bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivity of a polyamine macromonomer in radical copolymerization with 2‐hydroxyethyl methacrylate
Authors: Nabeshima Yoshikuni , Tsuruta Teiji 
Published: April 2003

AbstractA series of copolymerization reactions of polyamine macromonomer 1 having controlled molecular weight with 2‐hydroxyethyl methacrylate (HEMA) were examined, in order to obtain a reliable estimation of the reactivity of the macromonomer in radical copolymerization. The monomer reactivity ratio r2 (HEMA as M2) was estimated to be 0,49 by a newly developed method which is expressed by Eqs. (4) and (5). This method, however, could basically be applied only to the estimation of the r2 value. On the other hand, a novel method for the evaluation of the copolymer composition from the conversion of each monomer using gas chromatography and ultraviolet fourth‐order derivative spectra enabled us to estimate r1 as well as r2. Numerical values obtained for the system macromonomer 1 (M1)/HEMA (M2) amounted to r1 = 0,16 and r2 = 0,48; r1 is much smaller than the reactivity ratio of a low‐molecular‐weight analogue of 1, a fact which indicates that the reactivity of the growing radical with a 1 terminal toward 1 should be remarkably smaller than in case of a low‐molecular‐weight analogue of 1. This may be explained by the presence of the kinetic excluded volume effect.
Mesomorphism — structure relationships in polyesters based on twin p‐oxybenzoate mesogens
Authors: Caretti Daniele , Angeloni Annino S. , Laus Michele , Chiellini Emo , Galli Giancarlo 
Published: April 2003

AbstractThree homologous series of semiflexible polyesters constituted by twin spaced p‐oxybenzoyl diads were studied with respect to their mesomorphic behaviour as a function of the relative length of the two different spacers [oligo(oxyethylene) and polymethylene] connected in an alternating fashion in the repeating unit. Within each series the oligo(oxyethylene) segment was maintained constant (n = 2, 3, 4), whereas the polymethylene segment varied in steps of one methylene unit from pentamethylene to decamethylene (m = 5 to 10). Indications are gained of how the parity of both ether and hydrocarbon spacers may affect the phase diagrams of the samples. The parity of the oligo(oxyethylene) segments appears in particular very effective in maximizing the orientational correlation between the mesogenic p‐oxybenzoyl diads.
Synthesis and characterization of dextran carboxylates for the specific chemical modification of human hemoglobin
Authors: Sacco Daniel , Prouchayret Florence , Dellacherie Edith 
Published: April 2003

AbstractThe present study deals with the fixing of benzenehexacarboxylate (BHC) on dextran, with the aim of obtaining polyanionic polymers capable of decreasing the oxygen affinity of hemoglobin (Hb) by interacting with its phosphate binding site (allosteric site). The covalent coupling of these polymers onto oxyHb has been investigated for the synthesis of oxygen carriers with low oxygen affinity. This type of covalent conjugate could be of interest in intravascular use. Several steps were necessary to synthesize dextran with linked BHC (DEX‐BHC). In each step, the structure of the modified dextran was determined by means of gel permeation chromatography, 1H and 13C NMR spectroscopy, and low‐angle laser light scattering. The aim was to determine the conditions of the reaction which lead to a minimization of cross‐linking phenomena. The DEX‐BHC obtained (0,27 mmol BHC/g polymer) decreased the oxygen affinity of Hb in the same way as the natural effector, 2,3‐diphosphoglycerate (2,3‐DPG) i.e., by reacting specifically with the amines of the protein allosteric site. This decrease in oxygen affinity was more accentuated after covalent coupling onto oxyHb, which means that the fixing point was probably localized in the 2,3‐DPG binding site.
Enzyme‐analogue built polymers, 26. Enantioselective synthesis of amino acids using polymers possessing chiral cavities obtained by an imprinting procedure with template molecules
Authors: Wulff Günter , Vietmeier Jürgen 
Published: April 2003

