bluuebunny/crossref_metadata_2025_split huggingface dataset:
High conversion free‐radical suspension polymerization: End groups in poly(methyl methacrylate) and their influence on the thermal stability
Authors: Giannetti Enzo , Mazzocchi Romano , Fiore Leonardo , Visani Francesco 
Published: April 2003

AbstractSuspension free‐radical polymerization of vinyl monomers, carried out in the presence of alkyl mercaptans as chain‐transfer agents, is analyzed. A model which accounts for the development with conversion of the polymer weight fractions having particularly tagged end groups, namely sulfur‐containing and unsaturated end groups, is presented. The best current theories for diffusion‐controlled polymerizations are included in the model. The sulfur content of poly(methyl methacrylate), determined as a function of conversion by a microcoulometric method, is in good agreement with the values predicted from polymerization kinetics. The rate of weight loss of the produced polymers is then related to the content of the unsaturated end groups. By comparing experimental thermal stability indexes (from thermogravimetry and isothermal heating experiments) to calculated polymer weight fractions, it is shown that the thermal stability of poly(methyl methacrylate) produced in the presence of alkyl mercaptans approximately depends on the square of the weight fraction of the polymer chains with an unsaturated end group.
Isomeric bismaleimides and polyaspartimides
Authors: Bell Vernon L. , Young Philip R. 
Published: April 2003

AbstractA study was conducted of the effects of meta‐para isomerism on the synthesis and properties of aromatic bismaleimides and polyaspartimides. Three isomers, 3,3′‐, 3,4′‐, and 4,4′‐diaminodiphenylmethanes (methylenedianilines), were used to prepare three isomeric bismaleimides. The bismaleimides then were reacted with their respective isomeric diamines in m‐cresol solution to give a series of isomeric polyaspartimides. The properties of each of the isomeric series were measured and compared. Strong flexible films were solvent cast from the two polyaspartimides derived from the 3,4′‐ and 4,4′‐diamines and their respective bismaleimides. Tensile properties of the films from the 3,4′‐diamine/3,4′‐bismaleimide combination polyaspartimide were equivalent to those from the 4,4′‐diamine‐derived polymer. That finding, together with that polymer's lower softening temperature and the nonmutagenic nature of the 3,4′‐diamine monomer, suggested a potential usefulness for 3,4′‐diaminodiphenylmethane as a replacement for 4,4′‐diaminodiphenylmethane in addition polyimides.
Magnesium chloride supported high‐mileage catalysts for olefin polymerization. X. Effect of hydrogen and catalytic site deactivation
Authors: Chien James C. W. , Kuo Chi‐I. 
Published: April 2003

AbstractThe effect of H2on propylene polymerization initiated by a MgCl2/EB/PC/AlEt3/TiCl4–3 AlEt3/MPT catalyst was studied. Hydrogen increases significantly the initial rate during the early stage of the polymerization to give a higher yield of polymer than reactions without H2. But H2reduces the yield toward the latter stages so that the net effect on the total yield can be quite small. There is no appreciable effect of H2on either the isotacticity index or polydispersity of the products. It decreases molecular weight proportional to (pH2)1/2. The chain transfer by H2resulted in a decrease of total metal polymer bond concentration with time of polymerization. The rate constants of hydrogen chain transfer for the two kinds of isospecific and nonspecific sites are= 5.1 × 10−3,= 2.7 × 10−3,= 7.5 × 10−3,= 4.4 × 10−3, in units of torr1/2sec−1at 50°. Hydrogen assists in the deactivation of the catalytic sites as does propylene; rates of the former and the latter vary with (pH2)1/2and [C3H6]1/2, respectively, withk= (12.1 ± 0.9) M−1torr−1/2sec−1andk= (65.3 ± 3.3) M−3/2sec−1at 50° andA/T= 167. The mechanism for deactivation of catalytic sites are discussed.
Dye‐sensitized photopolymerization. III. Photopolymerization of methyl methacrylate initiated by acryflavin: Ascorbic acid system in aqueous solution
Authors: Lenka Subasini , Mohanty Indu B. 
Published: April 2003

