bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redox‐initiated radical polymerization of 2‐hydroxyethyl methacrylate, 3. Copolymerization with nine monomers, effect of structure and media on the reactivity of monomers
Authors: Mathew‐Krotz Jainamma , Mahadevan Venkatanarayana 
Published: April 2003

AbstractCopolymerization of 2‐hydroxyethyl methacrylate (HEMA) with eight acrylic monomers and vinyl acetate using redox initiators was carried out in DMF and in aqueous medium. Reactivity ratios were calculated according to the general copolymerization equation using Fineman‐Ross, Kelen‐Tüdős and the YBR methods. The results indicate that reactivity of the methacrylates towards growing HEMA radicals decreased in the order, methyl methacrylate > 2‐dimethylaminoethyl methacrylate > 2,3‐epoxypropyl methacrylate. Reactivity of the acrylates decreased in the order butyl acrylate > ethyl acrylate > methyl acrylate. In the HEMA‐acrylate systems, the intrinsic viscosity of the copolymers decreased with increasing content of the acrylates in the copolymer. On the other hand, the intrinsic viscosity of the copolymers of HEMA‐MMA showed an increasing trend with increasing content of MMA in the copolymer. Changing the polymerization medium from DMF to water resulted in copolymers having a higher HEMA content.
Synthesis and characterization of polymers containing 4‐cyanobiphenyl‐based side groups for nonlinear optical applications, 3. Poly(p‐chloromethylstyrene) derivatives
Authors: Noël Claudine , Gangadhara  , Ching Kathlen Chane , Large Maryanne , Reyx Danièle , Kajzar François 
Published: April 2003

AbstractPoly[p‐(4′‐cyanobiphenyl‐4‐yloxymethyl)styrene]s (PCBMS) were prepared by chemical modification of poly(p‐chloromethylstyrene) with the sodium salt of 4‐cyano‐4′‐hydroxybiphenyl or free radical polymerization of p‐(4′‐cyanobiphenyl‐4‐yloxymethyl)‐styrene (CBMS). The latter method appeared to be a good one for the preparation of polymers with high glass transition temperature and high chromophore content if performed in dimethyl sulfoxide. There was no real evidence for liquid crystal properties in the resulting polymers, which resemble typical amorphous isotropic polymers. This indicates that these polymers should be considered to be polyethylene containing the benzyl ether of 4‐cyano‐4′‐hydroxybiphenyl as the mesogenic group attached directly to the backbone, and not as polystyrenes containing the cyanobiphenyl group attached to the backbone through a OCH2spacer. Some preliminary Corona poling experiments were performed, and the second harmonic generation coefficients d31 and d33, were measured by Maker fringe analysis. Interestingly, the ratio of d33 to d31 was found to be 6, which is much larger than the value of 3 predicted by the molecular statistical model for electric field poling of isotropic systems. This was attributed to conformational constraints on chromophore ordering as expected in such polymers containing no flexible spacer.
Gas sorption in substituted polyacetylenes
Authors: Bondar Valeri , Alentiev Alexander , Masuda Toshio , Yampolskii Yuri 
Published: April 2003

AbstractSorption of several gases (He, N2, Ar, CH4, CO2, C2H6) was measured in an extended pressure range (up to 100 at m) in two glassy polyacetylenes: poly[1‐phenyl‐2‐(p‐tert‐butylphenyl)acetylene] and samples of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP), which were partly oxidized during long term storage in the ambient atmosphere. Sorption isotherms are concave to the pressure axis and can be described by the dual mode sorption model. Both polyacetylenes are distinguished by relatively large Langmuir sorption capacity parameters C′H. However, the C′H values and solubility coefficients are significantly lower than those of fresh PTMSP.
Polylactones, 38. Polymerization of L‐lactide with Fe(II) lactate and other resorbable Fe(II) salts
Authors: Kricheldorf Hans R. , Damrau Dirk‐Olaf 
Published: April 2003

AbstractCommercial FeCl2 and Fe(II) glycolate, Fe(II) L‐lactate or Fe(II) L‐mandelate were used as initiators for the polymerization of L‐lactide. All polymerizations were conducted in bulk at 150°C, because no conversion was observed in bulk at 120°C. The Fe(II) lactate was found to be more reactive than FeCl2, and it yielded slightly higher molecular weights than all other initiators. Under the optimum conditions, viscosity average molecular weights (M̄v) around 50 000 and yields above 90% were obtained. However, slight racemization (2–5%) of the isolated poly(L‐lactide) was also observed under most circumstances. Characterization of unreacted monomer proved that the racemization mainly involves the monomeric lactide due to its higher CH acidity.
Mobile macromolecular carriers of ionic substances, 1. Transport of heavy metal ions by polymer analogues of teichoic acids
Authors: Wódzki Romuald , Kałużyński Krzysztof , Kłosiński Paweł 
Published: April 2003

