bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo characteristics of low‐molecular‐weight copoly(L‐lactic acid/DL‐hydroxyisocaproic acid) with parabolic‐type and S‐type degradation pattersn
Authors: Fukuzaki Hironobu , Yoshida Masaru , Asano Masaharu , Kumakura Minoru , Mashimo Tooru , Yuasa Hisako , Imai Kyoichi , Yamanaka Hidetoshi 
Published: April 2003

AbstractAn amorphous copolyester of L‐lactic acid (LA) and DL‐hydroxyisocaproic acid (HICA) with a number‐average molecular weight (Mn) of 1600–4800 was synthesized by direct copolycondensation in the absence of catalysts, in order to develop a biodegradable carrier for drug delivery systems. The in vivo degradation pattern was changed into an S‐type from a parabolic‐type with an increase in molecular weight of copolyester. A luteinizing hormone‐releasing hormone agonist, des‐Gly10‐[D‐Leu6]‐LH‐RH ethylamide, was incorporated into a fine cylindrical copolyester formulation by the so‐called melt‐pressing technique. When the S‐type degradable and releasable copoly(LH/HICA) (70/30 mol‐%) formulations with Mn = 2200 were implanted subcutaneously in the back of rats, the most reasonable serum drug level was observed during the first 15 weeks period, keeping constant at approximately 3,5 ng/ml.
Synthèse et application de diols isomolécularies aux résines polyuréthannes
Authors: Boutevin Bernard , Chaib Messaoud , Robin J. J. 
Published: April 2003

AbstractDifferent methods of preparation of monodisperse diols were reviewed and a new synthesis of perfectly monodisperse macrodiol 5 is described, obtained by radical telomerization of monoester 3 b (prepared by esterification of 10‐undecenoic acid (3 a) with 1,6‐hexanediol) with dithiol 4. Macrodiol 5 was used to obtain prepolymers by reaction with aromatic or aliphatic diisocyanates (6 and 7). Finally, these prepolymers were extended by 1,4‐butanediol and led to polyurethanes. All the above products were analyzed by GPC, 1H NMR, and the resulting polyurethanes were tested mechanically. The study shows that monodisperse diols lead to better mechanical properties of the polyurethane than those obtained from polydisperse diols with equal molecular weight.
Diethynyl‐terminated siloxane‐based diamide. Preparation and polymerization
Authors: Mantecon Ana , Bartholin Michel , Garapon Jacques , Sillion Bernard 
Published: April 2003

Abstract1,3‐Bis[3‐(4‐ethynylbenzoylamino)propyl]hexamethyldisiloxane (3) was prepared and characterized. The flexible central unit of this product enables the easy and through polymerization of ethynyl groups at moderate temperature (220°C). The structure of the product resulting from the thermal polymerization of this diamide could not be elucidated so far. The product has a rather high Tg (260°C) and keeps it properties up to 250°C. On heating for a prolonged period of time at this temperature or at a higher one, the amide bond is cleaved, as evidenced by TG and FTIR data.
Crosslinking reactions of polyphenylene type polymers containing acetyl end‐groups with bis(hydridosilyl) derivatives of o‐carborane alcohols
Authors: Teplyakov Mikhail M. , Khotina Irina A. , Dmitrenko Alla V. , Kovalyov Aleksei I. , Kalinin Valeri N. , Korshak Vasili V. , Ismailov Boris A. 
Published: April 2003

AbstractCrosslinking reactions of prepolymers of the polyphenylene type carrying acetyl end‐groups, based on 4,4′‐oxydiacetophenone and acetophenone (FPP‐1), or 4‐acetylacetophenone and 4‐(4‐acetylphenoxy)phenyl‐o‐carborane (FPP‐2), by means of 20–80 wt.‐% of 1,2‐bis[hydrido‐(dimethyl)siloxymethyl]‐o‐carborane (1) were investigated. It was found that the prepolymer FPP‐1 is easily crosslinked in the presence of 30 wt.‐% of 1 at 300°C, and the prepolymer FPP‐2 at 350°C.
Soluble poly(1,4‐phenyleneethynylene)s
Authors: Giesa Reiner , Schulz Rolf C. 
Published: April 2003

