bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzyme‐analogue built polymers, 5. On the specificity distribution of chiral cavities prepared in synthetic polymers
Authors: Wulff G. , Grobe‐Einsler R. , Vesper W. , Sarhan A.
Published: April 2003

By copolymerization of 4‐nitrophenyl α‐D‐mannopyranoside‐2,3;4,6‐di‐O‐(4‐vinylphenylboronate) (1) with ethylene dimethacrylate and methyl methacrylate macroporous polymers were obtained, in which after cleavage of the template, 4‐nitrophenyl α‐D‐mannopyranoside (2), chiral cavities with two boronic acid groups are present. From the dependence of the specificity for the resolution of racemates on the covering percentage of the cavities the frequency distribution of the specificity of the cavities could be deduced. With the distribution curve at hand the factors are discussed, which govern the conservation and the loss of specificity.
Photopolymer design: Photocrosslinkable styrylpyridinium substituted vinyl polymers with absorption maxima from 270 nm to 540 nm
Authors: Borden Douglas G. , Williams Jack L. R.
Published: April 2003

Styrylpyridinium substituted vinyl polymers (6), which are in effect polymeric dyes, may easily be prepared by condensing poly[1‐(1,6‐dimethylpyridinium‐3‐yl)ethylene methyl sulfate] (3) with various aromatic aldehydes (5) using piperidine as catalyst. The preparation of 40 of these polymers prepared from 39 different aldehydes or combinations of them is reported. The spectral data show that they may be designed for maximum absorption almost anywhere from 270–540 nm and with a great variation in photosensitivity and solubility. It is possible to prepare the vinyl substituted styrylpyridinium salts and then polymerize them, or to prepare the styrylpyridine substituted vinyl polymer and then quaternize it, but the preferred method is to prepare the quaternized polymer 3 and then condense it with an aromatic aldehyde 5 to form the styrylpyridinium substituted vinyl polymer 6. These polymers do not require spectral sensitization and, in fact, we found no compounds that act as sensitizers.
13C NMR‐sequenzanalyse, 9. 1HNMR‐ und 13C NMR‐spektroskopische Untersuchungen zur cis/trans‐Isomerie bei niedermolekularen und polymeren Derivaten des Sarkosins
Authors: Kricheldorf Hans R. , Schilling Gerhard
Published: April 2003

The cis/trans‐isomerism of N‐formylsarcosine (1), its trimethylsilyl ester (3) and of N‐acetyl‐, N‐propionyl‐ as well as N‐pivaloyl sarcosine methyl ester (2a–c) was investigated by 1H and 13C NMR spectroscopy in various solvents. It was found that bulky N‐acyl groups favour the trans form, so that in the case of the pivaloyl group no cis form is detectable. The nuclear Overhauser effect of the formyl proton in 1 and 3 was determined in various solvents and the signals of cis and trans form could be assigned thereby unambiguously. The position of cis and trans signals relative to each other was found to be dependent on solvent and molecular structure. 1H and 13C NMR signals of polysarcosine (10) show in dimethyl sulfoxide more than four splittings, so that the influence of three peptide bonds on one signal is detectable. In water, formic acid and trifluoroacetic acid 1H NMR signals of 10 show only simple cis/trans splittings which demonstrate that trans bonds are preferred in these solvents. Sequence polypeptides like (‐β‐Ala‐Sar‐Gly‐)n (5a), (‐β‐Ala‐Sar‐D,L‐Ala‐)n (5b), or (‐β‐Ala‐Sar‐β‐Ala‐)n (5c) can be characterized by 13C NMR but not by 1H NMR spectroscopy. Only 13C NMR signals of the β‐Ala residue attached to the sarcosyl nitrogen show cis/trans splitting, whereas amino acids attached to the sarcosyl CO group do not. The free energy of activation (ΔG) for the rotation round the CO‐Sar bond was determined for some monomeric sarcosine derivatives as well as for 10 and its sequence polypeptides. Nearly identical values were found (ΔG = 75,3–76,2 kJ/mol (18,0–18,2 kcal/mol)) for all products.
Self polycondensation of oxalohydrazide, 2. Studies on the synthesis of poly(hydrazooxalyl)
Authors: Lehtinen Arja
Published: April 2003

A series of poly(hydrazooxalyl)s (2) is prepared by self polycondensation of oxalohydrazide (1a) and by polycondensation of various derivatives of oxalic acid with 1a or hydrazine hydrate under a variety of reaction conditions. The molecular weights of the polymers were found to remain low. IR spectroscopy, X‐ray diffraction, and thermogravimetry were used to study the structure and thermal properties of the prepared polymers. The structure and properties of the polymers were found to depend largely on the monomers and the reaction conditions used in the synthesis, most polymers being partially cyclodehydrated and semicrystalline. 2 seems to possess an extended planar zigzag chain conformation similar to that of polyamides of aliphatic acids, although several crystalline modifications were observed for this polymer. It could also be enolized with strong bases and behaves like a polyelectrolyte in aqueous base solutions.
Studies on aqueous polymerization of acrylamide. Potassium persulfate/2‐mercaptoethylamine hydrochloride redox system
Authors: Husain Md. Mukhtar , Misra Sada Nand
Published: April 2003

The kinetics of aqueous polymerization of acrylamide, initiated by the potassium persulfate(K2S2O8)/2‐mercaptoethylamine hydrochloride (MEAH) redox pair was studied under nitrogen atmosphere at 30 ± 0,1 °C. The initial rates of polymerization were found to be proportional to [K2S2O8]1,5 (in the range of 0,8 to 1,2 mmol−1), to [acrylamide]1 (in the range of 0,8.10−1 to 1,2.10−1 mol 1−1), and to [MEAH]1 (in the range of 1,0 to 7,0mmol 1−1), respectively. The overall energy of activation was found to be 9,8 kcal mol−1 (40kJ mol−1). Water miscible alcohols and common salts (NaF, NaCl, (CH3)4NI) appeared to depress both the polymerization rate and the maximum conversion. With MnSO4.4H2O the reverse influence was found.
Cationic polymerization of N‐vinylcarbazole by tropylium salts at low temperatures
Authors: Rooney John M.
Published: April 2003