AbstractThe asymmetric synthesis of a‐amino acids within chiral cavities of special crosslinked polymers was investigated. Chiral cavities prossessing definite shapes and specific arrangements of the functional groups were obtained by preparation of crosslinked polymers in the presence of suitable templates. Best results with an enantiomeric excess of 36% were obtained by using a polymer which was imprinted by L‐DOPA. The cavities contained a salicylaldehyde and a phenylboronic acid moiety each. L‐Threonine was prepared by reaction of the polymer bound anion of a salicylideneglycine nickel complex with acetaldehyde.
Ring‐opening polymerization of carbohydrate‐derived dialkoxyoxolanes. Approaches to functionalized poly(oxytetramethylene)s
Authors: Thiem Joachim , Strietholt Wilhelm A. , Häring Thomas 
Published: April 2003

AbstractA series of various cis‐3,4‐diacyloxy‐ and dialkyloxy‐oxolanes (4 to 14) as well as the oxolanes 16 and 17 were prepared. Ring‐opening polymerizations of the dialkyloxy derivatives 4, 6, and 11 using the super‐acids FSO3H and CF3SO3H led to novel functionalized poly[oxy(2,3‐dialkyloxy‐tetramethylene)]s. The reaction parameters were thoroughly studied, and optimum conditions lead to a DPn up to 35. All polyethers were fully assigned by polymer analytical procedures such as GPC, osmometry, 1H NMR spectroscopy and end group determination. In the case of the mixed benzyloxy methyloxy polymer 22, by subsequent hydrogenolysis a component with hydroxy functions was obtained. This procedure features a novel change of functionality in selectively derivatized polyethers originally derived from regrowing carbohydrate material.
Solvent effects on chain structure and conformation of poly(amic acids) and their crystallosolvate formation
Authors: Chu Ning‐Jo , Huang Jiann‐Wen , Chang C. H. , Whang W. T. 
Published: April 2003

AbstractPoly(amic acids) (PAAs) were prepared from pyromellitic dianhydride (PMDA) and diamines such as 2,2′‐difluoro‐, 3,3′‐difluoro‐ and 2,2′‐dichloro‐4,4′‐methylenedianiline. These PAAs form liquid crystals in N‐methyl‐2‐pyrrolidone (NMP) solution, in addition to the PMDA/4,4′‐methylenedianiline (MDA) system reported previously. NMP was the only solvent in which liquid crystals were formed. The “liquid crystal” was shown to be a polymer crystallosolvate (PCS) of PAA and NMP. 1H NMR spectroscopy revealed that PAAs derived from PMDA contain isophthalamide and terephthalamide repeating units in nearly equal proportion, which varies slightly between samples prepared in NMP and dimethylacetamide (DMAc). WAXS showed that the PAA from PMDA/MDA is non‐crystalline but forms a liquid crystalline state in NMP solution. The rate of crystallization is, however, vastly different between samples prepared in different solvents. This was attributed to their difference in chain conformation, which has to be an extended one for PCS formation. The morphologies of PCS are given, and limitations in PCS formation are discussed in terms of PAA structure and solvent.
Thermal polymerization of bis(trihalophenoxo)copper(II) complexes in excess dimethylformamide and dimethyl sulfoxide as ligands
Authors: Kisakürek Duygu , Sanli Oya 
Published: April 2003

AbstractThermal decomposition of bis(trihalophenoxo)copper(II) complexes was achieved at 50°C in dimethylformamide or dimethyl sulfoxide. The resulting polymers, poly(oxydihalophenylene)s (2), were characterized by FTIR, 1H NMR and 13C NMR spectroscopy and by differential scanning calorimetry. The molecular weights were determined by the vapour pressure method. Tribrominated phenol derivatives prefer 1,4‐substitution, whereas with trichlorophenol derivatives 1,2‐and 1,4‐substitutions take place at equal rates in either solvent.
Reactivities of 4‐trimethylsilylmethylstyrene and 4‐bis(trimethylsilyl)methylstyrene
Authors: Nagasaki Yukio , Tsuruta Teiji , Hirano Tsuneo 
Published: April 2003