AbstractNew monomers are described for the synthesis of rod‐like poly(1,4‐phenyleneethynylene)s with long flexible aliphatic side chains. By palladium catalyzed polycondensation soluble polymers with melting points around 100°C could be obtained. The molecular weight was estimated by GPC, VPO and elemental analysis: GPC showed a multimodale distribution with Pn = 9–15. NMR spectra were found to be in agreement with the assumed polymer structure, but signals of the acetylenic carbons could not be detected. A broad, structureless absorption with a maximum at λ = 410 nm is seen in the UV‐VIS‐spectra. The thermal decomposition of the substituted PPE's starts at about 400°C and is comparable to that of unsubstituted PPE in air.
Hydroxytelechelic polybutadiene, 12. Polymerization reactions between hydroxytelechelic polybutadiene with hexamethylene diisocyanate or 4,4′‐methylenedi(phenyl isocyanate). Kinetics of polymerization in toluene and in the bulk
Authors: Deschères Isabelle , Pham Quang Tho 
Published: April 2003

AbstractAddition polymerization of hydroxytelechelic polybutadiene (HTPB) with hexamethylene diisocyanate (HMDI) with a mole ratio NCO/OH = 0,8 in dilute solution of toluene as well as in bulk follows apparent 3rd order kinetics. The polymerization rates are twice as sensitive to temperature as in toluene, an effect which is attributed to intra‐ and/or intermolecular (OH, OH) auto‐association. The three alcoholic functions in HTPB are catalyzed equally by dibutyltin dilaurate. Even with high excess of NCO, free alcoholic functions were found in the product. They were determined quantitatively in moulded polyurethane sheets from HTPB + HMDI and HTPB + 4,4′‐methylenedi(phenyl isocyanate) which should be partially crosslinked:
Determination of functionality and molecular weight distributions in α‐hydroxy‐ω‐benzyloxyoligo(1,3,6‐trioxocane)s using HPLC methods
Authors: Krüger Hartmut , Much Helmut , Schulz Günter , Wehrstedt Carla 
Published: April 2003

AbstractThe cationic ring‐opening polymerization of 1,3,6‐trioxocane(TO) in presence of benzyl alcohol occurs in accordance with the activated monomer mechanism. In addition to their molecular weight distribution the reaction products exhibit a distribution of their end‐functionality caused by transacetalization. Two‐dimensional chromatography, including size‐exclusion and high‐performance liquid chromatography, was used to characterize quantitatively the molecular weight and functionality distribution. The postulated mechanism leading to a functionality distribution is supported by the experimental results obtained.
Molecular weight distribution in the activated monomer polymerization with nonequal propagation rate constants
Authors: Szymański Ryszard 
Published: April 2003

AbstractEquations are derived to calculate the molecular weight distribution (MWD) of polymer chains for polymerizations with nonequal propagation rate constants. The presented set of equations allows the determination of the relative propagation rate constants provided the mole fractions of the chains with different degrees of polymerization are known. Furthermore, the MWD function for a polymerization with linearly increasing propagation rate constants is given. Application of the presented relations to analyse the MWD of polymers obtained by activated monomer polymerization is proposed.
Influence of the addition of an aliphatic epoxide as reactive diluent on the cure kinetics of epoxy/amine formulations
Authors: Urbaczewski Eliane , Pascault Jean‐Pierre , Sautereau Henry , Riccardi Carmen C. , Moschiar Stella S. , Williams Roberto J. J. 
Published: April 2003