AbstractBioanalogous organic polyphosphates (PP) and polymer ion‐exchange membranes (IEM) were used to arrange a membrane system for the transportation of Zn(II), Mn(II), Cu(II), Co(II) and Ni(II) ions. The system consists of three membranes separating a feed and a strip solution with metal sulfates and sulfuric acid, respectively:

Poly(trimethylene phosphate), α‐hydroxy‐ω‐(2‐ethylhexyl)poly(trimethylene phosphate), poly(1,2‐glycerol phosphate) and poly(2,3‐acetoxyglycerol phosphate) were used as ionic carriers for mimicking some transport functions of natural teichoic acids. These polyelectrolytes were found to facilitate the exchange‐diffusion process of heavy metal ions and to exhibit fluxes in the range 3,5 · 10−9 – 6 · 10−9 mol M(II)/(cm2 · s). The specific stationary fluxes typically change in the order JCu > JCo > JNi > JMn > JZn. The observed transport preference is consistent with the affinity order of teichoic acids or the bacteria cell wall toward Cu(II), Mn(II) and Zn(II).
Solid state behaviour and properties of compression moulded poly(ether ether ketone)/polysulfone blends
Authors: Arzak Andone , Eguiazábal José Ignacio , Nazábal Jon 
Published: April 2003

AbstractPoly(ether ether ketone) (PEEK)/polysulfone (PSF) blends were obtained by kneading and compression moulding over the whole composition range. The blends were then both quenched and slowly cooled. Both cooling procedures provided blends with two practically pure phases and good small strain properties. Ductility was worsened, as expected, in slowly cooled blends. However, in quenched blends, which provided less phase‐separated fracture surfaces and no very different free volume, ductility showed unexpected good values which are tentatively attributed to common features of the chemical structure of both blend components.
Performance‐improved photo‐driven liquid crystal cell using azobenzene‐grafted ladderlike polysiloxane as command layer
Authors: Tang Yongxin , Xie Ping , Liu Dongsheng , Zhang Rongben , Zhang Zhiyong , Yao Naiyan 
Published: April 2003

AbstractIn comparison with our previous work1, the stability of the command layer based on an azobenzene‐grafted ladderlike copoly(hydromethylsilsesquioxane) (PMHSQ) coated on quartz plates, is improved evidently by linking through a coupling reagent (triethoxyvinylsilane) to the backbone. The liquid crystal (LC) cell filled with 4‐cyano‐4′‐pentylbiphenyl (5CB) exhibits a much faster switching behavior, so that activation is unnecessary. The results show that the photo‐driving behavior is strongly dependent on the nature of the LCs as well as the structure of the azobenzene (Az) side chains. The cyanobiphenyl type LC (5CB) with a strong polarity sandwiched between such two command layers changes the alignment between homeotropic and planar modes while TC3 (mainly phenylcyclohexanecarboxylates) with a weak polarity fails to do so. The Az units with longer spacer are more effective to induce changes of the LC alignment. It was found that the phenyl benzoates are not stable to ultraviolet (UV) irradiation and that they absorb the UV light strongly. Thus, we suppose that such negative aspects as the necessary activation and the slow response of our previously studied photo‐driven LC cell using commercial TEB‐30 (mainly cyanobiphenyls and phenyl benzoates as well) are caused by the phenyl benzoate components.
Network parameters and scaling behaviour of chemically crosslinked hydrogels of poly[(N,N‐dimethylacrylamide)‐co‐(methyl methacrylate)]
Authors: Liu Yan , Mao Runsheng , Huglin Malcolm B. , Holmes Paul A. 
Published: April 2003

AbstractCopolymerization of N,N‐dimethylacrylamide (DMA) with methyl methacrylate in both the presence and absence of ethylene dimethacrylate (EDMA) was effected to very high conversion by γ‐irradiation. The resultant xerogels were swollen to equilibrium in water at five specific temperatures within the interval 280.2–338.2 K. The volume fractions of the polymer ϕ2 in the hydrogels were determined from the measured dimensions, and compression‐strain measurements yielded the polymer‐water interaction parameter, the effective crosslinking densities, and Young's moduli Y. The observed dependence of these parameters on copolymer composition and content of EDMA is discussed. A scaling law of the form Y ∝ ϕ is obeyed well by hydrogels of xerogels containing 80 wt.‐% DMA (r = 2.37 ± 0.10) and moderately well by hydrogels of xerogels with only 50 wt.‐% DMA (r = 2.54 ± 0.10).
Bulk polymerization of lactides initiated by aluminium isopropoxide, 2. Beneficial effect of lewis bases and transfer agents
Authors: Degée Philippe , Dubois Philippe , Jérôme Robert 
Published: April 2003

