bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and characterization of polymides derived from bis(methoxycarbonyl)terephthaloyl chloride by interfacial condensation
Authors: Chern Yaw‐Terng 
Published: April 2003

AbstractA series of polyimides was synthesized by interfacial condensation of bis(methoxycarbonyl)terephthaloyl choride (1) with aromatic diamines and polycyclic aliphatic diamines. 1 (mixed isomers) was synthesized from pyromellitic dianhydride and contains about 60% para isomers and 40% meta isomer. The poly(amic ester)s 3 had inherent viscosities of 0.85–0.24 dL/g. All the poly(amic ester)s were soluble in NMP, DMAc, DMF, and DMSO, except for the polymer prepared from diamantane‐1,6‐diamine. Through thermal treatment the poly(amic‐ester)s formed imide structures. All the polyimides and poly(amic ester)s were amorphous due to X‐ray diffraction studies. The glass transition temperatures of these polyimides were in the range of 255–340°C, and the 5% weight loss temperatures were between 485 and 640 °C in nitrogen atmosphere. The polyimides (4c and 4d) with polycyclic aliphatic diamines such as adamantane‐1,3‐diamine and diamantane‐1,6‐diamine had good thermal stability, with a temperature of 5% weight loss above 485°C. The polyimides 4c and 4d also had high glass transition temperature of 340°C and 300°C, respectively.
Synthesis of poly(N‐tert‐butylaziridine) macromonomers and graft copolymers with uniform side chains
Authors: Christova Darina C. , Velichkova Rumiana S. 
Published: April 2003

AbstractPoly(N‐tert‐butylaziridine) (polyTBA) macromonomers with allylamino‐, allyloxy‐ and methacrylate end‐groups were synthesized via deactivation of living polyTBA with appropriate nucleophiles. The macromonomers were copolymerized with N‐vinyl‐2‐pyrrolidone (NVP), 2‐hydroxyethyl methacrylate (HEMA) and isoprene (Is). Two types of graft copolymers were obtained: the first one is constituted of hydrophilic backbone (polyNVP or polyHEMA) and hydrophobic uniform polyTBA side chains. The second type is composed of a flexible hydrophobic polyIs backbone and hard hydrophobic polyTBA side chains which, however, become water swellable after quaternization.
On the chirality of polyvinyl compounds, 19 Influence of double bond position on the asymmetric cyclocopolymerization
Authors: Wulff Günter , Gladow Stefan 
Published: April 2003

AbstractCyclocopolymerization of two new monomers, D‐mannitol 3,4‐O‐carbonate 1,2:5,6‐bis‐O‐[(2‐vinylphenyl)boronate] (2) and D‐mannitol 3,4‐O‐carbonate 1,2:5,6‐bis‐O‐[(3‐vinylphenyl)boronate] (3), was investigated. While copolymers of monomer 2, which has the double bond in ortho position, do not show optical activity after splitting off the chiral D‐mannitol template, optically active copolymers were obtained from monomer 3 with its double bond in meta position. The residual optical activity is due to the configuration of the main chain (main chain chirality). With the aid of circular dichroic (CD) spectra and optical rotation measurements the configuration of the (3‐vinylphenyl)boronic acid diads in the copolymer chain could be determined. When methyl methacrylate (MMA) was used as comonomer, the diads possessed (R,R) configuration. The mechanism of cyclopolymerization of monomer 3, which involves a 17‐membered transition state, could be explained by approximating its conformations of lowest energy with semiempirical methods (AM1).
Ductile‐brittle transition behavior of short‐chain branched polyethylenes at 80°C
Authors: Yeh Jen‐taut , Lee Wen‐Shuan 
Published: April 2003

