisotactic and threo‐disyndiotactic triads. The preference of the diisotactic triad was concluded from NMR data. A model was proposed to explain the stereoselectivity of the copolymerization reaction. This model also leads to the conclusion that the diisotactic triad should be preferred for steric reasons. 13C‐T1 values and nuclear Overhauser effect (NOE) values for these three copolymers were determined and discussed in terms of segmental motion.
Regio‐ and stereoregular copolymerisation of propene with carbon monoxide catalysed by palladium complexes containing atropisomeric diphosphine ligands
Authors: Bronco Simona , Consiglio Giambattista
Published: April 2003

The use of palladium catalysts, modified by chelate diphosphine ligands based on a diphenyl atropisomeric moiety, permits a good control of regio‐ and stereochemistry in the alternating copolymerisation of propene with carbon monoxide. The completely aromatic ligands (S)‐(6,6′‐dimethoxybiphenyl‐2,2′‐diyl)bis(diphenylphosphine) and (S)‐(6,6′‐dimethylbiphenyl‐2,2′‐diyl)bis(diphenylphosphine) give regioirregular materials. Their stereoregularity cannot be easily evaluated but appears to be rather low on the basis of optical activity determinations. Using ligands containing sterically hindered alkyl substituents on the phosphorus atoms (such as cyclohexyl or isopropyl) completely regioregular copolymerisation takes place. The produce copolymers show a high degree of stereoregularity approaching 96% of l‐diads. Ligands lacking C2 symmetry show only a small decrease in regioregularity and stereoregularity. Very high catalytic activity is observed with the ligand (all S)‐(Ra)‐(6,6′‐dimethoxybiphenyl‐2,2′‐diyl)bis(2,5‐dimethylphospholane). This ligand allows the production of a completely regioregular copolymer that shows almost complete atacticity.
Facile synthesis of new amine high‐loaded poly(meth)acrylamide‐based resins for solid phase peptide
Authors: Alfred Jean‐Claude , Daunis Jacques , Jacquier Robert
Published: April 2003

Two methods for the ready preparation of some protected primary amine‐functionalized (meth)acrylamide derivatives from amino halides or amino alcohols are described. The (meth)acryloyl moiety is introduced either in the last step from unsymmetrically N,N′‐disubstituted diamines or, more simply, in the first step, but that demands a special work‐up of the reaction mixture in order to prevent polymerization. Both methods are complementary. Reverse phase suspension polymerization of the title compounds with N‐acryloylpyrrolidine and N,N′‐ethylenebis(acrylamide) directly affords new beaded, high‐loaded aminefunctionalized resins for solid phase peptide synthesis.
Transfer constants from complete molecular weight distributions
Authors: Christie David I. , Gilbert Robert G.
Published: April 2003

Transfer constants to chain‐transfer agent (CTA) and to monomer can be obtained by consideration of the complete molecular weight distribution, using the slope of a plot of the natural logarithm of number‐molecular weight distribution against molecular weight, in the limit of high molecular weight and low radical flux (P. A. Clay, R. G. Gilbert, Macromolecules 28, 552 (1995)). This method is applied to the bulk polymerisations of methyl methacrylate (MMA) with added triethylamine (TEA) and with added tert‐dodecylmercaptan (mixture of 2,4,4,6,6‐pentamethylheptane‐2‐thiol and 2,2,4,6,6‐pentamethylheptane‐4‐thiol, TDM). The transfer rate coefficients are found to be 74 (±20) dm3 · mol− · s−l at 60°C for TEA, and 56 (±13) dm3 · mol−1 · s−1 at 25°C for TDM.
Poly(β‐hydroxynonanoate) and polystyrene or poly(methyl methacrylate) graft copolymers: microstructure characteristics and mechanical and thermal behavior
Authors: Hazer Baki
Published: April 2003

Active polymers containing peroxide groups were synthesized via polymerization of styrene or methyl methacrylate with oligo(adipoyl 2,5‐dimethylhexane‐2,5‐diyl peroxide) (OAHP) or oligo(2,5‐dimethylhexane‐2,5‐diyl 4,4′‐azobis(4‐cyanoperoxyvalerate)) (LUAB). Poly(β‐hydroxynonanoate) (PHN) and the active polymer were mixed, and free radical grafting reactions were carried out to optimize mechanical and viscoelastic properties of PHN. The “active” vinyl polymers polystyrene (PS) and poly(methyl methacrylate) (PMMA) were grafted onto PHN chains or cleaved them, depending on the PHN/active polymer mass ratio and the peroxygen content of the active polymer. The increase in tensile strength (f) and strain (ε) was observed to be maximum in graft copolymers having vinyl polymer contents less than 20 wt.‐%. SEM micrographs showed surface topography. Phaseseparated graft copolymers reveal dispersed phase particles, micrometer and submicrometer sized particles, and holes in the micrographs. The SEM observations are also wholly consistent with the glass transition temperature behavior obtained from differential scanning calorimetric (DSC) measurements.
Synthesis and liquid crystalline properties of thermotropic copolycarbonates
Authors: De Backer Christel , Ottenburgs Raoul , Van Beylen Marcel , Samyn Celest
Published: April 2003