AbstractThe dye‐sensitized photopolymerization of methyl methacrylate by acryflavin–ascorbic acid system in aqueous solution has been investigated. The systems were buffered with phosphate–citrate buffer (Na2HPO4, citrid acid) and the effects of monomer, dye, temperature, buffer, ascorbic acid, etc. on the rate of polymerization were studied. The rate of polymerization was evaluated gravimetrically. A suitable kinetic scheme was proposed and the composite rate constants were evaluated.
Infrared spectroscopic analysis of poly(methyl acrylate‐co‐styrene)
Authors: Kandil S. H. , El‐Gamal M. A. 
Published: April 2003

AbstractMethyl acrylate–styrene copolymers of different copolymer compositions were free‐radically prepared. The relative intensities of the carbonyl frequencies of the methyl acrylate units atv1730 cm−1were correlated with the copolymer composition. The positions and shapes of the carbonyl bands in the infrared absorption spectra of the copolymers‐dissolved in chloroform, were shown to depend on the composition of the copolymers and upon the presence of different proportions of methyl acrylate centered triads. The results obtained by infrared spectroscopy were compared with those obtained by13C‐NMR. Infrared spectra may be used to yield information about both the copolymer composition and the triad sequence distribution.
Potentiometric and viscosimetric titration of poly(N‐acyldehydroalanines) containing asymmetric nucleic acid base derivatives as pendant groups
Authors: Brandt K. A. , Overberger C. G. 
Published: April 2003

AbstractThe potentiometric and viscosimetric titration curves of poly(N‐acetyldehydroalanine) (PNAcDHA) were compared with those of the nucleic acid base‐containing dehydroalanine backbone polymers poly{(+ −) and (−)− [2‐(thymin‐1‐yl]{propanoamido}propenoic acid} (PTDHA and P(−)TDHA)). The behavior of PNAcDHA was similar to polyacids such as poly(acrylic acid), but PTDHA and P(−)TDHA displayed very strong nearest neighbor interactions, since the pH curves had an additional inflection at half neutralization that was sensitive to the ionic strength of the medium and the viscosity curves showed little expansion of the polymer coil with increasing ionization. NAcDHA–TDHA copolymers were prepared which showed similar behavior. These results suggested that PTDHA and P(−)TDHA were extended and conformationally restricted in aqueous solution compared to PNAcDHA, findings that agreed with the results of spectroscopic studies of these polymers.
Poly(methyl methacrylate‐g‐urethane). I. Synthesis
Authors: Akcelrud L. , Gomes A. S. 
Published: April 2003

AbstractPoly(methyl methacrylate‐g‐urethane) was prepared by coupling between poly(methyl methacrylate‐co‐2‐hydroxyethyl methacrylate) and polyurethane. The polyurethane was obtained by bulk polycondensation of tolylene diisocyanate and polypropylene glycol. The two polymeric species were synthesized and characterized separately, and the composition of the grafted products varied only by the spacing of the grafted segments. Grafted copolymers with 5, 10, 20, 25, 40, 50, 70, and 90% of incorporated polyurethane have been prepared.
Production of anomalous particles in the process of emulsifier‐free emulsion copolymerization of styrene and 2‐hydroxyethyl methacrylate
Authors: Kamei Shigeru , Okubo Masayoshi , Matsumoto Tsunetaka 
Published: April 2003

AbstractIt was found that copolymer particles produced by emulsifier‐free emulsion copolymerization of styrene and 2‐hydroxyethyl methacrylate had an anomalous shape with uneven surface. The formation mechanism is discussed.
Synthesis of poly(arylene sulfide)s by reaction of aromatic sulfides with AlCl3
Authors: Sergeyev Vladimir A. , Nedelkin Vladimir I. 
Published: April 2003

