bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms and kinetics of the anionic polymerization of acrylates, 1. Oligomerization of tert‐butyl acrylate and characterization of products
Authors: Janata Miroslav , Lochmann Lubomír , Müller Axel H. E.
Published: April 2003

The anionic polymerization of tert‐butyl acylate (tBuA) initiated by tert‐butyl α‐lithioisobutyrate was investigated in THF at 25°C. The individual oligomers were isolated and characterized by UV, IR and NMR spectroscopy. The distribution of products was determined in the range of reaction times 0,02 s ≤ t ≤ 1800 s. The oligomerization is extremely fast. Even after 0,02 s at ‐30°C, no residual monomer could be detected. After short reaction times the reaction mixture almost exclusively consists of linear oligomers of tBuA. This indicates that there is no termination reaction by Claisen condensation during polymerization. Nevertheless, the molecular weight distribution is rather broad (M̄w/M̄n = 2,15). The very large amount of dimer observed is an indication of its low reactivity. A two‐state mechanism is proposed to account for the high polydispersity. Only after longer reaction times side products are formed by Claisen condensation (“back‐bitting”). The termination product of the trimer is an enolized cyclic β‐ketoester.
The correlation of rotational isomers in polyethylene‐like crystals
Authors: Xenopoulos Alexander , Noid Donald W. , Sumpter Bobby G. , Wunderlich Bernhard
Published: April 2003

The molecular dynamics technique to simulate the behavior of polyethylene crystals, described earlier, is used to study the creation and mobility of rotational isomers of a polyethylene‐like chain in a crystal environment. Both a “gross defect” (formed by perturbation of the cartesian coordinates) and a “kinetic defect” (formed by placing a specific amount of kinetic energy that excites a pure local torsion) are added to the central chain of a polyethylene crystal. The initial dynamic instability quickly forms a more stable, but more or less static defect that, subsequently, moves somewhat along and between neighboring chains, and finally, gets quenched on a time scale of a few picoseconds. Increasing the temperature leads from a highly correlated state to a state where defects are created and quenched statistically (condis state). Increasing the energy input for defect generation leads to the creation of different static defects. The onset of conformational disorder is independent of the initial perturbation. There is a correspondence of the observed defects to the defects proposed for polyethylene based on molecular mechanics calculations, but lifetimes are relatively short.
Synthesis of novel functional styrene monomers having trimethylsilyl and hydroxyalkyl groups by the reaction between 4‐vinylbenzyllithium derivatives and oxiranes
Authors: Nagasaki Yukio , Takahashi Seiji , Tsuruta Teiji
Published: April 2003

New synthetic routes for styrene derivatives having both trimethylsilyl and hydroxyalkyl groups were investigated. Reactions between oxirane (5a) and chemical species present in an equilibrium system resulting from 4‐(trimethylsilylmethyl)styrene (1s) and lithium diisopropylamide (2) in tetrahydrofuran give an addition product (8a) between 2 and 5a preferentially. By using alkyl‐substituted oxiranes such as ethyloxirane (5c) and tert‐butyloxirane (5e), a 1 : 1 addition reaction of 1s with the oxiranes takes place predominantly to form 1‐alkyl‐3‐trimethylsilyl‐3‐p‐vinyl‐phenyl‐1‐propanol (8) homologues. From results of studies on the reaction between 2 and several oxiranes, it was concluded that the selective formation of 8 homologues was attained by suppression of reactions between oxirane and 2 owing to steric hindrance between alkyl substituents of oxirane and isopropyl groups of 2. The reactivity of 8 in polymerization reaction was also estimated on the basis of spectroscopic measurements. 8 was found to have a reactivity similar to that of 4‐(trimethylsilylmethyl)styrene (1s).
Conformational transition of block copolymers in dilute solution and their morphology in the solid state
Authors: Tsitsilianis Constantinos , Staikos George , Dondos Anastasios , Lutz Pierre , Rempp Paul , Benoît Henri
Published: April 2003

Block copolymers poly(methyl methacrylate)‐block‐polystyrene‐block‐poly(methyl methacrylate) and polystyrene‐block‐poly(tert‐butyl methacrylate) were prepared by anionic polymerization and were studied in dilute solution as well as in the bulk state. The viscometric study revealed that the block copolymers exhibit a conformational “transition” occurring in a narrow temperature range. Films were obtained with the same copolymers by casting at different temperatures, chosen below and above the “transition”. From the investigation of these films by differential scanning calorimetry, using the entropy relaxation method, and by dynamic mechanical measurements, it was shown that the block copolymers exhibit a rather segregated structure if they are obtained below the “transition” temperature, and that they adopt a quasi‐Gaussian conformation (implying a better miscibility of the two kinds of blocks) if the solvent is evaporated above the “transition” temperature.
Synthesis and properties of a thermotropic copolyester based on 4‐hydroxyacetophenone azine
Authors: Cimecioglu A. Levent , Fruitwala Hitesh , Weiss R. A.
Published: April 2003

The synthesis of a thermotropic copolyester based on 4‐hydroxyacetophenone azine (1) and a 50 : 50 (mole ratio) mixture of sebacoyl/dodecanedioyl dichlorides was investigated in chloroform via a low‐temperature solution route. Polymers with an inherent viscosity ηinh between 0,27–1,56 dL · g−1 were characterised by 1H NMR, IR, thermal analyses, gel permeation chromatography and static light scattering techniques: Enantiotropic polymers exhibit a large mesophase range (≈100°C) and the values of both crystal‐nematic and nematic‐isotropic transitions are molecular‐weight dependent. Intrinsic viscosity was determined to relate to molecular weight by [η]/(dL · g−1) = 9,6 · 10−4 M̄ in chloroform at 25°C, and the persistence length was calculated to be of the order of 27 Å.
Energy calculations on chain conformation and mode of packing of crystalline syndiotactic cis‐1,4‐poly(1,3‐pentadiene)
Authors: Napolitano Roberto
Published: April 2003