Copolycarbonates with flexible spacers have been prepared by melt condensation of 4,4′‐bis[(2‐hydroxyethyl)oxy]biphenyl, 1,5‐bis[(2‐hydroxyethyl)oxy]naphthalene and pentarespectively octamethylene diphenyl dicarbonate in varying concentrations. These random copolycarbonates show liquid crystalline behavior, with the formation of nematic phase over a temperature range of maximum 22°C respectively 47°C, this for at least 75 mol‐% of biphenyl units. Incorporation of 1,5‐bis[(6‐hydroxyhexyl)oxy]naphthalene does not lead to liquid crystallinity. Copolymers with 2,6‐bis[(6‐hydroxyhexyl)oxy]naphthalene and 4,4′‐bis[(6‐hydroxyhexyl)oxy]biphenyl show mesomorphic behavior, with the formation of a mesophase with a maximum width of 20°C, for incorporation up to 75 mol‐% of either of the mesogenic units. Copolycarbonates which contain only biphenyl mesogenic units and which differ in the length of the flexible spacers were also obtained; they behave liquid crystalline over the entire composition range with maximum 34°C for the nematic phase region.
Effects of pH on the supramolecular structure of polymeric molecular deposition films
Authors: Zhang Xi , Sun Yipeng , Gao Manglai , Kong Xiangxing , Shen Jiacong
Published: April 2003

A new kind of molecular deposition films was obtained by alternating deposition of a bipolar quaternary ammonium salt and poly(maleic acid monoester). The pH value of the cationic solution has great effect on the supramolecular structure of the polymeric ultrathin films. Two kinds of ultrathin films were formed according to a quasi‐symmetrical model and a quasi‐asymmetrical model.
Crystal structure of the blend of polyamide 1010 with a bismaleimide by WAXD and SAXS
Authors: Zhang Hongfang , Yang Baoquan , Zhang Lihua , Mo Zhishen
Published: April 2003

The blend polyamide 1010/N,N′‐(diphenylmethane‐4,4′‐diyl)bismaleimide (PA1010/BMI) has been investigated by means of WAXD and SAXS. The results obtained with the help of the Ruland, variance and 1D EDCF analysis showed that the degree of crystallinity (Wc,x) crystallite size (Lhkl), long period (L) and thickness of average crystal lamellae (d) decrease with BMI content. Experimental and calculated density values (ρc) are in good agreement. Addition of BMI to PA1010 causes an increase in structural distortion. The results from SAXS analysis also supported that a crystalline amorphous interphase exists in the lamellae of semicrystalline polymers, so that a three‐phase model instead of the traditional two‐phase model should be used.
The effect of crosslinking in elastomers investigated by NMR analysis of 13C edited transverse 1H NMR relaxation
Authors: Fülber Carsten , Demco Dan E. , Weintraub Ofer , Blümich Bernhard
Published: April 2003

The transverse nuclear 1H magnetization decay in poly(styrene‐co‐butadiene) (SBR) is investigated by editing 13C NMR spectra. This technique allows for the assignment of localized 1H dynamical information by discriminating the chemical sites based on their chemical shift in the 13C dimension. Here, the homo‐ and heteronuclear dipolar couplings contribute to the 1H NMR relaxation giving additional information to a homonuclear experiment. In this heteronuclear 2D experiment two prominent peaks are observed in the 13C dimension, which correspond to CH and CH2 groups, respectively. The decay rate in the 1H dimension is found for both groups to scale with the crosslink density. An additional ultra‐fast magnetization decay is reported. The effect of the carbon black filler is investigated for this component. The analysis of the 13C NMR edited transverse 1H magnetization relaxation is a useful tool in combining high resolution NMR spectra with information on molecular dynamics, providing insight into crosslink density and filler effects.
A novel synthetic route to poly(β‐ketone)s via poly(alkoxyethyne)s
Authors: Shoda Shin‐ichiro , Komenoi Akio , Fujioka Tomochika , Okumura Yasunori , Kobayashi Shiro
Published: April 2003

Isopropoxyethyne (1a) and tert‐butoxyethyne (1b) were polymerized using group 5 and 6 transition metal catalysts to give poly(isopropoxyethyne) (2a) and poly(tert‐butoxyethyne) (2b), respectively. The weight‐average molecular weight (M̄w) of the resulting poly(alkoxyethyne)s was up to 1.0 × 104. Among the transition metal catalysts, a tungsten alkoxide or a molybdenum alkoxide having low Lewis acidity were found to effectively promote the polymerization without causing side reactions. Poly(tert‐butoxyethyne) was successfully converted to poly(β‐ketone) 3 by acid hydrolysis of the tert‐butyl vinyl moiety.
Novel silicones for transdermal therapeutic system, 6. Preparation of oligodimethylsiloxane containing 2‐pyrrolidone moiety as a terminal group and its enhancing effect on transdermal drug penetration
Authors: Aoyagi Takao , Tadenuma Rie , Nagase Yu
Published: April 2003