AbstractMethods have been developed to obtain poly(arylene sulfide)s by high‐temperature bulk polycondensation of diphenyl sulfide, cyclic aromatic sulfides, as well as direct reaction of benzene with sulfur, under the action of AlCl3. The reaction proceeds via the formation of colored cation‐radical complexes of aromatic sulfides with AlCl3 and results in polymers of ladder structure with, predominantly, thianthrene units in the chain. Taking linear poly(1,4‐phenylene sulfide) as an example, AlCl3 is shown not only to act as a catalyst but also to exert an active influence on the chemical structure of the polymer.
Non‐newtonian viscosity of polypeptides in the helix–coil transition region
Authors: Jang Chun Hag , Kim Jong Ryul , Ree Taikyue 
Published: April 2003

AbstractThe non‐Newtonian intrinsic viscosities [η] of poly(γ‐methyl L‐glutamate) were measured in the helix–coil transition region under various conditions in this work. The helix content fH, which represents the degree of conformational transition, was obtained by using a polarimeter. Our experimental results show that the non‐Newtonian behavior of the polypeptide is markedly affected by its conformation; i.e., the non‐Newtonian effect becomes larger as fH increases. The effect of external pressure ΔP on [η] was studied carefully; [η] increases with fH when ΔP < 1.5 psi, but it decreases when ΔP > 1.5 psi and fH > 0.8. The reason for this result is considered in the text.
Spectroscopic studies of poly(ethylenimine) backbone polynucleotide analogs
Authors: Overberger C. G. , Peng Lin 
Published: April 2003

AbstractThe hypochromicity of poly(ethylene glycol methyl ether)‐b‐poly(ethylenimine) containing thymine derivatives as pendants was observed in water, 0.1N HCl and 0.1N NaOH solutions. The hypochromic effect of this compound is between 30% and 40%. Interactions between this polynucleotide analog and poly‐A was only found in water but not in 0.1N HCl or 0.1N NaOH solution.
Functional monomers and polymers. CXXXII. Template polymerization of methacrylamide derivatives containing nucleic acid bases
Authors: Inaki Yoshiaki , Ebisutani Kazushi , Takemoto Kiichi 
Published: April 2003

AbstractFree‐radical polymerizations of methacrylamide derivatives containing nucleic acid bases were studied in the presence of the polymethacrylamide having complementary nucleic acid bases as template polymers. The rate of the polymerization did not show remarkable difference in the presence or the absence of the template polymer. A stable polymer complex, however, was precipitated from the polymerization system, and was found to be different in a thermal analysis from the polymer complex which was obtained by mixing of the complementary polymers in solution. Free‐radical copolymerizations in the presence of the template polymers also supported the template polymerization.
Gas separation membranes plasma‐polymerized from perfluoromethylcyclohexane/methane mixture
Authors: Inagaki N. , Kawai H. 
Published: April 2003

AbstractPlasma‐polymerizations of perfluoromethylcyclohexane (PFMCH)/methane (CH4) mixture were investigated by elemental analysis, infrared spectroscopy, and ESCA; and gas transport characteristics of the plasma‐films formed were studied. The addition of CH4 molecules to PFMCH accelerated defluorination to form plasma‐polymers poor in fluorocarbon units. The surface energy of the plasma‐polymers increased with increasing the CH4 concentration. The oxygen and nitrogen permeation coefficients (PO2 and PN2) and the PO2/PN2 ratio for the polymer films formed from the PFMCH/CH4 mixture depended on the CH4 concentration. The small CH4 addition was effective in improvement of the PO2 value and of the PO2/PN2 ratio, but the much addition was ineffective. The oxygen transport through the plasma‐polymers was discussed.
Effect of water‐soluble polymers on fusion of egg yolk and soybean phospholipid liposomes
Authors: Abe Koji , Sakamoto Hidehiko , Itoh Yoshihiro , Senoh Saburo 
Published: April 2003