Conformational and packing energy calculations were performed on crystalline syndiotactic cis‐1,4‐poly(1,3‐pentadiene). The lowest energy conformation of a single polymer chain — under the constraint of the experimental identify period along the chain axis (8,5 Å) — was found. The analysis of modes of packing shows that the lowest packing energy is obtained in the P21/c space group. A possible structure of the polymer is suggested.
Telechelics via addition of dithiols onto alkadienes, 2. Base and acid catalysis
Authors: Nuyken Oskar , Völkel Thomas
Published: April 2003

The base‐catalyzed Michael‐type addition of dithiols onto activated diacrylates and dimethacrylates proceeds quantitatively and leads to products with anti‐Markovnikov orientation of the addition. This reaction was used to prepare telechelics using non‐stoichiometric ratios of monomers. The acid‐catalyzed addition of dithiols onto divinyl ethers also yields polymers and telechelics, however, these products show Markovnikov orientation of the addition.
A study of band texture formation of nematic solutions of poly(1,4‐phenyleneterephthalamide) in sulfuric acid
Authors: Chen Shouxi , Qian Renyuan
Published: April 2003

The band texture formation of nematic poly(1,4‐phenyleneterephthalamide) (PPTA)/H2SO4 solutions after shearing between rotating plates was studied. For a thickness of the solution layer larger than 20 μm the band texture appears immediately after the cessation of shearing, but a critical shear rate is needed which was demonstrated directly using polarizing microscopy. When the solution‐layer thickness was less than 10 μm, an induction time tb needed for the development of the band texture after the cessation of shearing was observed, which was of the order of 10 to 102 s. It is thus shown without any ambiguity that the band texture is formed during relaxation of shear orientation. The effects of solution concentration, solution‐layer thickness, shear rate, and shearing time on tb were studied. Once the band texture is formed from a sheared solution, it will take hours to relax completely to a randomly oriented domain texture. The factors influencing this relaxation time were also studied.
The laser‐flash‐initiated polymerization as a tool of evaluating (individual) kinetic constants of free‐radical polymerization, 6. The influence of monomer consumption during sample preparation
Authors: Schnöll‐Bitai Irene , Olaj Oskar Friedrich
Published: April 2003

The instantaneous differential molecular weight distribution curves for a polymer prepared under the influence of periodic laser flashes of constant intensity were calculated as a function of conversion and accumulated up to final conversions in the range between 0 and 20%. If these cumulated distributions are subjected to the conventional analysis with respect to the position of the inflection points, which are an excellent measure of kp · [M]t0 (kp = rate constant of chain propagation, [M] = monomer amount concentration, t0 = pulse separation), it is seen that this relationship, the validity of which was originally established in the limit of vanishing conversion, becomes the more deficient the higher is the conversion. This is even so when the initial monomer concentration is replaced by the average monomer concentration over the conversion interval examined. In the latter case, however, the deviations are reasonably small and do not exceed the limits of experimental accuracy in determining the position of the inflection point. Thus the application of this method of calculating kp is justified also for conversions up to at least 20%. The determination of k/t from rate of polymerization and weight‐average degree of polymerization (kt representing the rate constant of mutual chain termination) on the other hand, is completely insensitive towards conversion.
Kinetic investigation of the dispersion polymerization of N,N′‐methylenebis(acrylamide) in the presence of various emulsifiers
Authors: Capek Ignác , Funke Werner
Published: April 2003

The aqueous‐phase dispersion polymerization of N,N′w‐methylenebis(acrylamide) (MBA) in the presence of various additives was kinetically investigated at 50°C by conventional gravimetric and dilatometric methods. The rate of polymerization is found to be proportional to the concentration of sodium 1,2‐bis(2‐ethylhexyloxycarbonyl)ethanesulfonate (AOT) raised to the power of 0,42 (conc. of emulsifier <10−2) and to the conc. of ethylene glycol monooctylphenyl ether (TR) raised to the power of 0,23. On the other hand, it is independent of the conc. of poly(ethylene glycol) (PEG) and Tween 80 (TW). The rate of polymerization is proportional to the conc. of potassium peroxodisulfate (K2S2O8) raised to the power of 0,54 or 0,8 for systems with AOT or TW, respectively, and to the conc. of MBA raised to the power of 0,47 or 0,28 for the two respective systems. The effect of pH on the polymerization of MBA is assigned to the change of the decomposition rate of K2S2O8. The stabilization effect of the emulsifiers used decreases in the following order: AOT > TR ≈ PEG ≈ TW.
Cyclic oligo[oxymethyleneoligo(oxyethylene)]s and linear poly[oxymethyleneoligo(oxyethylene)]s studied by differential scanning calorimetry
Authors: Nekoomanesh Mehdi H. , Nicholas Christian V. , Booth Colin
Published: April 2003

Cyclic oligo[oxymethyleneoligo(oxyethylene)]s and linear poly[oxymethyleneoligo(oxyethylene)]s have been prepared by condensation of tri‐, tetra‐, penta‐ and hexaethylene glycols, including a number of samples not reported previously. The linear and cyclic products were characterised using nuclear magnetic resonance and gel‐permeation chromatography, and then studied using differential scanning calorimetry. Even‐odd effects in the values of the melting points and enthalpies of fusion of the samples are demonstrated.
The ene reaction between N‐isobutylallylnadimide and N‐isobutylmaleimide as a model for the cross‐linking reaction in bis(allyl)nadimide polymerization
Authors: Vijayakumar Chinnaswamy Thangavel , Lederer Klaus , Kramer Andreas
Published: April 2003