AbstractA systematic study on the ductile‐brittle transition of short‐chain branched polyethylenes (SBPEs) is reported. The values of threshold stress intensity, the time corresponding to the point of ductile‐brittle transition and the failure time (tf) of samples which failed in ductile and brittle regions were found to increase significantly with increasing branch length of the SBPEs. The fracture kinetics and the morphology at the notched root were distinguished for SBPE samples that failed in ductile and brittle regions. The values of (CC(notch opening displacement at the roof of notch)–BB(the thickness of the craze))/(AA(notch opening displacement at the surface of the specimen)–CC) are less than or equal to about 0.3 for all samples which failed in the brittle region, and these values are only about 20–30% of those of the samples which failed in the ductile region. Finally, an equation was developed to predict tf of SBPEs which failed in the ductile and brittle region in terms of stress intensity, branch length and other material and experimental parameters.
Side‐chain type liquid‐crystalline polyethers, 2 Effects of mesogenic moieties on the thermal properties and their self‐assembly behaviour
Authors: Akiyama Eiichi , Ohtomo Miki , Nagase Yu , Koide Naoyuki 
Published: April 2003

AbstractA series of polyethers having mesogenic moieties connected to the backbone without flexible spacer in the side‐chain were prepared by ring‐opening polymerization of the corresponding glycidyl ether derivatives containing various mesogens. As the mesogenic side‐chains, tolan and phenylene units with alkoxy or alkoxycarbonyl groups were introduced and compared with biphenyl type mesogens. The polyether with tolan derivative having butoxy group as the side‐chain end exhibited two kinds of highly ordered smectic phases. On the other hand, in the case of biphenyl or tolan as the rigid‐core, introduction of ester group as an end‐group decreased the thermal stability of liquid‐crystalline phase as compared with the case of alkoxy group as the end group. The polyethers with the p‐alkoxyphenyl group in the side‐chain exhibited a smectic A phase which formed a bilayer structure, while no mesophase was observed for those having the p‐alkoxycarbonylphenyl group in the side‐chain. The self‐assembly of bilayer structures, which consist of hydrophilic layer (polyether backbone) and hydrophobic layer (side‐chain), might be responsible for the appearance of liquid‐crystallinity in such polyethers whose mesogen consists only of a simple phenylene ring.
Assignment of finely resolved 13C NMR spectra of polyacrylates
Authors: Kawamura Tokiji , Toshima Naoki , Matsuzaki Kei 
Published: April 2003

Abstract13C NMR spectra of poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA), poly(isopropyl acrylate) (PIPA), poly(butyl acrylate) (PBA), and poly(isobutyl acrylate) (PIBA) with various tacticities were determined. It was found that methine carbon resonances of PIPA split into triad sequences and those of PEA, PBA and PIBA show a mm triad at high field. Methylene carbon spectra of polyacrylates were assigned in terms of hexad sequences using HECTOR (13C‐1H COSY) spectra.
Hydrophilic thermotropic block copolyetheresters with poly(pentamethylene p,p′‐bibenzoate) segments
Authors: Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing 
Published: April 2003

AbstractBlock copolyetheresters 1 with poly(pentamethylene p,p′‐bibenzoate) segments and poly(ethylene oxide) segments were prepared by melt polycondensation of dimethyl p,p′‐bibenzoate, 1,5‐pentanediol, and poly(ethylene glycol) (PEG) with molecular weights of 400, 1 000, or 2 000. The 1H NMR analysis shows that the feed mole ratio of PEG to dimethyl p,p′‐bibenzoate determines the composition of the block copolyetheresters. The differential scanning calorimetry (DSC) results indicate that some block copolyetheresters exhibit a monotropic smectic liquid‐crystalline phase due to the poly(pentamethylene p,p′‐bibenzoate) segments. The transitions depend on the content and the molecular weight of the PEG. The block copolyetheresters 1 show high water absorption due to the hydrophilic nature of the poly(ethylene oxide) segments. The water absorption increases with increasing PEG content. As the molecular weight of PEG increases, the water absorption increases significantly.
Influence of soluble parts in gelatin/water gels on their network structure in an ultracentrifugal field
Authors: Cölfen Helmut , Borchard Werner 
Published: April 2003