AbstractThe cure kinetics of two different diepoxy prepolymers and their mixtures with a single diamine was analyzed using size exclusion chromatography (SEC). One of the diepoxy prepolymers was based on bisphenol‐A diglycidyl ether (DGEBA), while the other one was the diglycidyl ether of 1,4‐butanediol (DGEBD), which is a typical reactive diluent. They were used either alone or as a 50% mixture (in equivalents). The cycloaliphatic diamine 4,4′‐diamino‐3,3′‐dimethyldicyclo‐hexylmethane (3DCM) was used in stoichiometric proportions in every formulation. SEC could be used to follow the conversion of each type of epoxy groups as a function of time, in the pre‐gel stage. The reaction rate followed an autocatalytic behavior (catalysis by OH groups) in every case. DGEBD was less reactive than DGEBA. Mixing of both diepoxy prepolymers led to an increase in the specific rate constant for DGEBD and a decrease of the one for DGEBA. This can be explained by the influence of the polarity of the reaction medium on the polymerization rate and the presence of chlorine impurities.
Synthesis and structural study of an ABA block copolymer consisting of poly(γ‐benzyl L‐glutamate) as the a block and poly(ethylene oxide) as the B block
Authors: Cho Chong‐Su , Kim Seon‐Woong , Komoto Tadashi 
Published: April 2003

AbstractABA‐type block copolymers composed of poly(γ‐benzyl L‐glutamate) (PBLG) as the A component and poly(ethylene oxide) (PEO) as the B component were synthesized by polymerization of γ‐benzyl L‐glutamate N‐carboxyanhydride initiated by primary amines located at both ends of the PEO chain. The morphology examined by transmission electron microscopy using ruthenium tetroxide staining revealed a lamellar type of microphase separation of the copolymers. From circular dichroism measurements in ethylene dichloride solution, as well as from infrared spectra measurements in the solid state, it was found that the polypeptide block exists in the α‐helical conformation, as in PBLG homopolymer. Wide‐angle X‐ray diffraction patterns for the block copolymers depend on the casting solvent and show basically similar reflections as the PBLG homopolymer.
Solvent dependence of lyotropic liquid‐crystalline phases of cellulose tricarbanilate
Authors: Siekmeyer Maria , Zugenmaier Peter 
Published: April 2003

AbstractCellulose tricarbanilate (CTC) represents a derivative of cellulose which is excellently suited for a systematic study of the formation of lyotropic liquid crystals with solvents containing ether, ester or keto groups. The dependence on temperature, concentration and on structural features of the solvents as well as the phase behaviour were investigated in detail, especially with glycols, the chemical constitution of which was varied with respect to the glycol chain length and to the end groups. CTC with a narrow molar mas distribution and a degree of polymerization (DP) between 30 and 500 was synthesized for this study through derivatization of cellulose with subsequent degradation and fractionation.
Asymmetric radical polymerization of (–)‐3‐p‐menthyl sorbate
Authors: Doiuchi Tohru , Dodoh Takeshi , Yamaguchi Hidemasa 
Published: April 2003

AbstractThe radical polymerization of (–)‐3‐p‐menthyl sorbate (2) was performed with azoisobutyronitrile (AIBN) as an initiator in benzene at 50°C. The chiral (–)‐menthyl group in the resulting poly‐2 was removed by hydrolysis in potassium hydroxide solution to give optically active poly(sorbic acid), indicating that an asymmetric induction took place during the polymerization. It was concluded from the results of ozonolysis and optical rotatory dispersion measurements on the poly(sorbic acid) that the asymmetry was induced only at 1‐position of the monomeric unit in the poly‐2 main chain.
Macrocyclic peptides, 4. Preparations and enantioface‐differentiating abilities of 27‐ and 36‐membered ring peptides containing N,N′‐ethylene‐bridged dipeptides and glycine
Authors: Yamashita Tetsushi , Maruo Joji , Fujimoto Atsuko , Shibata Kozo , Kojima Yoshitane , Ohsuka Akio 
Published: April 2003

