bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and side‐chain crystallization of comb‐like polymers obtained from isopropenyl‐1,3,5‐triazines carrying two, three, and four long alkyl groups
Authors: Kunisada Hideo , Yuki Yasuo , Kondo Shuji , Goto Ken‐ichi 
Published: April 2003

AbstractMonomers containing several octadecyl groups, e.g., 2‐isopropenyl‐4,6‐bis(octadecylamino)‐1,3,5‐triazine (2), 2‐dioctadecylamino‐4‐isopropenyl‐6‐octadecylamino‐1,3,5‐triazine (3) and 2,4‐bis(dioctadecylamino)‐6‐isopropenly‐1,3,5‐triazine (4) were prepared by the alkylation reaction of 2,4‐diamino‐6‐isopropenyl‐1,3,5‐triazine (1) with 1‐bromooctadecane in the presence of sodium hydride. In the free‐radical homopolymerization of these monomers, the polymer yield of 3 was lower than that of 2 due to a decrease in the ceiling temperature, and the polymerization of 4 did not proceed. Copolymerizations of these monomers with styrene or methyl methacrylate were carried out and the monomer reactivity ratios (r1 and r2) were determined. The monomer reactivity decreased with increasing the number of octadecyl groups in the monomers. Crystallinity of the octadecyl side chains in the resulting comb‐like polymers was evaluated by differential scanning calorimetry.
Preparation and characterization of poly(methyl‐3,3,3‐trifluoropropylsiloxane‐co‐dimethylsiloxane)
Authors: Kobayashi Hideki , Nishiumi Wataru 
Published: April 2003

AbstractMethyl‐3,3,3‐trifluoropropylsiloxane (F)‐dimethylsiloxane (D) random and block copolymers were prepared. The random copolymers were prepared by equilibrium copolymerization starting from a mixture of cyclic F and D siloxanes with potassium silanolate as the catalyst. The F‐D block copolymer was prepared by sequential anionic living polymerization of strained cyclic trisiloxanes using butyllithium as initiator, first polymerizing D3 then adding F3 after consumption of D3. The copolymer microstructure was established by means of 29Si NMR, differential scanning calorimetry (DSC), and gel‐permeation chromatography (GPC). Characteristic glass transition temperature (Tg) shifts were observed depending on the F:D ratio of the random copolymers. It was demonstrated that the tensile strength of the poly(methyl‐3,3,3‐trifluoropropylsiloxane)‐poly(dimethylsiloxane) (PTFPMS‐PDMS) blend system was improved when either of the copolymers was added.
Synthesis of chromophore‐labelled polystyrene/poly(ethylene oxide) diblock copolymers
Authors: Caldérara Frédŕic , Hruska Zdenek , Hurtrez Guy , Nugay Turgut , Riess Gérard , Winnik Mitchell A. 
Published: April 2003

AbstractPolystyrene/poly(ethylene oxide) diblock copolymers bearing anthracene or phenanthrene groups at the block junctions were synthesized by sequential anionic polymerization using cumylpotassium as initiator. Labelled copolymers were characterized by means of ultraviolet (UV) spectroscopy, gel‐permeation chromatography (GPC) and 1H NMR spectroscopy. The solutions of the prepared copolymers in water and 1,2‐dichloroethane/methanol mixtures were studied by fluorescence spectroscopy. The intermolecular energy transfer process confirms the presence of organized structures (micelles) in solutions.
NMR evidence of the block structure of poly(methyl methacrylate)‐block‐poly(ethyl acrylate) prepared by group transfer polymerization
Authors: Kříž Jaroslav , Masař Bohumil , Vlček Petr 
Published: April 2003