The reaction between N‐isobutylallylnadimide (NIBANI) and N‐isobutylmaleimide (NIBMI) was taken as a model reaction to obtain insight into the curing mechanism of polymeric alloys and composites consisting of bis‐ or tris(allyl)nadimides and bismaleimides. The reaction between NIBANI and NIBMI is not catalyzed by boron trifluoride etherate, neither at room temperature nor in refluxing methylene chloride. The thermally induced reaction (200°C) between NIBANI and NIBMI in equimolar quantities gives an indirect proof for the occurrence of an ene reaction. The high reactivity of the ene reaction product to undergo further Diels‐Alder reaction was proved by GPC and direct inlet mass spectral studies.
Dielectric relaxation of poly(benzyl methacrylate)
Authors: Kihira Yasuharu , Ichidayama Kouji , Takagi Sadao
Published: April 2003

The relaxation processes in atactic poly(benzyl methacrylate) were studied by means of dielectric measurements. Beside the α‐ and β‐relaxation processes due to the segmental motions of the main chain and of the entire side chain, respectively, a process designated as γ was found to occur in the temperature range between −60°C and 0°C. For the γ‐relaxation, the time‐temperature superposition principle is applicable. A linear relationship between temperature and the relaxation frequency fm or shift factor aT was found. Apparent activation energies estimated from the temperature dependence of fm and aT are 50 and 53 kJ · mol−1, respectively. The γ‐process is considered to result from the movement of the benzyl group in the side chain.
Imidization of polypromellitamic acid based on 4,4′‐methylenedianiline
Authors: Marek Miroslav , Schmidt Pavel , Schneider Bohdan , Bednář Bohumil , Králíček Jaroslav
Published: April 2003

Imidization of polyamic acid prepared from pyromellitic dianhydride and 4,4′‐methylenedianiline was investigated at 373–493 K. At a certain degree of imidization, depending on the reaction temperature, the reaction is significantly slowed down. For this reason, imidization was divided into two phases, a fast and a slow one, and the rate constants were calculated from the kinetic equation of a first‐order reaction. At imidization temperature above 443 K the activation enthalpy of the reaction decreases, probably due to the thermal decomposition of complexes of o‐carboxybenzamide groups with residues of the solvent. At higher imidization temperatures also the activation entropy of imidization decreases; this is probably caused by the higher rigidity of the film because of evaporation of the solvent which acts as a plasticizer.
On the chemical modifications of poly(maleic anhydride‐co‐isobutene) by means of hydrolysis, ammoniation or aminations
Authors: Bortel Edgar , Stysło Maria
Published: April 2003

Ring‐opening reactions of maleic anhydride (1)/isobutene (2) copolymer (M̄w = 2,76 · 105 g/mol), carried out by the use of: NaOH solution (hydrolysis); NH3; NH(CH3)2; N(CH3)3; NH(C2H5)2 and H2N(CH2CH2NH)2CH2CH2NH2 (TETA), resp., yielded water‐soluble products, with the exception of the TETA‐modified copolymer. The degrees of conversion α were found to be in the range between 87 to 100%, with the exception of the N(CH3)3‐reacted copolymer where α = 41,6%. As a result of the conversion reactions, the weight‐average molecular weights M̄w dropped significantly, by 30% in the case of hydrolysis, and by 40% in the cases of ammoniation or amination, despite the mild conditions which were employed. Based on nitrogen contents found analytically, as well as on 13C NMR spectra, it was concluded that under the given conditions the reactions using ammonia or amines do not proceed beyond the half‐amidation step. 13C NMR investigations on products of both the ammoniation and amination reactions indicate a directing influence produced by the CH3 groups of the isobutene unit. As a result, only those carbonyl groups remote from the pendant substitutents are prone to an attack which causes amidation.
A solid‐state 13C NMR study on heterogeneous Ziegler‐Natta catalyst components
Authors: Sormunen Pekka , Hjertberg Thomas , Iiskola Eero
Published: April 2003

Ziegler‐Natta catalysts supported on MgCl2 have been studied by CP‐MAS (cross‐polarization, magic‐angle spinning) 13C NMR spectroscopy. The support was activated mechanically and chemically, and then treated with a monoester (ethyl benzoate) or a diester (diisobutyl phthalate). Catalytic species were obtained by a treatment with TiCl4. Complexation and crystal disordering phenomena are clearly observed as changes in the chemical shifts and line broadenings. Line splittings were observed, especially for the diester due to nonequivalent crystal coordination sites. The diester shows a different behaviour compared to the monoester thus reflecting its better ability as a stereoselectivity‐controlling agent. The titanation led to the formation of a new, estercontaining and ordered complex on the surface of the carrier. The mobility of the surface complexes is restricted, crystalline complexes being more constrained.
New liquid‐crystalline side‐chain polymers with large transversal polarizability
Authors: Leube Hartmann F. , Finkelmann Heino
Published: April 2003

New side‐on liquid‐crystalline side‐chain polymers (LCSCP's) are presented as having a systematic variation of the anisotropy of polarizability with respect to the mesogenic short axis. Starting from hydroquinone as core of the rod, the polarizability perpendicular to the mesogenic long axis is increased stepwise upon replacing hydroquinone by naphthalene and anthracene derivatives. Naphthalene derivatives with cyclohexane carboxylic acid derivatives as side parts show to be the first side‐on attached LCSCP's exhibiting a smectic phase.
Polysilanes fonctionnels, 2. Synthèse d'α,ω‐bis(triméthylsilyl)poly(méthylvinylsilane)s. Caractérisation des octaméthyl‐divinyl‐2,3 tétrasilane et nonaméthyl‐trivinyl‐2,3,4 pentasilane
Authors: Noireaux Patrick , Mérand Philippe , Reyx Danièle
Published: April 2003

