bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of poly(ethylene terephthalate) in the presence of perfluoropolyethers. II. Effect of various catalysts
Authors: Pilati F. , Manaresi P. , Toselli M. , Re A.
Published: April 2003

Dimethylterephthalate and ethylene glycol have been polymerized to poly (ethylene terephthalate) (PETP) in the presence of perfluoropolyethers (PFPE) using various catalysts. The polymerizations were carried out at high temperature by the usual two‐stage method and the effect of the fluorinated compounds on the polymerization rate was investigated. Selective extractions were performed to estimated the fraction of PFPE bonded to PETP. In the presence of Fomblin ZDEAL®, a telechelic PFPE macromer bearing methyl ester end groups, the polymerization can only be carried out when the fluorinated macromer is added after the first stage is complete, because of the strong decrease of the transesterification rate with all the catalysts used. Polymerizations were therefore performed by adding Fomblin ZDEAL (10% wt) at the end of the first stage; about 30% of the amount of PFPE in the final products was found to be bonded to PETP for all the catalysts employed. In the presence of Fomblin Z/15®, a PFPE which has not functional end groups, the reaction rate is not decreased in the first stage, however, under the same reaction conditions, the intrinsic viscosity of final PETP is greatly reduced and the amount of PFPE in the resulting material is well below that initially added and is almost completely extractable meaning that a very limited fraction of PFPE is bonded to PETP.
Polymerization in nonuniform latex particles. II. Kinetics of two‐phase emulsion polymerization
Authors: Chern Chorng‐Shyan , Poehlein Gary W.
Published: April 2003

A new theory, based on the concept of nonuniform distribution of free radicals in polymerizing latex particles, has been developed for the kinetics of two‐phase emulsion polymerization reactions. This theory also takes into account the diffusion controlled termination and propagation reactions to describe the gel effect and limiting conversion. The kinetic model permits prediction of the distribution of free radicals in the two polymer phases and rate of polymerization as a function of reaction conditions. Experimental data for polystyrene/polymethyl methacrylate and polymethyl methacrylate/polystyrene (postformed polymer/preformed polymer) in the literature have been used to assess the proposed idea of nonuniform distribution of free radicals in the latex particle.
Polymerization in nonuniform latex particles. III. Kinetics of grafting in emulsion polymerization
Authors: Chern Chorng‐Shyan , Poehlein Gary W.
Published: April 2003

The concept of nonuniform distribution of free radicals in polymerizing latex particles has been incorporated into the development of a kinetic model for grafting reactions. This theory permits prediction of grafting efficiency as a function of reaction conditions. It can also be used for evaluation of rate constants for grafting reactions. Experimental data for emulsion polymerization of styrene in the presence of polybutadiene seed latex have been used to assess the proposed grafting theory. The predominant grafting reaction appears to be the attack of growing polystyrene chains on the allyl hydrogen atoms of polybutadiene. The results further reinforce the hypothesis that the entering oligomeric free radicals do not distribute uniformly within the particle volume.
Characterization of a thermally imidized soluble polyimide film
Authors: Young Philip R. , Davis Judith R. J. , Chang A. C. , Richardson John N.
Published: April 2003

A soluble aromatic poly (amic acid) film was converted to a soluble polyimide by staging at 25°C intervals to 325°C and characterized at each interval by several analytical methods. The behavior observed was consistent with an interpretation that a reduction occurred in molecular weight of the poly (amic acid) during the initial stages of cure before the ultimate molecular weight was achieved as a polyimide. This interpretation was supported by the results of solution viscosity, gel permeation chromatography, low angle laser light scattering photometry, and infrared spectroscopy analyses. The results of this study serve to increase our fundamental understanding of how polyimides are thermally formed from poly (amic acid)s.
Polymerization of methyl methacrylate with cupric laurate‐N,N‐dimethyl formamide as initiator system
Authors: Pal Prabir Kumar , Chaudhuri Ajit Kumar
Published: April 2003

The polymerization of methyl methacrylate with cupric laurate in combination with N,N‐dimethyl formamide as initiator was studied in carbon tetrachloride medium at 60°C. The rate of polymerization was found to be proportional to the 3/2th power of the monomer concentrations and to the square root of both cupric laurate and DMF concentrations. Spectroscopic investigations indicated a ternary complex formation involving cupric ion, methyl methacrylate, and DMF. A reaction scheme is suggested on the basis of these results and various kinetic constants have been evaluated.
Polymerization of cyclic acetals. II. Synthesis of amphiphilic block copolymers
Authors: Velichkova R. S. , Gancheva V. B. , Krüger H. , Rübner J.
Published: April 2003