AbstractA high increase in the bulk polymerization rate of L,L‐lactide and racemic D,L‐lactide is observed when aluminium isopropoxide is added with an equimolar amount of a Lewis base, such as triphenylphosphine (P(ϕ)3) and better 4‐picoline (C6H7N). Polylactide of high molecular weight and narrow molecular weight distribution is accordingly prepared in a controlled manner when the Al(OiPr)3 · C6H7N combination is used as an initiator over a large temperature range from 110 to 180°C. A secondary alcohol, such as 2‐propanol, has proved to be an efficient transfer agent, which allows the amount of Al per kg of polylactide to be advantageously reduced. All the alcohol molecules participate in the ring‐opening polymerization even at an [iPrOH]0/[Al] ratio as high as 103.
Bulk polymerization of lactides initiated by aluminium isopropoxide, 3. Thermal stability and viscoelastic properties
Authors: Degée Philippe , Dubois Philippe , Jérôme Robert 
Published: April 2003

AbstractThe thermal stability of poly(L‐lactide) and L/D‐lactide stereocopolymers polymerized in bulk with aluminium isopropoxide as initiator was investigated by thermogravimetric analysis, and time and temperature dependence of molecular weight and polydispersity. Compared to poly(L‐lactide) prepared with stannous octoate as catalyst the thermal stability of polylactides is remarkably enhanced when the ring‐opening polymerization is initiated by aluminium alkoxide. Ultimate mechanical properties and viscoelasticity of these melt‐stable thermoplastics have also been studied in relation to the polyester enantiomeric composition.
Low molecular weight poly(imide‐amide)s obtained by copolycondensation of 4,4′‐methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid in N‐methyl‐2‐pyrrolidone, 3. Absolute number‐average molecular weights and glass transition temperatures
Authors: Sintès‐Zydowicz Nathalie , Pham Quang Tho , Dubois Jacque , Michaud Philippe 
Published: April 2003

AbstractIn depth study of low molecular weight poly(imide‐amide)s (PIA) obtained by copolycondensation of 4,4′‐methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid by 1H and 13C NMR spectroscopy and size‐exclusion chromatography allows the determination of their absolute number‐average molecular weights M̄n, abs. Viscosimetric measurements reveal that, dissolved in N‐methyl‐2‐pyrrolidone, these low molecular weight PIAs should be semi‐rigid because of the presence of very short crystalline chains. By using the semi‐empirical Fox‐Flory relation, the extrapolated glass transition temperature equals 300°C for high molecular weight.
Regularities of γ‐ray induced polymerization for two mesogen‐containing acrylic monomers
Authors: Yuranova Tat'yana I. , Vasilets Victor N. , Kovalchuk Anatolii V. , Savenkov Gennadii N. , Zubarev Evgenii R. , Otmakhova Olga A. , Talroze Raisa V. 
Published: April 2003

AbstractThe possibility of γ‐ray induced polymerization for acrylic monomers with different mesogenic groups is studied. The irradiation of the monomers in the condensed phase shows the competition of decomposition and polymerization in the initial stage of the irradiation process. The influence of the phase state and chemical structure of initial monomers as well as irradiation conditions on the kinetics of γ‐ray induced polymerization and characteristics of resultant polymers is shown and discussed. For irradiation doses below 1 kGy, the phase behavior of monomer‐polymer systems depends on their miscibility below and above the melting point of the initial monomer and is quite different for the monomers investigated.
Preparation and properties of polymides, polyamides and poly(amide‐imide)s based on a spirobichroman dietheramine
Authors: Hsiao Sheng‐Huei , Yang Ching‐Yen 
Published: April 2003

