bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanismus der photopolymerisation des styrols, 3. Zur kinetik der photo‐elementarprozesse
Authors: Kauffmann Harald Friedrich
Published: April 2003

The photoinduced free radical bulk polymerization of styrene (M)—in the absence of any sensitizer or free radical initiator—was investigated at different intensities, Ja, and at different wavelengths, λe, of the exciting light (λe = 313 nm, 335 nm; 25°C). The polymer conversion was followed dilatometrically in optical cells and the photo‐oligomers which are built up simultaneously in the polymerizing system —cis‐1,2‐diphenylcyclobutane (c‐CB), trans‐1,2‐diphenylcyclobutane (tr‐CB), 1‐phenyl‐1,2,3,4‐tetrahydronaphthalene (1‐PhT), 2‐phenyl‐1,2,3,4‐tetrahydronaphthalene (2‐PhT), 1‐phenyl‐4‐(1‐phenylethyl)‐1,2,3,4‐tetrahydronaphthalene (T1) and 2‐phenyl‐4‐(1‐phenylethyl)‐1,2,3,4‐tetrahydronaphthalene (T2),—were quantitatively analyzed by GLC. The quantum yields were found to be φc‐CB = 0,10, φtr‐CB = 0,02, Φ1‐PhT = 0,0084, Φ2‐PhT = 3,7.10−3, ΦT = 5,0.10−4, respectively, and from the experimentally observed dependence of the rate of polymerization, VP, on the square root of the light intensity, Ja, the apparent quantum yield of the formation of radicals can be calculated to be ΦS = 5,6.10−4. On the basis on the proposed structure of the photointermediates, I, which had been previously confirmed by 1H NMR spectroscopy in enriched systems, the kinetic treatment of the photostationary state gives a complete data set of mean values of partial quantum yields, φ, concerning all the photo‐elementary processes of I under polymerizing conditions: φS = 2,56.10−3, φT = 2,3.10−3, φPhT = 5,5.10−2 and φ2M = 0,94 (retro‐Diels‐Alder decomposition).
Röntgenkleinwinkel‐untersuchungen zur struktur der crazes (fließzonen) in polycarbonat und polymethylmethacrylat
Authors: Paredes Edgar , Fischer Erhard W.
Published: April 2003

Small angle X‐ray scattering measurements were made on samples of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) containing crazes. A sharp, well pronounced maximum in the scattering intensity was observed in the direction perpendicular to the draw direction. The distribution of scattered intensity around the draw direction and the effect of contraction of the craze fibrils on the scattering curve, support the suggestion that the observed maximum in intensity arises from interfibrillar interference. Calculated scattering curves for a system of parallel cylinders with a liquid like order are in good qualitative agreement with the observations. The average fibril's diameter a can be determined from the position of the scattering intensity maximum and from the asymptotic behavior of the scattering curve. Very good agreement was obtained between the two methods. No alteration of a with Mw was found for the PMMA samples. For PC it was found that a increased with increasing draw temperature and decreased with increasing draw rate. We can attribute this behavior to the dependence of the yield stress σy on the drawing conditions, because aσy was found to remain constant. This quantity is defined as the fibrillation energy. On the basis of this observation the results are discussed in terms of the “meniscus instability” model of Argon and Salama. A simple explanation of the results can be given by proposing an energy balance during craze growth.
Polyene sequence distribution in degraded poly(vinyl chloride) as a function of the tacticity
Authors: Martinez Gerardo , Mijangos Carmen , José‐Luis‐Millán  , Gerrard Donald L. , Maddams William F.
Published: April 2003

Four fractions of poly(vinyl chloride) (PVC) having appreciably different tacticity distributions were prepared by selective extractions on samples polymerised at temperatures between +60 and −50°C. They were degraded thermally at 180°C in the solid state to conversions in the range 0,2 to 0,5% and in solution at 200°C to conversions in the range 1,6 to 5%. The polyene sequence distribution was investigated by ultra violet/visible (UV/VIS) and resonance Raman spectroscopy. The results show that the type of polyene sequence distribution depends markedly on the tacticity distribution of the polymer. Cross‐linking reactions occur more readily as the syndiotacticity increases. The results are discussed and interpreted with reference to previous work relating degradation processes and tacticity.
Polymerisation von fulvenen, 1. Synthese und eigenschaften kationischer polyfulvene
Authors: Rentsch Christoph , Slongo Mario , Schönholzer Stefan , Neuenschwander Markus
Published: April 2003

The cationic polymerization of a series of pentafulvenes with two exocyclic substituents yields highly reactive unsaturated polymers, which are soluble in nonpolar organic solvents. The preparative aspects as well as some properties of the polymers are discussed. Most polymers are very sensitive to oxygen. For instance poly(5‐isopropylidene‐3‐cyclopenten‐1,2‐ylene) (2a), which is obtained with molecular weights up to 350 000, consumes more than one mol‐equivalent of oxygen per repeating unit.
Poly(L‐lysine)/sulfated poly(vinyl alcohol)/acridine orange complex
Authors: Cho Chong‐Su , Kōmoto Tadashi , Kawai Tohru
Published: April 2003

In order to clarify the arrangement of sulfated poly(vinyl alcohol) (PVS) chains about the α‐helical poly(L‐lysine) (PLL) chain in the previously reported complexes of PLL/46 mole‐% sulfated poly(vinyl alcohol) (PVS‐46) and PLL/PVS‐95, induced circular dichroism was studied on PLL/PVS/acridine orange (AO) complexes in acidic aqueous solution. A positive ellipticity, [θ], of ca. 3 400 deg·cm2·dmol−1 at 465 am and small negative values of [θ] at 435 and 510 nm indicated a right‐handed super helical arrangement of AO molecules about the right‐handed α‐helix of PLL, where PVS chains were intercalated. The amount of AO molecules responsible for the induced CD was estimated as low as a few mole‐%. Taking into consideration the arrangement of ε‐amino groups of the right‐handed α‐helical PLL and the distance among the neighboring ε‐amino groups on the radial projection of the helix, the PVS chain segments could be arranged both in the right‐handed and in the left‐handed superhelices about the right‐handed α‐helix of PLL. In cases of the PLL/PVS‐25/AO and PLL/PVS‐30/AO complexes, no induced CD and a quite weak CD were obtained, resp., being consistent with random coil conformation of PLL in the PLL/PVS‐25 and PLL/PVS‐30 complexes mentioned previously.
Dependence of non‐Newtonian flow properties of polystyrene solutions on solvent viscosity
Authors: Ito Yoshio , Shishido Shunsuke
Published: April 2003