The sequential copolymerization of 1,3,6‐trioxacyclooctane (TOC) and 1,3‐dioxolane (DOL) (B) with various vinyl monomers (A) was investigated. Under appropriate conditions amphiphilic block copolymers of the type AB and ABA were formed. The reaction mixtures and the isolated polymers were analyzed by GPC (double detection—IR and UV at 254 nm), IR, 1H‐, and 13C‐NMR spectroscopy. Block copolymers with chosen molecular weights and low polydispersity could be obtained only by sequential copolymerization of p‐methoxystyrene on “living” TOC. In the polymerization of DOL with α‐methylstyrene and i‐butyl vinyl ether (IBVE) transfer reactions take place to a larger degree.
Aspects of the thermal properties of poly(2‐vinyl anthraquinone)
Authors: Gradwell A. J. , Guthrie J. T. , Kazlauciunas A.
Published: April 2003

2‐Vinyl anthraquinone was synthesized as described previously. In this article, three approaches to polymerization of 2‐vinyl anthraquinone are examined bulk thermal, chemical, and γ‐radiation‐induced. Polymerization in both the bulk phase and in solution were attempted. Thermal characterization has been carried out using differential scanning calorimetry (DSC), x‐ray diffraction (XRD), scanning electron microscopy (SEM) and hot‐stage optical microscopy (HSOM). Thermogravimetric analysis (TGA) has been used to provide procedural “apparent” activation energies for decomposition of the polymer.
Rigid‐Rod benzobisthiazole polymers with reactive fluorene moieties: Synthesis and characterization
Authors: Dotrong My , Evers Robert C.
Published: April 2003

High purity 2,7‐fluorenedicarboxylic acid chloride was synthesized in a multistep reaction scheme from 2,7‐dibromofluorene. Subsequent polycondensation in polyphosphoric acid of 2,5‐diamino‐1,4‐benzenedithiol dihydrochloride with terephthaloyl chloride and 2,7‐fluorenedicarboxylic acid chloride led to rigid‐rod benzobisthiazole polymers with reactive fluorene moieties. The proportion of fluorene in the resultant polymers was controlled through reaction stoichiometry. Soluble polymers with intrinsic viscosities as high as 33.7 dL/g (methanesulfonic acid, 30°C) were obtained if the polymerization temperature was not allowed to exceed 165°C. Insoluble, presumably crosslinked polymers were obtained at higher temperature (190–200°C). Thermal characterization of the polymers by differential thermal analysis and thermal gravimetric analysis/mass spectroscopy did not disclose any thermal transition to 450°C. Onset of weight loss in air did not occur until over 550°C.
Synthesis and ring‐opening polymerization of novel bicyclic oxalactams: 2‐oxa‐5‐azabicyclo[2.2.2]octan‐6‐one
Authors: Okada Masahiko , Sumitomo Hiroshi , Mori Hiroto , Hall H. K. , Chan Ray J. H. , Bruck M.
Published: April 2003

A novel bicyclic oxalactam 2‐oxa‐5‐azabicyclo [2.2.21 octan‐6‐one (2,5‐BOL) was synthesized from sodium 3,4‐dihydro‐2H‐pyran‐2‐carboxylate through a seven‐step reaction sequence. Anionic ring‐opening polymerization of 2,5‐BOL was carried out in bulk at 12OOC or in dimethyl sulfoxide at 40, 60, and 80°C by using potassium pyrrolidonate and the N‐benzoyl derivative of 2,5‐BOL as catalyst and activator, respectively. The polymerization gave a new polyamide containing cis‐ and trans‐2,5‐linked tetrahydropyran rings in the main chain. The cis/trans ratio varied from 70/30 to 95 /5 depending on the reaction conditions. The polyamide having number average molecular weights of 3000–8000 was soluble in a variety of solvents including methanol, ethanol, dimethyl sulfoxide, dimethylformamide, chloroform, and dichloromethane. It began to decompose at 280–32OOC depending on the compositions of the cis‐ and trans‐2,5‐linked structural units. The anionic ring‐opening polymerizability of 2,5‐BOL was found to be much lower than its structural isomer, 8‐oxa‐6‐azabicyclo[ 3.2.11 octan‐7‐one (8,6‐BOL).
Preparation and properties of new photosensitive polyimides from bis(4‐aminophenyl)tetramethyldisilane and various aromatic tetracarboxylic dianhydrides
Authors: Padmanaban Munirathina , Toriumi Masaru , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