AbstractThe structure of poly(methyl methacrylate)‐block‐poly(ethyl acrylate) prepared by group transfer polymerization was studied by 1H and 13C 1 D and 2D NMR methods including SINEPT, COSY, LR H‐H‐C RELAY and COLOC using model homopolymers of methyl methacrylate (MMA) and ethyl acrylate (EA) of a length equal to that of the blocks and prepared under the same conditions. The 1H and 13C spectra of the copolymer are shown to be a superposition of the respective spectra of the homopolymers, with the exception that the copolymer lacks the terminal group present in the MMA homopolymer and the initiating group of the EA polymer. Moreover, a new minor signal is found in the CH2 region of the copolymer which is shown to belong to the link of the blocks. The existence of a direct link between the blocks is further supported by the results of 1D and 2D coherence transfer methods, especially, those using the newly modified DS INEPT and H‐C‐C RELAY pulse sequences.
The polymerization of acrylonitrile by tetraaziridotitanium(IV)
Authors: Billingham Norman Ć. , Lees Peter D. 
Published: April 2003

AbstractThe polymerization of acrylonitrile by tetraaziridotitanium(IV) is very much more rapid than the same reaction initiated by tetrakis(dimethylamino)titanium(IV). The former reaction has dead‐end kinetics but both can be fitted with the same kinetic scheme. Polymerization is accompanied by initiator wastage via unidentified reactions. Insertion of saturated nitriles into the TiN bonds of tetrakis(dimethylamino)titanium can be monitored by NMR and gives products with high activity for the polymerization of acrylonitrile. Despite their high reactivity towards acrylonitrile none of the initiators will polymerize less reactive monomers.
Solution properties and light scattering measurements of poly(2,5‐pyrimidinediylterephthalamide)
Authors: Oertli Alfred G. , Schurtenberger Peter , Suter Ulrich W. 
Published: April 2003

AbstractA Series of chains of different molecular weight of the fully aromatic polyamide poly(2,5‐pyrimidinediylterephthalamide)IUPAC name: poly(2,5‐pyrimidinediyliminoterephthaloylimino).
(PPYMT) in the solvents 96 wt.‐% sulfuric acid and methanesulfonic acid have been characterized by means of static and dynamic light scattering, dilute solution viscosimetry and measurements of the critical polymer volume fraction for the onset of a nematic phase. The experimental results are in good agreement with a model of stiff worm‐like chains for the solution conformation of PPYMT, and the persistence length is estimated to be ca. 150 Å (lower limit: 50–100 Å).
Comb‐like poly(aryl‐ether‐ketones) containing naphthalene moieties in the main chain
Authors: Ritter Helmut , Thorwirth Ralf , Müller Gerd 
Published: April 2003

Abstract1,5‐Naphthalenediol was alkoxylated with 1‐alkyl bromides containing 3‐16 C‐atoms and then acylated with 4‐fluorobenzoyl chloride under Friedel‐Crafts conditions in 4‐ and 8‐position of the naphthalene ring. These new difluorides (3a–d) were condensated with hydroquinone, bisphenol‐A and 4,4′‐biphenyldiol, yielding the corresponding poly(aryl‐ether‐ketones) 4a–d, 5a–d and 6a–d. The melting points of both the difluorides and the poly(aryl‐ether‐ketones) decreased with increasing side chain length. The molecular weights of some of the poly(aryl‐ether‐ketones) were characterized by GPC measurements coupled with viscosity determinations, and they were found to be in the range of M̄n from 10 000 to 19 000. From polymer solutions, solid and mechanically stable films were produced on a glass plate by evaporating the solvents. A perpendicular order of the phenyl ring was calculated by the MMX method.
Aldol‐group‐transfer polymerization of 2‐phenyl‐1,3,2‐dioxaborole. Preparation of graft and comb‐like polymers
Authors: Wulff Günter , Birnbrich Paul 
Published: April 2003

AbstractThe aldol‐group‐transfer polymerization of 2‐phenyl‐1,3,2‐dioxaborole is described. By initiation with aldehydes the molecualr weights of the polymers can be controlled through the mole ratio of initiator to monomer, ranging between 700–130000. The phenylboronic ester groups can be removed from the polymer, yielding polymers carrying a hydroxyl group at each carbon atom of the chain. It was also possible to prepare polymerizable macromonomers by initiation with 4‐vinylbenzaldehyde. Polymerization of the macromonomers by radical initiation yields comb‐like arrangements. Similar polymers can be obtained by grafting phenyl‐1,3,2‐dioxaborole onto a polymer containing benzaldehyde moieties in the side chains.
Synthesis and properties of aromatic polyamides of 2,3‐bis(4‐aminophenoxy)naphthalene
Authors: Yang Chin‐Ping , Chen Wen‐Tung 
Published: April 2003

