bluuebunny/crossref_metadata_2025 huggingface dataset:
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

We 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

Novel 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

The 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

An 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

The 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

Preparation 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

Copoly(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

Polyarylates 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

The 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

A 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

The 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

Interfacial 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

The 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

Two 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

1,2‐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.
Probing organic‐inorganic interactions and curing processes in coatings by photoacoustic fourier transform infrared spectroscopy
Authors: Urban Marek W. , Salazar‐Rojas Evelisse M.
Published: April 2003

Photoacoustic Fourier transform infrared spectroscopy (PA FT‐IR) was utilized to follow the curing processes in pigmented linseed oil based coatings deposited on a substrate. This nondestructive technique allows us to monitor both chemical reactions and processes such as solvent evaporation and pigment stratification during auto‐oxidative curing. Spectroscopically detected solvent evaporation is correlated with the weight loss measurements. Apparently, only a small portion of the solvent molecules evaporates during the curing process and the remaining fraction participates in the crosslinking process.

The interactions between organic (binder) and inorganic (pigment) phases of the coatings are also detected. It is found that in order to obtain a uniform distribution of the inorganic phase across the coating, it is necessary to consider both the hydrogen bonding between the two phases and the gravitational forces imposed on the pigment particles. Essentially, a lack of hydrogen bonding leads to stratification of the pigment phase and pigment volume gradient (PVC) across the coating. These processes are monitored spectroscopically and indicate that the hydrogen bonding is equally significant with other processes such as crosslinking and degradation.
Electrical properties of poly‐trans‐2,5‐dimethylpiperazine‐fumaramide. II. Conduction and relaxation processes
Authors: Sandrolini Franco , Motori Antonio , Saccani Andrea
Published: April 2003

Dc and ac electrical properties of poly‐trans‐2,5‐dimethylpiperazine‐fumaramide samples with different inherent viscosities were investigated as a function of temperature, applied electrical field (dc properties), and frequency (ac properties). Dc electrical conductivity of such a polymer is chiefly electronic below 180°C and ionic above 200°C. Protons coming from unavoidable moisture absorption due to hydrophilic nature of the polymer should be the main source of ionic charge carriers. No usual polymer chains relaxation processes were found, due to the high polymer crystallinity, which does not allow to detect any glass transition. Only slight polarization processes of the interfacial Maxwell‐Wagner‐Sillars type seem therefore to occur in the polymer. No effect of polymer average molecular weight on the dc as well as ac electrical properties was found.
Chemical structure of networks resulting from curing of N,N‐diglycidylaniline‐type resins with aromatic amines. II. Detection and characterization of intermolecular etherification on model compounds
Authors: Attias A. J. , Ancelle J. , Bloch B. , Laupretre F.
Published: April 2003

The reactivity of model compounds representative of the structures resulting from the first steps of curing in uncatalyzed (or LiClO4‐catalyzed) N,N‐diglycidylaniline/aromatic amine systems was studied. The results indicate that the intermolecular etherification either does not occur or is very slow under these conditions. Moreover, the latter situation is observed only in the very specific configuration when two hydroxyl groups are very close to each other. From these experiments, it can be inferred that the most likely reactions occurring after the epoxy‐primary amine addition in uncatalyzed N,N‐diglycidylaniline/aromatic amine systems are the are the epoxy‐secondary‐amine addition and the cyclization reactions discussed in a previous paper.
Poly(Alkylene phosphate)s bearing tetrahydrofuran rings (1,4‐anhydroerythritol) in the main chain
Authors: Lapienis Grzegorz , Penczek Stanislaw
Published: April 2003

Poly(alkylene phosphate)s, bearing anhydroerythritol units in the chain, have been prepared by both polycondensation and polymerization methods. The highest molecular weight product (1.3 × 104) has been obtained by polycondensation of trans‐3,4‐dihydroxytetrahydrofuran (1) with bis(diethylamino)methoxyphosphine (2) with further oxidation and dealkylation. Polymerization (anionic) of the corresponding cyclic phosphite of cis‐diol gave lower molecular weight polyphosphite (˜ 3.0 × 103), whereas cyclic phosphoramidite of cis‐diol did not polymerize at all. Microstructure of the polymers has been analyzed on the basis of 1H‐, 13C‐, and 31P‐NMR spectra.
Trimethylsilyl trifluoromethanesulfonate as “initiator” of the cationic polymerization of styrenes
Authors: Lin Chih‐Hwa , Matyjaszewski Krzysztof
Published: April 2003