AbstractThe efficiencies of polyelectrolytes, i.e., polycations and polyanions, and several kinds of water‐soluble polymers as fusogens on soybean phospholipid liposome (SL) and egg yolk phospholipid liposome (EL) were investigated by the fluorescence quenching method. There were optimal concentrations for the induction of fusion in every system. Polycations induced fusion of liposomes at very low concentration in comparison with other polymers. Poly(carboxylic acid)s induced fusion at relatively high concentration. A strong acidic polyanion with high molecular weight also induced fusion of liposomes. The induction efficiency of poly(ethylene glycol) on fusion was higher than other nonionic polymers. The efficiency of fusion of EL was lower than that of SL in all systems because of the higher stability of EL membrane. It was found that electrostatic interactions, hydrogen bonding and/or hydrophobic interaction between these water‐soluble polymers and liposomal membranes played an important role on aggregation and fusion of liposomes.
Kinetics of successive seeding of monodisperse polystyrene latexes. II. Azo initiators with and without inhibitors
Authors: Sudol E. D. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractOil soluble azo initiators in combination with water soluble inhibitors were used to extend the particle size limit in studies of the kinetics of successive seeding of monodisperse polystyrene latexes. Monodisperse latexes were prepared up to 2.5 μm in diam using 4.0 mM AMBN and 14.5 mM hydroquinone with a constant 15% emulsifier (Aerosol–MA) surface coverage throughout the seven step sequence. The polymerization kinetics were measured in a piston/cylinder dilatometer designed for microgravity experiments. The Interval III kinetics were dominated by the gel effect although these were affected by the nature of the inhibitor. In general, the overall polymerization rate decreased with increasing particle size (decreasing Np) up to a size of about 1 μm. Thereafter, the kinetics were independent of these variables, exhibiting Smith‐Ewart Case 3 (bulk) kinetics. The initiator efficiencies were found to be of the order of 10%, considerably lower than reported for bulk polymerizations.
Studies on the mechanism of oligomerization of alkynes by group IVB catalysts
Authors: Farona Michael F. , Thanedar Shrinavas , Famili Amir 
Published: April 2003

AbstractThe homogeneous catalyst systems Cp2MCl2/C2H5AlCl2 (Cp = cyclopentadienyl; M = Ti, Zr) were found to promote homooligomerization of internal and terminal alkynes. Studies using titana‐ and zirconacyclopentadienes without cocatalysts revealed that these molecules were likely formed in the reactions and were active catalytic intermediates. Isolation of expanded metallacycles indicated that the mechanism of oligomerization proceeded by successive insertion reactions to produce larger metallacycles, eventually giving linear oligomers of low molecular weight.
Aliphatic polyimides from phenylene bis(succinic anhydride) and bis(glutaric anhydride)
Authors: Teshirogi Takuma 
Published: April 2003

AbstractMeta and para derivatives of phenylene bis(succinic anhydride) and bis(glutaric anhydride) were obtained from 1,3‐ and 1,4‐bis(β‐cyano‐β‐carbethoxyvinyl)benzene with potassium cyanide or Meldrum acid followed by hydrolysis with concentrated hydrochloric acid and dehydration with acetic anhydride. Aliphatic polyimides were prepared from these anhydrides with six aromatic diamines through thermal ring closure of polyamic acids obtained by solution polymerization in dimethylacetamide, and thermal stability of these polyimides was examined by thermogravimetric analysis.
Anionic polymerization with expansion in volume
Authors: Brady Robert F. , Simon Frederick E. 
Published: April 2003

AbstractNew bicyclic and tricyclic compounds have been synthesized by the Lewis acid‐catalyzed condensation of epoxides with cyclic acid anhydrides or cyclic bislactones. These materials take part in the anionic addition polymerization of amine‐functional polyamides with diepoxides, and modify the shrinkage that is characteristic of the reaction. It is possible to control the extent of shrinkage by choosing an appropriate comonomer and by adjusting the concentration of this material in the reaction mixture.
Mass spectrometric characterization of poly(ethylene terephthalate‐co‐p‐oxybenzoate)
Authors: Garozzo Domenico , Giuffrida Mario , Montaudo Giorgio , Lenz Robert W. 
Published: April 2003