AbstractA new polymer‐forming diamine, 2,3‐bis(4‐aminophenoxy)naphthalene, was synthesized in two steps from the condensation of 2,3‐naphthalenediol and p‐chloronitrobenzene, giving 2,3‐bis(4‐nitrophenoxy)naphthalene, followed by the reduction with hydrazine/Pd‐C system. A series of novel aromatic polyamides (aramids) were synthesized by direct polycondensation of the diamine with various aromatic dicarboxylic acids in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. These aramids have inherent viscosities of 0,70–1,48 dL/g and were obtained in quantitative yield. The polymers are generally soluble in a wide range of solvents, such as N,N‐dimethylacetamide, NMP, dimethyl sulfoxide, pyridine, and tetrahydrofuran, and afford transparent, flexible, and tough films upon casting from their solutions. The glass transition temperatures of these aramids are in the range of 242−267°C, and the 10% weight loss temperatures are above 503°C in nitrogen and above 496°C in air.
Investigation of poly(arylenevinylene)s, 40. Electrochemical studies on poly(p‐phenylenevinylene)s
Authors: Helbig Manfred , Hörhold Hans‐Heinrich 
Published: April 2003

AbstractDifferential pulse polarography (DPP) and cyclovoltammetry (CV) were conducted to study the redox behaviour of poly(p‐phenylenevinylene) (PPV; E = 0,76 V; E = −1,74 V) as well as of three insoluble PPV‐derivatives and four soluble aryl‐substituted PPV's. Oxidation studies of DP‐PPV, DMOP‐PPV and DPOP‐PPV in comparison with two series of the oligomeric model compounds 1a–e and 2a–d lead to the conclusion that for DMOP‐PPV (E = 0,98, 1,24,1,31 V) and DPOP‐PPV (E = 1,10, 1,29, 1,44 V) three distinct oxidation stages exist, which are reversibly occupied and represent 1/2, 1 and 2 positive charges per repeating unit. In DP‐PPV two oxidation stages representing 1/2 and 1 positive charges were found to be reversibly occupied (E = 1,17, 1,69 V), whereas at higher potentials irreversible dehydrocyclization occurred.
Synthesis of poly(bisphenol‐a carbonate)‐graft‐polystyrene via the macromonomer technique
Authors: Rohrbach Peter , Heitz Thomas , Keul Helmut , Höcker Hartwig , Buning Gerhard H. Werumeus 
Published: April 2003

AbstractThe synthesis of poly(bisphenol‐A carbonate)‐graft‐polystyrene with grafts of definite, predictable, nearly identical length was achieved using the macromonomer technique, i.e., copolycondensation of polystyrene macromonomers, carrying aromatic hydroxyl function, with bisphenol‐A and triphosgene in pyridine/methylene chloride solution. The incorporation of the macromonomer into the polycarbonate backbone was examined both qualitatively and quantitatively. The copolycarbonate show — in the contrast to polystyrene/polycarbonate blends of comparable molecular weights and composition — only one glass transition temperature, which proved to be dependent on the polystyrene content, following the Fox equation. The title compounds exhibit reduced stress‐induced birefringence compared to polycarbonate.
Polylactones, 24. Polymerizations of racemic and meso‐D,L‐lactide with AlO initiators. Analyses of stereosequences
Authors: Kricheldorf Hans R. , Boettcher Caroline 
Published: April 2003