Oligodimethylsiloxanes (ODMSs) containing a 2‐pyrrolidone moiety at one chain end were prepared to develop a silicone‐based transdermal penetration enhancer. The 1‐alkyl‐2‐pyrrolidon‐3‐yl group was introduced as a terminal group of ODMS via the initiator method, i.e., the anionic ring‐opening polymerization of hexamethylcyclotrisiloxane was initiated with the silanolate anion derived from (1‐alkyl‐2‐pyrrolidon‐3‐ylmethyl)dimethylsilanol. The disiloxanes were also prepared from the silanol derivatives by reaction with chlorotrimethylsilane. The enhancing activity of drug penetration was evaluated by in vitro experiments using a two‐chamber diffusion cell. Indomethacin and antipyrine were used as model drugs, and the amounts of drugs permeating through the rabbit abdominal skin were measured with and without the ODMSs or disiloxanes. The enhancing activities are influenced by the chain length of the siloxane components and the chemical structure of their end groups. A suitable balance between the hydrophobic ODMS chain and the polar end group might be decisive for a high enhancing activity of drug penetration.
Synthesis and mesomorphic properties of fishbone‐like liquid crystalline polysilsesquioxanes, 3. Fishbone‐like, azo‐based liquid crystalline polysilsesquioxane
Authors: Xie Ping , Wan Youzi , Zhou Bisan , Hou Jianang , Dai Daorong , Li Ze , Liu Dongsheng , Zhang Rongben
Published: April 2003

Homopolymeric H‐FP (FP: fishbone‐like, azo‐based liquid crystalline polysilsesquioxanes) and copolymeric C‐FP were synthesized by hydrosilylation reaction of a vinylterminated azo compound with a ladder‐like poly(hydrosilsesquioxane) (H‐T) and random poly(methylhydrosilsesquioxane) (MH‐T), respectively, in the presence of Cp2PtCl2 (Cp: cyclopentadienyl) used as the catalyst. This new type of liquid crystalline polymers is thermotropic. With increasing temperature FP's first enter a mesophase showing a normal texture, and then some peculiar textures different from the ordinary mesophase appear at an elevated temperature showing some bright belts, lines and spots on the black background, which can be supposed to be a self‐organized structure originating from ladder‐like main chain aggregation or association via interaction between the mesomorphic side chains.
Surface studies of stereoregular poly(methyl methacrylate)s: Effect of interface on near‐surface composition and crystallinity
Authors: Tretinnikov Oleg N. , Nakao Kimiko , Ohta Koji , Iwamoto Reikichi
Published: April 2003

The surface microstructure of the cast films of syndiotactic and stereocomplex poly(methyl methacrylate)s (PMMA) was studied by the attenuated total reflection IR (IR/ATR) method. For comparison, the bulk structure was analyzed by transmission IR spectroscopy. For the syndiotactic PMMA, the relative intensity of the “crystalline” band at 860 cm−1 to the “amorphous” band at 841 cm−1 in the IR/ATR spectra indicates that the degree of crystallinity is enhanced or reduced near the surface region, depending on the degree of polymer stereoregularity and the contacting medium. For a stereocomplex PMMA film it was found that the surface regions are less crystalline than the bulk of the film. The relative intensity of the peak at 750 cm−1 to that at 758 cm−1 in the IR spectra also indicates that the stereocomplex film contains an excess of the syndiotactic component in the surfaces and that the surface enrichment is stronger at the air‐side surface.
Synthesis, polymerization and structural characterization of a novel liquid crystalline side‐chain poly(vinyl ether) containing dicyanovinyl groups and displaying coexisting smectic phases
Authors: Trollsås Mikael , Ihre Henrik , Gedde Ulf W. , Hult Anders
Published: April 2003

The synthesis and cationic polymerization of the new monomer 4‐(2,2‐dicyanovinyl)‐4′‐(11‐vinyloxyundecyloxy)biphenyl (6) is described. The dicyanovinyl group tolerated thermally initiated and photoinitiated cationic bulk polymerization using onium salts as well as the BF3 · (EtO)2‐initiated solution polymerization in CH2Cl2 at −15°C. Monomer 6 was crystalline, whereas poly(6) with increasing temperature exhibited coexisting SAd and SC phases, an SAd phase with extensive thermal stability and an isotropic phase. Poly(6) exhibited a glass transition at 20°C.
Synthesis of poly(dihalophenylene oxide)s by solid‐state thermal decomposition of manganese phenolate complexes with ethylenediamine ligand
Authors: Pulat Mehlika , Şanli Oya
Published: April 2003