Abstract27‐ and 36‐membered ring peptides were prepared using glycine, (2S, 3′ S)‐4‐methyl‐2‐(2′‐oxo‐3′‐isobutyl‐1′‐piperazinyl) pentanoic acid (2) and (2S,3′ S)‐3‐phenyl‐2‐(2′‐oxo‐3′‐benzyl‐1′‐piperazinyl)propanoic acid as the units of peptides. The interactions of 1‐phenylethylammonium (1) and p‐methoxy‐1‐phenylethylammonium bromides (11) with these cyclic peptides were studied by 1H and 13C NMR measurements in CDCl3. It was found from these results that the peptides distinguish the enantiomers (R‐ and S‐isomers) of the substrates. Furthermore, it was shown that the enantioface‐differentiating abilities of 36‐membered ring peptides are superior to those of 27‐membered rings.
Molecular design of biodegradable functional polymers, 2 Poly(carboxylic acid) containing xylopyranosediyl groups in the backbone
Authors: Matsumura Shuichi , Maeda Shuichi , Yoshikawa Sadao 
Published: April 2003

AbstractPolymer 2, containing unreacted xylopyranosediyl groups in the backbone, was prepared from xylan by the conversion of vicinal hydroxyl groups to carboxylic groups using periodic acid/sodium chlorite. 2 was found to be biodegraded quickly by the activated sludge. Arthrobacter sp. KM810 and Flavobacterium sp. KM811 were isolated as 2‐degrading strains. It was found that these strains biodegraded all molecular‐weight fractions of 2. 2 shows a good calcium sequestration capacity which is comparable to that of poly(sodium acrylate).
Polymères photoréticulables à unités cinnamiques, 1 Synthèse des monomères et polymérisation
Authors: Remmas Miloud , Soutif Jean‐Claude 
Published: April 2003

AbstractThe synthesis of cinnamic acid derivatives with a carbon‐carbon double bond in para position was studied by a Knoevenagel reaction with p‐chloromethylstyrene. The latter was obtained via a several‐step reaction from 2‐phenylethanol. The monomers can be polymerized by a free‐radical process without affecting the cinnamic group. Copolymerization is effective only with monomers such as maleic anhydride, p‐vinylbenzaldehyde or methyl methacrylate, having a π‐acid character like the cinnamic acid derivatives used in our study.
Grafting of a vinyl acetate/methyl acrylate mixture onto cellulose. Effect of temperature and nature of substrate
Authors: Fernández María Jesús , Casinos Ismael , Guzmán Gonzalo Martín 
Published: April 2003

AbstractA mixture of vinyl acetate and methyl acrylate was grafted onto cellulose by using ceric ions as initiator. The influence of temperature, oxygen and of the nature of the polymeric substrate (mercerized cellulose and grafted cellulose) on the grafting parameters was studied. High temperatures favour homopolymerization more than grafting. Successive oxidation of cellulose by ceric ions suggests two types of reaction sites in cellulose. A gel effect occurs when high grafting yield is reached. Polymerization is inhibited by oxygen.
Effect of annealing on the thermal properties of poly(4‐hydroxybenzoate‐co‐p‐phenylene isophthalate)s
Authors: Tsai Hong‐Bing , Lee Chyun , Chang Nien‐Shi , Chang Shinn‐Jen , Chen Mei‐Sui 
Published: April 2003