Steady shear viscosities were measured over a range of shear rates from lower to upper‐Newtonian flow region for solutions of polystyrene in the high‐viscosity solvent tricresyl phosphate at three different temperatures. The influence of solvent viscosity on the non‐Newtonian flow property was studied and compared with the results obtained previously by use of a lowviscosity solvent with similar solvent power for polystyrene as tricresyl phosphate. For the moderately concentrated solutions, the non‐Newtonian viscosity could be explained by Graessley's entanglement viscosity theory modified by a frictional viscosity. The result shows that only the frictional viscosity is affected by variation of solvent viscosity. As the entanglement viscosity decreases with increasing shear rate and is practically masked by the shear independent frictional viscosity, the flow appears as to be upper‐Newtonian in spite of the difference in solvent viscosity. The lower critical concentration for entanglement was determined on the basis of a lower limit for the applicability of the modified Graessley theory. The values of the critical concentrations are independent of the magnitude of solvent viscosities.
Interpretation of rates of polymer‐polymer reactions in terms of statistical thermodynamics of dilute polymer solutions
Authors: Iwata Hiroo , Ikada Yoshito
Published: April 2003

The influence of long‐range polymer interactions on intermolecular polymer reactions is studied for those cases where the rate‐determining step is not diffusion‐controlled but chemical process controlled. Rate consants are derived for the reaction between a reactive group linked to the l1th segment of polymer 1 and a ractive group linked to the m2th segment of polymer 2 as well as for the reaction between polymers 1 and 2 carrying both randomly distributed reactive groups. The rate constant is closely related to the second virial coefficient in the latter case. After formation of the bond between polymers 1 and 2, the second reaction is assumed to take place between the remaining reactive groups A and B within the two linked chains. The apparent second‐order rate constant of this reaction is predicted to increase with decreasing concentration of the reactive groups.
Polymeric viologens as electron donors in hydrogen production by intact cells of Clostridium pasteurianum, Desulfovibrio desulfuricans, and Rhodospirillum rubrum
Authors: Chuaqui Claudio A. , Lynn Kenneth R. , Williams Ross E. , Martin Stanley M.
Published: April 2003

The behaviour of 5 polymeric viologens 2a – e as electron donors in the production of hydrogen by intact cells of Cl. pasteurianum, D. desulfuricans, and R. rubrum was studied. The hydrogen production was followed by gas chromatography and the results indicate that Cl. pasteurianum and D. desulfuricans are much more active than R. rubrum. Polymeric viologens 2a – e show lower initial rates than the low molecular weight viologens 1a and 1b. However, this is independent of the final amount of hydrogen produced, since the polymers are as efficient or more efficient than 1a and 1b. The results are briefly discussed in terms of redox potentials, substituent effects and conformational factors.
NMR investigation on oligo‐ and poly(galacturonic acid)s; gel formation in the presence of Ca2+ counterions
Authors: Rinaudo M. , Ravanat G. , Vincedon M.
Published: April 2003

In this paper, the assignment of the 1H and 13C NMR spectra of poly(galacturonic acid)s is proposed; the 4C1 chair conformation of the monomeric unit in poly(galacturonic acid) is confirmed and the composition of the anomeric mixture at the reducing end (α−D)/(β−D) = 35 : 65 mol/mol independent of the degree of polymerization DP (2 ⩽ DP ⩽ 5) is given. It is demonstrated on oligomers that both 13C and 1H chemical shifts and coupling constants are nearly unaffected by exchanging Na counterions with Ca; the osmotic coefficient of Ca depends on the DP just as predicted by an electrostatic mechanism. The intrinsic viscosity of the polymer increases and the intensity of 13C NMR signals decreases suddenly for 0,3 equivalents Ca2+ per carboxylic site. These results confirm a multichain association followed by a rigid gel formation; the crosslink is proposed to correspond to a cooperative “egg‐box” mechanism on chain segments randomly distributed in the gel.
Reaction mechanism of oxygen‐initiated ethylene polymerization at high pressure
Authors: Tatsukami Yoshiharu , Takahashi Tsutomu , Yoshioka Hiroshi
Published: April 2003

The kinetics of the oxygen‐initiated polymerization of ethylene at high pressure up to 2,220 kbar was systematically investigated in a constant volume system in a temperature range from 60 to 250°C. In the higher temperature range (above 190°C), where no induction period exists, rate equations for both the oxygen consumption and the polymerization were derived by considering a retardation reaction by oxygen. The numerical calculation of these equations by the Runge‐Kutta‐Gil method indicated an excellent agreement with experimental results.
Solution properties of poly(N‐1,1‐dimethyl‐3‐oxobutylacrylamide), 1. unperturbed chain dimensions
Authors: Chiantore Oscar , Trossarelli Luigi , Guaita Marino
Published: April 2003