Low‐molecular‐weight organosilane polymers containing the methylvinylsilanediyl unit were prepared by sodium coupling of the corresponding organochlorosilanes. GPC, IR and 1H NMR analyses were performed. Principal objectives in this work were to isolate the first oligomers, tetra‐and pentasilane, to determine their spectroscopic characteristics and to compare the GPC characteristics with those of hydrocarbon polymers.
Kinetics of 1,3‐cyclohexadiene polymerization initiated by organolithium compounds in a non‐polar medium, 1. Pure propagation step
Authors: Zhong Xing Fu , François Bernard
Published: April 2003

The kinetics of propagation of the anionic polymerization of 1,3‐cyclohexadiene initiated by organolithium compounds in cyclohexane is reported. At low monomer concentrations secondary reactions are avoided. The propagation follows a half‐order kinetics with respect to living‐chain concentration, suggesting an association of two of these chains. The apparent rate constant is found to be 6,9 · 10−4 L1/2 · mol1/2 · s−1 at 20°C with an apparent activation energy of 16,6 kcal/mol (69,5 kJ/mol).
Conformational and packing energy calculations on the low‐temperature phase (phase II) of poly(tetrafluoroethylene)
Authors: Napolitano Roberto , Pucciariello Rachele , Villani Vincenzo
Published: April 2003

Conformational energy calculations were performed on phase II of poly(tetrafluoroethylene) under the constraint of three different experimentally proposed chain repeating distances. The corresponding conformations were used in packing energy calculations effected for the different unit cells reported in the literature. The results suggest the existence of both conformational and structural disorder in the crystalline state.
Morphology of ABA triblock copolymers consisting of poly(γ‐benzyl L‐glutamate) as the A component and polystyrene as the B component
Authors: Janssen Koen , van Beylen Marcel , Samyn Celeste , Scherrenberg Rolf , Reynaers Harry
Published: April 2003

The morphology in the solid state of ABA triblock copolymers consisting of poly(γ‐benzyl L‐glutamate) (A) and polystyrene (B) was investigated. Transmission electron microscopic measurements (TEM) revealed that the morphology varied with the length of the polypeptide block. Small‐angle X‐ray scattering (SAXS) data were in accordance with these TEM‐results. Wide‐angle X‐ray (WAXS) data showed that the distance between the α‐helices in the polypeptide lamellae changed with the composition of the block copolymers.
Chiral liquid‐crystalline poly(ester/β‐sulfoxide)s by asymmetric oxidation of prochiral nematic poly(ester/β‐sulfide)s
Authors: Angeloni Annino S. , Laus Michele , Caretti Daniele , Chiellini Emo , Galli Giancarlo
Published: April 2003

A new class of prochiral liquid‐crystalline poly(ester/β‐sulfide)s 2 and 3 containing the SC6H4S group was prepared, which were then asymmetrically oxidized to chiral liquidcrystalline poly(ester/β‐sulfoxide)s 4 and 5 comprising the \documentclass{article}\pagestyle{empty}\begin{document}$\hbox{---} \mathop {\rm S}\limits^ * \left( {\rm O} \right)\hbox{---} {\rm C}_6 {\rm H}_4 \hbox{---} \mathop {\rm S}\limits^ * \left( {\rm O} \right)\hbox{---}$\end{document} group. A chiral 2‐sulfonyloxaziridine 6 was used as the asymmetric oxidant and the reaction is highly chemoselective with quantitative yield. A 13C NMR analysis of a model poly(ester/β‐sulfoxide) 8 is performed, which allows to evaluate the asymmetric induction and the enantiomeric excess for the asymmetric oxidation product. While the parent polymers 2 and 3 are nematic, the chiral modified polymers 4 and 5 are cholesteric.
Tailoring of macromolecule conjugates using reversed micelles as matrix microreactors
Authors: Kabanov Alexander V. , Levashov Andrey V. , Khrutskaya Maria M. , Kabanov Victor A.
Published: April 2003

Being solubilized in systems of reversed micelles of a surfactant, the macromolecules incorporate into the inner cavities of the micelles, whose size can be changed by varying the degree of hydration, w0 = [H2O]/[surfactant]. The conjugates of proteins (α‐chymotrypsin, bovine serum albumin (BSA), monoclonal antibodies to insulin) with linear polyelectrolytes (poly(methacrylic acid), quaternized poly(4‐vinylpyridine)) are synthesized in reversed micelles of Aerosol OT (sodium bis(2‐ethylhexyl)sulfosuccinate) in the octane with 100% yield. The yield critically depends on the degree of hydration: the reaction does not proceed at low w0, but if w0 exceeds a threshold value (which differs for various macromolecules) the yield increases sharply and reaches 100%. Using the ultracentrifugation it was demonstrated that at low w0 the polyelectrolyte represents a compact globule compressed by the micellar matrix in the inner cavity of a micelle. Under these conditions, there is no space for the protein in a micelle which contains polyelectrolyte, and therefore reaction does not proceed. If w0 exceeds a threshold value the micelles become large enough to entrap the conjugated macromolecules simultaneously. The possibility of regulation of the conjugate composition by variation of w0 (via the size of the micellar matrix) was demonstrated by a conjugate of BSA with quaternized poly(4‐vinylpyridine).
Polyarylenes and poly(arylenevinylene)s, 4. Novel anthracene‐containing poly(arylenevinylene)s via poly‐Heck reaction
Authors: Weitzel Hans‐Peter , Müllen Klaus
Published: April 2003

Heck reactions with anthracene‐containing compounds are investigated. Some oligomeric model compounds as well as polymers were synthesized. The reason for the failure of 9,10‐divinylanthracene to undergo the Heck reaction are described. The solution of the synthetic problem was achieved by using the yet unknown 9,10‐bis(1,3‐butadienyl)anthracene.
Effect of catalyst isospecificity on olefin copolymerization
Authors: Soga Kazuo , Uozumi Toshiya , Park Joon Ryeo
Published: April 2003