Abstract4‐Trimethylsilylmethylstyrene (1), and 4‐bis(trimethylsilyl)methylstyrene (2) were synthesized and polymerized. The reactivities of 1 and 2 in free radical and nucleophilic reactions are discussed, referring to 1H NMR and UV spectral data. The absolute values of the negative e‐ values were found to be higher than those of styrene and other styrene derivatives such as 4‐methylstyrene. The reactivities of these monomers toward nucleophilic reagents are lower than those of other styrenes. From these investigations it was concluded that the trimethylsilylmethyl group, located at 4‐position of vinylbenzene, exhibits an electron donating effect. As anticipated, the effect of the bis(trimethylsilyl)methyl group is larger than that of the trimethylsilylmethyl group. AM1 calculations showed that the effect is attributable to the σ‐π‐hyperconjugation between the SiC σ‐bond and the π‐electron system of the phenyl ring. The larger effect of 2 as compared with 1 may be explained by additional σ‐π‐hyperconjugation between the second CSi bond in horizontal position and the phenyl π‐orbital in addition to the σ‐π‐hyperconjugation of the first CSi bond in vertical position.
Synthesis and oligomerization of a paramagnetic monomer
Authors: Seidemann Rolf 
Published: April 2003

AbstractThe synthesis of the paramagnetic amino acid ester 19, starting from 2,2,6,6‐tetramethyl‐4‐oxopiperidine (8) via eight reaction steps was optimized. Saponification, disilylation and phosgenation were performed to obtain the new radical monomer 3‐(2,5‐dioxo‐1,3‐oxazolidine‐4‐ylmethyl)‐2,2,5,5‐tetramethyl‐3‐pyrrolin‐1‐yloxyl (7), which was oligomerized without destroying the paramagnetic centre. These stable oligospins may have interesting magnetic properties.
Polymeric prodrugs, 6. Synthesis and examination of 6‐purinethiol bound to poly(1‐vinyl‐2‐pyrrolidone‐co‐maleic acid)
Authors: Móra Melinda , Pató János , Tüdős Ferenc 
Published: April 2003

AbstractA low‐molecular‐weight disulfide derivative of the antileukemic agent 6‐purinethiol (2) was used for coupling with a macromolecular carrier, poly(1‐vinyl‐2‐pyrrolidone‐co‐maleic acid) via spacer groups. The in vitro hydrolytic stabilities of the polymeric prodrugs were examined at pH 7,2 and 8,8. An enhanced cleavage of the disulfide bridge yielding 6‐purinethiol was observed. Enzymatic hydrolysis of the prodrug containing an enzyme‐sensitive spacer was also done in the presence of elastase.
Synthesis and characterization of copolymers from acrylamide and methacrylamide carrying peptide side chains
Authors: Boulahia Jalel , Carrière François , Sekiguchi Hikaru 
Published: April 2003

AbstractN‐Benzylacrylamide (1) and N‐(3‐aminopropyl)methacrylamide hydrochloride (2) were copolymerized to give poly[N‐benzylacrylamide‐co‐N‐(3‐aminopropyl)methacrylamide hydrochloride] (3). The reactivity ratios r1 and r2 were found to be r1 = 0,87 and r2 = 0,66 in which r1r2 < 1 indicate a statistical copolymer composition. Dehydrochlorination of the copolymer liberated primary amino groups to which peptide chains were grafted by reaction with L‐alanine‐NCA. The solubility of the resulting graft copolymers (6) in trifluoroacetic acid allowed the characterization of the products both by NMR and polarimetry. These methods and IR spectroscopy showed that the primary amino groups have only partially participated in initiating the NCA polymerization. The length of grafted peptide chains was found to be always higher than the one calculated from the ratio [NCA]/[NH2].
Preparation of ABCBA‐type block copolymers by use of macro‐initiators containing peroxy and azo groups
Authors: Hazer Baki , Ayas Alipaşa , Beşirli Necati , Saltek Necdet , Baysal Bahattin M. 
Published: April 2003