AbstractRacemic D,L‐lactide and meso‐D,L‐lactide were polymerized with four different initiators: Al(isopropoxide)3, AIEt3/neopentyl alcohol (1 : 1, mole ratio), AIEt3/(+)‐menthol (1 : 1, mole ratio) and methylaumoxane. Most polymerizations were conducted in xylene at 60, 90 and 120°C, but at 60°C the yields were below 10%. 1H NMR end‐group analyses revealed the formation of alkyl ester end‐groups from all Al‐alkoxide initiators, in agreement with an insertion mechanism. The highest molecular weights were obtained with the methylalumoxane initiator. The stereosequences of the isolated poly(D,L‐lactide)s were analyzed by 1H and 13C NMR spectroscopy on the basis of tetrad effects. poly(D,L‐Iactide)s prepared from racemic D,L‐lactide suggest a stereospecific polymerization favoring syndiotactic growing steps. In the case of meso‐D,L‐lactide all polymerizations follow Bernoullian statistics. Transesterification is poor or absent at temperatures ≤ 120°C. However, random stereosequences may be obtained by bulk polymerizations at 180°C. DSC measurements revealed that the glass transition temperature mainly depends on the molecular weight and not on slight differences in the stereosequences.
Microstructure determination of styrene/ethyl acrylate copolymers by NMR spectroscopy and its correlation with glass transition temperature
Authors: Brar Ajaib Singh , Sunita  
Published: April 2003

AbstractStyrene/ethyl acrylate (S/E) copolymers of different compositions were prepared by bulk polymerization using benzoyl peroxide as an initiator. Copolymer compositions were determined from NMR spectra and reactivity ratios r1 and r2 were calculated using a non‐linear least‐squares errors‐in‐variables method (EVM) which gives more reliable values of r1 and r2. The copolymerization parameters such as terminal, penultimate reactivity ratios, diad concentrations, conditional probabilities, number‐average sequence lengths and run numbers in the copolymers were calculated by evaluating 13C{1H} NMR spectra. The observed sequence concentrations of triads as determined from 13C{1H} NMR spectra were in good agreement with those calculated from the reactivity ratios. The coisotacticity parameter (σ) was calculated from NMR spectroscopy data using the oxymethylene resonance signal in 1H NMR spectra. The glass transition temperatures (Tg) of various copolymers were obtained from Barton's equation (using diad relation) and are in agreement with those determined by means of differential scanning calorimetry.
Synthesis of nonlinear optical polymers functionalized with 4‐amino‐4′‐cyanostilbene and ‐azobenzene dyes. Second harmonic generation in corona‐poled thin films
Authors: S'Heeren Gert , Persoons André , Rondou Philippe , Wiersma John , van Beylen Marcel , Samyn Celest 
Published: April 2003

AbstractThe synthesis and susceptibilities χ and χ to two series of polymethacrylates functionalized with 4‐dialkylamino‐4′‐cyanoazobenzene and 4‐dialkylamino‐4′‐cyanostilbene dyes are reported. The monomeric dyes were homo‐ and copolymerized with methyl methacrylate in various ratios, to produce polymers useful for nonlinear optical (NLO) applications. The second‐order nonlinear optical properties of corona‐poled aligned polymers were evaluated by second harmonic generation measurements. The χ results for the azo‐dye polymers are in the range of 25–324 · 10−9 esu, and for the stilbene‐dye polymers in the range of 42–57 · 10−9 esu, depending on the functionalisation degree of the copolymers. The poled films do not show a significant decay in the second harmonic signal after four months.
13C cross polarization/magic‐angle spinning NMR and infrared spectroscopic study of poly(ε‐caprolactam) and of poly(ε‐caprolactam)/polystyrene blends
Authors: Schmidt Pavel , Dybal Jiří , Straka Jaroslav , Schneider Bohdan 
Published: April 2003

