bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer drying. III. Comparison of molecular desorption from poly(styrene‐co‐divinylbenzene) in the gel‐state and in the glass‐state
Authors: Errede L. A. 
Published: April 2003

AbstractThe results observed in 44 time‐studies that monitored evaporation from liquid‐saturated poly(Sty‐co‐DVB) particles enmeshed in poly(tetrafluoroethylene) microfibers under conditions that precluded decrease in area of the microporous composite film sample verified that after the enmeshed particles undergo transition from the gel‐state to the glass‐state, the number of residual adsorbed molecules per phenyl group of polymer is given by a linear combination of n < 7 exponential decay functions, the first order rate constants of which are related to one another by the equation: log ki = log k0 − mi, where m is characteristic of the polymer, and k0 is characteristic of the sorbed liquid such that k1 is about 105 times faster than k6. The results also show that k1 of the set of nki for desorption from poly(Sty‐co‐DVB) in the glass‐state is equal to kgel, the first‐order rate constant for desorption of the test‐liquid from that polymer in the gel‐state. These results are interpreted to mean that i, the identification number of the ith population, reflects the number of phenyl groups in the “host” polymer with which the “guest” volatile molecule is associated simultaneously as discussed in the text.
Polymer drying. IV. A molecular interpretation of polymer drying
Authors: Errede L. A. 
Published: April 2003

AbstractFurther consideration of data already collected, in many time‐studies that monitored gravimetrically evaporations of acetone, toluene, and chloroform from the corresponding liquid‐saturated poly(styrene‐co‐divinylbenzene) samples, show that αt, the residual number of sorbed molecules per phenyl group at a given level of desorption, is a linear function of αs, the number of adsorbed molecules per accessible phenyl group in the polymer at thermodynamic equilibrium with excess test‐liquid. Such linear relationships were noted at successive break‐points in the kinetics of desorption (from gel‐saturation to virtual dryness) that signaled sequentially (a) incipient elimination of adsorbed molecules from polymer in the rubbery state, (b) incipient transition from the rubbery state to the glassy state, (c) completion of this transition, and (d) successive depletions of five of the six populations of residual adsorbed molecules that were trapped in six different molecular environments by rigidification of the system during the transition. These results support the viewpoint that αs is a parameter that reflects how well the molecular structure of the sorbed molecule can be accommodated by that of the monomer unit of the polymer.
Efficient, “one‐pot” synthesis of silylene–acetylene and disilylene–acetylene preceramic polymers from trichloroethylene
Authors: Ijadi‐Maghsoodi Sina , Pang Yi , Barton Thomas J. 
Published: April 2003

AbstractAn extremely efficient process has been developed for the synthesis of linear silylene‐acetylene and disilylene‐acetylene polymers. Trichloroethylene is quantitatively converted by n‐butyllithium to dilithioacetylene. Quenching with dialkyl‐or diaryldichlorosilanes affords high yields of the polymers, \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm SiR}_{\rm 2} \hbox{---} {\rm C} \equiv {\rm C\rlap{--} ]}_n ,{\rm and }\rlap{--} [{\rm SiMe}_{\rm 2} {\rm SiMe}_{\rm 2} - {\rm C} \equiv {\rm C\rlap{--} ]}_n $\end{document} if ClMe2SiSiMe2Cl is employed. Molecular weights are much higher with this route than when acetylene is used as the dilithio‐ or dimagnesium acetylide precursor. Some of these polymers can be pulled into continuous fibers, and all can be cast into coherent films and thermally converted into silicon carbide.
Radical copolymerization of 2‐acryloyl thioxanthone with methyl methacrylate
Authors: Catalina F. , Peinado C. , Madruga E. L. , Sastre R. , Mateo J. L. , Allen N. S. 
Published: April 2003

AbstractA novel monomer, 2‐acryloyl thioxanthone (TXA), was prepared by reaction of 2‐hydroxy thioxanthone with acryloyl chloride. Copolymerization of TXA with methyl methacrylate (MMA) in DMF at 80°C was studied in order to evaluate relative reactivities of these monomers. Values of 1.36 and 0.5 were found for the respective reactivity ratios of MMA and TXA, respectively. The resonance stabilization and polar properties were determined and discussed in terms of spectroscopic data.
Modeling of unseeded emulsion copolymerization of styrene and methyl methacrylate
Authors: Forcada J. , Asúa J. M. 
Published: April 2003