Cationic polymerizations of N‐vinylcarbazole (NVC) in methylene dichloride containing approximately 1% nitromethane were studied by adiabatic calorimetry at temperatures between −40 and −70°C. Tropylium salts containing AsF, SbF and SbCl counterions were used as initiators. Reaction halflives ranged from 2 to 80 seconds and first‐order plots displayed induction periods. Evidence indicated that the majority of the initiator was consumed, permitting estimation of propagation rate constants. For polymerizations involving the SbF counterion, these rate constants were found to be relatively insensitive to the concentration of initiator or excess anion and the conclusion is drawn that paired and unpaired PNVC+ SbF ions have similar reactivities at low temperatures. Correlation of the present results with those from previous work at 20 and 0°C yielded an Arrhenius exponential factor for propagation by unpaired ions of 30±9 kJ mol−1. The degree of polymerization approached the ratio [M]0/[1]0 at −70°C. At higher temperatures, molecular weights appeared to be governed by transfer reactions. The absence of significant chlorine content in polymer samples precluded the possibility of chain transfer to solvent.
Determination of the elastic modulus of polyamide crystals along the chain axis by x‐ray diffraction, 1. The α‐form of nylon‐6
Authors: Kaji Keisuke , Sakurada Ichiro
Published: April 2003

Studies were carried out to determine the crystalline elastic modulus E1 along the chain axis for the α‐form of nylon‐6 [poly(ε‐caprolactam)] by X‐ray diffraction. To obtain an inherent E1 value of this polymer the problem was solved that different orders of meridional reflections give different E1 values. Thus the disagreement was found to be due to the increase of the crystallite size by the applied stress. When corrected for this effect, the values from the 040 and 0.14.0 reflections agreed well with each other. The resulting modulus was 183 GN/m2 at 23°C, which was much lower than a theoretically calculated value of 262,8 GN/m2 for the fully extended structure model by Manley and Martin. This seems to be due to the slight shortening at the amide group of the molecular chain because it was confirmed from the intensity changes of the 040 and 0.14.0 reflections of this polymer by the applied stress that the amide part is more extensible than the polymethylene section.

Judging from similar considerations the previously reported E1 values for nylon‐66 and nylon‐6,10 are valid.
NMR spectra of some model compounds of polyisoprene
Authors: Dolinskaya Eleonora R. , Khatchaturov Aleksander S. , Poletayeva Irina A. , Kormer Vitali A.
Published: April 2003

1H, 2D, and 13C NMR spectra of five compounds modelling various types of monomer units addition in linear polyisoprene were investigated: 1,8‐hexadeuterio‐6‐methyl‐2‐trideuteriomethyl‐2,6‐octadiene (1), squalene (2), 4,7methyl‐3,7‐decadiene (3), 2,15‐bis(trideuteriomethyl)‐1,16‐hexadeuterio‐6,11‐dimethyl‐2,6,10,14‐hexadecatetraene (4), and 4,8‐dimethyl‐4,8‐dodecadiene (5). Compounds 1 and 3 were prepared for the first time. Analysis of the whole complex of spectral characteristics obtained made it possible to accomplish the assignment of lines in the carbon spectra of the compounds. It could be shown, that for linear bonding of isoprene units in case of the head‐to‐head type of addition sequence the methylene carbons in cis‐ and trans‐units absorb at 31,5 and 38,6ppm, respectively, and in case of tail‐to‐tail type of addition sequence the absorption is observed in the region of 28,4–28,8 ppm for both isomeric units.
Solution fractionation of polystyrene by different methods
Authors: Klein Joachim , Werner Michael
Published: April 2003

Systematic investigations of the solution fractionation of polystyrene were made in the system butyl acetate (solvent) and 1‐propanol (nonsolvent). For the method of “complete elution” it was possible to show, that (a) the amount of a dissolved fraction increases proportional to the loading of the support material with polymer, (b) the average molecular weight of a fraction is independent of the elution velocity. Subfractions from complete elution show an approach to a limiting value of the average molecular weight and a common high molecular range in gel permeation chromatograms. The existence of a critical limiting molecular weight M+ of polymer solubility, which is a necessary theoretical assumption of the complete elution method, could thus be verified experimentally. Comparison of fractions from complete elution with corresponding fractions from discontinuous solution fractionation demonstrates a better separation efficiency—more uniform fractions and less mutual overlapping of consecutive fractions—for the method of complete elution.
Polymorphie, kristallinität und schmelzwärme von poly(ε‐caprolactam), 2. Kalorimetrische untersuchungen
Authors: Illers Karl‐Heinz
Published: April 2003

The transition between the amorphous state and 3 crystalline modifications of poly(ε‐caprolactam) (polyamide‐6) has been investigated in Part 1 by IR spectroscopy. With these results as background the relation between heat of fusion ΔH* and specific volume v is now investigated as a function of crystallization temperature and time, using isothermal crystallization conditions from the melt as well as cold crystallization. The changes of ΔH* and v, which occur in the course of isothermal crystallization, allow qualitative statements on crystallinity changes and transitions between different crystalline modifications as a function of crystallization temperature. Quantitative results are obtained only in rare special cases, if either only one of the 3 crystalline modifications (α, γ, γ*) is formed or if the amount of one further modification is independent of crystallization time. Additionally, the situation is complicated by the fact, that for constant molecular weight and identical crystallization conditions the results strongly depend on (a) the origin of the polyamide‐6 pellets and (b) the mechanical prehistory of the melt. The reasons for these difficulties are differences in the number of (a) heterogeneous and (b) orientation‐induced homogeneous nuclei. This results in strongly varying crystallization rates, which has a considerable influence upon the relation between ΔH* and v.
Conformational changes of poly(oxymethylene) induced by pressure and mechanical treatment
Authors: Terlemezyan Levon , Mihailov Marin , Schmidt Pavel , Schneider Bohdan
Published: April 2003