AbstractIf gels are investigated in an analytical ultracentrifuge by means of sedimentation equilibrium experiments, so called soluble parts which are originally not incorporated into the network influence the swelling pressure equilibria of the gels. For gelatin/water, it can be shown that an irreversible process takes place which is dependent on the rotational speed of the experiment. Experimental evidence is given that soluble parts which are partly associated and aggregated to the polymer network can act as a branching and/or crosslinking agent. A model for this process is given. In such a case an application of the results of the swelling theory, e.g. that of Flory and Huggins assuming a constant number of network junctions, cannot be applied anymore. A universal procedure is described how swelling pressure equilibria can be identified, although the crosslinking density is changed. It can be shown that the gradient of the soluble parts, respectively the additional structural changes of the gel by the soluble parts, is reproducible and with it the swelling pressure equilibria. Furthermore the radial distribution of dyed soluble parts inside the gel phase is presented as a function of time during a sedimentation equilibrium run with a gelatin/water gel. It can be shown that the back diffusion process of the soluble parts in the gel is very slow and does not lead to the sedimentation‐diffusion equlibrium of free soluble parts in the considered time interval of 4 months. In combination with the detected fast sedimentation of the soluble component in the gel phase this gives further evidence for the association of the soluble parts to the gel network forming a gradient gel. The predicted formation of the anisotropic gel could be proved by a swelling experiment.
Poly(amido‐amine)s and poly(ester‐amine)s based on aromatic amines containing carboxyl groups
Authors: Loan Do Thi Bich , Rashkov Ilya B. , Panayotov Ivan M. 
Published: April 2003

AbstractThe preparation of poly(amido‐amine)s and poly(ester‐amine)s via polyaddition between aromatic amines containing free or esterified carboxyl groups and compounds with activated double bounds [N,N′‐methylenebis(acrylamide), 1,4‐diacryloylpiperazine and 1,3‐propanediyl diacrylate] is described. The products obtained are typical polyelectrolytes, their solutions exhibiting anomalous viscosity behaviour.
New polymer syntheses, 81 . Poly(3‐oxybenzoate) randomly branched with 3,5‐dihydroxybenzoic acid or 5‐hydroxyisophthalic acid
Authors: Kricheldorf Hans R. , Stöber Olaf , Lübbers Dierk 
Published: April 2003

AbstractRandomly branched (hyperbranched) Poly(3‐hydroxybenzoate), poly(3‐Hybe), was prepared by polycondensation of silylated 3‐acetoxybenzoic acid with either silylated 3,5‐diacetoxybenzoic acid or bis(trimethylsilyl) 5‐acetoxyisophthalate. The number of branching points was varied by changing the feed ratio of difunctional and trifunctional monomers. 1H NMR and 13C NMR spectroscopy proved the nearly random incorporation of the trifunctional “branching units”. Cocondensations with small amounts of acetylated bisphenol‐P allowed one to control the degree of polymerization (DP) and to determine the DP by 1H NMR spectroscopy. However, analogous copolycondensations with silylated 2‐(4‐tert‐butylphenoxy)terephthalic acid failed. According to GPC measurements, weight‐average molecular weights above 105 were obtained. DSC measurements revealed that the glass transition temperatures (Tg's) vary largely with the degree of branching (DB) and with the nature of the end‐groups. In the case of phenolic OH and acetate end‐groups, the relationship Tg vs. number of branching points passes through a minimum.
A preliminary study of poly(p‐phenylene) based nonlinear optical materials
Authors: Wright Michael E. , Toplikar Edward G. , Lackritz Hilary S. , Subrahmanyan Suchitra 
Published: April 2003