AbstractCopolyesters containing ethylene terephthalate and p‐oxybenzoate units in mole ratios of ca. 80:20, 70:30, 40:60, and 20:80, respectively, were examined by direct pyrolysis–mass spectrometry to obtain information about the thermal stabilities and the sequences distributions of the two types of units as a function of composition. Thermal stability as measured by rate of volatilization increased with increasing oxybenzoate content, as did the amount of char residue formed. The electron impact mass spectrum of the volatile fragments showed the formation of predominantly linear fragments with carboxyl and vinyl end groups. Dimer, trimer, and tetramer fragments containing either or both types of units could be identified and their relative amounts could be estimated from peak intensities. The results were consistent with those expected for random distributions of the two units, i.e., for statistical copolymers.
Synthesis and characterization of poly[3,5′‐(3‐pyridyl methyl)‐2,6,‐diaminotoluene] and its condensation product, poly[4‐(3‐pyridyl),8‐methyl,2,3‐6,7‐quinolino]
Authors: Ruan J. Z. , Litt M. H. 
Published: April 2003

Abstract2,6‐Diaminotoluene was reacted with 3‐pyridinecarboxaldehyde in acidic medium and the intermediate polymer was further condensed in polyphosphoric acid at high temperature (335°C) to obtain a soluble heterocyclic ladder polymer, poly[4‐(3‐pyridyl),8‐methyl,2,3–6,7‐quinolino] (PPMQ). The molecular weight of the intermediate polymer depended on the reaction temperature and the rate of reactant addition. The NMR spectra of the intermediate polymer indicated that a linear polymer with resonable molecular weight was formed. Element analysis and IR spectra confirmed the structure of the final polymer.
Polymers containing the [2H]‐1,2,4‐triazoline‐3‐thione ring
Authors: Katritzky Alan R. , Cato Stephen J. , Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R. 
Published: April 2003

AbstractHigh‐molecular‐weight polymers containing [2H]‐1,2,4‐triazoline‐3‐thione rings are prepared by the condensations of diisothiocyanates with bis(acid hydrazides) to give intermediate polymeric acylthiosemicarbazides that are ring‐closed by refluxing in 1M aqueous sodium carbonate. Thermal cyclization of the polymeric acylthiosemicarbazides leads to cross‐linked insoluble products. The acylation of bis(thiosemicarbazides) with bis(acid chlorides) produces polymers of a similar structure but lower molecular weight.
New polymer syntheses 16. LC‐copolyesters of 3‐(4‐hydroxyphenyl) propionic acid and 4‐hydroxy benzoic acids
Authors: Kricheldorf Hans R. , Conradi Arnd 
Published: April 2003

AbstractThe polycondensation of 3‐(4‐hydroxy phenyl)‐propionic acid, 4‐Hypp, by means of acetanhydride or acetylchloride was conducted either in the presence or in the absence of a liquid reaction medium. DSC measurements, polarizing microscope, and X‐ray diffraction studies indicate poly(4‐Hypp) possesses at about 215°C a reversible first order transition between two solid phases. Copolyesters containing various mole ratios of 4‐Hypp and 4‐hydroxy benzoic acid, 4‐Hybe, were prepared by bulk condensation with acetanhydride at 320°C. At 4‐Hypp/4‐Hybe ratios less than 1.0:1.5 the reaction product was heterogeneous, containing crystals of pure poly(4‐Hybe). Neither increasing the reaction time nor the variation of the transesterification catalyst resulted in an entirely homogeneous copolyester. However, for 4‐Hypp/4‐Hybe ratios greater than 1.0:1.5, 13C NMR spectra indicate perfectly random sequences. Also, terpolyesters containing 3‐chloro‐4‐hydroxy‐ or 3,5‐dichloro‐4‐hydroxy‐benzoic acid were heterogeneous with less than 30 mol % 4‐Hypp. DSC measurements revealed for all polyesters a glass transition in the range of 55–78°C. Temperature dependent X‐ray diffraction studies confirm that the solid phase is a s.c. LC‐glss. Correspondingly low heat distortion temperatures were found by thermomechanical analyses. The copolyesters display under the polarizing microscope LC‐phase up to temperatures of 450–480°C, where rapid thermal degradation prevents further investigations. In the case of the 4‐Hypp/4‐Hybe 1:1 copolyester, the LC‐phase extends over a temperature range of about 400°C. TGA measurements indicate beginning thermal degradation at temperatures between 350 and 380°C.
Graft polymerization of acrylic monomers onto starch fractions. IV. Effect of reaction time on the grafting of butyl acrylate onto amylose
Authors: Vazquez M. B. , Goñi I. , Gurruchaga M. , Valero M. , Guzman G. M. 
Published: April 2003