IR spectra of hexagonal poly(oxymethylene) samples prepared by various polymerization procedures have been studied. The samples were further modified by pressure and by milling in liquid nitrogen. It was found that the considerable differences observed in IR spectra in the range 900–1250 cm−1 are caused by irregularities of the G conformation of the polymer chain. The regularity of the G conformational structure increases by pressing and milling.
Cationic polymerization of methyl substituted 1,3‐dioxepanes
Authors: Okada Masahiko , Hisada Takako , Sumitomo Hiroshi
Published: April 2003

The polymerization of 4‐methyl‐1,3‐dioxepane (1a), 2,4‐dimethyl‐1,3‐dioxepane (1b), and 4,4‐dimethyl‐1,3‐dioxepane (1c) was investigated in 1,2‐dichloroethane at different temperatures ranging from −60 to 0°C by using boron trifluoride etherate as initiator. The polymerization of 1a involves an equilibrium between monomer and polymer, and gives a viscous polymer along with some cyclic oligomers of different sizes. 1H NMR and 13C NMR analysis of the polymer revealed that the bond cleavage of the unsymmetrical 1,3‐dioxepane ring in the polymerization occurred nearly randomly at the two acetal CO bonds. The thermodynamic parameters for the polymerization were determined from the temperature dependence of the equilibrium monomer concentrations: ΔH=−9,3±1,3 kJ · mol−1 and ΔS=−38,8±7,8J · mol−1 · K−1. Dimethyl substituted 1,3‐dioxepanes were found to be very reluctant to polymerize: Only a liquid oligomer was formed in very low yield from 1b, and even oligomer was not obtained from 1c. The effect of methyl substituents on the cationic polymerizability of 1,3‐dioxepanes is discussed from the thermodynamic point of view.
Some remarks to the kinetics of anionic polymerization of ethylene oxide in dimethyl sulfoxide
Authors: Kazanskii Konstantin S. , Solovyanov Alexander A. , Dubrovsky Sergej A.
Published: April 2003

The kinetics of ethylene oxide (EO) polymerization in dimethyl sulfoxide with potassium tert‐butoxide as initiator at 323, 333, and 343 K has been studied. The process follows the first order with respect to initiator in the concentration range 1,5–5,9 · 10−3 mol · dm−3 and the rates are the same as in the polymerization of EO with dimsylpotassium (potassium methylsulfinylmethanide). It is supposed that the tert‐butoxide and dimsyl anions are equally effective as initiators and their ionization equilibrium does not affect the polymerization rate. The above conclusion agrees well with the very slow chain transfer to dimethyl sulfoxide in the anionic polymerization of EO.
Mechanism of the oxidative coupling of phenols: Influence of pH upon the electrochemical oxidation of xylenol in methanol
Authors: Roubaty Jean‐Louis , Bréant Mylène , Lavergne Madeleine , Revillon André
Published: April 2003

In acidic methanol, xylenol undergoes a bielectronic one step oxidation leading to the phenoxonium cation. Above pH 5,2 the reaction takes place in two monoelectronic steps, the first of which leading to a free radical. CC coupling, leading to quinones, occurs with the cation, whereas the free monomeric radical undergoes polymerization by CO coupling. The influence of the pyridine concentration upon the orientation of the coupling may be explained by the coincidence between the pKA of pyridine in methanol and the pH which favours disproportionation of the monomer radical.
Model compounds and 13C NMR investigation of isolated ethylene units in ethylene/propene copolymers
Authors: Zambelli Adolfo , Bajo Giuseppe , Rigamonti Ennio
Published: April 2003

The stereochemical environment of the isolated ethylene units, and the arrangement of the neighbouring propylene units, in ethylene/propene copolymers, prepared in the presence of syndiotactic‐specific and isotactic‐specific catalysts are investigated by comparing 13C NMR spectra of selectively 13C‐enriched copolymers and suitable model compounds. The implications of copolymer structure on polymerization mechanism are considered. In the presence of homogeneous syndiotactic specific catalyst systems both the regiospecificity and the stereospecificity are controlled by the last unit of the growing chain end. Regiospecificity and stereospecificity are unaffected by the ethylene units in the isotactic polymerization.
Studies on the polymerization of vinyl compounds in the presence of metal salts, 13. Polymerization of methyl methacrylate initiated by diaminomaleonitrile (DAMN)/copper ion/carbon tetrachloride
Authors: Narita Hiroshi , Hoshii Yasuhiro , Araki Mikio , Machida Seishi
Published: April 2003

The polymerization of methyl methacrylate initiated by the system diaminomaleonitrile (DAMN)/copper ion/carbon tetrachloride was investigated. The polymerization requires the presence of these three components, and both the cupric and the cuprous ion are suitable. The initial rate of polymerization with the cuprous ion is greater than that with the cupric ion. The cuprous ion was detected in both systems. It is considered that the cupric ion is reduced to the cuprous ion by DAMN, and the cuprous ion takes part in the initiation of the polymerization.
Kinetics and mechanism of the aniline‐formaldehyde reaction in acid medium
Authors: Nayar Mazhuvadyil R. Gopinathan , Francis Joseph D.
Published: April 2003