AbstractThis paper describes preliminary work exploring the feasibility of preparing high‐performance nonlinear optical (NLO) materials based on the polyp‐phenylene (PPP) backbone. Three new monomer/NLO‐phores of the general formula: 4‐RSO2C6H4C(4‐XC6H4) (where R = 2,5‐dichlorophenyl; 2a, X = H; 2b, X = OCH3; 2c X = N(CH3)2) were synthesized and then homopolymerized using catalytic nickel and stoichiometric zinc to produce the poly(p‐phenylenes), 3a–c, respectively, as low‐molecular‐weight materials (number‐average molecular weight Mn = 1800–6000). NLO‐phores 2b–c and low‐molecular‐weight oligomers of 3c were dispersed in a poly(methyl methacrylate) (PMMA) host. Spin‐cast films of these guest‐host systems were subjected to corona poling above the glass transition temperature. Tg. Following poling, both monomer NLO‐phore/PMMA guest‐host systems displayed optical nonlinearity with second‐order nonlinear optical susceptibility χ(2) values of 1.7 pm/V and 0.9 pm/V for 2c and 2b, respectively. Both systems exhibited good temporal stability at room temperature, with about 12% loss in second harmonic signal over more than 100h. However, the oligomeric material 3c dispersed in PMMA showed a smaller NLO signal when poled above Tg. Attempts to induce dipolar asymmetry in the homopolymers 3b and 3c were unsuccessful. The observed response during poling and the relaxation of the chromophore orientation following poling, have been discussed in terms of structure and composition of these systems.
Synthesis of polymers containing pseudohalide groups by cationic polymerization, 13. “Living” polymerization of 2‐methylpropene initiated by the system 1,4‐bis(1‐azido‐1‐methylethyl)benzene/BCl3/dimethyl sulfoxide
Authors: Rajabalitabar Berhooz , Nguyen Hung Anh , Cheradame Hervé 
Published: April 2003

AbstractPolymerizations of 2‐methylpropene (MP) initiated by the system 1,4‐bis(1‐azido‐1‐methylethyl)benzene (DAMEB)/BCl3 in the presence of DMSO were carried out by “all monomer in” (AMI) technique at −70°C in CH2Cl2 solution. FT‐IR, 1H NMR and SEC analyses of polymers (PMP) showed that the Mn versus weight of PMP plot is a straight line without intercept and azide Fn3 and aromatic ring Fϕ functionalities are close to the theoretical values of 2 and 1, respectively. A polymerization of MP initiated by the system α,ω‐diazido‐PMP/BCl3/DMSO led to a final poly(2‐methylpropene) (PMP) with an increase of Mn corresponding to the amount of MP introduced and presenting the same functionalities FN3 and Fϕ as the starting PMP. These results indicate that the polymerization system MP/DAMEB/BCl3/DMSO is a “living” one, because in an acceptably large range of molecular weight (Mn < 50000) the Mayo plot 1/DP versus 1/DP0 is a straight line. The intercept gives ktrM/kp = 4 · 10−5, showing the transfer reaction proceeds at very low rate.
Preparation of ordered and crosslinked films from liquid crystalline p‐vinylphenoxy‐based monomers
Authors: Andersson Henrik , Trollsås Mikael , Gedde Ulf W. , Hult Anders 
Published: April 2003

AbstractThe synthesis of the following monofunctional and bifunctional liquid crystalline p‐vinylphenoxy‐based monomers is described: 4‐methoxyphenyl 4‐[11‐(4‐vinylphenoxy)‐undecyloxy]benzoate (1), 4‐cyanophenyl 4‐[11‐(4‐vinylphenoxy)undecyloxy]benzoate (2) and 3‐(4‐vinylphenoxy)propyl 4‐{4‐[11‐(4‐vinylphenoxy)undecyloxy]benzoyloxy}benzoate (3). Both free radical and cationic polymerization of the monofunctional monomers 1 and 2 yielded side‐chain liquid crystalline polymers exhibiting smectic A mesomorphism. The polymers exhibited high molar masses (Mn = 40000 – 100000 g/mol) and relatively narrow molar mass distributions (Mw/Mn between 1.5 and 3). Ordered thin films were prepared by in‐situ photopolymerization of monomers 1, 2 and 3 oriented in their nematic mesophases. Thin films of a thermally stabilized ordered side‐chain liquid crystalline polymer were prepared by copolymerization of the monofunctional monomer 1 and the bifunctional monomer 3, the latter present in low concentration. The films regained orientation when cooled down from temperatures above the isotropization point (137°C) as evidenced by polarized FT‐Raman measurements.
Structural study of thermotropic liquid crystalline poly(ethyleneiminium) salts alkylated with mesogenic side chains
Authors: Masson Patrick , Gramain Philippe , Guillon Daniel 
Published: April 2003