Copolymerizations of ethylene with propene, ethylene with 1‐hexene, and propene with 1‐hexene were performed at 40°C under atmospheric pressure by using the aspecific catalyst composed of TiCl3/MgCl2 and Al(C2H5)3 and the isospecific Solvay‐type catalyst composed of TiCl3 and Cp2Ti(CH3)2. In case of ethylene‐propene copolymerization, the catalyst isospecificity affects neither the monomer reactivity ratios nor the monomer distribution in poly(ethylene‐co‐propene). The thermal properties of poly(ethylene‐co‐propene) are, however, not the same for the two catalysts due to the different tacticity of long propylene sequences contained in the copolymers. In the copolymerizations of ethylene and 1‐hexene and of propene and 1‐hexene, the monomer reactivity ratios differ to some extent between the two catalyst systems. The aspecific catalyst facilitates incorporation of 1‐hexene both in poly(ethylene‐co‐1‐hexene) and poly(propene‐co‐1‐hexene). The monomer distributions are also different in these copolymers. The aspecific and isospecific catalysts show a tendency to give random and blocky copolymers, respectively.
Polycondensation versus metal template condensation of 2,2′‐ethylenedithiodianiline with glyoxal
Authors: Biçak Niyazi , Hizal Gurkan , Yagci Yusuf , Barlas Hulusi
Published: April 2003

A polymer with azomethine linkages is formed upon reaction of 2,2′‐ethylenedithiodianiline (1) with glyoxal. The same reaction in the presence of Ni(II) and Cu(II) ions yields the corresponding metal complexes of the macrocyclic ligand. The driving force for the selectivity of this reaction may be attributed to the template effect of the metal ions. In the case of Co(II) ions, the polymer is formed as a by‐product, together with the macrocyclic complex.
Contribution to the study of the kinetics of radical homo‐ and copolymerization of fluoroalkyl methacrylates, 2. 2,2,3,4,4,4‐hexafluorobutyl methacrylate and 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate
Authors: Kárpátyová Angela , Bartoň Jaroslav , Paleta Oldřich
Published: April 2003

The kinetics of radical homopolymerization of 2,2,3,4,4,4‐hexafluorobutyl methacrylate (HFBMA) and 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate (OFPMA) was investigated in four different solvents. The rate of polymerization (Rp) of both monomers was found to increase with increasing donor number of the solvents, the increase being more marked in the case of OFPMA. This is probably associated with the leveling of the electron density of the double bonds of HFBMA and OFPMA by the influence of solvents as well as with the gel effect in the polymerization. Copolymerization parameters for HFBMA and OFPMA with butyl acrylate, styrene and methyl methacrylate were determined in benzene at 60°C and the values of resonance and polarity terms, Q and e, were also established.
Thermodynamics of mixing of ethylene oxide oligomers with different endgroups in tetrachloromethane
Authors: Killmann Erwin , Cordt Frank , Möller Friedrich
Published: April 2003

Enthalpies and Gibbs energies of mixing of liquid ethylene oxide oligomers with hydroxyl and methoxy end groups in tetrachloromethane are obtained by microcalorimetry and vapour pressure measurements. In this part of the publication the thermodynamic excess quantities ΔH, ΔGE and ΔSE are fitted by power series as functions of the weight fraction. Polymer‐ and solvent‐specific as well as partial thermodynamic quantities are deduced. The qualitative explanation of the strongly end group specific mixing behaviour demonstrated by these quantities is based on the induced dipol interactions of the ethylene oxide middle segments and on the hydrogen bond interactions of the OH end groups.
Zur frage der Existenz ternärer azeotrope bei Donator‐Acceptor Copolymeren
Authors: Schmidt‐Naake Gudrun , Schmidt Hermann , Litauszki Beata , Bieger Wolfgang
Published: April 2003

Using the suitable terpolymerization equations for the copolymerization of donor‐acceptor copolymer systems no ternary azeotrope could be calculated. Copolymerization reactivity ratios taken from literature show that there is no chance to find an azeotrope.
Side‐chain liquid‐crystalline polyacrylates containing heterocyclic mesogenic groups, 2. Influence of the length of the spacer group on the mesomorphous properties
Authors: Legrand Cécile , Borgne Alain Le , Bunel Claude , Lacoudre Nelly , Barny Pierre Le , Spassky Nicolas , Vairon Jean‐Pierre
Published: April 2003

The synthesis of a series of side‐chain liquid‐crystalline polyacrylates having mesogenic groups containing the trans‐2‐(4‐cyanophenyl)‐1,3‐dioxan‐5‐yl moiety is reported. Methylenic spacer groups of different lengths have been used. Polymers were prepared by radical polymerization of the corresponding acrylates. The liquid‐crystalline nature of these polymers has been established by calorimetric measurements and optical texture observations. The phase behaviour is strongly dependent on the length of the spacer group. With (CH2)6, the unusual INSANre sequence is observed.
Photoreactive cellulose derivatives with comb‐like structure, 1. Modification of O‐trialkylsilylcellulose with cinnamic acid‐containing side chains
Authors: Klemm Dieter , Schnabelrauch Matthias , Stein Armin , Niemann Manfred , Ritter Helmut
Published: April 2003

Trimethyl‐ and tert‐butyldimethylsilylcellulose were esterified with cinnamic acid, 4‐nitrocinnamic acid, 4‐(hexyloxy)cinnamic acid, 4‐(hexadecyloxy)cinnamic acid and N‐cinnamoyl‐11‐aminoundecanoic acid yielding photosensitive comb‐like cellulose derivatives. The UV‐irradiation of solid films of tert‐butyldimethylsilylcellulose cinnamate, trimethylsilylcellulose 4‐nitrocinnamate and tert‐butyldimethylsilylcellulose‐4‐hexyloxycinnamate were performed and the decrease of the absorption maxima was correlated with E/Z isomerisation and [2 + 2]‐cycloaddition. A possible application of the described photoreactive cellulose esters in the area of membrane technology is discussed.
Chirality of poly(vinyl compounds), 12. α‐(trityloxymethyl)acrylonitrile, a new monomer forming optically active, single‐sense helical polymers
Authors: Wulff Günter , Wu Yonghua
Published: April 2003