AbstractSome new macroinitiators (5) containing azo and peroxy groups were synthesized by transformation of esters of poly(ethylene glycol) (1) (PEG) of different molecular weight with hydroxyl end groups and an azo group in the middle into the corresponding polymers with tert‐butylperoxycarbonyl end groups by reaction with terephthaloyl chloride and subsequently with tert‐butyl hydroporoxide. Decomposition in the presence of styrene at 60°C or with 3,6,9‐triazaun‐decane‐1,11‐diamine in presence of methyl methacrylate gave the corresponding ABA block copolymer 6 and the ABBA block copolymer 7, respectively. Both block copolymers were used as polymeric initiators. The ABCBA block copolymer 8 was synthesized from 6 and methyl methacrylate or from 7 and styrene by thermally induced polymerization at 80°C. The resulting block copolymers were separated from the homopolymers by selective solvent extraction and characterized by spectroscopic and fractional precipitation methods.
Supported propene polymerization catalysts, 2. Supports derived from dialkylmagnesium/dibutyl butylphosphonate complexes
Authors: Karayannis Nicholas M. , Skryantz John S. , Johnson Bryce V. , Hoppin Charles R. , Khelghatian Habet M. 
Published: April 2003

AbstractFollowing the earlier development of highly active supported propene polymerization catalysts prepared by activating supports derived from Mg dialkyl complexes with the rare and very expensive ethyl esters of 2,6‐dimethyl‐ (1) or 2,4,6‐trimethylbenzoic acid (2), research was undertaken to uncover low‐cost and commercially available substitutes for 1 and 2. Several phosphonate, phosphate, and phosphite alkyl esters, as well as ethers and amines, were investigated. Dibutyl butylphosphonate (5b) adducts with Mg dialkyl were found to produce catalysts with comparable activity, improved, narrower particle size distribution, and only slightly lower stereospecificity and polymer powder bulk density relative to catalysts made using MgR2 adducts with 1 or 2 as starting materials (R = n‐C4H9). Optimized catalysts based on MgR2 · 5b adducts, prepared by precipitating the support by reaction of a solution of the adduct with SiCl4 and subsequent activation by treatment of the support with TiCl4 and diisobutyl phthalate in chlorobenzene, realize yields of 16–17 kg polypropylene/g catalyst in 2‐h hexane slurry polymerizations at 70°C, 10,2 atm, with 1,2–1,5 wt.‐% boiling hexane extractables and 0,40–0,41 g/ml polymer powder bulk density. The cocatalyst‐external modifier package used consists of Al(C2H5)3‐dimethoxydiphenylsilane. The narrow particle size distribution of the polymer powder produced renders the new catalysts suitable for use in both slurry and solventless propene polymerization processes, while the low cost and ready availability of 5b make the catalyst preparation commercially feasible.
Polyimides based on poly(2,5‐furandiylmethylene), 1
Authors: Patel Hasmukh S. , Lad Babu D. 
Published: April 2003

AbstractPolyimides were prepared by Diels‐Alder (DA) reaction of furfuryl alcohol (FA) resin [poly(2,5‐furandiylmethylene)] with the bis(maleimides) N,N′‐hexamethylenebis(maleimide) and N,N′‐1,4‐phenylenebis(maleimide), respectively. The DA reaction was carried out in tetrahydrofuran as solvent, as well as in bulk, followed by aromatization of tetrahydrophthalimide intermediates in the presence of acetic anhydride. All the polyimides were characterized by elemental analyses, IR spectral studies and thermogravimetry. The results show that polyimides based on FA resin exhibit moderate thermal stability. The results of preliminary tests for glass reinforcement of produced polyimides suggest that laminates with good mechanical strength can be obtained.
Analysis of composition data for copolymers of N‐phenylmaleimide with styrene in terms of various copolymerization models
Authors: Florjańczyk Zbigniew , Krawiec Włodzimierz 
Published: April 2003

AbstractComposition data for the copolymerization of N‐phenylmaleimide (M) with styrene (S) in toluene at 60°C were obtained and analyzed according to terminal, penultimate and Lowry's model, using a non‐linear least squares optimization routine. Lowry's mechanism involving depropagation of a monomeric unit of M, if it is attached to another monomeric unit of M, was found to be the most adequate one to describe the system studied. According to this model the reactivity ratios of the monomers are equal to rS = 0,0066, rM = 0,1615 and the constant for the propagation‐depropagation equilibrium in homoaddition of M is equal to 0,9196 dm3 · mol−1.
Interaction between the amino and carbonyl groups in copoly(2‐dimethylaminoethyl methacrylate/N‐phenylmaleimide)
Authors: Přádný Martin , Lokaj Jan , Novotná Miroslava , Ševčík Stanislav 
Published: April 2003