AbstractA mathematical model for the unseeded emulsion copolymerization of styrene and methyl methacrylate has been developed. This model, which includes a new rate coefficient for radical desorption, was used to analyze the effect of the styrene/methyl methacrylate molar ratio in the initial charge on the number of particles, overall conversion and copolymer composition. It was found that the number of particles increased with the methyl methacrylate content and that a drift of the copolymer composition resulted during the polymerization of styrene/methyl methacrylate molar ratios other than 50/50. Good agreement between experimental results and model predictions was achieved.
The polymerization of 3‐chloro‐1‐propyne and 3‐bromo‐1‐propyne with Mocl5 and WCL6 based initiators and the structure of the resulting polymers
Authors: Kunzler J. , Percec V. 
Published: April 2003

AbstractThe WCl6 and MoCl5 initiated polymerizations of 3‐chloro‐1‐propyne and 3‐bromo‐1‐propyne were performed in both halogenated and aliphatic non‐nucleophilic and in aromatic nucleophilic solvents. The structure of the obtained polymers suggested that the polymerization reaction occurs in two steps. In both nucleophilic and non‐nucleophilic solvents, the first step consists of the metathesis polymerization of 3‐chloro(bromo)‐1‐propyne followed by electrophilic cis–trans isomerization leading to polymers containing trans‐cisoidal allyl chloride or bromide structural units. When the polymerization is performed in non‐nucleophilic solvents, in the second step an intramolecular electrophilic addition followed by elimination takes place. The resulting polymers contain a highly conjugated cyclopentadiene ladder structure. When the polymerization is performed in nucleophilic aromatic solvents, the intramolecular electrophilic addition competes with the electrophilic substitution of the solvent resulting in polymers containing high concentrations of arylpropenyl structural units. Subsequently, depending on the nucleophilicity of the polymerization solvent, the polymer structure contains structural units based on cyclopentadiene and/or arylpropenyl groups.
On the synthesis of pure (meth) acrylate esters and their corresponding homopolymers
Authors: Evans Stacy B. , Mulvaney J. E. , Hall H. K. 
Published: April 2003

AbstractWe have observed that homopolymers of certain (meth)acrylate esters, prepared by the Schotten–Baumann method of (meth)acryloyl chloride and desired alcohol, in the presence of triethylamine or pyridine, formed gels. The mechanism of gelation was investigated and found to be due to a diene impurity, (meth)acrylic anhydride, which cannot be easily separated from many (meth)acrylate esters. For preparation of pure (meth)acrylate esters, the SN2 displacement reaction of (meth)acrylate anion with the desired chloro compound is recommended. The yields of the two reactions are comparable, and even t‐butoxycarbonylmethyl methacrylate is produced in 73% yield by the recommended method.
Novel regular network polyester films from benezenetricarboxylic acids and glycols
Authors: Kiyotsukuri Tsuyoshi , Tsutsumi Naoto , Chen Ying‐Hsien 
Published: April 2003

AbstractNovel regular network polyester films were prepared from benzenetricarboxylic acids of trimesic (Y) and trimellitic (Z) acids, and glycols of ethylene (2G), tetramethylene (4G), and hexamethylene (6G) glycols. Prepolymers prepared by melt polycondensation for a short period within 1 h were cast from a DMF solution and successively post‐polymerized at various temperatures and times to form a network. The resultant films were transparent, flexible, and insoluble in any solvents. Distortion temperature measured by a penetration mode of thermomechanical analysis (TMA) increased with increasing post polymerization time and temperature, and leveled out at 222, 168, 125 and 75°C, for the 2GY, 2GZ, 4GY, and 6GY films, respectively. Temperatures close to 400°C at which the probe had completely penetrated corresponded to the thermal decomposition temperature of these films. Two broad but strong peaks in the x‐ray diffraction curves appears for the 2GY, 4GY, and 6GY, suggesting the formation of some ordered supramolecular structure owing to the regular network formed by symmetrical trimesic acid moiety, and the intensity of diffraction peaks became higher with increasing length of the methylene chain of the glycol monomer. Densities of the 2GY and 2GZ films decreased with increasing post‐polymerization time and temperature. Tensile strength and Young's modulus increased and elongation decreased with increasing network formation. These tensile properties was affected by the chemical structure of the network films.
Synthesis and evaluation of photolytically and thermally crosslinkable polyimide copolymers with diacetylene functionality
Authors: Chao Herbert S.‐I. , Vallance Michael A. 
Published: April 2003