The new monomer, α‐(trityloxymethyl)acrylonitrile (2), was prepared. It can be polymerized anionically with optically active initiator systems to yield an insoluble polymer showing strong optical activity. In contrast to trityl methacrylate optically active polymers are obtained from 2 in toluene as well as in tetrahydrofuran. After removal of the trityl groups the optical activity is completely lost in the resulting poly[α‐(hydroxymethyl)acrylonitrile]. It is therefore concluded that an atropisomeric helical arrangement is present in poly[α‐(trityloxymethyl)acrylonitrile]. Compared to trityl methacrylate and its polymer the new monomer 2 and the corresponding polymer show higher stability against splitting off of the trityl groups.
The synthesis of polymers bearing terminal fluorescent and fluorescence‐quenching groups, 1. The incorporation of fluorescent groups at one end of the macromoleculer by means of the initiation process
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M.
Published: April 2003

Suitably substituted vinylidene compounds, incapable of undergoing anionic polymerisation, are reacted with butyllithium to produce an initiator for the anionic polymerisation of methyl methacrylate. Thus poly(methyl methacrylate)s are obtained, the macromolecules of which carry a single fluorescent (or fluorescence quenching) moiety at the initiating end of each chain.
The synthesis of polymers bearing terminal fluorescent and fluorescence‐quenching groups, 2. The incorporation of fluorescent and fluorescence‐quenching groups by means of a direct termination process
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M.
Published: April 2003

Attempts to terminate anionic polymerisation by suitably substituted (i. e. chromophoric) compounds, such as 9‐anthrylacetyl chloride, 1‐naphthoyl chloride, 1‐naphthylacetyl chloride, 1‐(1‐naphthyl)‐1‐phenylethylene, 1‐chloromethylnaphthalene or 1‐pyrenylmethyl bromide are described. In combination with the procedure described in part 1 of this series, it is possible to synthesise polymer molecules in which either one or both end‐groups contain the above‐mentioned photophysically‐active moieties. In the difunctional case, the chosen active groups may be either identical or different.
The synthesis of polymers bearing terminal fluorescent and fluorescence‐quenching groups, 3. The incorporation of fluorescent and fluorescence‐quenching groups by means of an indirect termination process
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M.
Published: April 2003

A useful general method is reported for incorporating specific groups at the terminal unit on a polymer prepared anionically. The living polymer anions are terminated by reaction with allyl iodide, the product converted to the corresponding saturated alcohol through hydroboration, and the alcohol coupled with an acyl chloride RCOCl, where R is the desired specific group. In the examples described here, the chosen terminal moieties are hydroxyl, vinyl, and certain fluorescent (or fluorescence‐quenching) groups, such as pyrenyl.
Amphiphilic properties of synthetic glycolipids based on amide linkages, 4.13C NMR spectroscopic studies on the gelation of N‐octyl‐D‐gluconamide in aqueous solution
Authors: Taravel François R. , Pfannemüller Beate
Published: April 2003

13C NMR measurements were taken on cooling of aqueous solutions of N‐octyl‐D‐gluconamide to follow the process of gelation. On cooling from 90°C gelation sharply occurs at 60–62°C. In the pre‐stage of gelation at 64°C an aggregated species, probably a dimeric form of octylgluconamide, is detected. Additional signals for sugar carbons C‐1, C‐4 and C‐6 indicate hydrogen bonding. As a side reaction conversion of the octylgluconamide to the ammonium salt takes place. Assignments of the new signals were made with the ammonium salt formed from D‐gluconamide and the corresponding octylammonium salt of gluconic acid. When the solution of octylgluconamide is kept at 64°C for a longer period, octylgluconamide, free and aggregated, and its ammonium salt coexist. At 64°C relaxation times t1 of the sugar carbons corresponding to the octylgluconamide species are much shorter than those of the salt, indicating a decrease of the mobility of the sugar carbons of the former in the pre‐stage of gelation.
Pervaporation of water‐ethanol mixtures through poly(acrylonitrile‐co‐acrylic acid) membranes
Authors: Lee Young Moo , Wang Wun Jae
Published: April 2003

Pervaporation performance of poly(acrylonitrile‐co‐acrylic acid) membranes was examined at several feed ethanol concentrations and temperatures. The incorporation of carboxylic acid groups into the glassy polyacrylonitrile membrane made it possible to selectively separate water from aqueous ethanol solution by pervaporation. Carboxylic groups play a role as carriers for water. Concentration dependent diffusion of water through the membranes was assumed and a new permeation equation is proposed and discussed.
Bimechanistic phase transfer catalyzed polythioetherification
Authors: Shaffer Timothy D. , Kramer Michael C.
Published: April 2003

Relative concentrations of catalysts, sulfide catalyst structure, and organic phase monomer concentration were studied for the bimechanistic phase transfer catalyzed (BPTC) polymerization of aqueous sodium sulfide with 1,8‐dibromooctane (DBO). BPTC is a new phase transfer mechanism which combines the effects of normal phase transfer with “inverse” phase transfer catalyzed reactions. Two catalysts are used: an ammonium salt and a cyclic or acyclic sulfide. With hexadecyltrimethylammonium chloride (CTMAC) and tetrahydrothiophene (THT), the optimum catalyst concentrations were found to be 10 mol‐% and 5 mol‐%, respectively, per DBO, but each was independent of the other. Diluting the monomer with o‐dichlorobenzene did not significantly alter the mechanism's profile, but expectedly lowered obtainable molecular weight. Of five sulfide catalysts examined, pentamethylene sulfide and dimethyl sulfide were the best, producing the highest molecular weight polyaliphatic sulfides with polydispersities M̄w/M̄n of ca. 1,3.
In‐situ photopolymerization of oriented liquid‐crystalline acrylates, 5.. Influence of the alkylene spacer on the properties of the mesogenic monomers and the formation and properties of oriented polymer networks
Authors: Broer Dirk J. , Mol Grietje N. , Challa Ger
Published: April 2003