The synthesis of poly(dihalophenylene oxide)s by solid‐state thermal decomposition of manganese phenolate complexes with ethylenediamine ligand was achieved. The complexes were characterized by infrared (IR) spectroscopy and C, H, N elemental analysis. The dependence of the yield of polymers on temperature and decomposition time of the manganese complexes with 2,4,6‐trichlorophenol, 2,4,6‐tribromophenol and 2,6‐dibromo‐4‐chlorophenol was investigated. The polymers obtained were characterized by 1H NMR, IR spectroscopy and differential scanning calorimetry and found to be branched. 1,2‐Catenation is favoured over 1,4‐addition in 2,4,6‐tribromophenoxide and 2,6‐dibromo‐4‐chlorophenoxide derived polymers, however, polymers synthesized from trichlorophenolate display a selectivity in favour of 1,2‐catenation.
γ‐ray polymerization of mesogenic diacrylates in the crystalline, liquid crystalline and liquid state — a kinetic study
Authors: Hohn Wilfried , Tieke Bernd
Published: April 2003

A kinetic study of the γ‐ray polymerization of three mesogenic diacrylates, 4,4′‐bis(3‐acryloyloxypropoxy)biphenyl (DAPB), 4,4′‐bis(6‐acryloyloxyhexyloxy)biphenyl (DAHB) and 4,4′‐bis(11‐acryloyloxyundecyloxy)biphenyl (DAUB), is presented. All compounds were studied on their polymerizability in the crystalline state. It was found that they can be completely polymerized though the reaction rates are very different and increase with increasing length of the alkylene spacer unit. Up to moderate conversion, solid‐state polymerization is comparable with that of acrylamide and follows a t2 rate law. DAPB was chosen for a detailed kinetic study of the in‐source and post‐polymerization in the crystalline, liquid crystalline and liquid phase. In‐source polymerization is complete in the various phases though reaction rates and curve shapes of dose vs. conversion curves are very different. Possible origins such as enhanced molecular diffusion at elevated temperatures are discussed. X‐ray studies indicate that a well‐ordered polymer can be obtained from polymerization in a smectic phase, while polymers obtained from a crystaline or melt phase are considerably less ordered. Post‐polymerization was studied as a function of the radiation dose and the temperature of the subsequent annealing process. It was found that the limiting conversion increases with increasing radiation dose and temperature of the annealing process, but the polymerization is always incomplete. Even post‐polymerization in the melt phase does not exceed 55 percent conversion. The post‐polymerization behaviour is comparable with that of acrylamide and can be described by a linear relation between conversion and annealing time t.
Polymerization of olefins with zirconocene catalysts using methylaluminoxane modified with hydroquinone as cocatalyst
Authors: Jin Jizhu , Uozumi Toshiya , Soga Kazuo
Published: April 2003

Methylaluminoxane (MAO) was reacted with a small quantity of p‐hydroquinone to obtain a modified MAO insoluble in toluene. Ethylene and propylene homo‐ and copolymerization were conducted with zirconocene using the modified MAO as cocatalyst both in the presence and absence of triisobutylaluminium. It was found that the modified MAO alone cannot activate the zirconocene catalyst, whereas polymers with high molecular weights are obtained when combined with triisobutylaluminium. The catalytic activity is markedly dependent on the mole ratio of p‐hydroquinone to MAO as well as the amount of triisobutyl‐aluminium.
Activation of rac‐ethylenebis(indenyl)zirconium dichloride with a low amount of methylaluminoxane (MAO) for olefin polymerizations
Authors: Coevoet Dorothée , Cramail Henri , Deffieux Alain
Published: April 2003

The homopolymerization of hex‐1‐ene catalyzed by the system rac‐Etlnd2ZrCl2/MAO was investigated in solvents of various polarity (toluene, methylene dichloride and heptane). Polymerization kinetics were monitored by dilatometry. It is shown that reaction proceeds by long‐lived active species rapidly formed and remaining at constant concentration during the whole polymerization. However, the molar masses of the polymer remain controlled by a transfer process. A strong enhancement of the activity is observed in pure CH2Cl2 compared to the one measured in toluene. Besides, the use of CH2Cl2 allows to reduce the amount of methylaluminoxane (MAO) by a factor 20 to reach the plateau of maximum activity, without affecting the isotacticity of the polymer. The increase of activity in CH2Cl2, even for low MAO/Zr ratios, is explained by an easier ionic dissociation of the Zr‐X bond (X = Cl or methyl) yielding the formation of cation‐like active species. A preformation of the catalytic system in minute amount of CH2Cl2 followed by hex‐1‐ene polymerization in heptane or toluene was found to yield also high catalytic activity at a low MAO/Zr ratio. These results suggest that the beneficial effect of methylene dichloride on the formation of the active species is preserved. A tentative explanation is proposed. A first extension of the results obtained with the α‐olefin to ethylene polymerization is also presented.
H2‐D2 exchange reaction with MgCl2‐supported Ziegler catalyst by stopped‐flow method
Authors: Mori Hideharu , Tashino Kunihiko , Terano Minoru
Published: April 2003