AbstractThe polyimide block copolymers with diacetylene functionality were prepared in a two‐step process: (1) oligomeric imide formation terminated with 1‐amino‐3‐ethynylbenzene, and (2) oxidative coupling of the acetylene‐terminated polyimides with p‐ and/or m‐diethynylbenzene or bispropargyl ether of Bisphenol A to form block copolymers, or oxidative coupling within themselves in the presence of a copper (I) catalyst. The resulting copolymers were crosslinked with UV irradiation or thermal treatment. The thermal crosslinking process and the thermal stability of the crosslinked materials were studied by differential scanning calorimetry (DSC) and isothermal gravimetric analysis (IGA), respectively.
Terpolymerization of ethylene, propylene, and butene‐1 with highly active supported titanium catalyst
Authors: Sun Lixin , Lin Shangan 
Published: April 2003

AbstractAn investigation of ethylene‐propylene‐butene‐1 terpolymerization in the presence of TiCl4, Ti(OBu)4/MgCl2/ethylbenzoate (EB)/π2SiCl2/AlEt3 catalyst is described. The catalytic efficiency is very high, i.e., 86000g/g Ti under ambient conditions. The decay rate of terpolymerization with time fulfills the equation: Rt = Rs + (R0 ‐ Rs)e−βt. Characterizations with DSC, WAXD, 13C‐NMR, and solvent extraction of the resulting terpolymers were studied. Terpolymers of certain composition are elastomers without detectable crystallinity, which demonstrates a rather random sequence distribution and makes them promising for quality rubber. The assignment of the chemical shifts in 13C‐NMR spectra is made. The gas permeabilities of the terpolymer membrane is of PO2 = 2.35 × 10‐9 cm3 (STP) cm/cm2 s cm Hg and PO2/PN2 = 3.8 under optimum conditions.
Conformal transition of form II to form I in poly(L‐proline) and the aggregation of form I. I. Acetic acid–propanol solvent system
Authors: Kim Hyun Don , Jang Chun Hag , Ree Taikyue 
Published: April 2003

AbstractThe conformational transition of Form II → Form I of Poly‐L‐proline and the intermolecular aggregation of the product Form I during and after the transition in the HOAc‐propanol mixture solvent were studied, the ratio of HOAc:propanol being changed as 1:9, 1:6, and 1:4 v/v. For the study, the viscosity, light scattering, and dynamic light scattering of the system were measured. The experimental results exhibit that the concentration of Form II promotes the end‐to‐end type aggregation during and after the transition Form II → I. The extent of the aggregation is reduced in the order of the ratios of HOAc/propanol 1:9, 1:6, and 1:4 v/v. The end‐to‐end type aggregation is also reduced at higher temperatures. It was also observed that the end‐to‐end type aggregation occurs abruptly and strongly after the transition of Form II → I occurred to some extent. The point of the abrupt occurrence depends on the solvents and temperature. The light scattering and translational diffusion‐coefficient measurements showed also similar phenomena. It was also observed that the side‐by‐side type aggregation occurs when the initial concentration of Form II of poly‐L‐proline is relatively small, and the transition temperature is relatively high (35 and 45°C). All the above mentioned experimental results are explained by a simple principle described in the text.
Synthesis of diols containing 5‐benzyluracil base and their polymers
Authors: Lu C. X. , Lu Deshun 
Published: April 2003

AbstractPreparation of analogs of acyclic nucleoside, two diols containing 5‐benzyluracil base derived from 2‐(5‐benzyluracil‐1‐yl)propanoic acid (BUPA), and the corresponding model polymers of polynucleotide with linear polyester backbone and 2‐(5‐benzyluracil‐1‐yl)propionamido‐type pendant as a side chain are described. N‐(1′,3′‐Dihydroxy‐2′‐methyl‐2′‐propyl)‐2‐(5‐benzyluracil‐1‐yl)propionamide (HEBUPA) and its isomer N(β,β′‐dihydroxyethyl)‐2‐(5‐benzyluracil‐1‐yl)propionamide (HEBUPA) were prepared through the selective N‐acylation of primary aminodiol, 2‐methyl‐2‐amino‐1,3‐propanediol and secondary aminodiol, diethanolamine with BUPA, respectively, by the active ester‐N‐hydroxy‐5‐norbornene‐2,3‐dicarboximide (HONB) method. The resulting diols were polycondensed with active diamide of benzotriazole (HBT) such as 1,1′‐(terephthaloyl)bisbenzotriazole (PBBT), 1,1′‐(isophthaloyl)bisbenzotriazole (IPBBT), 1,1′‐(sebacocyl)bisbenzotriazole (SeBBT), giving semirigid and flexible polyesters containing 5‐benzyluracil derivative as the side group, by the selective O‐acylation of active diamide‐benzotriazole technique. Diols HMBUPA and HEBUPA were found to be very potent inhibitors of uridine phosphorylase isolated from Sarcoma 180 cells, with Ki values of 0.13 and 0.11 μM, respectively.
Thermal and transport properties of copoly(γ‐stearyl L‐glutamate‐γ‐methyl L‐glutamate)
Authors: Tsujita Yoshiharu , Ojika Ryoko , Takizawa Akira , Kinoshita Takatoshi 
Published: April 2003