The kinetics and mechanism of the condensation of aniline and formaldehyde in acid medium were studied under various experimental conditions using a thin layer chromatographic method developed for this purpose. The reaction was found to be kinetically of first‐order with respect to formaldehyde. 4‐Aminobenzyl alcohol (1), N‐(4‐aminobenzyl)aniline (4), 4‐(4‐aminobenzyl)aniline (2), and a basic compound of unknown structure were found to be the initial products. By a judicious choice of concentrations and reaction conditions the individual reactions leading to the formation of the above products were isolated and their kinetics and energetic parameter were studied. A probable mechanism of the reactions is suggested.
Haupt‐ und seitenkettenkristallinität bei isotaktischen poly(1‐alkylethylen)en, 2. Röntgenographische, kalorimetrische und ramanspektroskopische untersuchungen am it‐poly(1‐eicosylethylen)
Authors: Trafara Gundolf , Koch Reimer , Sausen Eckhard
Published: April 2003

Isotactic poly(1‐eicosylethylene) shows three polymorphic modifications. The orthorhombic modification I is formed during melt crystallization at a cooling rate ϕ<2,5K.s−1. The dimensions of the unit cell are calculated to be a=0,75 nm, b=8,8 nm and c=0,67 nm. The heat of fusion is 145J.g−1, the melting point is 363K. The monoclinic modification II is crystallized from the polymer solution (a=0,53 nm, b=10,8 nm, c=0,77 nm, β=94°). The heat of fusion amounts to 120J.g−1, the melting point is 356K. Modification III is formed during rapid quenching of the melt. The side‐chains crystallized closely packed in layers. Modification III shows no main‐chain crystallinity. The heat of fusion is 40J.g−1, the melting point is 348 K. The crystal field splitting in the Raman spectrum of modification +1418/1440cm−1 indicates an arrangement of the side‐chains as in orthorhombic polyethylene with two chains in the subcell. The subcells of both modifications II and III contain only one chain each.
Reactive polymers, 22 Hydrolysis of schiff's bases and of hydrazones bonded on a crosslinked copolymer
Authors: Zacharieva Ekaterina I. , Mikeš František , Žůrková Eva , Kálal Jaroslav
Published: April 2003

The hydrolysis of Schiff's bases and hydrazones prepared by reactions of methylamine, ethylenediamine, butylamine, tert‐butylamine, sec‐butylamine, isobutylamine, octylamine, benzylamine, and isonicotino‐hydrazide with free aldehyde groups of the crosslinked macroporous copolymer divinylbenzene‐methacryl‐aldehyde, was investigated. The highest initial rate of hydrolysis was observed in the range of a high proton concentration. The initial hydrolysis rate increases and the conversion of the hydrolysis reaction decreases with increasing basicity of the amines. Comparison with the corresponding low‐molecular‐weight Schiff's bases indicated considerable polymer effects on the hydrolysis reaction.
Die orientierung der kristallinen und der nichtkristallinen bereiche in verstreckten polyethylenterephthalat‐folien
Authors: Biangardi Harald J.
Published: April 2003

Films of poly(ethylene terephthalate) were stretched at 100°C with different stretching rates. By this, oriented films with birefringences between 3.10−3 and 100.10−3 were produced. After a crystallization with fixed ends at 150°C, 200°C and 240°C, the orientation function of the crystalline regions, the density, and the birefringence were measured. From this data, the orientation function of the noncrystalline regions was computed. The results obtained show, that only a qualitative but not a quantitative computation of the orientation function is possible. With increasing birefringence of the material before crystallization, the orientation of the crystalline and the noncrystalline regions increases. Up to birefringences of Δn0=40.10−3 in both regions a strong increase of the orientation function is observed. At higher birefringences Δn0, the increase diminishes and depends strongly on the crystallization temperature. The orientation of the crystals after crystallization is better than the initial average orientation of the sample before crystallization. Further the orientation function of former reported structure models for the crystalline regions were computed in dependence of the structure parameters. Comparing the computed and experimental results one finds, that the change from structures consisting of twisted lamellae into such of bended lamellae occurs at a birefringence Δn0=20.10−3.
13C NMR sequence analysis, 17. Investigation on polyesters from diacids and diols
Authors: Kricheldorf Hans R.
Published: April 2003

Numerous polyesters were prepared from 1,2‐ethanediol, 1,3‐propanediol, 1,4‐butanediol, 1,6‐hexanediol, 1,12‐dodecanediol, 1,4‐phenylenedimethanol, and hydroquinone on the one hand and succinyl chloride, glutaroyl chloride, adipoyl chloride, suberoyl chloride, sebacoyl chloride, isophthaloyl chloride, and tetephthalolyl chloride on the other hand. The 13C NMR spectra of all polyesters were measured in trifluoroacetic acid and relationships between the structure of the monomeric units and the chemical shifts of the carbonyl and OCH2‐signals were established. Copolyesters were prepared either by cocondensation of two diacid dichlorides and two diols or by thermal transesterification of two homopolyesters. The 13C NMR spectra allow one to distinguish copolyesters from mixtures of corresponding homopolyesters and they allow the determination of the length of homogeneous blocks.
Ethylene‐butadiene copolymers, 1. Preparation with modified vanadium catalysts
Authors: Bruzzone Mario , Carbonaro Antonio , Corno Carlo
Published: April 2003

The copolymerization of ethylene with 1,3‐butadiene to give crystalline, homopolymer‐free, high molecular weight, substantially linear copolymer is described. Butadiene polimerizes almost exclusively in a trans‐1,4 structure, ranging in content from zero to 50 mole‐%. At relatively low content of butadiene monomeric units (≤30 mole‐%) X‐ray crystallinity is of polyethylene type with a slight variation of the structural parameters. At higher levels of butadiene monomeric units, crystallinity of trans‐1,4‐polybutadiene is also observed. The products with little unsaturation (1–5 mole‐%) melt at about 132°C and are able to crosslink with sulfur‐based recipes. A 13C NMR study shows a block‐type structure, but the copolymer appears homogeneous in composition. The product of the reactivity ratios was evaluated. The catalyst system consists of vanadium tris(acetylacetonate), diethylaluminium chloride, and an acidic compound or its precursor. The nature and the amount of the acidic modifier regulate the polymerization rate as well as the molecular weight, composition, and long branching of the copolymer, so that a strict control of the catalyst system is required. The behaviour of the catalyst is tentatively explained by the polarity of the active carbon‐vanadium bond, which depends on substituents and complexing agents.
Ethylene‐butadiene copolymers, 2. Long branching, double bond distribution and their effect on polymer properties
Authors: Bruzzone Mario , Giuliani Giampaolo , Paiella Roberto
Published: April 2003

The principal structural characteristics of ethylene‐butadiene copolymers prepared with a modified vanadium catalyst are described. The distribution of the butadiene monomeric units, though non‐random, is sufficiently homogeneous at low monomeric units content of butadiene (1–3 mole‐%) that a ready and efficient vulcanization with sulfur based systems is easily achieved.