The effect of hydrogen on the chain transfer reaction in the initial stage of propene polymerization with MgCl2‐supported Ziegler catalyst was studied through H2‐D2 exchange reaction using the stopped‐flow method. When the exchange reaction was carried out with various catalyst components at room temperature for 5 min, HD was produced only in case of using the catalyst with Al(C2H5)3. In case of the stopped‐flow method (reaction time ca. 0.1 s), the catalyst without pre‐treatment with Al(C2H5)3 showed no activity for the H2‐D2 exchange reaction (no HD produced), while the catalyst with pre‐treatment had exchange activity. As the chain transfer activity of H2 in propene polymerization shows the same tendency, it is evident that chain transfer with H2 occurs via atomic hydrogen generated on the pre‐treated catalyst.
Preparation and polymerization behavior of 2‐[2,2,2‐tris‐(alkoxycarbonyl)ethyl]acrylic ester as a sterically congested monomer
Authors: Yamada Bunichiro , Kobatake Seiya , Konosu Osamu
Published: April 2003

Methyl 2‐[2,2,2‐tris(methoxycarbonyl)ethyl]acrylate and methyl 2‐[2,2,2‐tris(ethoxycarbonyl)ethyl]acrylate [M(TE)EA] were synthesized for the first time by the reaction of methyl 2‐(bromomethyl)acrylate with the corresponding tris(alkoxycarbonyl)methane in the presence of triethylamine at room temperature in 90 and 89% yields, respectively. Attempted homopolymerization of these particular acrylates did hardly occur. However, the radical produced by attack of the primary radical from 2,2′‐azo‐2,4,4‐trimethylpentane at the β‐carbon of M(TE)EA was detected via its 5‐line ESR spectrum, and a similar spectrum was observed using tert‐butyl peroxide as initiator. These findings imply that persistency of the adduct radical of M(TE)EA suppresses further propagation to high molecular weight polymer. Steric congestion of the adduct radical was shown by ESR spectral change at different temperatures. Copolymerization of M(TE)EA with methyl methacrylate proceeded at a slow rate and yielded products containing only 1,7–2,7 units of M(TE)EA per polymer chain irrespective of comonomer composition. When the content of M(TE)EA was lower than 10 mol‐% in the monomer mixtures of M(TE)EA with styrene and methyl acrylate, copolymers whose molecular weights decreased with an increase in M(TE)EA content in monomer mixture were obtained. The copolymerization rates were also reduced considerably with increasing content of M(TE)EA in the feed.
Étude de la copolymérisation de monomères acryliques fluorés avec le méthacrylate de morpholinoéthyle
Authors: Guyot Bernard , Boutevin Bernard , Améduri Bruno
Published: April 2003

The copolymerization of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluorodecyl acrylate (AC8), methacrylate (MAC8) and α‐acetoxyacrylate (αAC8) with morpholinoethyl methacrylate (MEMA) is presented. For these three systems, the values of the reactivity ratios (ri) of both comonomers were determined by means of four methods (Jaacks, Macret, Fineman‐Ross and Tidwell‐Mortimer) usually used, and these results were compared. In each case, the copolymer obtained exhibits a structure with a higher content of the fluorinated base unit. A reactivity scale in the radical copolymerization with MEMA is proposed and shows that αAC8 and MAC8 are more reactive than AC8, contrary to their homopolymerization behaviour. An explanation of such a tendency was suggested taking into account the Q‐e scheme of Alfrey and Price of hydrocarbon homologues.
4‐methoxy substituted trityl groups in 6‐O protection of cellulose: Homogeneous synthesis, characterization, detritylation
Authors: Gömez Juan A. Camacho , Erler Ulrich W. , Klemm Dieter O.
Published: April 2003

The reaction of cellulose with methoxy‐substituted triphenylmethyl chlorides under homogeneous conditions in the presence of pyridine was carried out with the aim to develop new protective groups for cellulose simply introducable and completely removable under mild conditions. The obtained cellulose ethers dissolve well in solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, 1,4‐dioxane and tetrahydrofuran and show a high 6‐O selectivity. The study proves that the speed of tritylation as well as of detritylation increases in the order unsubstituted trityl/monomethoxytrityl/dimethoxytrityl/trimethoxytrityl. The substituent distribution of the methoxy‐substituted triphenylmethyl ethers of cellulose was determined by means of 13C NMR spectroscopy of the polymers and by high‐performance liquid chromatography after chain‐degradation. Since the methoxy substituted trityl groups were introduced faster and removed easier than the unsubstituted trityl group, they are, therefore, useful tools for a regioselective synthesis of 2,3‐functionalized cellulose derivatives.
Irreversibility of structural changes induced by stretching in poly(vinyl chloride)
Authors: Elicegui Amaia , del Val Juan José , Colmenero Juan , Martínez Gerardo , Millán José Luis , Bellenger Veronique , Verdu Jacques
Published: April 2003