AbstractInteractions between the carbonyl and amino groups in copolymers of 2‐dimethylaminoethyl methacrylate with N‐phenylmaleimide are reported. The existence of interactions ensues from potentiometric measurements and UV‐VIS spectra. Interactions in these copolymers result in the formation of energetically very advantageous chromophores, reflected in an intense red colour of the substances obtained.
Solution polymerization of selected polyphosphazenes
Authors: Mujumdar Ashutosh N. , Young Scott G. , Merker Robert L. , Magill Joseph H. 
Published: April 2003

AbstractSeveral alkoxy/aryloxy‐substituted phosphazene polymers [P(OR)2  N]n, where R = C6H5, CH2CF3, C8H10, were prepared by the reaction of polydichlorophosphazene with their corresponding sodium salts. The polydichlorophosphazene was obtained by the solution polymerization of hexachlorocyclotriphosphazene in 1,2,4‐trichlorobenzene. Sulfamic acid and ammonium sulfamate were used as catalysts. Apparently, sulfamic acid functions as a catalyst through its acid group in some decomposed form. New catalysts, p‐toluenesulfonic acid and sulfobenzoic aicd, have been developed for this solution polymerization. The polymerization favors a cationic mechanism. A promoter, CaSO4·2H2O, was found to speed up the polymerization reaction. Effect of several parameters such as dilution, catalyst concentration, and promoter concentration on the properties of the final polymer were investigated. The polymers were characterized by differential scanning calorimetry, gel permeation chromatography, and 31P solution NMR spectroscopy.
Synthèse de composé photoréticulables, 9. Modification du polybutadiène carboxytéléchélique par des monomères acryliques
Authors: Boutevin Bernard , Fleury Etienne , Parisi Jean‐Pierre , Piétrasanta Yves 
Published: April 2003

AbstractThe addition of mercaptoacetic acid upon radical initiation onto carboxytelechelic polybutadienes (1) which have an average mass M̄n = 4400 gives polyacids having about twelve carboxylic groups. The reaction is followed by 13C NMR, 1H NMR and by GPC. The thiol disappears according to a first order law. Besides, the value of the modification rate obtained from acido‐basic titration confirms that obtained from NMR. In a second step, 2,3‐epoxypropyl methacrylate is added to the acid groups to obtain an insaturated and carboxylated polydienic oligomer 5. An application of these oligomers processed with a reactive diluter shows their high cross‐linking ability under UV irradiation and confirms the improvement of the flexibility properties compared to those of traditional insaturated oligomers.
Synthesis of a polydimethylsiloxane macromonomer and its copolymerization with ethylene
Authors: Li Weidong , Huang Baotong 
Published: April 2003

AbstractAn allyl‐terminated polydimethylsiloxane (PDMS) macromonomer was synthesized by anionic polymerization of hexamethylcyclotrisiloxane (D3) initiated by allyllithium. The molecular weight (MW) of the macromonomer was consistent with that calculated from the ratio of the monomer consumed to the amount of the initiator used, and the molecular weight distribution (MWD) of the macromonomer was narrow. Graft copolymers with polyethylene backbone and uniform PDMS grafts, PE‐g‐PDMS, were prepared by copolymerization of the macromonomer with ethylene using VOCl3/Et2AlCl as the catalyst. Under the copolymerization conditions, the scission of SiOSi bonds by the catalyst is negligible, so that MW and MWD of the PDMS grafts could be considered to be the same as those of the original PDMS macromonomer.
Synthesis of biodegradable poly(L‐lactic acid‐co‐D,L‐mandelic acid) with relatively low molecular weight
Authors: Fukuzaki Hironobu , Aiba Yoshikazu , Yoshida Masaru , Asano Masaharu , Kumakura Minoru 
Published: April 2003