AbstractCopoly(γ‐stearyl L‐glutamate‐γ‐methyl L‐glutamate)s with various compositions were synthesized by ester exchange of poly(γ‐methyl L‐glutamate) with stearyl alcohol. The temperature dependence of the volume and helical spacing of the copolyglutamates thus prepared was examined from 0 to 100°C, observing the melting and crystallization of the long alkyl side chain attached to the polypeptide backbone. The melting temperature of the long side chain increased with increasing stearyl L‐glutamate content. With increasing temperature, the α helical spacing decreased, especially with the melting of the side chain. On the other hand, the volume increased with increasing temperature and a marked increase was observed on melting. The above two phenomena were elucidated according to the structural model of the long side chain of the copolyglutamates proposed here. The transport properties, permeability coefficients were found to be considerably affected by the side‐chain structure of the copolyglutamate and by the melting or crystallization of the side chain. The permeability coefficient of the copolyglutamate with 67% degree of stearylation, varied as much as two orders of magnitude before and after melting or crystallization. It was also confirmed that the permeability coefficient is controllable by the side‐chain structural change of polypeptides.
Preparation and properties of polyarylates from 5‐t‐butylisophthaloyl chloride and various bisphenols
Authors: Yang Chin‐Ping , Oishi Yoshiyuki , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractPolyarylates containing a t‐butyl pendant group were prepared from 5‐t‐butylisophthaloyl chloride and various bisphenols through the phase‐transfer catalyzed two‐phase polycondensation. The polyarylates having inherent viscosities up to 3.1 dL/g were obtained quantitatively. They were readily soluble in various solvents such as chloroform, m‐cresol, and pyridine. Coloreless, transparent, and flexible films could be cast from the chloroform solutions of the polymers. The polyarylates had glass transition temperatures between 210 and 320°C, and did not lose weight below 350°C, with 10% weight loss being recorded at 395–450°C in air.
Unsaturated polyoxalates: Synthesis and mass spectral study of their thermal behavior
Authors: Thibeault Bryan , Stickles Eleanor M. , Weininger Stephen J. , Remy David E. 
Published: April 2003

AbstractThe thermal decomposition of a series of four saturated and unsaturated C4 polyoxalates shows competing modes of depolymerization, fragmentation to polyenes and CO2, and crosslinking. These decompositions, which were studied by DSC and TGA, and intensively by EI‐ and CI‐MS, could be rationalized in terms of the structure of the alcohol portions of the polyesters. The polymers were synthesized by ester interchange, which gave materials with DP values of 5–32.
Strong acidic ion exchangers structure by inverse steric exclusion chromatography
Authors: Jer̂ábek Karel , Setínek Karel 
Published: April 2003

AbstractA number of strongly acidic ion exchangers, both of the standard gel and of the macroreticular type, were investigated by inverse steric exclusion chromatography in an aqueous medium, using D2O, sugars, and dextrans as standard solutes. Their structure was characterized as an assembly of isoporous fractions by using Ogston's model of the porous medium. The data thus obtained were correlated with those on the catalytic activity of ion exchangers for the hydrolysis of saccharose.
Liquid crystal elastomers: Synthesis and characterization
Authors: Davis Frederick J. , Gilbert Andrew , Mann John , Mitchell Geoffrey R. 
Published: April 2003