It has been shown that certain structural (X‐ray diffraction) and physical (infrared dichroïsm, α‐relaxation dynamics) characteristics of poly(vinyl chloride) undergo irreversible changes upon sample drawing. This behaviour reveals some non‐equilibrium character of the polymer, even in tetrahydrofuran (THF) solution or in the rubbery state (at, typically, glass transition temperature Tg + 10°C). Two tentative ways of explanation have been proposed. The first one would attribute the cause of this peculiar behaviour to physical crosslinks linked to strong interchain bonding. These bonds would resist to dissolution in THF at room temperature but would be broken during stretching. The second way of explanation involves the presence of a metastable GTTG−TT conformation at the end of an isotactic sequence in an mmr chain segment. Like the above mentioned physical crosslinks, it would be transformed upon mechanical loading but not during dissolution in THF or heating to 90°C. Both hypotheses are not necessarily incompatible: as a matter of fact, GTTG− conformations at the end of the isotactic triads could represent sites of especially high intermolecular interaction, distributed along the polymeric chain.
Molecular dynamics in polystyrene from electron spin resonance (ESR) measurements: comparison between spinprobes and ‐labels attached to the chain ends
Authors: Volkmer Thomas , Wiesner Ulrich , Brombacher Lothar , Spiess Hans Wolfgang
Published: April 2003

The commercially available 15N‐Tempone

N‐Tempone: 4‐oxo‐2,2,6,6‐tetramethylpiperidine‐15N‐oxyl; Tempol: 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine ‐15N‐oxyl.

nitroxide radical has been used for the endfunctionalization of anionically polymerized polystyrene. The temperature dependence of molecular motions of the nitroxide radicals in this chain end labeled polystyrene (PS) and a PS/Tempol mixture has been studied using cw‐ESR. Furthermore, these two samples were compared with a mixture of PS with a biradical which has a large molecular volume and is used in its unoxidized form as a polymer additive in commercial products. The temperature dependent spectra were evaluated to give T50G. This allows the volume for reorientation of the radicals and that of a polymer unit to be compared. The temperature dependent spectra were simulated in order to yield the rotational correlation time τR. In contrast to the Tempol probe radical which is highly mobile even at temperatures well below the glass transition temperature (Tg) the spin‐label strongly couples to the α‐process of polystyrene. The biradical exhibits an intermediate mobility and seems to be weakly coupled to the glass transition dynamics. Line shape analysis shows that the motional behavior of the PS/Tempol mixture can adequately be described by the model of isotropic rotational diffusion, whereas for the chain end label significant deviations from this model are observed indicating anisotropic motion due to restrictions imposed by the polymer chain.
Synthesis and characterization of poly(amide‐imide)s containing 1,6‐diamantane moieties in the main chain
Authors: Chern Yaw‐Terng , Chung Wan‐Ho
Published: April 2003

A series of new poly(amide‐imide)s were synthesized by direct polycondensation of the 1,6‐bis(trimellitimido)diamantane (1) with various aromatic diamines in N‐methyl‐2‐pyrrolidone (NMP) containing lithium chloride. The poly(amide‐imide)s had inherent viscosities of 0.33–1.55 dL/g. The new polycyclic monomer 1 was synthesized from 1,6‐diaminodiamantane with trimellitic anhydride. Dynamic mechanical analysis revealed polymers 3a–c to have main transitions at 385°C, 385°C, and 330°C, respectively. Moreover, these polymers were stable at high temperatures and maintained good mechanical properties (G′ ≈ 108 Pa) up to temperatures close to the main transition well above 350°C. Their 5% weight loss temperatures ranged from 421 to 448°C in nitrogen, and from 417 to 426°C in air. A glass transition of poly(amide‐imide)s 3 was not observed. Poly(amide‐imide)s 3 (except 3e) were soluble in NMP, pyridine, and o‐chlorophenol. Some of the polymers (3a–c) could be cast into flexible films. Their cast films had tensile strengths ranging from 35.5 to 46.9 MPa, elongations at break from 5.8 to 7.5%, and initial moduli from 1.8 to 2.1 GPa.
Synthesis and properties of aromatic polyamides based on 4,4′‐[1,4(1,3 or 1,2)‐phenylenedioxy]dibenzoic acid
Authors: Hsiao Sheng‐Huei , Chang Chih‐Fen
Published: April 2003