AbstractA series of poly(4‐hydroxybenzoate‐co‐p‐phenylene isophthalate)s (1) was prepared by melt polycondensation of 4‐acetoxybenzoic acid, p‐phenylene diacetate, and isophthalic acid followed by solid state polymerization. The thermal properties of the as‐made samples were found to be significantly different from the second run thermal properties. The copolyesters with the same thermal history were annealed at 270°C in the DSC at various time intervals, and the thermal properties were further determined by DSC. For different compositions, annealing had different effects on the thermal properties of the copolyesters. With increasing annealing time the transition temperature and transition heat of 1 containing 50 and 60 mol‐% of monomeric units (m. u.) of 4‐hydroxybenzoic acid (HBA50 and HBA60) were found to increase. The second run DSC curves of HBA40, HBA30 and HBA20 (containing 40, 30 and 20 mol‐% of 4‐hydroxybenzoic acid m. u.) show two endotherms; transition heat and transition temperature of the lower temperature transition increase with the annealing time, but the transition heat of the higher temperature transition decreases. Finally, only one endotherm was observed for long‐time annealing. The difference in thermal properties between the as‐made sample and the second run could be described as annealing effect during solid state polymerization.
Monomères acryliques à fonction carbonate cyclique, 2 Modification chimique de copolymères à groupements carbonate cyclique lateraux
Authors: Couvret Denis , Brosse Jean‐Claude , Chevalier Sammy , Senet Jean‐Pierre 
Published: April 2003

AbstractAcrylic monomers with a cyclic carbonate function, their synthesis having been described previously, are used to synthesize copolymers with pendent cyclic carbonate side groups. Their chemical modification by ring opening addition reactions provides a convenient method for preparing functional polymers. The study of reactions with amines, on model compounds and on polymers, shows the possibility of obtaining a macromolecular network with crosslinking groups of carbamate type.
Poly(oxy‐1,4‐phenylene) macromonomers for polycondensation
Authors: Nießner Norbert , Heitz Walter 
Published: April 2003

AbstractMacromonomers based on poly(oxy‐1,4‐phenylene) (POP) with end groups suitable for polycondensation were synthesized. In a one‐step reaction, α‐(2,5‐dimethoxyphenyl)‐ω‐bromooligo‐(oxy‐1,4‐phenylene) (3) was obtained by Ullmann reaction of 1‐bromo‐2,5‐dimethoxybenzene (2) and potassium 4‐bromophenolate (1). Ether bond cleavage with boron tribromide yields the α‐(2,5‐dihydroxyphenyl) derivative 5, a novel type of macromonomers. Cocondensation with tert‐butylhydroquinone and trifluoromethylterephthaloyl dichloride results in the formation of a liquid‐crystalline graft copolymer (7).
Synthesis and controlled release behaviour of esters from amylose and 1‐naphthylacetyl chloride
Authors: Sánchez‐Chaves Manuel , Arranz Félix 
Published: April 2003

AbstractThis work deals with the modification reaction of amylose with 1‐naphthylacetyl chloride using pyridine as catalyst and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on the concentration of polymer, 1‐naphthylacetyl chloride and pyridine was found. The activation energy was found to be 32,4 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound from tablets is dependent on the hydrophilic character of the modified amylose as well as on the pH value of the medium.
The use of activated benzyl vinyl ethers to control molecular weight in free radical polymerizations
Authors: Meijs Gordon F. , Rizzardo Ezio 
Published: April 2003

AbstractThe vinyl ethers, α‐benzyloxyacrylonitrile (4), methyl α‐benzyloxyacrylate (5), and α‐benzyloxy‐acrylamide (6), act as sulfur‐free chain transfer agents in the polymerization of methyl methacrylate (chain transfer constant Cx = 0,081–0.47), styrene (Cx = 0,036–0,14), methyl acrylate (Cx = 0,3–1,1), and vinyl acetate (Cx = 12–20) initiated by AIBN at 60°C. With methyl methacrylate and styrene, the conversions of the polymerizations are relatively unaffected by the vinyl ethers. With methyl acrylate and vinyl acetate, however, some retardation occurs. The activity of the compounds is compared with that of α‐benzyloxystyrene (1), which undergoes chain transfer by a novel free radical addition‐fragmentation pathway.
Conditions of microgel formation in homogeneous anionic polymerization of 1,4‐divinylbenzene
Authors: Okay Oguz , Funke Werner 
Published: April 2003