AbstractA novel diamine, 7,7′‐bis(4‐aminophenoxy)‐4,4,4′,4′‐tetramethyl‐2,2′‐spirobichroman (3), was synthesized and used as a monomer with various aromatic tetracarboxylic dianhydrides, dicarboxylic acids and imide ring‐containing dicarboxylic acids, to synthesize polymides, polyamides and poly(amide‐imide)s, respectively. The polyimides 5a–f were prepared from diamine 3 and various aromatic tetracarboxylic dianhydrides via a conventional two‐stage procedure. The intermediate poly(amic acid)s had inherent viscosities of 0,84 – 1,65 dL/g and could be thermally converted into transparent, flexible, and tough polyimide films. Some polyimides were readily soluble in polar solvents such as N,N‐dimethylacetamide (DMAc) and N‐methyl‐2‐pyrrolidone (NMP). The glass transition temperatures (Tg) of these polyimides were in the range of 155–280°C, and 10% weight loss temperatures were above 450°C in air or nitrogen. Furthermore, a series of polyamides and poly(amide‐imide)s having inherent viscosity between 0,40–1,69 dL/g were prepared by direct polycondensation of the diamine 3 with various aromatic dicarboxylic acids and imide ring‐containing dicarboxylic acids. All the polyamides and poly(amide‐imide)s were soluble in a variety of organic solvents and could be solution‐cast into flexible and tough films. They had Tg values in the 150–237°C range and showed no significant weight loss below 400°C in air and nitrogen atmosphere.
Synthesis and optical properties of polyureas with azoaromatic groups in the main chain
Authors: Lee Taek Seung , Kim Dong‐Yu , Jiang Xin Li , Li Lian , Kumar Jayant , Tripathy Sukant 
Published: April 2003

AbstractWe report the synthesis and optical properties of two different polyureas containing azo units in the main chain. The polymers were synthesized from the reaction between a diisocyanate and a diaminoazo compound (4,4′‐diaminoazobenzene) with good yield. These polyureas have glass transition temperatures around 197°C and the films of these polymers show an absorption maximum at 380 nm due to the azo chromophore. Upon polarized laser irradiation at 488 nm, dichroism was optically induced in these main‐chain azoaromatic polymers with a fairly high glass transition temperature. In addition we observed a degree of polar order by corona poling and a build up of second harmonic signal. It is conjectured that the induced order results mainly from an alignment of azo units through trans‐cis‐trans isomerization, as well as from the molecular rearrangement of the polyurea backbone. We further observed regularly‐spaced surface relief gratings on the polyurea film upon exposure to an interference pattern of polarized argon laser beams. Large scale molecular migration in this high glass transition temperature (Tg) polymer at room temperature was achieved for the first time.
Dethreading during the preparation of polyrotaxanes
Authors: Gong Caiguo , Gibson Harry W. 
Published: April 2003

AbstractUsing a diol blocking group, bis(p‐tert‐butylphenyl)bis[p‐(2‐(2‐hydroxyethoxy)ethoxy)phenyl]methane (diol BG 1), a diol with a sterically large core, copolysebacate 30‐crown‐10 (30C10) rotaxanes 8, 9 and 10 were synthesized by incorporating different amounts of 1,10‐decanediol. These copolymeric rotaxanes were characterized by different techniques, including proton NMR spectra, hydrolytic recovery of 30C10 and 2D NOESY. It was found that threaded 30C10 displayed a range of chemical shifts corresponding to the various sequence structures in which it was constrained. In addition, it was proved that the threading efficiency (m/n value, the average number of cyclic molecules per repeating unit) increased with feed ratio of diol BG 1 vs. 1,10‐decanediol. A linear relationship of threading or dethreading degree vs. the percentage of diol BG in the total diol feed was revealed; more BG, less dethreading. The results demonstrate that dethreading occurs during the polycondensation in the absence of BGs.
Branched poly(ethylene glycol) linkers
Authors: Martinez Anthony , Pendri Annapurna , Xia Jing , Greenwald Richard B. 
Published: April 2003

AbstractNovel types of methoxy poly(ethylene glycol) (PEG) linkers (U‐PEG linkers) have been synthesized. These PEG linkers are linear polymers that attach to bioactive agents via a functional group, derived from a 2° alcohol, located in the center of the polymer chain versus the traditional terminal attachment site. These new types of linkers can be prepared with different functional groups (e.g. active ester, succinimidyl carbonate, and carbazate) for selected point of attachment, including ethylene oxide oligomers to provide “stems” when steric factors need to be addressed. Conversion of p‐nitrophenyl carbonates to the more desirable succinimidyl carbonates has also been accomplished by a novel nucleophilic displacement procedure. Modification of proteins with these reagents is easily accomplished and is illustrated by the conjugation of a U‐PEG linker with L‐asparaginase.
Photo‐cross‐linkable poly(p‐phenylene)s. Synthesis, Langmuir‐Blodgett multilayer film properties and pattern formation
Authors: Remmers Marcus , Neher Dieter , Wegner Gerhard 
Published: April 2003