Three isomeric bis(ether carboxylic acid)s, 4,4′‐[1,2(1,3 or 1,4)‐phenylenedioxy]dibenzoic acid (o‐, m‐, or p‐3) were prepared by nucleophilic substitution reaction of the potassium phenolate of catechol, resorcinol, and hydroquinone, respectively, with p‐fluorobenzonitrile, giving the corresponding bis(ether nitrile)s, followed by alkaline hydrolysis. There series of isomeric polyamides were synthesized by direct polycondensation of the bis(ether carboxylic acid)s with various aromatic diamines in N‐methyl‐2‐pyrrolidone (NMP) solution containing dissolved metal salts such as CaCl2 or LiCl using triphenyl phosphite and pyridine as condensing agents. The resultant polyamides had inherent viscosities of 0,52–1,63 dL/g. Most of the polymers were soluble in polar aprotic solvents such as N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), NMP, and dimethyl sulfoxide. The catechol‐based polyamides revealed markedly higher solubility than those based on hydroquinone or resorcinol. Transparent, flexible and tough films could be cast from the DMAc or NMP solutions of most of the polyamides. All the casting films were characterized by tensile tests. The glass transition temperatures (Tg's) of most polyamides could be determined with the help of differential scanning calorimetry (DSC) traces, which were recorded in the range of 183–232°C. In general, the polyamides based on catechol had Tg's comparable with the ones of the hydroquinone‐based polyamides and higher Tg's than the corresponding resorcinol‐based ones. Thermogravimetric analysis data of these polymers indicated that all the polyamides were stable up to 400°C in both air and nitrogen atmospheres.
Oligomerization and copolymerization of γ‐butyrolactone — a monomer known as unable to homopolymerize, 1. Copolymerization with ε‐caprolactone
Authors: Duda Andrzej , Penczek Stanislaw , Dubois Philippe , Mecerreyes David , Jérôme Robert
Published: April 2003

Copolymerization of γ‐butyrolactone (γBL) with ε‐caprolactone (εCL) initiated with aluminium isopropoxide trimer ([Al(OiPr)3]3, (A3)) is described. Copolymers with molecular weights (Mn) up to 3 · 104 and containing up to 43 mol‐% repeating units derived from γBL are prepared. Their molecular weight is controlled by the concentrations of the consumed comonomers and the starting concentration of initiator {Mn = (86.09 · [γBL]c + 114.14 · [εCL]c)/3[Al(OiPr)3] + 60.10}. 13C NMR and DSC data are indicative of a pseudoperiodic or random copolymer structure.
The preparation of new types of polymerizable vinyl sugars with CC bonds between sugar and double bond
Authors: Wulff Günter , Schmid Jürgen , Venhoff Theodor P.
Published: April 2003

The syntheses of new types of vinyl sugars are described whose vinyl groups are connected with the monosaccharide by a CC bond. Such monomers can be polymerized by radical as well as by anionic initiation. Starting from D‐mannitol, D‐gluconolactone, D‐galactose, and D‐fructose, the isopropylidene‐protected aldehydes (R)‐2,3‐isopropylidene‐D‐glyceraldehyde (3), 2,3;4,5‐di‐O‐isopropylidene‐aldehydo‐D‐arabinose (4), 1,2;3,4‐di‐O‐isopropylidene‐α‐D‐galacto‐hexodialdo‐1,5‐pyranose (5), and 2,3;4,5‐di‐O‐isopropylidene‐β‐D‐arabino‐hexosulo‐2,6‐pyranose (6) were prepared. Grignard reaction of the aldehyde compounds with 4‐vinylphenylmagnesium chloride in tetrahydrofuran (THF) yielded the new styryl monomers of type 1, in each case as a mixture of two diastereoisomers. The corresponding reaction with vinylmagnesium bromide furnished a mixture of two diastereoisomeric allyl alcohol derivatives. Subsequent Swern oxidation (DMSO/(COCl)2) gave the vinyl ketones of type 2. A scale‐up procedure (20 L flask) allowed eight different monomers to be prepared on a 50–200 g scale. Furthermore, the synthesis of the 2,3;4,5‐di‐O‐isopropylidene‐β‐D‐fructopyranose could be considerably improved.
Poly(butylene terephthalate) oligomers containing organosilane end groups
Authors: Boutevin Bernard , Khamlichi Mohammed , Robin Jean‐Jacques
Published: April 2003

Oligomers with poly(butylene terephthalate) (PBT) containing organosilane extremities were prepared by reacting an α‐allylic oligomer of PBT with silanethiols or with silanes. The α‐allylic oligomer of PBT was synthesized by condensation of allyl alcohol, 1,4‐butanediol and terephthaloyl dichloride. All the oligomers were characterized by means of proton nuclear magnetic resonance, Fourier‐transform infrared spectroscopy, size‐exclusion chromatography, gas chromatography and high‐performance liquid chromatography. Their thermal properties were also investigated.
The Förster radius for energy transfer from naphthalene to anthracene in polyesters with oxyethylene spacers
Authors: Bravo Julio , Mendicuti Francisco , Saiz Enrique , Mattice Wayne L.
Published: April 2003