The cationic polymerization of styrene and p‐methylstyrene has been initiated in the presence of trimethylsilyl trifluoromethanesulfonate. In a dry system, no polymerization was observed. In wet systems, polymers were formed in agreement with earlier reports. In the presence of hindered pyridines, used as proton traps, polymerization has started after complete protonation of the hindered pyridines; at the same time hexamethyldisiloxane was formed. These results indicate that silyl triflates cannot react directly with styrenes, and that initiation proceeds via triflic acid which is formed by hydrolysis of silyl triflate.
A study of XPS O1s spectrum of poly(ethylene terephthalate)
Authors: Nakayama Youichi , Takahagi Takayuki , Soeda Fusami , Ishitani Akira , Kosugi Nobuhiro , Kuroda Haruo
Published: April 2003

The XPS (x–ray photoelectron spectroscopy) O1s spectrum of PET [poly(ethylene terephthalate)] was examined in detail. Spectra of related compounds were also studied for comparison. The O1s peak profile of asymmetric doublet with π–π* satellites characteristic of PET was successfully explained both from comparison with the observed O1s spectra of the related compounds and from ab initio δSCF calculation.
Microemulsion polymerization of styrene: A study using pulsed laser initiation
Authors: Holdcroft S. , Guillet J. E.
Published: April 2003

Microemulsions of styrene were polymerized using pulsed UV lasers. Molecular weights of the polystyrene produced were linearly dependent on the time interval between pulses when the number of photons absorbed per mL of microemulsion was ca. 5 × 1015. In contrast, laser pulses with much higher intensity produced polymers with molecular weights which were nonlinear with laser repetition rate.
Studies of poly(ortho‐acylstyrene)s. II. Photoreactions of poly(o‐acetylstyrene)
Authors: Weir N. A. , Whiting K. , Arct J.
Published: April 2003

Poly(o‐acetylstyrene) (POAS) films were exposed under vacuum conditions to long wave ultraviolet radiation (λ ≥ 300 nm). Gaseous products, determined quantitatively by mass spectrometry, were methane, ethane and CO (trace), their formation indicating that POAS was undergoing Norrish Type I photodecompositions. Quantum yields for CH4 and C2H6 formation were more than an order of magnitude lower than the corresponding values for the isomeric poly(vinylacetophenone) (PVAP). Transient spectral measurements at 390 nm indicate the presence of enols (syn and anti), which result from the photoenolization of the ketone. Lifetimes are 161 and 4500 ns, respectively. The polymer undergoes crosslinking, the rate being much lower than that of PVAP. The mechanisms of the reactions are discussed, and it is proposed that the photostability of POAS (relative to PVAP) is the result of photoenolization, which competes favourably with degradation. POAS has considerable potential in sunlight storage applications.
Control of Y1Ba2Cu3Ox microstructures by polymer‐metal‐complex precursor synthesis
Authors: Chien James C. W. , Gong Ben Ming , Mu Xiangi , Yang Yingsong
Published: April 2003

Single phase Y1Ba2Cu3Ox material (1,2,3‐compound) have been synthesized from polymer‐metal‐complex (PMC) precursor between 860 and 950°C using a reaction time as short as 0.5 h. The morphology of the films and of fibers prepared by this process have been investigated. At low calcination temperatures the material is comprised of submicron grains, which are extensively interconnected forming a natural percolation network. Nodules with outgrowths are formed at intermediate temperatures; oblong shaped discs are obtained at high temperatures. The size and shape of grains are remarkably uniform in a given preparation; the former increases monotonically with the increase of calcination temperature. The 1,2,3‐compounds produced are pure according to x‐ray; they possess good superconducting properties (Tc (midpoint) = 90.6 K; ΔTc (90%‐10% resistivity) < 1 K) as prepared. Similar control of grain size and microstructure has been achieved for fibers of the 1,2,3‐compound, the mechanical strength of which is inversely related to grain size. Pure Y2Ba1Cu2O5 has also been prepared by the precursor method. X‐ray diffraction gave unit cell dimension of a = 12.18 Å, b = 5.66 Å and c = 7.13 Å belong to Pnma or P space group.
Analytical and kinetic approaches for the basic type of MgCl2‐supported high yield catalysts
Authors: Terano Minoru , Kataoka Takuo , Keii Tominaga
Published: April 2003