AbstractIonic liquid crystalline polymers were obtained from linear poly(ethyleneimine) (PEI) substituted with 6‐(4‐methoxy‐4′‐biphenyloxy)hexyl bromide or 12‐(4‐methoxy‐4′‐biphenylyloxy)dodecyl bromide, and quaternised with dimethyl sulfate or hydrobromic acid. Their thermotropic polymorphism was studied by means of differential scanning calorimetry (DSC), polarising optical microscopy and X‐ray diffraction. A smectic A mesophase was identified and described from a structural point of view with the help of computer modelling. The completely alkylated and quaternised PEI derivative was shown to form a single layered smectic A structure with pendant groups all on the same side of the polymer backbone in a double row ribbon‐like configuration. The ribbon‐like polymer chains are packed side by side with the polymer backbone parallel to the smectic layers and the mesogenic groups perpendicular to them. For partially alkylated or quaternised PEI derivatives, the layer spacing in the smectic A mesophase is generally different from that of the corresponding molecular length calculated for fully functionalised polymers.
Stereocomplex formation in ABA triblock copolymers of poly(lactide) (A) and poly(ethylene glycol) (B)
Authors: Stevels Willem M. , Ankone Marc J. K. , Dijkstra Pieter J. , Feijén Jan 
Published: April 2003

AbstractTwo series of triblock copolymers of poly(ethylene glycol) (PEG, number‐average molecular weight Mn = 6000) and poly(L‐lactide) (PLLA) or poly(D‐lactide) (PDLA) were prepared by ring‐opening polymerization of lactide initiated by PEG end groups using stannous octoate as a catalyst, either in refluxing toluene or in the melt at 175°C. The weight percentage of PLA in the polymers varied between 15 and 75 wt.‐%. Blends of polymers containing blocks of opposite chirality were prepared by co‐precipitation from homogeneous solutions. The melting temperatures of the crystalline PEG and PLA phases strongly depended on the composition of the polymers. The melting temperature of the PLA phase in the blends was approximately 40°C higher than that of the single block copolymers. Stereocomplex formation between blocks of enantiomeric poly(lactides) in PEG/PLA block copolymers was established for the first time. Water uptake of polymeric films prepared by solution casting was solely determined by the PEG content of the film.
X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) analysis of UV‐exposed polystyrene
Authors: France Richard M. , O'Toole Liam , Short Robert D. , Pollicino Nino 
Published: April 2003

AbstractThe surface photochemistry of polystyrene is shown to exhibit features that distinguish it from the bulk and from the polymer in solution. We report on the use of medium‐ and high‐resolution time‐of‐flight secondary ion mass spectrometry and X‐ray photoelectron spectroscopy in an investigation of the changes that occur as a result of exposure to UV light from a ‘black lamp’ source. The experiment mimics closely the effects of natural sunlight. It is shown that there are substantial changes occurring in the surface molecular structure of polystyrene on irradiation, which correspond to loss of aromaticity, and that these changes precede any uptake of oxygen.
Télomères et cotéloméres d'intérêt biologique et biomédical, 7. Synthèse, évaluations physico‐chimiques et biologiques de télomères amphiphiles de type acryloylamino‐acide
Authors: Polidori Ange , Pucci Bernard , Pavia André A. , Lamaty Gérard , Leydet Alain , Roque Jean Pierre 
Published: April 2003