The Mark‐Houwink relationship for poly(N‐1,1‐dimethyl‐3‐oxobutylacrylamide), (poly[1‐(1,1‐dimethyl‐3‐oxo‐butylaminocarbonyl)ethylene]), in 2‐butanone at 25°C and the unperturbed chain dimensions have been obtained following standard procedures. The characteristic ratio and the steric factor are quite large, indicating that the lateral substituents are effective in expanding the unperturbed dimensions owing either to their bulkiness or to the possibility of being involved in intramolecular hydrogen bonds.
The spinning of silk, 1. Molecular weight, subunit structure, and molecular shape of bombyx mori fibroin
Authors: Trefiletti Vincenzo , Conio Giuseppina , Pioli Franco , Cavazza Barbara , Perico Angelo , Patrone Eligio
Published: April 2003

The molecular structure of Bombyx mori fibroin is still subjected to much controversy; there are discordant reports in the literature on both the value of the molecular weight and the subunit structure of the molecule. The method reported in the present paper allows the molecular weight of Na2CO3 extracted fibroin samples to be unambiguously determined, and investigations on the composition and the molecular weight of the peptides arising from the degradation process succeeded in establishing some overall aspects of the structure of the subunits. The main results are: (1) the molecular weight of undegraded fibrion is 4 · 105; (2) two small subunits are disulfide linked to the main chain; (3) the subunits are located near the terminals of the main chain; (4) in agreement with previous partial literature data, the small subunits are rich in bulky and acid amino acids; our work further shows that they possess a three‐block structure, consisting of a central hydrophobic core bearing two strongly acid sequences at the terminals. The mechanism of degradation of the fiber appears to be directed by structural, rather than chemical, factors, and its detailed investigation may represent a valuable method to determine the molecular architecture of the fiber.
Redox polymerization, 3. Kinetics of acrylonitrile polymerization initiated by the redox systems cyanoacetic acid/Mn(III) and 2‐butanone/Mn(III) in aqueous sulfuric acid
Authors: Jayakrishnan Athipettah , Mahadevan Venkatanarayana
Published: April 2003

The kinetics of Polymerization of acrylonitrile initiated by the redox systems cyanoacetic acid/Mn(III) and 2‐butanone/Mn(III) were investigated in the temperature range of 30 – 50°C in aqueous sulfuric acid. The kinetics are consistent with the formation of a 1 : 1 complex between the reducing agent and Mn(III), its unimolecular decomposition yielding the initiating radical. Extensive oxidation of the primary radical with exclusively mutual termination of growing radicals accounts for the kinetics of the polymerization. Rate and equilibrium constants as well as thermodynamic parameters were evaluated and their significance is discussed.
On the kinetics of polymer degradation in solution, 9. Pulse radiolysis of poly(ethylene oxide)
Authors: Gröllmann Ulrich , Schnabel Wolfram
Published: April 2003

Poly(ethylene oxide) was irradiated with pulses of 16 MeV electrons (pulse length up to 100 ns) in aqueous and acetonitrile solutions in the absence and presence of oxygen. The change of the light scattering intensity (LSI) after the pulse was monitored. In acetonitrile solution, at a concentration of 2,3 · 10−2base mol/1, main chain rupture occurred both in the presence and in the absence of O2. In aqueous solutions at [PEO] = 2,3 · 10−2base mol/1 the LSI increased after the pulse in the absence of O2(crosslinking) and decreased at [O2] = 1,4. 10−3mol/1 (main chain scission). The rate of LSI decrease was correlated with a diffusion process in the case of O2free acetonitrile solution and with a chemical reaction in the cases of O2saturated aqueous and acetonitrile solutions. In the latter two cases it was found that a bimolecular reaction precedes bond scission in the main chain. It is assumed that peroxyl macroradicals (PO) react with each other forming oxyl macroradicals (PO•) which decompose relatively rapidly by main chain scission.
Polyimidines, 7. Synthesis and the polymerization of 3‐(p‐Aminophenyl)‐3‐phenylphthalide
Authors: Lohr Raymond A. , Cassidy Patrick E.
Published: April 2003

A new monomer for the preparation for polyimidines has been synthesized from 3,3‐diphenylphthalide. The starting material can be mononitrated on one of the pendant phenyl groups by the use of acetyl nitrate or nitronium tetrafluoroborate. The resulting nitrophthalide is then reduced to the amine with hydrogen over PtO2 or with ammonium sulfide with overall yields of 85–90%. 3‐(p‐Aminophenyl)‐3‐phenylphthalide then can undergo self‐condensation to provide a new polyimidine with a rigid backbone structure which may be a candidate for liquid crystal formation. The condensation can take place at temperatures of 180–350°C, either in polyphosphoric acid or nitrobenzene as solvents, or without solvent in a sealed tube. The yield from the polymerization is as high as 89% and inherent viscosities range up to 0,19 dl/g. Thermal stabilities in air and nitrogen are as high as 520 and 565°C, respectively; however a significant difference occurs in thermal stability for different methods of synthesis. All polymers were soluble in chloroform, dimethylformamide and other organic solvents.
Dynamic mechanical relaxations in poly(oxyoctamethylene)
Authors: Pereña José M. , Marco Carlos
Published: April 2003

Dynamic mechanical, calorimetric and X‐ray diffraction measurements of poly(oxyoctamethylene) are carried out, in order to determine its viscoelastic relaxations and to elucidate the influence of the crystalline form of this polyether on its degree of crystallinity. The dynamic mechanical measurements were performed using a dynamic viscoelastometer at four frequencies ranging from 3,5 to 110 Hz, in the temperature range from −150°C to 60°C. Two relaxations are observed. The one occurring at the lowest temperature (−139°C at 3,5 Hz) has an activation energy of 10 ± 1 kcal/mol (42 ± 4 kJ/mol) and is considered as the γ relaxation which takes place in all the polymers with three or more adjacent methylenic units. The other one appears at −24°C and its activation energy is higher than 100 kcal/mol. The assignment of other of the two relaxations as glass transition of the polymer is discussed in context of the relaxation maxima of other members of the polyether series.
Kinetik und mechanismus der kationischen polymerisation von trioxan: Ein katalysierter kristallwachstumsprozeß
Authors: Wegner Gerhard , Rodriguez‐Baeza Mario , Lücke Andreas , Lieser Günter
Published: April 2003