The photoinitiated bulk polymerization of macroscopically oriented 1,4‐phenylene bis{4‐(ω‐acryloyloxyalkyloxy)benzoate} produces densely crosslinked oriented polymer networks. The influence of the length of the alkylene spacer between the aromatic central core and the polymerizable acrylate end‐groups on the mesomorphic behaviour of the monomer, the molecular orientation in the monomeric and polymeric state and the process of photoinitiated polymerization in the ordered state is studied. Some optical properties of the oriented networks are presented.
Dispersion of trans‐polyoctenylene in isotactic poly(propylene), 1. Morphology/mechanical properties relationships
Authors: Wenig Werner , Fiedel Heinz‐Werner
Published: April 2003

Blends of isotactic poly(propylene) (iPP) and trans‐polyoctenylene (TOR), prepared from solution, exhibit unexpected mechanical properties at specific mass fractions of TOR: While generally the elastic modulus E decreases continuously with increasing TOR content, it surpasses a maximum for mass fractions of TOR around 0,10. The reason for this behaviour is investigated. It turns out that the crystallinity as well as the crystal morphology (which is investigated by evaluating small‐angle X‐ray scattering by interface distribution functions) does not explain the mechanical behaviour. The order of the lamellar stacks (number of orientation‐correlated crystals) proves to be well correlated with the course of the elastic modulus. This order is a consequence of the increasing dispersion of TOR at mass fractions between 0,075 and 0,20 creating interfaces and infecting subsequently the crystallization conditions in the sample.
Dithiocarbamate telechelic polymers: Synthesis and block copolymerization
Authors: Van Kerckhoven Christel , Van den Broeck Hilde , Smets Georges , Huybrechts Jos
Published: April 2003

The iniferter method of Otsu was studied for the synthesis of polyvinyl block copolymers of relatively low molecular weight using tetramethylthiuram disulfide (TD) and benzyl N,N‐diethyldithiocarbamate (BDC) as initiator. Considering the low quantum yield of dissociation (ϕd) of TD (2,5 · 10−3 in cyclohexane), TD was used as thermal initiator (95°C) for the synthesis of dithiocarbamate‐polystyrene (TD‐PS) telechelics. 13C NMR analysis of this TD‐PS shows two 13CS signals corresponding to two different end‐groups: Et2NCSSCH(C6H5)CH2 and Et2NCSSCH2CH(C6H5). Several styrene polymerizations were also carried out in presence of azoisobutyronitrile (AIBN) as thermal initiator and TD as chain‐transfer reagent. Depending on the mole ratio AIBN/TD, mono‐ and difunctional TD‐PS's are formed, as evidenced by NMR analysis. These TD‐PS's were used for the photochemical initiations of ethyl acrylate (EA), acrylic acid (AA) and methyl methacrylate (MMA). It is assumed that the quantum yield of dissociation of the dithiocarbamate end‐group is equal to that of BDC (ϕd : 0,06). TD‐PS nonfunctional polymers were also prepared, either photochemically by dissociation of BDC, or thermally in presence of AIBN and BDC as transfer agent. They were used for block copolymerization with MMA. Inversely, TD‐PMMA's were prepared in a first step; in this case ϕd = 0,026. They were then used for the polymerization of EA. The block copolymers were fractionated; their composition and molecular weights were determined by 1H NMR and gelpermeation chromatography, respectively.
Synthesis and properties of well‐defined multiblock copolymers: poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene
Authors: Dems Andrzej , Strobin Grażyna
Published: April 2003

Well‐defined poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene multiblock copolymers, PC‐b‐PS, were prepared by condensation of PC prepolymers having chloroformyl end‐groups with PS prepolymers having hydroxyl end‐groups. Both prepolymers had narrow molecular weight distribution (PC prepolymer: M̄w/M̄n ≤ 1,31, PS prepolymer: M̄w/M̄n ≤ 1,03). The course of the polycondensation reaction depends on the molecular weight of the prepolymers used as substrates. After fractionation, the obtained multiblock copolymers are homogeneous in chemical composition and have a narrow molecular weight distribution. The mechanical properties of the copolymers depend on the weight fraction of the PS blocks. All copolymers exhibit two glass transition temperatures, close to those of the parent homopolymers.
Optically active comb‐branch liquid‐crystalline polymers having the chiral centre in the flexible spacer, 2.. The synthesis and characterisation of copolymers containing the novel chiral monomer (S)‐2‐[2‐4‐methoxy‐4′‐biphenylyloxy)‐1‐methylethoxy]ethyl methacrylate
Authors: Cowie John M. G. , Hunter Hugh W.
Published: April 2003

A new series of optically active liquid‐crystalline comb‐branch copolymers was prepared from (S‐2‐[2‐(4‐methoxy‐4′‐biphenylyloxy)‐1‐methylethoxy]ethyl methacrylate (1) and the nematogenic monomer 4‐cyanophenyl 4‐(6‐acryloyloxyhexyloxy)benzoate (2). These copolymers are characterised by the chiral centre being positioned in the flexible spacer. The copolymers form chiral nematic phases with temperature‐dependent reflection colours at low chiral monomer compositions, and crystalline phases at higher compositions. One of the copolymers of intermediate composition forms a smectic phase in addition to a chiral nematic phase.
Thermotropic polyesters, 6. New approach to the synthesis of segmented liquid‐crystalline polymers with an increased with an increased length of mesogenic and flexible elements
Authors: Bilibin Alexander Yu. , Piraner Olga N.
Published: April 2003