Long chain branching, which has a detrimental effect on the copolymer properties, can be measured rheologically and controlled at a very low level by the catalyst system. Vulcanized ethylene‐butadiene copolymers show improved mechanical properties with respect to high density polyethylene and good processability before curing.
Polypeptides containing adenine and uracil residues
Authors: Draminski Marcin , Pitha Josef
Published: April 2003

Amino acids containing uracil, adenine and imidazole residues were prepared and polymerized by reacting with phosgene in ethylene carbonate. The polymers did not have a simple polypeptidic structure but were soluble in aqueous dimethylformamide and interacted with complementary polynucleotides. Alternative polymerization of amino acids by N,N′‐carbonyldiimidazole in aqueous neutral buffers proceeded with very low conversion but pure polypeptides resulted from the reaction. The following amino acids were prepared: β‐adenin‐9‐yl‐α‐alanine (1a), N‐methyl‐β‐(adenin‐9‐yl)‐α‐alanine (1b), β‐(uracil‐1‐yl)‐α‐alanine, (2a), N‐methyl‐β‐(uracil‐1‐yl)‐α‐alanine (2b), β‐(5,6‐trimethyleneuracil‐1‐yl)‐α‐alanine (3), and β‐(imidazol‐1‐yl)‐α‐alanine.
Etude cinétique de la dégradation du poly(oxytétraméthylèneoxytéréphtaloyle)
Authors: Devaux Jaques , Godard Pierre , Mercier Jean‐Pierre
Published: April 2003

The kinetics of thermal degradation of poly(oxytetramethyleneoxyterephthaloyl) was studied. This polyester undergoes a pyrolysis reaction in the temperature range of processing via a statistical mechanism proceeding by a random scission of the carbon‐oxygen bondings. This phenomenon is characterized by an energy of activation of 189,2kJ/mol (45,2kcal·mol−1) and by a negative entropy of activation [−20,3J·mol−1·K−1 (−4,84cal·mol−1·K−1)]. Like most of the esters with a hydrogen atom in β position, this polyester undergoes degradation by an intramolecular mechanism involving the formation of a cyclic transition state. The very high value of the degradation constant of this polycondensate is probably a result of the presence, in this chain, of the very flexible tetramethylene segment.
Syntheses and properties of polysaccharide‐type polymers, 2. Poly(cis‐3,4‐dihydroxytetrahydropyran‐6,2‐dihyloxymethylene)
Authors: Komada Hajime , Okada Masahiko , Sumitomo Hiroshi
Published: April 2003

Poly(cis‐3,4‐dihydroxytetrahydropyran‐6,2‐diyloxymethylene) (5a), a new polysaccharide‐type polymer having the same backbone structure as that of natural dextran but differing in the number and configuration of hydroxylic groups in the repeating unit, was successfully prepared by osmium tetroxide oxidation of poly(5,6‐dihydro‐2H‐pyran‐6,2‐diyloxymethylene) under mild conditions. The structure of 5a was established from 1H and 13C NMR analyses of 5a and its methylated product 5b. Water absorption of 5a was measured at different humidities ranging from 43 to 97% at 20°C and compared with those of relevant polymers having analogous structures. The polymer 5a was found to be degraded microbiologically.
Molecular weight dependence of magnetic circular dichroism for polystyrenes in solution
Authors: Ishii Tadahiro , Utena Yoshio , Handa Takashi
Published: April 2003

The molecular weight dependence of the magnetic circular dichroism (MCD) for polystyrenes (PS) has been studied in various solvents by using the normalized dipole‐strength D*. The normalized MCD intensity B* is not so much affected by the molecular weight as the normalized dipole strength D+. The ratio of the Faraday parameter to the dipole strength, B*/D*, decreases as the molecular weight increases to 4,0.103 and is constant above it. The increase of the normalized D* with the increase of molecular weight is interpreted in terms of the closer approach of chromophores. These results indicate that MCD for polystyrenes is influenced by the interaction of chromophores in a polymer chain: the decrease of B*/D* comes from the increase of the interaction of chromophores. This tendency is enhanced by solvent effects on MCD.
Effect of a polymeric ligand on the formation of some cobalt(III) and copper(II) complexes with partially quarternized poly(4‐vinylpyridine)
Authors: Kurimura Yoshimi , Wakayama Katsuhiko , Nishikawa Hiroshi , Tsuchida Eishun
Published: April 2003