The kinetics of the cationic polymerization of trioxane initiated by perchloric acid is analyzed as a simultaneous polymerization and crystallization process. The details of the crystal growth such as nucleation, distribution of crystal sizes, development of growth spirals etc. have been investigated by electron and light microscopic techniques. The mechanism of polymerization can be understood as a catalyzed crystal growth. A well defined population of crystals is formed during a nucleation event at the start of the polymerization. An adsorption equilibrium with regard to the catalyst is then established in the presence of the rather large surface area of the growing polymer crystals. Assuming a Langmuir‐type adsorption behaviour, the observed growth features (growth spirals) can be quantitatively interpreted on the basis of the BCF‐theory of crystal growth. The current concepts on the molecular mechanism of cationic polymerization of cyclic formals have been modified such as to take into account that each chemical step of the polymerization is a building step of the crystal too.
A mesophasic polymer: Poly(oxydodecandioyloxy‐1,4‐phenylene‐2‐methylvinylene‐1,4‐phenylene)
Authors: Roviello Antonio , Sirigu Augusto
Published: April 2003

Poly(oxydodecandioyloxy‐1,4‐phenylene‐2‐methylvinylene‐1,4‐phenylene) (1) was synthesized and partially characterized by differential scanning calorimetry and X‐ray diffraction methods. The polymer shows a thermotropic liquid crystalline behavior. The X‐ray diffraction spectrum of the anisotropic liquid is coherent with a nematic phase. Solid state polymorphism is also observed.
Application of the spin trapping technique to radical polymerization, 19. Reactions of the tert‐butoxyl radical with some N‐alkyl‐substituted acryl‐ and methacrylamides
Authors: Otsu Takayuki , Tanaka Hitoshi , Sato Tsuneyuki , Quach Loc
Published: April 2003

The reactions of tert‐butoxyl radical with some N‐alkyl‐substituted acryl‐ and methacrylamides were investigated at room temperature in benzene by means of the spin trapping technique. 2‐Methyl‐2‐nitrosopropane (BNO) was used as a spin trapping reagent. The tert‐butoxyl radical was found to undergo both hydrogen‐abstraction from N‐methyl groups and double bond addition in its reactions with N‐methylacrylamide (NMAm) and with N,N‐dimethylacrylamide. Contrary to this, the benzoylthio radical reacted exclusively with the double bond of NMAm. In the reaction of the tert‐butoxyl radical with N‐methylmethacrylamide (NMMAm), only double bond addition was observed. However, when the tert‐butoxyl radical reacted with N,N‐dimethylmethacrylamide (NDMMAm), it mainly attacked the N‐methyl group of NDMMAm. The tert‐butyl radical abstracted a hydrogen atom from the α‐methyl group of NMMAm and NDMMAm, keeping their N‐methyl group unreacted. Furthermore, in the reaction of the tert‐butoxyl radical with N‐propyldimethacryloylamine (NPDMAm) in the presence of BNO, both a methylene radical which was derived from intramolecular cyclopropagation giving a five‐membered ring and a radical derived from the addition to the double bond of NPDMAm were trapped as their aminyl radicals.
Metathetische spaltung von butadien‐styrol‐copolymeren; abbauprodukte
Authors: Thorn‐Csányi Emma , Abendroth Henning , Perner Helmut
Published: April 2003

The metathetical degradation of styrene(S)‐butadiene(B) copolymers gives a wide spectrum of fragments which are characteristic for the microstructure. We also determined degradation of products of S‐1, 2B‐ and 1,2B‐S‐sequences.
Polymere phthalocyanine und ihre vorstufen, 1. Reaktive oktafunktionelle phthalocyanine aus 1,2,4,5‐tetracyanbenzol
Authors: Wöhrle Dieter , Meyer Gunter , Wahl Bernd
Published: April 2003

1,2,4,5‐Tetracyanobenzene reacts under mild conditions with anionic reagents not to polymer but to low molecular weight, high substituted phthalocyanines: 2,3,9,10,16,17,23,24‐octacyanophthalocyanine (3a) and tetrakis(1‐imino‐3‐propoxyisoindolo)porphyrazine (3b). 3a is saponified to the octacarboxyphthalocyanine 3c and converted with hydrazine to tetrakis(1,4‐diaminophthalazino)porphyrazine (3d). Low molecular metal chelates are synthesized starting from 3a and 3c. IR‐ and UV/VIS‐spectra are discussed.
Syntheses of N‐(nitrophenyl)amine substituted diacetylene alcohol monomers
Authors: Horner Charles J. , Garito Anthony F.
Published: April 2003

A procedure for the preparation of a novel class of nitroaniline substituted diacetylene alcohols is reported. The polymerization behavior of one member of this class, 6‐(4‐nitro‐2‐trifluoromethylanilino)‐2,4‐hexadiyn‐1‐ol (11a), has been studied using X‐ray irradiation.
Polymers containing enzymatically degradable bonds, 1. Chymotrypsin catalyzed hydrolysis of p‐nitroanilides of phenylalanine and tyrosine attached to side‐chains of copolymers of N‐(2‐hydroxypropyl)methacrylamide
Authors: Kopeček Jindřich , Rejmanová Pavla , Chytrý Vladimír
Published: April 2003