AbstractA kinetic model of the homogeneous anionic polymerization of 1,4‐divinylbenzene (1,4‐DVB) in dilute solutions with instantaneous initiation and without cyclization and termination reactions is proposed. The monomer and pendant vinyl group conversions, degrees of polymerization of the primary chains and the crosslinking densities were predicted as a function of the reaction time as well as 1,4‐DVB and initiator (butyllithium) concentrations. The previous experimental data concerning the formation of the microgels can be explained using the kinetic mechanism of the polymerization reaction and neglecting cyclization. Calculations indicate that reactive 1,4‐DVB microgels can be synthesized in the whole concentration range of the initiator.
Free‐radical polymerization up to high conversion. A general kinetic treatment
Authors: Buback Michael 
Published: April 2003

AbstractThe dependence of propagation and termination rate coefficients on conversion in free‐radical polymerization is described by a purely kinetic model which considers contributions of segmental diffusion, translational diffusion, and reaction diffusion to termination and which also takes diffusion‐control of the propagation step into account. The kinetic scheme provides a satisfactory representation and interpretation of the termination rate coefficient measured in an extended range of conversion for ethylene, butyl acrylate, and methyl methacrylate polymerization. Reaction diffusion is of primary importance for termination at moderate and high conversion, which leads to fairly simple expressions for kinetic parameters even at conversions where the solution viscosity exceeds the pure monomer viscosity by several orders of magnitude.
Friedel‐Crafts acylations of crosslinked polystyrenes using ω‐halogenoacyl chlorides
Authors: Caze Claude , Hodge Philip 
Published: April 2003

AbstractThe Friedel‐Crafts acylation of various crosslinked polystyrenes, both microporous and macroporous, by ω‐halogenoacyl chlorides, a reaction used by others to functionalise polystyrenes, was carefully investigated. As judged by elemental analyses, the desired reaction to give ω‐halogenoacyl residues is always accompanied by side reactions. Infrared spectroscopy indicates that these include crosslinking and the introduction of carboxylic acid groups. The side reactions are less pronounced with the ω‐chloro compounds and with the 2% crosslinked microporous polymer. For many applications these side reactions will not be important, but in some cases an awareness of their occurrence could be crucial.
Characterization of methylalumoxane by means of gel permeation chromatography
Authors: Cam Darinn , Albizzati Enrico , Cinquina Patrizia 
Published: April 2003

AbstractCharacterization of methylalumoxane (MAO) by gel permeation chromatography reveals the presence of different oligomeric products. Using suitable series of columns and alkylaluminium compounds with known molecular weight, it is possible to obtain the average molecular weights of most species which are present in a sample of MAO. The study of the chromatograms reveals modifications in composition of the MAO oligomers in relation to the time of residence in solution at given temperatures.
Action of the cellulase multienzyme complex on the degree of polymerization of high‐molecular‐weight cellulose
Authors: Marx‐Figini Marianne , Blanco Silvia , Ellenrieder Guillermo v. 
Published: April 2003

AbstractA study of the viscosity‐average degree of polymerization DPη as a function of time under the action of a cellulase multienzyme complex was carried out using Trichoderma Reesei QM9414 for the production of the enzyme complex and cotton cellulose with a DPη ≈ 6 800 as substrate. Simultaneously the fractions of material dissolved by the enzyme action during various times of hydrolysis were determined. The study revealed that the enzymatic hydrolysis of cellulose using the multienzyme complex comprises several consecutive stages, one stage of appreciably decreasing DP alternating with one in which the DP is nearly constant. The portion of cellulose transformed (through its degradation) to soluble products, however, increases continuously with time also in the stages of constant DP. These results permit the conclusion that there exists a synergism of endo‐ and exocellulases, and that within this synergism the hydrolytical cleavage of internal glucosidic linkages catalysed by the endoenzyme is a necessary first step. The statistical degradation of cellulose molecules generates new chain ends which are then susceptible to the action of exocellulases, provoking and end‐wise depolymerization process.