AbstractNew ionic telomeric surfactants derived from acryloylamino acids were synthesized and their tensioactive properties compared to those of non‐ionic analogs previously reported. We also compared their anti HIV behavior with that of other polymeric polyanionic derivatives. Acryloyl monomers of various amino acids such as glycine, alanine, aspartic, glutamic and γ‐aminobutyric acid were prepared and telomerized in the presence of various alkanes or perfluoroalkanethiols as chain transfer reagents. For a given amino acid, the critical micellar concentration (CMC) was shown to depend upon the nature and the length of the hydrophobic tail and not the size of the hydrophilic head, i.e., the number average degree of polymerization (DPn). None of the telomeric polyanionic derivatives reported herein induced HIV inhibition.
Polymerization of 2‐allylnorbornane using Ziegler‐Natta catalysts: Homopolymerization
Authors: Marathe Sujata , Mohandas Thekke Pangil , Sivaram Swaminathan 
Published: April 2003

AbstractPolymerization of 2‐allylnorbornane using TiCl4 catalyst results in a polymer which is 40% insoluble in o‐xylene at 130°C, whereas with TiCl3 catalyst, a polymer with 88% insolubility in o‐xylene at 130°C is obtained. The o‐xylene‐insoluble fractions gave a very high melting point Tm = 355°C. The main features of these polymerizations are low catalyst activity and, in the case of TiCl4 catalyst, competitive isomerization of the monomer. Based on a comparison with the properties of an acyclic analogue, poly(4‐methyl‐1‐pentene), the partly insoluble nature of poly(2‐allylnorbornane) and its high melting point can be attributed to the presence of the bicyclic pendant.
The glass transition of mixtures of polystyrene with alkyl‐terminated oligostyrene — experimental evidence for microphase separation in a polymer blend
Authors: Abetz Volker , Müller Gunther , Stadler Reimund , Schlick Shulamith 
Published: April 2003

AbstractMixtures of high molecular weight polystyrene (Pn = 961.5; Tg = 373 K) and sec‐butyl‐terminated oligostyrene (Pn = 10.6; Tg = 302 K) show a dependence of the glass transition on the composition (i.e. number‐average molecular weight) which cannot be described by the classic equations of Fox & Flory or Kanig & Ueberreiter. Addition of small amounts of the oligostyrene strongly decreases the glass transition, and above an oligomer content of 40 wt.‐% the glass transition remains constant within experimental error. This behavior can be attributed to the unfavorable interactions between the alkyl‐terminated oligomer and the high molecular weight PS. As a result the oligomer is a bad solvent but — according to the requirements defined by Kanig — an efficient plasticizer. This behaviour is even more pronounced in mixtures of the alkyl‐terminated oligostyrene with a poly(styrene‐co‐maleic anhydride) of low maleic anhydride content. In this case, ESR spectra of the spin‐labelled styrene copolymer demonstrate the existence of microheterogeneities on the 2–5 nm scale. The findings are in qualitative agreement with recent theoretical work of Khokhlov & Erukhimovich on entropy‐induced microphase separation in blends.
Télomérisation radicalarie de monomères N‐acryloyl‐N‐alkylamino esters d'intXérêt biologique
Authors: Leydet Alain , Barragan Véronique , Boyer Bernard , Roque Jean‐Pierre , Pucci Bernard , Pavia André A. 
Published: April 2003

AbstractThree methyl 11‐(N‐acryloyl‐N‐alkylamino)undecanoates were synthesized from acryloyl chloride and amino‐or alkylaminoundecanoic acid esters. These compounds were telomerized in the presence of 1‐dodecanethiol as telogen to yield telomers with molecular weight lower than 5000. These telomers are likely to generate HIV inhibitor polyanions with good biocompatibility. The K/Kt value was assessed from a kinetic study of the telomerization reaction. NMR spectroscopy analysis indicates that the polymerization degree DPn are in good agreement with expectation for methyl 11‐(N‐acryloylamino)undecanoate. However, they were lower than expected for methyl 11‐(N‐acryloyl‐N‐alkylamino)undecanoate.