bluuebunny/crossref_metadata_2025_split 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractMicrogels 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

AbstractDynamic 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

AbstractThe 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

AbstractThe 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

AbstractTwo 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

AbstractTransfer 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

AbstractActive 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

AbstractCopolycarbonates 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractIsopropoxyethyne (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

AbstractOligodimethylsiloxanes (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

AbstractHomopolymeric 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.