A series of copolymers of N‐(2‐hydroxypropyl)methacrylamide were prepared, which contained side chains of the general formula ‐Gly‐X‐Y‐NAp, where Gly ¨ glycine; X ¨ glycine, alanine, β‐alanine, valine, leucine, isoleucine, phenylalanine; Y ¨ phenylalanine or tyrosine; NAp ¨ p‐nitroanilide, the latter modelling biologically active compounds. The rates of chymotrypsin‐catalyzed hydrolysis of p‐nitroanilide groups at pH = 8,0 and 25°C were determined over a range of substrate concentrations to derive values for kcat and KM. The results allowed us to determine the influence of the structure of side chains on the rate of cleavage of Y‐NAp. The increase in the susceptibility to chymotrypsin attack with an increasing spacing of the Y‐NAp residue from the backbone of the polymer chains is demonstrated by comparing the kinetic data of copolymers containing ‐Gly‐Gly‐Phe‐Phe‐NAp, ‐Gly‐Gly‐Phe‐NAp and ‐Gly‐Phe‐NAp side chains. Results obtained with α‐chymotrypsin were compared with the cleavage of the above polymer substrates with chymotrypsin covalently bound to a copolymer of N‐(2‐hydroxypropyl)methacrylamide.
The counterion effect on the steric course of the cationic polymerization of tert‐butyl vinyl ether
Authors: Kunitake Toyoki , Takarabe Kunihide
Published: April 2003

The cationic polymerization of tert‐butyl vinyl ether was carried out at −76°C with a variety of triphenylmethyl salts as initiator. The microtacticity of the polymer was determined by 1H NMR spectroscopy after conversion to poly(vinyl alcohol). The fraction of isotactic units, Pm, increased with decreasing polarity of the polymerization medium, in consistence with the published data for metal halide initiators. The Pm value decreased gradually from 0,85 to 0,72–0,75 in 7 : 3 (v/v) CH2Cl2‐toluene by increasing the counteranion radius from 2,4 Å (BF−4) to ca. 4 Å (AlCl−4). A further increase in the counteranion size, however, did not notably influence the steric structure of the polymer. These structure variations are discussed in terms of the steric course of cationic propagation. In the case of pentacoordinate counteranions (SnCl−5 and ZrCl−5), the steric structure depended also on the counteranion concentration, as already reported for other monomers.
Investigation of the copolymerization of mono‐ and bifunctional monomers of methacrylic esters
Authors: Krakovyak Marc , Ananieva Tatiana , Anufrieva Elisaveta , Gotlib Yulii , Nekrasova Tatiana , Skorokhodov Serguei
Published: April 2003

The relationships of free‐radical copolymerization of mono‐ and bifunctional monomers were investigated taking as an example a model system of monomers: methyl methacrylate (MMA) and 9,10‐dianthrylenedimethyl dimethacrylate (1). The copolymerization was carried out in toluene at 60°C at a 525: 1 mole ratio of MMA to 1, with AIBN as initiator. Chemical and luminescent methods for the quantitative determination of bridge bonds containing anthracene moieties in the polymer system and the method of their selective cleavage were developed. Experimental dependences of the concentration of monomers and single and double bonded monomeric units of 1 in the copolymers on the copolymerization time were established. It was found that during the copolymerization the activity of each monomer double bond and that of the pendent double bonds in the monomeric units of 1 in the copolymer are similar. It was shown that over a specific range of changes in the content of bridge bonds (the position of which depends on the length of the chains being crosslinked) the values of the intrinsic viscosity of the copolymer solutions increase cooperatively and gel fraction is formed subsequently.
The influence of molecular interaction on polymerization, 5. Copolymerization of benzyl methacrylate with maleic anhydride
Authors: Boudevska Hrissanta , Platchkova Svetla
Published: April 2003

Copolymerization of benzyl methacrylate (BMA) with maleic anhydride (MA), initiated by 2,2′‐azoisobutyronitrile at 70°C in chloroform or acetonitrile, were investigated. The complex formation between the two monomers in chloroform was studied by 1H NMR spectroscopy. The stability constant of the complex was found to be 0,25 l.mol−1. The following copolymerization reactivity ratios were found: in chloroform: rBMA = 0,188 ± 0,035 and rMA = 0,003 ± 0,005, in acetonitrile: rBMA = 0,116 ± 0,093 and rMA = 0,231 ± 0,027. By 1H NMR investigations it could be shown that the results correlate with the changes of the reactivity ratios depending on the solvent used.
Interaction of human serum proteins with synthetic polymers in homogeneous systems
Authors: Ohno Hiroyuki , Abe Koji , Tsuchida Eishun
Published: April 2003

Human serum albumin and γ‐globulin form complexes with various synthetic polymers through some secondary binding forces. This complex formation between serum proteins and ionic or nonionic polymers is discussed. Polycations and polyanions interact with serum proteins through electrostatic interaction force mainly. There is strong pH dependence on the interaction, because these proteins show amphoteric properties. When ionic polymers interact strongly with proteins, the conformations of both proteins are changed by the complexation. In case of complexation with nonionic polymers, γ‐globulin tends to be precipitated at higher pH than 6. In addition, there exists suitable hydrophobicity of nonionic polymers for complex formation with high efficiency. On the contrary, albumin is easily precipitated by nonionic polymers in the lower pH region. There are little conformational changes of proteins through complexation with nonionic polymers except for the case of poly(N‐vinyl‐2‐pyrrolidone) treatment. Selective complexation is achieved by some nonionic polymers having less hydrophobicity such as poly(ethylene oxide). High efficiency of selective complexation is observed by control of the pH and the hydrophobic properties of the noionic polymers.
Time resolved small angle scattering during isothermal crystallization of unoriented poly(ethylene terephthalate) using synchrotron radiation
Authors: Elsner G. , Koch M. H. J. , Bordas J. , Zachmann H. G.
Published: April 2003

The time course of the small angle scattering pattern of amorphous poly(ethylene terephthalate), (PET), was measured during isothermal crystallization using synchrotron radiation. The samples were heated to temperatures between 117 and 145°C in an oven placed in the path of the X‐ray beam. The scattering curves were measured within 10 s at intervals of 1 s so as to follow the kinetics of the process continuously. It appears that the distance between the centres of mass of the crystallites decreases with increasing crystallization time as in oriented PET. The integrated small angle scattering follows approximately the same time course as the increase in the degree of crystallinity during an isothermal crystallization yielding Avrami exponents between 5 and 7. Guinier plots of the low angle region show that the scattering can be attributed to rod‐like particles.
Thermal decomposition of flame retardant acrylonitrile polymers, 2. Effect of red phosphorus
Authors: Ballistreri A. , Foti S. , Montaudo G. , Scamporrino E. , Arnesano A. , Calgari S.
Published: April 2003