Thermal analysis in combination with infrared spectroscopy was applied to investigate the states of ethylbenzoate (EB) and TiCl4 in the simple type of the MgCl2‐supported high‐yield catalysts. A further attempt was made to evaluate kinetic parameters in the initial stage of propylene polymerization (< 1s) by a stopped flow method. The catalysts employed in the present study were prepared by co‐grinding MgCl2 and TiCl4 · EB complex. Thermal analysis and infrared spectroscopy showed that TiCl4 · EB complex decomposes during co‐grinding process. It was also indicated that EB, thus produced, has strong interaction with MgCl2. This was consistent with observations made by infrared spectroscopy. It was deduced that EB and TiCl4 are supported at separate sites of MgCl2 in the co‐ground catalyst. Kinetic parameters including rate constants of propagation (kp) and transfer (ktr), and concentration of polymerization centers ([C*]) were determined. The values of kp and ktr remained almost constant throughout the range of co‐grinding time, but [C*] increased with time of co‐grinding. No significant changes in the value of ktr were observed. Accordingly, the improvement of catalyst activity was attributed to an increase in [C*] rather than kp. These results lead to the conclusion that the complex decomposes during the co‐grinding to yield EB and TiCl4 which interact only with MgCl2.
Attachment of fluorescent dyes to polyacrylamides in aqueous media
Authors: Borg Robert , Winnik Mitchell A.
Published: April 2003

Fluorescent derivatives of polyacrylamide can be prepared by reacting an acidic aqueous solution of the polymer with xanthenol and dibenzosuberenol. These reactions take advantage of the carbocation stability of these dyes when they are treated with acid (i.e., pKR+ values near zero). In this way the O‐alkylated amide that one expects to be formed is too unstable to persist, and, eventually, the stable N‐alkylated derivative is formed. UV absorption and fluorescence spectra for the labelled polymers are reported. The presence of the dye affects the hydrophobic–hydrophilic balance of the polymer.
A new method for the production of large spherical monosized polymer particles for biomedical and chromatographic applications
Authors: Colvin M. , Chung S. K. , Hyson M. T. , Chang M. , Rhim W. K.
Published: April 2003

Monosized droplets of 2‐hydroxyethyl methacrylate (HEMA) and glycerol monomethacrylate (GMA) were made by passing the monomers under pressure through a nozzle coupled to an energized piezoelectric crystal. The droplets were allowed to fall into liquid nitrogen where they vitrified. The radiation post‐polymerization of the monomer spheres was investigated. Uniform monosized poly‐HEMA particles in the 100–300 μm diameter range were prepared with a coefficient of variation of 1.57% for particles of 155 μm in diameter. Monosized poly‐GMA was also prepared. The post‐polymerization conversion of pre‐irradiated GMA vitrified monomer droplets as a function of thawing rate and radiation dosage was investigated.
Copolymerization kinetics of 4‐methoxystyrene with methyl methacrylate and 4‐methoxystyrene with styrene: A test of the penultimate model
Authors: Piton Mark C. , Winnik Mitchell A. , Davis Thomas P. , O'driscoll Kenneth F.
Published: April 2003

The propagation kinetics for the copolymerization of 4‐methoxystyrene with methyl methacrylate and 4‐methoxystyrene with styrene have been investigated using a pulsed laser technique. The dependence of the copolymerization propagation rate constant on the monomer feed ratio shows a diviation from classic Mayo–Lewis model kinetics for 4‐methoxystyrene with methyl methacrylate but not for 4‐methoxystyrene with styrene. These results have been interpreted to indicate that a penultimate effect is apparent in the first monomer pair but not in the second. With r1r2 = 0.092 for the copolymerization of 4‐methoxystyrene with methyl methacrylate and r1r2 = 0.95 for 4‐methoxystyrene with styrene, it is suggested that a deviation of the product of the coplymerization reactivity ratios from unity may be an indication of the presence of a penultimate effect.
Aqueous polymerization on clay surfaces. V. Role of lattice substituted iron in montmorillonite in polymerizing methyl methacrylate in the presence of thiourea
Authors: Bhattacharyya J. , Saha S. K. , Guhaniyogi S. C.
Published: April 2003