AbstractThe synthesis is described of some acrylate based polymers containing both a mesogenic group (4‐cyanophenyl benzoate) connected to the polymer backbone by a flexible spacer, and varying degrees of crosslinking, introduced by copolymerization. Optical and calorimetric techniques are used to determine the phase behavior, which is found to depend strongly on the crosslink density (and the flexible spacer length); though (nominally) a relatively high degree of crosslinking is possible without completely destroying the liquid crystal phase. Mechanical measurements in conjunction with supplementary analytical data, where available, are used to determine the efficiency of copolymerization at introducing intermolecular crosslinking. Some possible explanations for the unexpectedly low efficiency of this process are discussed. The properties of materials prepared in this fashion are compared briefly with some examples where crosslinking is introduced after polymerization; this latter process is seen to be rather more efficient.
The interfacial polycarbonate reaction: Modeling the kinetics of carbamate side reactions
Authors: Kosky P. G. , Boden E. P. 
Published: April 2003

AbstractInterfacial phosgenation of bisphenols to form polycarbonates is catalyzed by trialkylamines. Trialkylamines also react with chloroformate‐terminated intermediates and form acyl ammonium salts. These salts are important intermediates in the polymerization but also may undergo decomposition to chain‐terminating carbamates that contaminate the polymer. We model these side reactions by the use of phenyl chloroformate and triethylamine which leads to the formation of N,N‐diethyl phenyl carbamate. The reaction is exothermic but has been measured under isothermal conditions in refluxing dichloromethane (at 39°C). The initial salt‐forming step is quickly established at near equilibrium conditions; its apparent equilibrium constant is 21 ± 2 L/mol and its rate constant is estimated to be at least an order of magnitude greater than 30 L/mol/min. Subsequent decomposition of the salt appears to follow first order kinetics in the salt concentration. Its rate constant is 1.3 ± 0.2 min‐1 under the experimental conditions. The various components of the reaction were examined by high field NMR and GC/MS. It was possible definitively to exclude base abstraction as an ancillary mechanism. NMR showed that unreacted triethylamine is loosely associated with species within the reaction and does not exist as free amine.
The effects of aromatic solvents on the photopolymerization rates of isoprene, ethyl methacrylate, and styrene
Authors: Chang B. C. , Chen C. D. , Chang T. C. , Ho S. Y. 
Published: April 2003

AbstractThe photochemical polymerization rates of isoprene, ethyl methacrylate, and of styrene in various aromatic solvents were measured. The average lifetimes of propagating radicals were measured by the rotating sector method. The polymerization rate constants, Kp, were determined and compared with dipole moments (μ) and Hammett σ constants for the aromatic solvents. Linear correlations of log(kp/kp, benzene) vs. μ and σ were obtained.
Alkylated styrene ionomers with variable length spacers. I. Synthesis
Authors: Gauthier Mario , Eisenberg Adi 
Published: April 2003

AbstractTwo analogous series of ionomer precursors based on 4‐substituted styrene copolymers were prepared with substituents R = ‐(CH2)nCO2Me (n = 1, 5, 10), or R = ‐O(CH2)nCO2Me (n = 1, 4, 10), and degrees of substitution from 10 to 15 mol%. The synthesis of the alkyl series compounds involved either chloromethylation of polystyrene or bromoalkylation via lithiation of a styrene‐4‐bromostyrene copolymer, followed by conversion to the nitriles. Methyl esters were then produced by reaction of the nitriles with methanol/HCl gas. The ether series compounds were obtained directly by reacting a styrene‐4‐hydroxystyrene copolymer with the methyl esters of the corresponding ω‐bromoaliphatic carboxylic acids in a Williamson ether‐type synthesis.
Preparation and properties of disilane‐containing photodegradable aromatic polyamides from bis(p‐aminophenyl)tetramethyldisilane and aromatic diacid chlorides
Authors: Padmanaban Munirathina , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

Abstract1,2‐Bis(p‐aminophenyl)tetramethyldisilane was synthesized from 1,2‐dichlorotetramethyldisilane and 4‐[N,N‐bis(trimethylsilyl)amino]phenyllithium. The diamine was reacted with various aromatic diacid chlorides giving disilane‐containing aromatic polyamides (aramids), whose inherent viscosities were between 0.27 and 0.70 dL/g, depending on the diacid chlorides used. The aramids had glass transition temperatures between 194 and 255°C. No weight loss was observed below 350°C. Some of the polymers were found to be semicrystalline based on their x‐ray diffractograms. The aramid films showed a strong ultraviolet (UV) absorption at 287 nm, which decreased during irradiation with UV light, suggesting that cleavage of the silicon‐silicon bond in the aramid backbone occurs. A decrease in the inherent viscosity and molecular weight of the soluble aramid derived from phenylindanedicarbonyl chloride was also observed by irradiation with UV light.