AbstractInfrared and 13C cross polarization/magic‐angle spinning nuclear magnetic resonance (13C CP/MAS NMR) spectra and T relaxation times of differently treated poly(ε‐caprolactam)1Systematic IUPAC name: poly[imino(1‐oxohexamethylene)].
(PCL) and of poly(ε‐caprolactam)/polystyrene blends were measured and the fractions of the α‐ and α‐crystalline and mesomorphous PCL forms were determined. The amounts of the α‐form obtained from the infrared and 13C CP/MAS NMR spectra are in agreement. In the blends, the fraction of the PCL α‐crystalline form is higher as compared with extruded pure PCL. The existence of a single T parameter for PCL in each of the samples indicates small dimensions of the crystalline regions; the obtained T values correspond to the PCL phase composition.
Anionic polymerization of ε‐caprolactam, 63. Catalysis by potassium‐graphite intercalate
Authors: Puffr Rudolf , Vladimirov Nikolay 
Published: April 2003

AbstractThe overall rate constants of the isothermal bulk polymerization of ε‐caprolactam were determined for the non‐activated polymerization with a heterogeneous catalyst (KC24) and a homogeneous catalyst (potassium ε‐caprolactamate), and also for the corresponding polymerizations activated with N‐benzoyl‐ε‐caprolactam. In comparison to the homogeneous catalysis, the non‐activated polymerizations with KC24 are slower, proceed with an induction period and give polyamide with a low molecular weight that does not diminish when the polymerization approaches equilibrium.
Unsteady diffusion kinetics of Ziegler‐Natta heterogeneous catalyst polymerization, 4. Prediction of experimental results of propylene/ethylene/1‐hexadecene terpolymerization
Authors: Wang Jian‐Guo , Chen Hai , Huang Bao‐Tong 
Published: April 2003

AbstractThe prediction, based on unsteady diffusion kinetics, of the enhancement of reactivity and incorporation of 1‐hexadecene in its copolymerization with propylene on adding a small amount of ethylene (increase from 5,2 mol‐% to 10,8 mol‐% when 2% of ethylene was added, and to 16, 1 mol‐% when 5% was added) was verified in the terpolymerization of propylene/ 1‐hexadecene/ ethylene on a commercial Solvay‐type δ‐TiCl3 catalyst. The catalyst efficiency was thus also increased. These augmentations originate from the increase in diffusion coefficient of 1‐hexadecene at the catalyst surface when the PP crystallinity decreases on introduction of ethylene. Calculation based on unsteady diffusion kinetics showed that the order of diffusion coefficients ethylene > propylene > 1‐hexadecene is reversed as the monomer concentration increases when the monomers are not at their equilibrium concentration. Sequence distribution as determined by means of 13C NMR revealed a tendency of blocky structure rather than a Bernoullian one. The terpolymer compositions obtained by means of an IR method developed in this work conform rather well with the NMR results. Results in this work not only support the unsteady diffusion kinetics but also provide a new route to prepare olefinic copolymer rubbers with heterogeneous titanium catalysts.
Preparation of polyvinylamine from polyacrylamide: a reinvestigation of the hofmann reaction
Authors: Achari Ahmida El , Coqueret Xavier , Lablache‐Combier Alain , Loucheux Claude 
Published: April 2003

AbstractThe Hofmann modification of polyacrylamide to yield vinylamine homo‐ or copolymers was reinvestigated in order to determine the real scope of a procedure of great potential interest in polymer chemistry. The conditions of the treatment by sodium hypochlorite followed by concentrated sodium hydroxide at low temperature (0°C) were adjusted to avoid or to limit side‐reactions between pendant reactive groups. A broad range of initial mole ratio a of sodium hypochlorite per initial amide function (0,05 < a < 1,10) was explored. The reported procedure allows to prepare in excellent yield water‐soluble polymers of controlled vinylamine content. The presence of carboxylic acid function (2 – 10 mol‐%) on the main chain, observed with low values of a, or of urea functions (1 – 5 mol‐%) observed with the highest values of a, was evidenced on the basis of analytic and spectroscopic measurements. Simple mechanistic consideration allow to propose rational schemes accounting for the side‐reactions leading to the detected minor functionalities.
Spontaneous polymerization of amphiphilic vinyl monomers, 4. Spontaneous polymerization of methacrylic derivatives of quaternary ammonium bromides with a long alkyl chain
Authors: Yasuda Yutaka , Rindo Katsuhiko , Tsushima Rikio , Aoki Shuzo 
Published: April 2003