It was found that the formation constants (K) of CuX(QPVP)n− (X = ethylenediaminetetraacetate ion (edta) and N‐(2‐hydroxyethyl)ethylenediamine‐N,N′,N′,‐triacetate ion (hedta), QPVP = partially quarternized poly(4‐vinylpyridine)) increase sharply with increasing degree of quarternization (Q) of QPVP. In the Cu(edta)2−/QPVP system. K values are 481.mol−1 for Q = 0%, 8701.mol−1, for Q = 25%, and 1,1.103l.mol−1 for Q = 61%, in aqueous methanol (volume ratio 1:1) at μ = 0,1 mol.l−1, pH = 8,0. and T = 25°C. In the system CH3Co(dmg)2H2O/QPVP, K decreases linearly with increasing degree of quarternization of QPVP from K = 1,7.103l.mol−1 for Q = 0% to K = 95l.mol−1 for Q = 61% in aqueous methanol (volume ratio 3:7) at μ = 0,05, pH = 8,0, and T = 25°C. The decrease in K is +scribed to a relatively large decrease in the rate constant of the forward reaction and a small increase in that of the backward reaction.
Effect of the heteroatom x in the catalytic system ZnR2/o‐ or m‐HXC6H4XH on the copolymerization of carbon dioxide with propylene oxide
Authors: Kuran Witold , Rokicki Andrzej , Wilińska Elžbieta
Published: April 2003

A series of new catalytic systems ZnEt2/cocatalyst were prepared and their activity in the alternating copolymerization of carbon dioxide with propylene oxide was studied. The systems ZnEt2/m‐HXC6H4XH (mole ratio 1:1) system (X = NH, S) were chosen to elucidate the influence of the heteroatom on the activity of the catalytic system. The obtained results were discussed in terms of the influence of the basicity of the heteroatom and of its hybridization on the structure and association of the catalyst molecule.
Effects of some carcinogens on conformation of histones
Authors: Su Ying‐Yet Thomas , Jirgensons Bruno
Published: April 2003

Conformational transitions of histones F1 (H1), F2a (H2A), F2b (H2B), and F3 (H3) in the presence of carcinogens 4‐nitroquinoline‐N‐oxide, 13‐H‐dibenzo[c,j]carbazole, and 7‐H‐dibenzo[c,q]carbazole were studied by the circular dichroism (CD) probe. The polypeptide main chain conformation of the very lysine rich histone F1 was not affected by these carcinogens, but the tertiary structure was modified slightly by the carbazoles. The secondary structure of histone F2a was significantly modified by the carbazoles which enhanced the helix content, whereas the effect of the 4‐nitroquinoline‐N‐oxide on the backbone conformation was weak. The tertiary structure of F2a was affected by all three carcinogens, whereby the 7‐H‐dibenzo[c,g]carbazole produced the strongest enhancement of the CD bands assigned to tyrosine and phenylalanine chromophores. Moreover, this carcinogen produced extrinsic Cotton effects in the 300–380nm spectral zone. Similar effects of the carbazoles were observed with histone F2b, although in this case the main chain conformation was changed only slightly. The secondary structure of histone F3 was slightly affected by the carcinogens but the tertiary structure was significantly modified by the carbazoles. The CD bands of F3 which were assigned to the tyrosine and phenylalanine chromophores were most strongly enhanced by the 13‐H‐dibenzo[c,j]carbazole.
Synthesis of polyamides from diamines and dinitriles with basic catalysts
Authors: Ree Keiu , Tanabe Kenji , Minoura Yuji
Published: April 2003

The reaction of a nitrile (acetonitrile) with a metalated amine (aniline and benzylamine) was attempted, in order to obtain the corresponding amide via hydrolysis of the amidine. This reaction was also applied for the preparation of polyamides, using diamines and dinitriles. The reaction of aliphatic diamines with aliphatic dinitriles yielded 20–30% of polyamides of low degrees of polymerization.
Chemische synthese verzweigter Polysaccharide, 8. Vergleichende struckturuntersuchungen an amylose‐ und Cellulosederivaten mit verschiedenen Substituenten an C‐6 durch optische Rotationsdispersion und circular‐dichroismus
Authors: Pfannemüller Beate , Berg Annette
Published: April 2003

Carbanilated and tritylated derivatives of amylose and cellulose previously studied by light scattering were further characterized by measurement of optical rotatory dispersion (ORD) and circular dichroism (CD). No anomalous ORD and only a weak CD was found for 6‐tritylamylose in 1,4‐dioxane, indicating a widely unordered structure which is in accordance with the low viscosity of the compound. In comparison with the other carbanilated derivatives having substituents in C‐6 position, i.e. trityl‐, carbanilyl‐ or glucosyl groups, 2,3‐dicarbanilylamylose is distinguished by an especially high Cotton effect. This result suggests a helical chain,— clearly visible by excition splitting—, that may adopt a more regular orientation in case of free C‐6 hydroxyl groups, whereas trityl‐, carbanilyl‐, and glucosyl groups almost equally will contribute to a lower state of orientation. Conversely in the cellulose derivatives a clear steric dependence on the size of the C‐6 substituent was found. The increase of the Cotton effect observed for the bulky trityl group may arise from the β(1 → 4) linkage that causes an alternating or syndiotactic like structure in cellulose, which is more sensitive to restrictions of the free rotation due to steric effect. In addition, viscosity and optical rotation in NMP and 1,4‐dioxane were measured in the range of 20 to 70°C. An unusual behaviour is observed for 6‐trityl‐2,3‐dicarbanilylamylose in NMP indicating a conformation transition near 45°C, and is discussed in connection with the findings from light scattering measurements.
Synthesis of polyamides from esteramide‐diamines
Authors: Chau Nguyen , Matsuda Shoko , Iwakura Yoshio
Published: April 2003

Diamines containing ester and amide linkages were obtained by the addition reaction of p‐aminobenzoic acid with arylenebis(2‐oxazolines) in N,N‐dimethylformamide. These diamines were subjected to polycondensation with various diacid dichlorides to obtain polyamides containing regular ester and amide sequences in the polymer chain.
Laser flash photolysis of poly(p‐vinylbenzophenone) in solution. Intramolecular triplet deactivation processes
Authors: Schnabel Wolfram
Published: April 2003