AbstractWe describe the synthesis of a soluble poly(p‐phenylene) (PPP) derivative with hydroxy‐functionalities in the side chain by copolycondensation. This allows the introduction of further functionalities by polymer analogous reactions. Esterification with cinnamoyl chloride leads to a photo‐reactive material that can be processed by the Langmuir‐Blodgett (LB)‐technique to form ultrathin, highly anisotropic films. Photo‐irradiation of these films leads to the formation of cross‐links which lock in the long range ordered structure of the layered films which then becomes stable to temperatures of more than 160°C. Cross‐linking is achieved by direct irradiation into the absorption band of the photo‐reactive units or by use of sensitizers, which gives rise to more efficient reaction conditions with fewer side‐reactions. Since the cross‐linked film is insoluble in all solvents, the photo‐reactive material serves as photo‐resist. Irradiation through a mask followed by dissolution of the non‐cross‐linked film can be used for microlithography at micron scale resolution.
Vapour‐liquid equilibria of concentrated poly(styrene‐co‐butadiene) and poly(styrene‐co‐acrylonitrile) solutions
Authors: Wohlfarth Christian 
Published: April 2003

AbstractIsopiestic vapor sorption measurements were carried out for concentrated solutions of poly(styrene‐co‐butadiene) (SBR) and poly(styrene‐co‐acrylonitrile) (SAN) in a number of aromatic solvents in the temperature range of 343 to 398 K. Henry constants were determined by means of inverse gas‐liquid chromatography in the temperature range of 373 K (SBR) or 423 K (SAN) to 473 K, to obtain additional data at infinite dilution for the solvents, and for two of the monomers, styrene and 1,3‐butadiene, in SBR.The chain‐of‐rotators (COR) equation of state model was used to calculate the thermodynamic quantities applying a group‐contribution approach. In general, good agreement is observed between experimental and calculated results.
Aromatic polyethers with oxadiazole units – synthesis and application in organic light emitting diodes
Authors: Brütting Rita , Pösch Peter , Strohriegl Peter , Buchwald Elke , Brütting Wolfgang , Schwoerer Markus 
Published: April 2003

AbstractDetailed synthetic aspects of new aromatic polyethers containing oxadiazole units are described. They are obtained by the nucleophilic displacement reaction of 2,2‐bis(4‐hydroxyphenyl)hexafluoropropane with 2,5‐bis(4‐fluorophenyl)‐1,3,4‐oxadiazole and 2,5‐bis(4‐fluoronaphthyl)‐1,3,4‐oxadiazole. The purity of the polyethers strongly depends on the reaction solvent. Best results were achieved with Ph2SO2 as compared to N‐methyl‐2‐pyrrolidone (NMP) and 1,3‐dimethyltetrahydro‐2(1H)‐pyrimidinone (DMPU) in the temperature range from 190–200°C. All polyethers are fully soluble in common organic solvents and excellent films are obtained by spin‐coating. High molecular weight polyethers without oligomers were only achieved, when Ph2SO2 was used as solvent. All polyethers are characterized by high thermal stability and high glass transition temperatures. The substitution of bisphenyloxadiazole by bisnaphthyloxadiazole units in the polyethers leads to a bathochromic shift of the absorption from 299 nm to 345 nm. Polyethers with bisnaphthyloxadiazole units show a blue fluorescence with a maximum at 427 nm. The application of these novel polyethers as efficient electron transport and injection layer in bilayer light emitting diodes based on poly(1,4‐phenylenevinylene) is shown. The best results were obtained with oxadiazole polyethers containing bisnaphthyloxadiazole units.
Propene polymerization with zirconocene catalysts supported on siloxane copolymers
Authors: Soga Kazuo , Ban Hoang The , Arai Takashi , Uozumi Toshiya 
Published: April 2003

AbstractA supported version of zirconocene catalysts on siloxane copolymers having 1,2,3,4‐tetramethylcyclopentadienyl (Cp″)‐fluorenyl (Flu) (I) or cyclopentadienyl (Cp)‐fluorenyl (II) groups as substituents was prepared and applied to propene polymerization using methylalumoxane (MAO) or [Ph3C][B(C6F5)4] as cocatalyst. Catalyst (I), which was soluble in toluene, exhibited very low activity, whereas catalyst (II), which was composed of a toluene soluble (Cat‐A) and an insoluble fraction (Cat‐B), displayed a fairly high activity. Both catalysts (A and B) give a mixture of syndiotactic, atactic and a small quantity of isotactic polypropene, with a fraction of syndiotactic pentads ranging from about 50–75%. In contrast, the corresponding non‐supported catalyst gives almost completely atactic polypropene.