The aqueous polymerization of methyl metacrylate in the presence of thiourea and hydrogen montmorillonite was initiated by radicals generated in situ. A part of the polymer was bound to the clay. Electrochemical analysis by cyclic voltammetry on this system and FeCl3/thiourea indicated that a slow one‐electron transfer process was responsible for the formation of the amidosulfenyl radical. The oxidant in the clay was lattice substituted Fe3+.
Imide–aryl ether benzoxazole block copolymers
Authors: Hedrick J. L. , Hilborn J. , Palmer T. D. , Labadie J. W. , Volksen W.
Published: April 2003

Imide–aryl ether benzoxazole multiblock copolymers were investigated. A key feature of these copolymers is the preparation of bis(amino) aryl ether benzoxazole (PBO) oligomers via nucleophilic aromatic substitution. The molecular weights of the oligomers were 10,500 and 26,000 g/mol with T'gs of 210 and 227°C, respectively. The oligomers were co‐reacted with 4,4′‐oxydianaline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in a N‐methyl‐2‐pyrrolidone/cyclohexanone solvent mixture in the presence of N‐methylmorpholine. The resulting amic ethyl ester‐aryl ether benzoxazoles were isolated and washed to remove homopolymer contamination. Copolymer compositions, determined by 1H‐NMR, ranged from 7 to 54 wt% PBO and the measured compositions were close to those charged. Solutions of the copolymers were cast and cured (350°C) to effect imidization producing clear films. The films showed tough ductile mechanical properties (∼50% elongations) with moduli comparable to PMDA/ODA polyimide. The copolymers displayed good thermal stability with decompositions temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of PBO block lengths or compositions. Good auto‐adhension was achieved in the copolymers containing the high PBO compositions.
Liquid crystalline properties of the copolyesters prepared from n‐octylhydroquinone, resorcinol, and 1,4‐bis(4‐carboxyphenoxy) butane
Authors: Rami Reddy C. , Kameswara Rao K. , Jin Jung‐Il , Lenz Robert W.
Published: April 2003

A series of copolyesters was prepared by the melt reaction of a mixture of n‐octylhydroquinone and resorcinol in varying ratios with 1,4‐bis(4‐chloroformylphenoxy)butane. Resorcinol was used as a comonomer to study the effect of a nonmesogenic structural unit on the thermotropic properties of a main chain liquid crystalline polyester with a flexible spacer. The effect of a tetramethylene spacer was compared with that of a longer, decamethylene spacer, which was included in similar copolyesters reported earlier by us. The inclusion of resorcinol units in increasing amounts destroyed the ability of the copolyesters to crystallize, as expected, and the copolymer containing as low as 20 mol % resorcinol showed no melting transition on analysis by differential thermal analysis (DSC). In contrast, the ability to form a liquid crystalline phase persisted until at least 40 mol % resorcinol was present. As expected, the isotropization temperature and the enthalpy and entropy changes for isotropization decreased with increasing non‐mesogenic comonomer content.
Effect of the way of addition of the reactants in the graft copolymerization of a vinyl acetate–methyl acrylate mixture onto cellulose
Authors: Fernandez M. J. , Casinos I. , Guzman G. M.
Published: April 2003

In order to graft a vinyl acetate–methyl acrylate mixture onto cellulose, an exploration of the way of addition of the reactants has been made. The influence of several factors on the grafting parameters was studied, i.e., the order of addition of the ceric ion initiator and the monomer mixture, the removal of the ceric ion solution after a cellulose‐ceric ion contact time, and the delayed addition along the polymerization period of the more reactive monomer (methyl acrylate) towards the cellulosic radicals. Some grafting parameters were determined: grafting yield, grafting efficiency, cellulose conversion, molecular weight, ceric ion consumption, grafting frequency, number of grafted chains, and synthetic copolymer composition. After a short period (ca. 15 min) for the ceric adsorption on cellulose, a fast formation of cellulosic radicals arises in the initial stages of the polymerization. These initial cellulosic radicals should be trapped by a sufficiently reactive monomer if high grafting yield and high number of grafted chains are to be reached. A portion of the synthetic polymer chains anchored to cellulose that are formed in the first stages of the polymerization, which are generated from cellulosic hemiacetal groups, should constitute block copolymer.
A method for the extraction of the unreacted cellulose from its graft copolymers
Authors: Fernandez M. J. , Casinos I. , Guzman G. M.
Published: April 2003