Elemental red phosphorus was found to be an efficient flame retardant for poly(acrylonitrile) homopolymer (PAN) and, to a lesser extent, also for a modified acrylic resin containing 36 wt.‐% of vinylidene chloride (VC2) as comonomer. The data collected show that condensedphase and gas‐phase mechanisms are both responsible for the flame inhibition effect of red phosphorus on PAN. On the contrary, a gas‐phase mechanism seems to be responsible for the flame inhibition effect of red phosphorus on the AN‐VC2 copolymer. Flash‐pyrolysis GC data, with pyrolysis products MS identification, are reported for both polymers studied.
The anionic polymerization of 2‐pyrrolidone in bulk and in suspension
Authors: Costa Giovanna , Nencioni Macro , Russo Saverio , Semeghini Gian Luigi
Published: April 2003

A study on the anionic polymerization of 2‐pyrrolidone in bulk and suspension under isothermal conditions is described. After a discussion about the disadvantages of the bulk process carried out by using N‐potassium‐2‐pyrrolidone as initiator and N‐acetyl‐ε‐caprolactam as activator, a possible alternative way is proposed on the basis of the suspension polymerization initiated by N‐potassium‐2‐pyrrolidone and activated by silicon tetrachloride. The ultraviolet absorption spectra of the polymer samples obtained by the above methods reveal that undesiderable side reactions leading to degradation of the keto amide groups, are almost negligible under the aforementioned conditions.
Thermally initiated emulsion polymerization of styrene
Authors: Kast Hans , Funke Werner
Published: April 2003

The thermal polymerization of styrene in emulsion was studied by determination of the number of particles, the rate of polymerization, and the average molecular weight of the polymer formed as a function of the emulsifier concentration. For the number of particles the relation N ∼ [E]1,4 was found, whereas the rate of polymerization showed a dependence of vbr ∼ [E]0,7, only up to an emulsifier content of 0,2 mol. dm−3, but remained constant at higher concentrations. A transfer of low molecular weight radical species from the organic to the aqueous phase is discussed as a prerequisite of polymerization in the latex particles. The deviations from the Smith‐Ewart theory are explained by the low rate of radical formation, which does not provide a constant radical concentration per particle.
Polymerization of L‐leucineN‐carboxyanhydride with 1,6‐hexanediamine as initiator
Authors: El‐Sabbah Mohamed M. B. , Elias Hans‐G.
Published: April 2003

L‐Leucine N‐carboxyanhydride was polymerized in N,N‐dimethylformamide (DMF) or 1,4‐dioxane (DIO) at 25°C with either 1,6‐hexanediamine (1) or its monocarbamate 2 using a constant volume apparatus, initially filled with nitrogen or carbon dioxide. Number average molar masses from amino end group titrations on one hand and from initial monomer/initiator ratios and conversions on the other were practically identical for monomer conversions between 25 and 79%, indicating both the living nature of the polymerization and a participation of all initially present amino groups, despite the fact that polymer precipitation was observed at higher conversions for all systems and an additional precipitation of the carbonate 2 for the system 1/DIO/CO2 at low conversions. Two kinetic stages were observed for the latter system, but three kinetic stages for all other ones. The absence of a rapid initial polymerization period for the system, 1/DIO/CO2 as contrasted to the high initial rates for the systems 1/DMF/CO2 or 1/DMF/N2 points towards a carbamate mechanism in the first case and an amine mechanism in the second. The relation between intrinsic viscosities and number average molar masses of poly(L‐leucine) in trifluoroacetic acid at 25°C was found as [η] = 0,0169 〈Mn0,86 ± 0,04 ml/g.
Structural change of amorphous cellulose by water‐ and heat‐treatment
Authors: Hatakeyama Hyoe , Hatakeyama Tatsuko
Published: April 2003

Strips of amorphous cellulose film were conditioned under wet atmospheres of 80 and 100% relative humidity or heated at 393 K in vacuo for different time intervals. The structural change of these samples was investigated using differential scanning calorimetry (DSC), IR spectrometry, x‐ray diffractometry (x‐ray), and the density‐gradient column method. In the initial stage of conditioning of cellulose samples at a wet atmosphere, it was found that the thermally determined relative volume fraction (α) of the amorphous part of cellulose stays constant while the diffusion coefficient (Dod), calculated from the rate of H → D exchange of OH groups observed in IR, decreases rapidly. This fact seems to show that the rearrangement of cellulose molecules does not occur as a whole but only partly in the vicinity of the OH groups which affect the process of H → D exchange. If large amounts of water are supplied, however, cellulose molecules rearrange freely and provide a crystalline structure, as observed clearly by x‐ray. On the other hand, during the heat‐treatment of amorphous cellulose, the decrease of α and Dod can be clearly observed by DSC and IR from the initial stage of treatment. Judging from the change of α and Dod, it was inferred that the hydrogen bond formation occurs step by step simultaneously with the rearrangement of cellulose molecules by heat‐treatment.
Solubilization of homopolymers and copolymers by block copolymer micelles in dilute solutions
Authors: Tuzar Zdeněk , Bahadur Pratap , Kratochvíl Pavel
Published: April 2003