AbstractA homopolymer of L‐lactic acid (LA), which was synthesized by direct polycondensation in the absence of a catalyst at 200°C, is crystalline, in contrast to the homopolymer of D,L‐mandelic acid (MA) which is amorphous. Poly(LA‐co‐MA), obtained under the above conditions, is amorphous over a wide range of composition from 15 to 100 mol‐% of monomeric units of MA. The in vitro degradation mechanism of these homopolymers shows a parabola‐type degradation pattern for poly(LA) and no degradation throughout an experimental period of 15 weeks for poly(MA). In poly(LA‐co‐MA) the degradation mechanism leads to a typical S‐type degradation pattern, which may be divided into two processes, initial swelling at the surface of the matrix without degradation (induction period), followed by the erosion of oligomers produced by degradation of the main chain in the swollen state.
Membrane from a graft copolymer of butyl methacrylate with the macromonomer 2‐(N‐methyl‐N‐4‐vinylphenethylamino)‐ethylaminopoly[N5‐(ω‐hydroxyalkyl)‐L‐glutamine]. Effect of conformation of the polypeptide branch on the permeability of phenyl‐1,2‐ethanediol across the membrane
Authors: Ishiyama Naoko , Chung Dae‐won , Maeda Mizuo , Inoue Shohei 
Published: April 2003

AbstractGraft copolymers composed of monomeric units of hydrophobic butyl methacrylate and those of the hydrophilic, non‐ionizable macromonomer 2‐(N‐methyl‐N‐4‐vinylphenethylamino)ethylaminopoly[N5‐(2‐hydroxyethyl) or (3‐hydroxypropyl)‐L‐glutamine] (4a or 4b) were synthesized. The permeability of phenyl‐1,2‐ethanediol across the membranes prepared from these copolymers was found to be affected by the conformation of the poly[N5‐(ω‐hydroxyalkyl)‐L‐glutamine] branch which depends on its chain length and the hydrophobicity of the solvent (water or water/methanol mixture).
Polymeric chiral crown ethers, 5. Synthesis of polymers by cyclopolymerization of divinyl ethers containing moieties deriving from L‐tartaric acid, and the chiral recognition toward amino acids
Authors: Kakuchi Toyoji , Takaoka Tohru , Yokota Kazuaki 
Published: April 2003

AbstractThe synthesis of polymers with chiral crown ether units containing moieties deriving from L‐tartaric acid via cyclopolymerization of divinyl ethers was studied. 1,4‐Di‐O‐benzyl‐ and 1,4‐di‐O‐trityl‐2,3‐bis{O‐[2‐(2‐vinyloxyethoxy)ethyl]}‐L‐threitol (1a and 1b) were polymerized with cationic catalysts to produce polymers (2a and 2b) consisting of only cyclic constitutional units. The trityl groups in polymer 2b were easily cleaved by hydrogen chloride to form a water‐soluble, chiral polymer. Polymer 2b was found to complex predominantly with the L‐enantiomer of ester salts of phenylglycine, phenylalanine, valine, and methionine in the same way as a chiral polymer incorporating 1,3:4,6‐di‐O‐benzylidene‐D‐mannitol moieties.
Conformational study of sodium pectate from circular dichroism induced in dyes
Authors: Pal Medini Kanta , Mandal Nemai 
Published: April 2003

AbstractSodium pectate (1c) induces strong circular dichroism (CD) in 3,7‐bis(dimethylamino)‐1,9‐dimethylphenothiazinium chloride (2b) and weak CD in 1‐ethyl‐2‐[3‐(1‐ethyl‐2‐(1H)‐quinolylidene)propen‐2‐yl]quinolinium chloride (pinacyanol chloride) (4) and 2,8‐bis(dimethylamino)‐acridinium chloride (Acridine Orange) (3), and no CD in 3,7‐bis(dimethylamino)phenothiazinium chloride (Methylene Blue) (2a), besides inducing strong metachromasia in all these dyes. The signs of the CD spectra induced in the dyes 2b, 3 and 4 by pectate are opposite to those induced by hyaluronate (HYAT). Pectate is, thus, inferred to have a 31 helical conformation (like HYAT) with the sense of helicity opposite to that of HYAT. Such an inference is also in harmony with the reported 3‐fold screw axis of pectate fibre from X‐ray crystallography. Since left‐handed extended helical polyglutamate induces negative biphasic CD, 1c, depicting positive biphasic CD with the same dye, may be assigned by analogy to have a right‐handed helicity.