The extraction of the ungrafted cellulose allows us to know some grafting parameters as the cellulose conversion and the true frequency of grafting. The extraction of the unreacted cellulose from cellulose‐g‐poly(vinyl acetate‐co‐methyl acrylate) was tried by several approaches but only one of them has been successful. The other attempts have failed because an undesired chemical modification of the synthetic grafted polymer occurs while the unreacted cellulose was extracted. The method proposed here is particularly suggested for the cellulose extraction from its graft copolymers whose grafted chains arise from acrylic and vinylic esters. The effect of the reaction time on the graft polymerization of the vinyl acetate‐methyl acrylate mixture onto cellulose was also studied. The very similar average composition of grafted polymer and homo‐copolymer suggests that the polymerization site is the same for both types of growing chains.
Polymerization of epoxides in the presence of tertiary amino alcohols
Authors: Vazquez A. , Matĕjka L. , S̆pac̆ek P. , Dus̆ek K.
Published: April 2003

Polymerizations of phenyl glycidyl ether (PGE) and the diglycidyl ether of Bisphenol A (DGEBA) were initiated with tertiary amino alcohols. The reaction was followed by means of HPLC and IR spectroscopy. The main products isolated from the reaction mixture were identified by using mass spectrometry. The sol fraction and the critical conversion at the gel point were determined for the crosslinking polymerization of DGEBA.

Three series of oligomers arise from three initiating centers during the polymerization of PGE. In addition to the amino alcohol—a product of the secondary amine addition to the epoxy group—the phenol arising in the reaction mixture also acts as an initiator. The third oligomer series propagates by an anionic mechanism from a quaternary ammonium base originating from the reaction of PGE with the amino alcohol. Formation of the new initiating centers during the reaction results in a decrease in the molecular weight of the polymer relative to the value predicted from the amount of initiator initially added. The relative content of products of the particular oligomeric series in the reaction mixture depends on temperature and on the concentration of the initiator.
Phthalocyanine polymers. I. Synthesis and characterization of fused copper phthalocyanine polymers
Authors: Liao Ming Sy , Kuo Kung‐Tu
Published: April 2003

Fused copper phthalocyanine polymers have been prepared by reacting an equimolar mixture of pyromellitic dianhydride and phthalic anhydride with urea, ammonium chloride, ammonium molybdate, and copper sulfate via a baking method. The products have been characterized by elemental analyses, infrared, near‐infrared, UV/VIS spectroscopies and conductivity measurement. It has been found that: (1) the reaction temperature must exceed 350°C during this synthesis to obtain product of good yield and higher molecular weight; (2) a high reaction temperature favored the reaction of PA with PMDA to form polymer; (3) the peripheral end groups of the crude products, untreated with acid or base, were imide structures; (4) additional vacuum and heat treatment increased the purity and structural uniformity and, therefore, increased the conductivity of polymers.
Kinetics of emulsifier‐free emulsion polymerization of styrene
Authors: Song Zhiqiang , Poehlein Gary W.
Published: April 2003

The influence of initiator concentration, monomer/water ratio, reaction temperature, and agitator speed on the kinetic behavior of emulsifier‐free emulsion polymerization of styrene with potassium persulfate initiator has been investigated. Polymerization rate and the particle number increased with increasing initiator concentration and reaction temperature. The particle size distribution became broader as the initiator concentration decreased. Monomer conversion, at a common time, was smaller when the initial monomer/water ratio was increased. Particle size, at the same conversion, increased with an increasing initial monomer charge. High agitator speed caused significant particle coagulation. As a result, a smaller number of larger particles with broad size distribution were produced when the agitation was intense. Reaction rate decreased with increasing agitator speed. The two‐stage model developed in this paper can describe the kinetics of emulsifier‐free emulsion polymerization of styrene when potassium persulfate is used as initiator. Values of the termination rate constant, ktp, obtained from fitting the model to the experimental data are in agreement with ktp data reported in the literature for emulsion polymerization. ktp increases with increasing agitator speed because of a reduced gel effect. The rate coefficient for particle coagulation, Kf, increases with decreasing initiator concentration, with decreasing reaction temperature and with increasing agitator speed. The rate coefficient for radical capture by particles, kc, increases with increasing reaction temperature and with increasing agitator speed.
Anionic polymerization of N‐substituted maleimide. VI. Effects of counter cation on the anionic polymerization of N‐phenylmaleimide with alkali metal tert‐butoxides
Authors: Hagiwara Tokio , Shimizu Takamasa , Hamana Hiroshi , Narita Tadashi
Published: April 2003