AbstractStudies were carried out on the grafting of butyl acrylate (BA) to amylose by the ceric ion method. After removing the homo‐PBA with THF and toluene, and the ungrafted amylose with 0.5NNaOH, the PBA content of the graft copolymers was determined by acid hydrolysis with 1N HCl. The influence of reaction time on the grafting yields was determined and the largest values were: 82% for the grafting efficiency, 246% for the percent grafting, 62% for the grafted amylose, 48% for the grafted PBA, and 64% for the total conversion.
The synthesis of biodegradable polymers with functional side chains
Authors: Pitt Colin G. , Gu Zhong‐Wei , Ingram Peter , Hendren R. Wayne 
Published: April 2003

AbstractTrifunctional hydroxy‐terminated oligomeric polyesters, Mn 500, 1000, and 2000, were prepared by initiating ring‐opening copolymerization of δ‐valerolactone and ε‐caprolactone with glycerol. The prepolymers were converted to crosslinked polyester‐urethanes by their reaction with hexane‐1,6‐diisocyanate in proportions corresponding to 70, 80, 90, and 100% of the hydroxyl content. The moduli of the resulting elastomers varied between 0.12 MPa and 3.83 MPa, and the elongation at break between 60 and 2000%. The residual hydroxyl groups were derivatized by heterogeneous reaction with chloroacetic anhydride or excess hexane‐1,6‐diisocyanate, and these and further transformations of the functional groups were verified by infrared spectroscopy and electron probe x‐ray microanalysis. A second series of hydroxy‐substituted elastomers was synthesized by copolymerization of δ‐valerolactone, ε‐caprolactone, and 4‐(t‐butyldimethylsilyloxy)‐ε‐caprolactone, using different amounts of 2,2‐bis(caprolacton‐4‐yl)propane as the crosslinking agent; removal of the t‐butyldimethylsilyl group to liberate pendant hydroxyl groups was achieved with acetic acid but not fluoride ion. The hydroxylated polyester (but not the polyesterurethanes) was shown to undergo enzymatic surface erosion in rabbit. The biodegradation data were compared with results previously obtained with low‐modulus elastomeric polyesters.
o‐nitrovinylbenzaldehyde polymers: Precursors of photosensitive acetals
Authors: Kamogawa Hiroyoshi , Takei Mitsuhiko 
Published: April 2003

Abstract2‐Nitro‐3‐vinyl, 2‐nitro‐5‐vinyl, and 4‐nitro‐3‐vinylbenzaldehydes were synthesized starting with the corresponding dimethylnitrobenzenes via brominations of the two methyl groups, subjection of one of the resulting two bromomethyl groups to the Wittig reaction, and further subjection of the remaining one to the Kröhnke reaction.An attempt to prepare 2‐nitro‐4‐vinylbenzaldehyde (21) from the 2‐nitro‐4‐vinylaniline (19), synthesized starting with 2‐nitro‐4‐methylaniline following the same vinylation procedure, failed.The three nitrovinylbenzaldehydes and 19 were polymerized with AIBN in the conventional manner to afford low molecular weight polymers in low conversions. The polymer of 19 was then converted to the 21 polymer. All nitrobenzaldehyde polymers were converted to acetals with ethylene glycol and 2‐hydroxyethyl salicylate and the latter in benzene solutions were irradiated with UV to afford the o‐nitrosobenzoate polymers with half‐cleavages of the alcohol residues.