Model compounds for a series of polyesters in which 3,6,9, and 12‐rotatable CH2O and CH2CH2 bonds separate rigid units have been studied using the efficiency of nonradiative singlet energy transfer from naphthalene to anthracene. The model compounds have the structure naph‐CO(OCH2CH2)mOOC‐anth with m of 1–4, where naph and anth denote 2‐naphthyl and 9‐anthranyl groups, respectively. This series of compounds covers a larger range of potential separation of the two chromophores than was possible in an earlier study, in which the flexible spacers consisted of 2–6 methylene units. The nonradiative singlet energy transfer has an efficiency that depends on the solvent viscosity and on m. The theoretical analysis employs a rotational isomeric state model for the conformations of these molecules. The Förster radius for transfer from naphthalene to anthracene in this system is 16 ± 2 Å, and is nearly independent of whether the spacers are constructed from oxyethylene or methylene units.
Polymer bound chromogenic crown ethers for optical ion‐detection devices
Authors: Klok Harm‐Anton , Möller Martin
Published: April 2003

The concept of photoinduced electron transfer has been explored for the development of polymeric transducers for optical ion‐detection devices. For this purpose, a series of N‐(9‐anthrylmethyl)monoaza‐18‐crown‐6 substituted poly(methacrylate)s were prepared, which differ in the chemical nature of the backbone. The fluorescent signaling in these systems is based on disturbances, upon complexation of K⊕, in the competition between de‐excitation pathways of fluorescence and photoinduced electron transfer. The sensitivity and the ultimate enhancement of the fluorescence of these materials upon complexation of K⊕ were found to be strongly influenced by the chemical structure of the polymer backbone.
Local chain motions in a dilute solution of phenolphthalein poly(ether sulfone)
Authors: Wang Jianli , Zhang Jianguo , Li Binyao , Feng Zhiliu
Published: April 2003

13C and 1H relaxation times were measured as a function of temperature in two magnetic fields for dilute solutions of phenolphthalein poly(ether sulfone) (PES‐C) in deuterated chloroform. The spin‐lattice relaxation times were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (J. S. model). The phenyl group rotation is treated as a stochastic diffusion by the J. S. model. The restricted butterfly motion of the phenyl group attached to the cardo ring in PES‐C is mentioned but is not discussed in detail in this work. Correlation times for the segmental motion are in the picosecond range which indicates the high flexibility of PES‐C chains. The correlation time for the phenyl group internal rotation is similar to that of the segmental motion. The temperature dependence of these motions is weak. The apparent activation energy of the motions considered is less than 10kJ/mol. The simulating results for PES are also reasonable considering the differences in structure compared with PES‐C. The correlation times and the apparent activation energy obtained using the J. S. model for the main chain motion of PES‐C are the same as those obtained using the damped orientational diffusion model and the conformational jump model.
Modification of poly(L‐lactides) by blending: mechanical and hydrolytic behavior
Authors: Hiljanen‐Vainio Mari , Varpomaa Paula , Seppälä Jukka , Törmälä Pertti
Published: April 2003

Two different poly(L‐lactides) (PLLAb and PLLAa) were blended with poly(ε‐caprolactone) (PCL) and an elastic poly(ε‐caprolactone/L‐lactide) P(CL/L‐LA) copolymer to modify the mechanical properties of PLLA. Blends of both PLLAs with 20 wt.‐% of PCL were prepared. PLLAa was blended with 20 wt.‐% of P(CL/L‐LA) copolymer, and blends of PLLAb and P(CL/L‐LA) copolymer were made with copolymer contents of 5, 10, 20 and 30 wt.‐%. The tensile properties and impact and shear strengths were determined as a measure of the mechanical properties. The hydrolytic behavior of the blends was investigated, and the changes in shear strength as a function of hydrolysis were followed. The structure of the hydrolyzed samples was studied by means of scanning electron microscopy (SEM). The properties of PLLA changed considerably when blended with PCL or P(CL/L‐LA) copolymer. An increasing amount of copolymer in PLLAb decreased tensile modulus and shear strength, but improved the strain and impact strength. In hydrolysis, blends containing PLLAa degraded slower than blends of PLLAb because of the higher initial molar mass and purity of PLLAa. The molar masses of PLLAb blends decreased dramatically, and less than 10% of the initial molar masses and shear strengths were left after 12 weeks in vitro. The morphology of the blends affected the degradation. The blends containing P(CL/L‐LA) copolymer had a porous structure which facilitated water absorption into the blend.
Ethylene oligomerization catalyzed with dichlorobis‐(β‐diketonato)zirconium/organoaluminium chloride systems
Authors: Oouchi Kunihiro , Mitani Makoto , Hayakawa Michiya , Yamada Tohru , Mukaiyama Teruaki
Published: April 2003

The combination of a dichlorobis(β‐diketonato)zirconium compound 1 and dimethyl‐aluminium chloride was found to be an active catalyst for the oligomerization of ethylene to produce linear C4–C22 α‐olefins. The catalytic activity and the product distribution of the resulting oligomers was influenced by the structure of the β‐diketonato ligands, which affect the electron density at the zirconium center.