Effects of counter cation on the anionic polymerization of N‐phenylmaleimide (N‐PMI) were investigated with alkali metal tert‐butoxides. N‐PMI was more rapidly polymerized in the polymerization system with a larger size of counter cation (K+ > Na+ > Li+, e.g., 100% for K+, 20 min, and 2.7% for Li+, 90 min, in THF at −72°C). A significant temperature effect was observed for lithium tert‐butoxide as at 0°C the polymer yield was increased to 89% in THF. On the solvent effect, the overall polymerization rates for the every system initiated with alkali tert‐butoxide were lowered in toluene compared to those in THF. The polymerization system with sodium as counter cation showed the unique solvent effect that the fairly high polymerization rate in THF comparable to that observed in the system with potassium cation was drastically reduced in toluene to the almost same rate as that with lithium cation. The influences of crown ethers and common salt were also investigated. The molecular weight distribution of the poly(N‐PMI) was also influenced by the counter cation size. The polymerization system with lithium cation gave the narrowest molecular weight distribution and it became broader as the size of counter cation was increased.
Ethynyl‐terminated polyethers from new end‐capping agents: Synthesis and characterization
Authors: Delfort B. , Lucotte G. , Cormier L.
Published: April 2003

Different main chain acetylene terminated polyethers with various molecular weights were prepared in a one‐step polyetherification reaction. This process requires the synthesis of new acetylene end‐capping agents, 4‐ethynyl‐4′‐fluorobenzophenone and 4‐ethynyl‐4′‐fluorodiphenyl sulfone. These reagents were prepared with good yields in a three‐step route. The thermally induced reaction of the ethynyl groups in an easy process leads to materials with improved solvent resistance and good thermostability. The fracture toughness was evaluated and was found to increase with the molecular weight of the precursor oligomers. High values were obtained, especially when 4,4′‐benzophenone and 4,4′‐diphenyl sulfone units are present in the polymer main chain.
Polymers containing cyanoimidazole pendant groups
Authors: Allan David S. , Thurber Ernest L. , Rasmussen Paul G.
Published: April 2003

Dicyanoimidazole (I) was attached to a polystyrene backbone in order to prepare polymers containing electron‐accepting pendant groups to complement the existing body of electron‐donating polymers. The preparation of poly[4,5‐dicyano‐1‐(vinylbenzyl)imidazole] (III), poly[4,5‐dicyano‐1‐(vinylbenzyl)imidazole‐co‐9‐(vinylbenzyl) carbazole] and attempted polymerization of 4,5‐dicyano‐1‐vinylimidazole are described. Cyclic voltammetry and charge transfer studies are used to characterize the electron‐accepting strength of the cyanoimidazole model compounds. These studies show that while cyanoimidazoles are moderate electron acceptors, they do not form charge transfer complexes with the donor molecules investigated.
Polyimides synthesized from 4,4′‐(1,2‐ethynediyl) bis (phthalic anhydride)
Authors: Nye S. A.
Published: April 2003

A novel substituted acetylene monomer, 4,4′‐(1,2‐ethynediyl) bis (phthalic anhydride) (EBPA) was made in six steps from 4‐nitro‐N‐methylphthalimide (4‐NPI) including two palladium‐catalyzed acetylene coupling steps. Several new polyimides were prepared from this monomer and six aromatic diamines. In addition, copolymers were made with EBPA and BPADA with meta‐phenylene diamine. All of the polymers had high glass transition temperatures, high thermal stability and good solvent resistance. The copolymer containing twenty % EBPA had a glass transition temperature 33°C higher than Ultem® (a registered trademark of GE) and improved solvent resistance.
Synthesis and characterization of some halogen‐containing poly(esterurethane)s
Authors: Tamareselvy K. , Venkatarao K. , Kothandaraman H.
Published: April 2003