Solubilization by micelles of a three‐block copolymer poly(styrene‐butadiene‐styrene) with a polybutadiene core was studied by the light scattering method on three types of solubilizate: polybutadiene with (a) low and (b) high molar mass (with respect to the polybutadiene block of the copolymer), and (c) a block copolymer poly(styrene‐butadiene‐styrene) with a high content of butadiene. True solubilization of polybutadiene into the cores of spherical micelles occurs in case (a); in case (b) polybutadiene forms partially stabilized, emulsion‐like large droplets. In case (c) stable mixed micelles are formed having either lower or higher molar mass with respect to that of the original micelles, depending on the ratio of molar masses and on the composition of both copolymers. A similarity between solubilization of hydrocarbons by micelles of soaps or surfactants in aqueous solutions and solubilization of polymers by copolymer micelles in selective solvents is pointed out.
Comportement de copolymères greffés en milieu solvant sélectif des greffons. Cas des copolymères poly(styrène‐g‐bromure de vinyl‐4 N‐éthylpyridinium)
Authors: Selb Joseph , Gallot Yves
Published: April 2003

The dilute solution properties of amphiphilic graft copolymers with an “insoluble” polystyrene backbone (PS) bearing “soluble” poly(4‐vinyl N‐ethylpyridinium bromide) grafts (PVPQ), were studied in water‐methanol‐LiBr (0,1 mol/l) mixtures. In contrast to block copolymers with an identical chemical nature and in the same solvents, graft copolymers do not present intermolecular association. Viscometric data clearly show that a single graft molecule (or “monomolecular pseudo‐micelle”), has a structure similar to that of a “plurimolecular micelle” of a block copolymer, and exhibits a compact star‐like structure.
Polymers containing enzymatically degradable bonds, 3. Poly[N‐(2‐hydroxypropyl)methacrylamide] chains connected by oligopeptide sequences cleavable by trypsin
Authors: Ulbrich Karel , Strohalm Jiří , Kopeček Jindřich
Published: April 2003

Copolymers (12–20) of N‐(2‐hydroxypropyl)methacrylamide (1) with p‐nitrophenyl esters of N‐methacryloylated oligopeptides (2–10) were prepared. These copolymers were crosslinked below the gel‐point with N,N′‐bis(Nε‐Boc‐lysine)hexamethylenediamine (11). The crosslinks connecting poly[N‐(2‐hydroxypropyl)methacrylamide] chains contained an oligopeptide sequence of 2–4 amino acids: ‐Gly‐Nε‐Boc‐Lys‐; ‐Gly‐X‐Nε‐Boc‐Lys‐ (X…Gly, Val, Leu, Phe, D‐Phe); ‐Ala‐Gly‐Val‐Nε‐Boc‐Lys; ‐Gly‐Gly‐Y‐Nε‐Boc‐Lys‐(Y…Phe, Val). After removal of the Boc blockade of lysine, copolymers degradable by trypsin were obtained. Changes in the molecular weight distribution of the polymers studied after incubation with trypsin allowed us to evaluate the influence of steric effects and of subsite interactions on the degradability of polymeric substrates.
Linear oligopeptides, 77. The effect of the insertion of a proline residue on the solid‐state conformation of host peptides
Authors: Toniolo Claudio , Bonora Gian Maria , Mutter Manfred , Pillai V. N. Rajasekharan
Published: April 2003

The conformational properties of two series of monodispersed, chemically and optically pure, PEG

The following abbreviations have been used in the text: PEG, poly(ethylene glycol); ‐NHPEG, “amino‐PEG”; ‐NHPEG‐M, “amino‐PEG” monomethyl ether; NPS, o‐nitrophenylsulfenyl; t‐Boc, tert‐butoxycarbonyl; Z, benzyloxycarbonyl; Met, methionine; Pro, proline; OBzl, benzyloxy; OMe, methoxy; OEt, ethoxy; NHEt, ethylamino; Glu, glutamic acid; IR, infrared; MeOH, methanol; TFE, 2,2,2‐trifluoroethanol.

‐bound linear host oligopeptides of the general formula \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} (L - Met\rlap{--} )}_n {\rm NHPEG} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} [L - Glu(OBl)\rlap{--} ]}_n {\rm NHPEG - M} $\end{document} containing a single guest L‐Pro residue at different positions in the main chain have been investigated in the solid state using IR absorption. The corresponding N‐deblocked peptides have also been examined. The incorporation of a L‐Pro residue in a central position of a β‐conformation appears to induce the onset of a structural irregularity characterized by IR absorption bands in the vicinity of 3 325 cm−1 and 1 575 cm−1.
Linear oligopeptides, 78. The effect of the insertion of the proline residue on the solution conformation of host peptides
Authors: Toniolo Claudio , Bonora Gian Maria , Mutter Manfred , Pillai V. N. Rajasekharan
Published: April 2003

The conformational properties of three series of monodispersed, chemically and optically pure, PEG

The following abbreviations have been used in the text: PEG, poly(ethylene glycol); ‐NHPEG, “amino‐PEG”; ‐NHPEG‐M, “amino‐PEG” ‐monomethyl ether; t‐Boc, tert‐butyloxycarbonyl; Z, benzyloxycarbonyl; Ala, alanine; Met, methionine; Gly, glycine; Glu, glutamic acid; Pro, proline; OBzl, benzyloxy; OEt, ethoxy; CD, circular dichroism; MeOH, methanol; TFE, 2,2,2‐trifluoroethanol; HFIP, 1,1,1,3,3,3‐hexafluoro‐2‐propanol.