AbstractAmphiphilic surface active vinyl monomers (alkyl‐2‐methacryloyloxyethyldimethylammonium bromides) with a long alkyl chain (C8/, C12, C14, C16, and C18) were investigated with respect to their polymerization behavior in the absence of an initiator. These monomers polymerized spontaneously in water, through a free‐radical mechanism, except for the ‘C8 monomer’. In the polymerization of the ‘C16 monomer’, the polymer yield depended on polymerization temperature, and the intrinsic viscosity of the resulting polymer varied with the initial concentration of the monomer just like in ordinary polymerization. The ‘C18 monomer’, having low reactivity, became highly polymerizable upon mixing with a quaternary surfactant (dodecyl‐2‐isobutyryl‐oxyethyldimethylammonium bromide) in a particular mole ratio, owing to a change in the monomer aggregation state. In benzene, all of the quaternary methacrylates polymerized spontaneously, too. It is obvious that formation of monomer aggregates, micelles or reverse micelles is essential for the spontaneous polymerization. The spontaneous polymerization of other quaternary monomers, having a hexadecyl group and a polymerzable acryloyl, acrylamido, or methacrylamido moiety, did also occur, yet with lower rate than in case of the methacrylate.
Poly(ether‐ketone)s with indan structure elements
Authors: Maier Gerhard , Yang Dazhong , Nuyken Oskar 
Published: April 2003

Abstract1,1,3‐Trimethyl‐3‐[4‐(4‐fluorobenzoyl)phenyl]‐6‐(4‐fluorobenzoyl)indan (5a) and the isomer 5b were synthesized by Friedel‐Crafts acylation of 1,1,3‐trimethyl‐3‐phenylindan with 4‐fluorobenzoyl chloride. This reaction yields a mixture of two isomer. The pure isomer as well as the isomer mixture were employed in the synthesis of poly(ether‐ketone)s via nucleophilic displacement of activated aromatic halogens by different diphenols. The influence of the indan structure element on the polymer properties such as glass transition temperature, crystallinity, solubility, and thermal stability was investigated.
Macrocyclic peptides, 8. Enantiomeric differentiations of various (R)‐ and (S)‐ ammonium and (R)‐ and (S)‐α‐amino acid ester salts by macrocyclic pseudopeptides
Authors: Miyake Hiroyuki , Kojima Yoshitane , Yamashita Tetsushi , Ohsuka Akio 
Published: April 2003

AbstractThe interactions of the hydrobromides of (R)‐ and (S)‐alanine‐N‐methylanilides (1) with 24‐, 27‐ and 36‐membered ring pseudopeptides (H‐24, H‐27 and H‐36, respectively) derived from glycine and (2S,3′ S)‐4‐methyl‐2‐(2′‐oxo‐3′‐isobutyl‐1′‐piperazinyl)pentanoic acid were studied by means of 1H and 13C NMR measurements in CDCl3. It was found from these results that H‐24 and H‐27 distinguished (R)‐ and (S)‐isomers of 1, while H‐36 did not entirely. Moreover, the enantioface‐differentiating abilities of these cyclic peptides were investigated by means of 1H NMR measurements in CDCI3 using (R)‐ and (S)‐1‐phenylethylammonium and (R)‐ and (S)‐p‐methoxy‐1‐phenylethylammonium bromides as the substrates, showing that the enantio‐selectivity of H‐36 is superior to those of H‐24 and H‐27. Also, the chiral recognition ability of H‐24 for the hydrochlorides of (R)‐ and (S)‐alanine (Ala), ‐leucine (Leu), ‐methionine (Met), ‐phenylalanine (Phe), ‐proline (Pro) and ‐valine (Val) methyl esters were examined by 1H and 13C NMR measurements in CDCl3. Among these hydrochlorides, HCl · PheOCH3 was distinguished more effectively with H‐24.