Poly(p‐vinylbenzophenone) (poly[1‐(4‐benzoylphenyl)ethylene], PVBP) and p‐isopropylbenzophenone (IPB) were irradiated in benzene solution at room temperature with 347, 1 nm laser flashes (duration 25 ns). Triplet‐triplet spectra were recorded at the end of the flash. Upon following the decay of the T‐T spectra a pronounced polymer effect was found: the decay followed 2nd order kinetics in the case of the polymer and 1st order kinetics in the case of the model compound. The halflife times differ by a factor of about five (τ1/2(PVBP) < τ1/2(IPB)). Whereas τ1/2(IPB) was not influenced, τ1/2(PVBP) decreased with increasing absorbed dose per flash. From the results it is inferred that at relatively high dose rates PVBP triplets decay essentially via intramolecular T‐T annihilation and at lower dose rates via intramolecular selfquenching processes. At comparable conditions IPB triplets were essentially deactivated via interactions with solvent molecules.
Interaction between poly(L‐lysine) and sulfated poly(vinyl alcohol)
Authors: Cho Chong‐Su , Kōmoto Tadashi , Nakagami Akira , Kawai Tohru
Published: April 2003

Ionic polymer‐polymer interaction was studied in aqueous solution for poly(L‐lysine) (PLL) and sulfated poly(vinyl alcohol) (PVS) as functions of pH, the degree of sulfation, the functional unit mole ratio of the two polymers and temperature by means of circular dichroism and viscosity measurements. In all the cases studied, strong inter‐polymer complexes were formed at the functional unit mole ratio (VS)/(LL) higher than 1. Although PLL itself is well known to take the α‐helical conformation at such a high pH as 11, the PLL conformation in the PLL/PVS complexes did not depend on pH but on the degree of sulfation: at room temperature, PLL took random coil conformation in PLL/PVS‐25 (25: degree of sulfation in mole‐%) and PLL/PVS‐30, and the α‐helical conformation (helicity of 70%) in PLL/PVS‐46 and PLL/PVS‐95. Models for the complex structures are postulated. Methanesulfonic acid did not influence the conformational transition of PLL, supporting that a polymer effect took place in the complex formation between PLL and PVS. Thermal effect on the PLL conformation in the complex is also discussed.
The 13C NMR spectra of ring‐opened copolymers of cyclopentene and norbornene; reactivity ratios
Authors: Ivin Kenneth J. , O'Donnell James H. , Rooney John J. , Stewart Cecil D.
Published: April 2003

Ring‐opened copolymers of cyclopentene (M1) and norbornene (M2) were prepared by WCl6/(C6H5)4Sn initiation in chlorobenzene and analysed by 13C NMR spectroscopy. At low conversion and for feed composition in the range f1 = 0–0,7 the copolymerization behaviour is ideal, with r1 = 1/r2 = 0,44; at high conversion the copolymer tends to contain more than the ideal proportion of M2 units. For copolymers in the composition range F1 = 0–0,5 the dyad distribution is random but for F1 > 0,6 there is a tendency to blockiness. The fraction of double bonds having cis structure is 0,5–0,6 for M2M2, 0,4–0,6 for M1M2, and 0,4–0,7 for M1M1 dyads. The pair sequence of cis and trans double bonds is somewhat blocky for both M2M2M and M1M2M triads (M = M1 or M2). The chemical shifts of the central non‐olefinic carbons in both M1 and M2 units (C5 and C3) show sensitivity to triad structure provided at least one adjacent double bond is cis. This unusual ϵ‐substitution effect is interpreted in terms of conformational restrictions about certain of the main‐chain bonds when an adjacent double bond is cis. WCl6/(CH2CHCH2)4Sn initiation gives a copolymer containing practically no M1 units.
Modification au deuxième degré de polymères époxydés, 1. Etude sur molécules modèles des polyalcadiènes
Authors: Brosse Jean‐Claude , Soutif Jean‐Claude , Pinazzi Christian
Published: April 2003

The addition of benzoic acid to the oxirane ring of model compounds for epoxidized polymers of dienes was studied. A convenient reaction rate was observed for temperatures of about 100°C. It was found that the addition reaction can be catalysed by basic compounds. Kinetic studies showed the influence of solvent nature, of concentration of reagents, of catalysts, and of the epoxide structure. The reactivities of various acids showing particular properties (drugs, UV‐absorbers, herbicides) were investigated.
Crosslinking statistics, 1. Relation between molecular‐size distribution and partial conversion degrees expressed by equability criterion
Authors: Luby P. , Kuniak Ľ.
Published: April 2003

One‐to‐one correspondent relationships between the link distribution and the molecular‐size distribution for a polymer formed by a trifunctional homopolymerization of a single kind of repeating unit R(X1X2X3) are derived, where X1, X2, X3 denote functional groups of unequal reactivity. These equations make it possible to evaluate the relative reactivities of functional groups by means of partial conversion degrees α1, α2, α3 at any stage of reaction of the average conversion degree. The values of the three weight fractions of mono‐, di‐ and trimers are required as entering data, and these are the necessary and sufficient condition for a complete description of the relative reactivities. The present mathematical model is based on the condition that substitution effect and ring formation are negligible.
Cationic polymerization of cyclic thioacetals by triethyloxonium tetrafluoroborate
Authors: Kawakami Yuhsuke , Mizutani Yutaka , Yamashita Yuya
Published: April 2003

Polymerization of 1‐oxa‐3‐thiacyclopentane with catalytic amounts of triethyloxonium tetrafluoroborate was studied. The initiation reaction was a fast and quantitative formation of ethylsulfonium salt of monomer. The propagation reaction was a slow and quite complex reaction with sulfonium transfer reactions. The reaction mechanism is discussed.
One and two component hydrogels, 3. Deswelling and compression measurements on one component hydrogels
Authors: Good William R. , Cantow Hans‐Joachim
Published: April 2003

The value of the Flory‐Huggins interaction parameter for water and poly(N‐vinyl‐2‐pyrrolidone)

Systematic nomenclature: Poly[l‐(2‐oxo‐l‐pyrrolidinyl)ethylene].