‐bound linear host oligopeptides of the general formula \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} (L - Met\rlap{--} )}_n {\rm NHPEG} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} (L - X\rlap{--} )}_n {\rm NHPEG - M} $\end{document} [X = Ala, Glu(OBzl)] containing a single guest L‐Pro residue at different positions in the main chain have been investigated in aqueous and alcoholic solutions as a function of concentration, temperature, and added salts using CD. The corresponding N‐deblocked peptides have also been examined. The incorporation of the L‐Pro residue into a host petide chain blocks the extension of the α‐helical conformation at the level of the segment containing the guest residue at its N‐terminal end. The investigations reveal asymmetric helixnucleation properties of the L‐Pro residue as predicted by theory. In β‐structure‐forming oligopeptides, the insertion of a L‐Pro residue results in a significant destabilization of the ordered conformation. Thus, aggregation of peptide chains is less pronounced in these co‐oligopeptides.
Kinetics of radical polymerization of tolyl methacrylates
Authors: Vrhovac Ljubica , Veličković Jovan
Published: April 2003

The kinetics of radical polymerization of tolyl methacrylates, initiated with 2,2′‐azodiisobutyronitrile and dibenzoyl peroxide were studied using dilatometric and gravimetric techniques. The initial rates of polymerization depend on the position of the methyl subsitution in the aromatic ring. With both initiators the initial rates of polymerization in the range within 50 and 70°C increase in the order: ortho < meta < para substitution. The overall rate constants and activation energies were determined. The different rates observed are discussed in terms of steric effects, monomer constitution, and other factors which might affect the reactivity of the radical propagation.
Styrene‐divinylbenzene copolymers, 3. Revisited IR analysis
Authors: Bartholin Michel , Boissier Giselle , Dubois Joelle
Published: April 2003

A critical analysis of the styrene‐divinylbenzene resin infra‐red spectra was made using previous works and new results. A method for the determination of pendent double bonds and also crosslinking degree and composition of the resin is drawn. A few examples of application are given.
Effect of curing environment on network formation of polyurethane
Authors: Furukawa Mutsuhisa , Yokoyama Tetsuo
Published: April 2003

The variation of the allophanate concentration with curing time was determined by an amine degradation method. It was concluded that the properties of polyurethane networks prepared with the same formulation differ considerably if crosslinking reactions are carried out under different conditions.
Temperature effect on the stereoelective polymerization of methylthiirane in homogeneous phase
Authors: Dumas Philippe , Sigwalt Pierre , Guérin Philippe
Published: April 2003

Chiral cadmium thiolates of cysteine with cyclohexyl or (−)menthyl ester groups were prepared and compared with similar compounds (with isopropyl or methyl ester groups) as initiators for stereospecific polymerization of methylthiirane in homogeneous phase. The resulting polymers are highly isotactic and in all cases stereoelection can be reversed with a small change in polymerization temperature. This temperature effect permitted to differentiate two stages in the polymerization corresponding to the formation of a precursor and to that of a high polymer, respectively.
On the temperature dependence of interdiffusion coefficients for the cellodextrins
Authors: Amu Thomas C.
Published: April 2003

Interdiffusion coefficients at infinite dilution were measured for the cellodextrins (glucose to cellohexaose) in aqueous solutions at 25 and 35°C using the modified Rayleigh interference optics. Diffusion data were also obtained for glucose in DMSO and formamide at 25, 30, 35, and 45°C. The experimental results are discussed with due regards to effects resulting from solute‐solvent interactions and also hydration of these oligomers.
A convenient method for the preparation of a highyl active MgCl2‐supported TiCl3 catalyst for the polymerization of propylene
Authors: Soga Kazuo , Terano Minoru
Published: April 2003

A highly dispersed MgCl2‐supported TiCl3 catalyst was conveniently prepared by treating the complex of TiCl3 · 3 C5H5N with AlEt2Cl in the presence of MgCl2. The catalyst combined with AlEt3 showed a very high activity for the polymerization of propylene, and gave a polymer with considerably high isotacticity. The catalyst displayed a sharp ESR signal with a g‐value of 1,94, which is identical with that of the ground H‐grade TiCl3.
Telechelics 6. Oligostyrenes by radical polymerization
Authors: Konter Wolfgang , Bömer Bruno , Köhler Karl‐Heinz , Heitz Walter
Published: April 2003

Styrene polymerized by AIBN as initiator results in telechelic α,ω‐bis(1‐cyano‐1‐methylethyl)oligostyrenes (1). The functionality, fCN, was found to be 1,99 ± 0,05 in the molecular weight range up to 2000 and the Mw/Mn‐values were found to be < 1,5 after complete consumption of the initiator. Using methyl 2,2′‐azoisobutyrate as initiator, oligostyrenes with two ester endgroups were obtained. The conversion of styrene was limited by “dead end” conditions as described by Tobolsky. The efficiency was 0,9 under the preparative conditions used. The cyano endgroups were converted into amino endgroups by hydrogenation and into carboxyl endgroups by hydrolysis. Telechelic α,ω‐bis(2‐isocyanato‐1,1‐dimethylethyl)‐ and α,ω‐bis(1‐isocyanato‐1‐methylethyl)oligostyrenes 4 and 6 were obtained from the amino product 2 by the phosgene method and from the carboxyl product 3 by the Weinstock/Curtius reaction, respectively. Connecting these telechelic styrene blocks by a polyreaction results in polymers in the 20 000 – 50 000 molecular weight range.
Preparation of polycations by polymerizing biscations and the conductivity of their TCNQ salts
Authors: Watanabe Masayoshi , Kamiya Tamotsu , Goto Kuniyuki , Matsubara Noriaki , Tsuchikura Akira , Shinohara Isao
Published: April 2003

The conductivity of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) salts of biscations and polycations was investigated in dependence of the cation structures. The biscations, which were considered to be a model unit of polycations, were prepared by the Menshutkin reaction of aromatic amines, such as pyridine and quinoline, with α,ω‐dibromoalkanes. The polycations were synthesized by polymerizing bifunctional biscations bearing two amino groups with diisocyanates. The conductivity of the biscation‐TCNQ complex salts was mainly influenced by the interval between N+ atoms and the polarizability of the biscations. Biscations which had an optimum interval between N+ atoms and high polarizability were effective to obtain high conductive TCNQ salts. The TCNQ complex salts of polycations containing such biscation parts showed similar conductivity as the corresponding biscation‐TCNQ complex salts. It is suggested that the TCNQ molecules, under the influence of the biscation parts, dominated the conductivity of the polycation‐TCNQ complex salts.