A new approach to the synthesis of segmented liquid‐crystalline (LC) polymers with an increased length of both mesogenic and flexible moieties is suggested. It consists in the preparation of intermediate polymeric compounds on the basis of aliphatic diols and a “triade” type complex monomer, 4,4′‐(oxalyldioxy)dibenzoyl dichloride (6), whose central oxalyl unit plays the role of a bifunctional protective group and proves to be the structural element of the main chain of the intermediate polymer. The chemodegradation of the latter to bifunctional alkylene bis(4‐hydroxybenzoate)s (3), which differ from the initial complex monomer, is achieved by selective removal of the oxalyl protective group. The desired LC polymers may be synthesized on the basis of such hydroxy‐bifunctional compounds 3 and another triade type monomer carrying two acyl chloride functions, 4,4′‐(terephthaloyldioxy)dibenzoyl dichloride. The features of each stage of the synthesis are discussed. Special attentional is paid to the selectivity of hydrolysis procedure of the intermediate polymers. A series of segmented LC polyesters containing five or seven 1,4‐phenylene units in the mesogenic group are synthesized, their thermal properties are compared with the properties of LC polymers described earlier.
New thermotropic liquid‐crystalline polyesters with a metalchelated 1,3‐diphenyl‐1,3‐propanedione segment
Authors: Hanabusa Kenji , Tanimura Yoei , Suzuki Takashi , Koyama Toshiki , Shirai Hirofusa
Published: April 2003

New thermotropic liquid‐crystalline polyesters (2–4) containing a mesogenic β‐diketone segment, which can coordinate to a metal ion as bidentate ligand, were synthesized by polycondensation of a mixture of 1,6‐hexanediol (x mol), 1,3‐bis(p‐hydroxyphenyl)‐1,3‐propanedione (y mol), and 4,4′‐hexamethylenedioxydibenzoyl chloride (x + y mol). Homopolyester 1, prepared from 1,6‐hexanediol and 4,4′‐hexamethylenedioxydibenzoyl chloride, and copolyesters 2 and 3 (x/y = 0,8/0,2 and 0,5/0,5, respectively) show a nematic phase, whereas homopolyester 4, prepared from 1,3‐bis(p‐hydroxyphenyl)‐1,3‐propanedione and 4,4′‐hexamethylenedioxydibenzoyl chloride, exhibits a smectic phase. The wide‐angle X‐ray diffraction patterns from the melt‐drawn fibers prepared at mesophase temperatures suggested no orientation for 1, a monoaxial orientation and a crystalline state for 2, a monoaxial orientation and a frozen‐in nematic phase for 3, and a biaxial orientation and a frozen‐in smectic A phase for 4. Introduction of a transition metal (CuCl2 or NiCl2) into copolyesters 2 and 3 gave the corresponding metal‐chelated thermotropic liquid‐crystalline polyesters (5a–c, 6a–c, and 7a–c). Formation of a metal complex among polymer chains by introduction of a metal ion also resulted in better monoaxial orientation according to X‐ray diffraction patterns. The ESR spectra of fibers of copper‐containing polyesters (5a–c and 6a–c) indicated that the plane of the square planar copper complex in the polymers is oriented parallel to the fiber axis.
13C NMR characterization of ethylene oxide/epichlorohydrin copolymer
Authors: Cheng H. N. , Smith David A.
Published: April 2003

The 13C NMR spectra of ethylene oxide/epichlorohydrin copolymers are fully assigned. Information available includes copolymer composition, comonomer sequence distribution, and epichlorohydrin tacticity. The comonomer sequence distribution can be fitted to a two‐component (Bernoullian/Bernoullian) statistical model.
Study on the internal friction characteristics of a polyaryl ether sulfone with bulky substituent below the glass transition temperature
Authors: Zhang Mingqiu , Zeng Hanmin , Zhang Jinxiu
Published: April 2003

The temperature and frequency dependence of internal friction of a polyaryl ether sulfone with cardo side groups

Systematic name: poly(phthalidylidene‐1,4‐phenyleneoxy‐1,4‐phenylenesulfonyl‐1,4‐phenyleneoxy‐1,4‐phenylene).

(1) are measured using a multi‐function torsion pendulum below the glass transition temperature (531 K). Two relaxation peaks are observed at 328 K and 150 K (for 0,1 Hz). The elementary processes of the two relaxations are found to be different from each other: the relaxation at higher temperature is an ordering process and that at lower temperature is a disordering one.
Conformational changes of amorphous poly(ethylene terephthalate) films during uniaxial stretching
Authors: Shen Deyan , Long Fujin , Wen Zaiqing , Qian Renyuan
Published: April 2003

Rapid scanning Fourier transform infra‐red spectroscopy was used to follow the changes in the population of trans conformers and in the infra‐red dichroic functions of the bands characterizing the trans (T) and gauche (G) conformers and the chains in the amorphous regions during stretching of a solution‐cast amorphous poly(ethylene terephthalate) (PET) film A in the glassy state (67°C) and in the rubbery state (88°C). Stretching at 67°C showed a yield stress peak followed by strain softening in the stress‐strain curve. The population of trans conformers in the amorphous and crystalline regions, Ta + Tc, decreased in the pre‐yielding region and then increased continuously after yielding. The T conformers formed during post‐yield stretching showed high orientation, while the G conformers remained in low degree of orientation. Stretching at 88°C showed no pronounced yield stress peak in the stress‐strain curve, and the population of T conformers did not change until the beginning strain‐induced crystallization. A solvent‐cast PET film annealed at 67°C for 24 h, the film N, showed a sharp and high yield stress peak in the stress‐strain curve, and strain‐induced crystallization occurred at lower draw ratio as compared to the film A. The film A showed a non‐equilibrium high population of Ta conformers, part of which reverted to G conformers during sub‐Tg annealing.