(PVP), networks is determined by combining uni‐directional compression measurements in the swollen state with network deswelling measurements. It was found that the dependance of the parameter on crosslink density can be explained by considering the interaction of water with the crosslinking molecule, a very water insoluble compound. Moreover, it was found that the interaction parameter within the swelling range studied is independant of network concentration. The number of elastically effective network chains is overestimated by a substantial margin.
The anionic polymerization of styrene under pressure
Authors: Bunge M. , Höcker H. , Schulz G. V.
Published: April 2003

The kinetics of the anionic polymerization of styrene were investigated under pressure (1≤p/bar < 1800) with Na+ as counter ion in tetrahydropyran (THP) as solvent and with Cs+ as counter ion in 1,2‐dimethoxyethane (DME) as solvent. The results yielded the activation volume of the contact ion pair ΔV and the sum (ΔV + ΔVcs) of the activation volume of the solvent separated ion pair ΔV and the volume change upon formation of solvent separated ion pairs from contact ion pairs ΔVcs. The numerical values are negative. The activation volume of the solvent separated ion pairs could be estimated.
Poly(9,10‐anthrylen)e
Authors: Hinterhofer Otto
Published: April 2003

Based on a previous work the polymerization mechanism of anthracene was studied and it was found that the initial reaction step is represented by the formation of a radical ion. Poly(9,10‐anthrylene) was prepared in order to study the relevant properties with respect to its technological applicability. Pure poly(9,10‐anthrylene)s even of relatively low molecular weight (about 3 000) are infusable and nearly insoluble. Poly(9,10‐anthrylene)s show good photoconduction.
Preparation and 13C NMR spectra of model compounds for poly(4‐bromostyrene)
Authors: Nguyên‐Trân Tuyet Mai , Lauprêtre Françoise , Jasse Bruno
Published: April 2003

The preparations of 2,4‐bis(4‐bromophenyl)pentane (1b) and 2,4,6‐tris(4‐bromophenyl)heptane (2b) are described. The study of the different isomers of 1b and 2b by 13C NMR allows a comparison of the various configurational sequences of these compounds in terms of their chemical shifts. Methyl, methylene, and aromatic C1 carbons of 1b and 2b could be deduced from the values obtained from corresponding polystyrene model compounds by a mere translation. From the aromatic C1 chemical shifts it was possible to propose an assignment of the corresponding triads of poly(4‐bromostyrene).
Thermodynamics of hydrogen bonding polymer‐solute interactions by inverse gas chromatography
Authors: DiPaola‐Baranyi Giuseppa , Guillet James E. , Jeberien Hans‐Edwin , Klein Joachim
Published: April 2003

The gaschromatographic retention behaviour of a series of solutes with potential hydrogen bonding activity has been studied, using polyethylene, poly(ethylene‐vinyl acetate), poly(vinyl acetate), and poly(ethylene glycol) as stationary phases. Measurements were performed at various temperatures above the melting point and/or glass transition temperature of the polymers and the slopes of the ln V versus 1/T‐functions (where V is the specific retention volume) were used to calculate partial molar heats of solution (ΔHs). Correspondingly, the temperature dependence of the activity coefficient can be used to calculate partial molar heats of mixing (ΔH̄1infin;) of the solute at infinite dilution in the polymer. Based on a “homomorph” concept with the inherent assumption of additive group contributions to the total interaction energy, hydrogen bonding energies of polymer‐solute systems could be separated using polyethylene on one hand and appropriate model solutes on the other hand as reference materials.
Effect of UV light on the system styrene/maleic anhydride at −196°C
Authors: Bartoň Jaroslav , Capek Ignác , Tiňo Jozef
Published: April 2003

The effect of UV light (λ > 300 nm) on the system styrene/maleic anhydride/solvent (acetone or chloroform) in the presence and/or absence of the alternating styrene/maleic anhydride copolymer was studied by the ESR method at −196°C. It was found that the concentration of paramagnetic species increased with the time of irradiation. The intensity of the ESR spectra at −196°C did not change when the light was cut off. By analysis of the ESR spectra of the systems studied the methyl (aH = 2,3 mT), dichloromethyl (aH = 1,66 mT), and acetyl (aH = 0,52 mT) radicals as well as the radicals A and D (aHα = 2,25 mT, aHβ = 3,19 mT) and (aHβ = 1,1 mT), respectively, were identified.
The effect of stereochemical structure on the viscoelastic behaviour of poly(ethyl methacrylate)
Authors: Hrouz Jaroslav , Ilavský Michal , Spěváček Jiří , Trekoval Jiří
Published: April 2003

The low‐frequency viscoelastic behaviour of three stereoregular samples of poly(ethyl methacrylate) (PEMA) in the main transition region was investigated. The main effect of tacticity in the transition from the syndiotactic sample to the isotactic one consists in a shift of the main transition region (or of the glass transition temperatures, Tg) to lower temperatures by ≈ 70 K. The temperature dependence of the shift factor of all samples could not be adequately described by the single Williams‐Landel‐Ferry (WLF) equation within the whole range of temperatures; in the range T>Tg+60K, isotactic PEMA exhibited the largest departures from the WLF equation. In all cases, departures from the WLF equation could be quantitatively described in terms of the temperature dependence of the Andreade coefficient β. The temperature dependence of the Andreade compliance, JA, was also most pronounced for the isotactic sample. Vertical correction of the complex modulus G*, with WLF horizontal shifts preserved, led to the lowest activation energy ΔH for the isotactic sample, which means the highest magnitude of secondary relaxation mechanism in this sample. The birefringence measurement showed that the molecular nature of the deformational birefringence is independent of the tacticity of the sample and does not vary in the range Tg+25K<T<Tg+100K. In all the characteristics mentioned here, parameters of a conventional sample obtained by radical polymerization approached those of the syndiotactic sample.