A series of halogen‐containing poly (esterurethane)s was synthesized from the prepolymers, i.e., hydroxy‐terminated polyesters containing chlorine and fluorine and the diisocyanates such as toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). Polyesterification of halogenated phthalic anhydride with an excess of diols such as ethylene glycol, 1,2‐propanediol, and 1,4‐butanediol in the presence of trifluoroacetic anhydride (TFAA) was carried out to prepare prepolymers. The prepolymers and the poly (esterurethane)s were characterized by infrared (IR), 1H nuclear magnetic resonance (NMR), viscosity, end‐group analysis, solubility and thermal analysis namely thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Kinetics of thermal degradation was also studied. Resistance of the polymers to alkaline agents and combustion was also tested.
Mathematical models of the initial stage of the thermal degradation of poly(vinyl chloride). I. The thermal degradation of the low molecular weight models of macromolecules of poly(vinyl chloride) having no abnormal fragments
Authors: Troitskii B. B. , Troitskaya L. S.
Published: April 2003

Some mathematical models of the initial stage of the thermal degradation of the low molecular weight models for the normal units of PVC have been considered. The equations have been deduced. If the values of the average length of kinetic chain of dehydrochlorination of the polymer and the model compound are equal to each other, these equations may be used for the thermal degradation of idealized PVC.
Thermal properties ofN‐substituted 4‐vinylpyridinium ions and their polymers
Authors: Ranganathan Prema , Fife Wilmer K. , Zeldin Martel
Published: April 2003

4‐Vinylpyridinium trifluoromethanesulfonate monomers substituted at nitrogen with H, O, CH3, C2H5, C6H13, and C12H25were synthesized and characterized spectroscopically. Thermal analyses (DSC and TGA) were carried out on all the compounds. The solid monomers (NH, NCH3, NC6H13, and NC12H25) exhibited endothermic melting followed by exothermic polymerization and exothermic decomposition (>400°C). Liquid NC2H5monomer revealed only exothermic polymerization and decomposition. The NO polymer underwent thermal decomposition below 300°C. The N–C12H25homopolymer, prepared from monomer in the DSC or in bulk, displayed an unusual thermal transition at 250°C, which has been attributed to a polymer backbone reorientation leading to side‐chain ordering of the dodecyl groups.
Synthesis and characterization of poly[(3,4‐dihydro‐2h‐pyran)‐alt‐(maleic anhydride)] and its derivatives: Biologically active polymers
Authors: Han Man Jung , Kim Ki Ho , Cho Tae Joon , Choi Keun Bae
Published: April 2003

The syntheses of several monomers, bioactive poly[(3, 4‐dihydro‐2H‐pyran)‐alt‐(maleic anhydride)] and its derivatives, which have different substituents (e.g., acetoxy, methoxy, ethoxy, methoxycarbonyl, formyl, acetoxymethyl, and tosyloxymethyl groups) in the 2‐position of the tetrahydropyran ring of the copolymer backbone, are described. The alternating sequences in copolymers of the dihydropyran derivatives and maleic anhydride were obtained from the equimolar and larger ratios of maleic anhydride to dihydropyran derivative at the onset of the copolymerization. The molecular weights of the copolymers were found to be low (Mn = 1000–7500) due to a transfer reaction of the dihydropyran derivatives. Hydrolyses of the anhydride groups in the copolymers without catalyst afforded poly[(dihydropyran)‐alt‐(maleic acid)] and its derivatives, whereas an additional three copolymers having substituents, e.g., hydroxy, hydroxymethyl, and carboxyl groups were obtained by hydrolyses of the pendent groups (acetoxy, acetoxymethyl, and methoxycarbonyl) with the aid of a hydroxide catalyst. Carbamoyl groups on the polymers were obtained from ammonolysis of methoxycarbonyl groups. The polymers having mercaptomethyl or aminomethyl groups were obtained by substitution of hydrogen sulfide or ammonia for tosyloxylmethyl groups.