New photosensitive polymides containing photosensitive disilane unit were synthesised from 1,2‐bis(4‐aminophenyl)tetramethyldisilane and various aromatic tetracarboxylic dianhydrides by the usual two‐step procedure that includes ring‐opening polyaddition to yield the precursor polyamic acids, followed by cyclodehydration giving the respective polyimides. The polymaic acids had inherent viscosities between 0.63 and 0.85 dL/g depending on the tetracarboxylic dianhydride used. Excepting the polyimide obtained from pyromellitic dianhydride, all other polyimides were soluble in N‐methyl‐2‐pyrrolidone, m‐cresol, and pyridine. While the polyimide containing diphenyl sulfone unit was amorphous, the other polyimides were semi‐crystalline polymers based on their x‐ray diffractograms. The polyimides had glass transition temperatures between 235 and 304°C. They were thermally stable up to 380°C in both air and nitrogen atmospheres. All the polyamic acids showed a drastic decrease in the inherent viscosity upon UV light irradiation, implying the inherent photosensitivity of the polymers containing the disilane moiety.
The reactivities of diarylbutadienes towards the benzoyloxy radical: the cases of 1‐(1′‐naphthyl)‐4‐phenylbuta‐l,3‐diene and 1,4‐Di (1′‐Naphthyl)buta‐1,3‐Diene
Authors: Bevington J. C. , Breuer S. W. , Huckerby T. N. , Jones Rosie F. D. , Barson C. A.
Published: April 2003

A study has been made of end‐groups in poly(methyl methacrylate) prepared using benzoyl peroxide as initiator and either 1‐(1′‐naphthyl)4‐phenylbuta‐1,3‐diene or 1,4‐di(1′‐naphthyl)buta‐1,3‐diene as additive. At 60°C, these dienes are 500–600 times as effective as methyl methacrylate in capturing benzoyloxy radicals and more than twice as effective as 1,4‐diphenylbuta‐1,3‐diene.
Polymerization of methyl methacrylate by charge‐transfer mechanism with aliphatic primary amines and carbon tetrachloride
Authors: Dwivedi P. C. , Srivastava Archana , Rathi R. S.
Published: April 2003

Polymerization of methyl methacrylate (MMA) with aliphatic primary amines and carbon tetrachloride has been investigated in th dimethylsulfoxide medium by employing a dilatometric technique at 60°C. The rate of polymerization (Rp) has been evaluated under the conditions, [CCl4]/[amine] < 1 and > 1. The kinetic data indicate possible participation of the charge transfer complexes formed between the amine + CCl4 and the amine + MMA in the polymerization of MMA. In the absence of CCl4 or amine, no polymerization of MMA was observed under the present experimental conditions. The polymerization of MMA was inhibited by hydroquinone, indicating a free radical initiation. The energy of activation varied from 32 to 58 kJ mol−1.
Synthesis and characterization of novel aromatic polyamides from 3,4‐bis(4‐aminophenyl)‐2,5‐diphenylfuran and aromatic diacid chlorides
Authors: Jeong Hwa‐Jin , Oishi Yoshiyuki , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

A new highly phenylated heterocyclic diamine, 3,4‐bis(4‐aminophenyl)‐2,5‐diphenylfuran, was synthesized in three steps from 4–‐nitrodeoxybenzoin. The low temperature solution polycondensation of the diamine with various aromatic diacid chlorides afforded tetraphenylfuran‐containing aromatic polyamides with inherent viscosities of 0.2–0.8 dL/g. Copolyterephthalamides were obtained from the diamine and 4,4′‐oxydianiline. The polyamides were generally soluble in a wide range of solvents that included N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone, pyridine, and m‐cresol. Glass transition temperatures of the polyamides and copolyamides ranged from 302–342°C, and 10% weight loss was observed above 480°C in nitrogen.
Allylic polymers. I. Copolymerization of allyl esters with vinyl acetate
Authors: Shigetomi Yasumasa , Kojima Takehiro , Ono Naruhito
Published: April 2003

The radical copolymerization of allyl esters with vinyl acetate has been studied in the range from 10 to 90 mol % allyl esters in the feed. The Kelen‐Tüdos method was employed to determine the monomer reactivity ratios. The following values were found for the reactivity ratios: allyl propionate (M1)–vinyl acetate (M2), r1 = 0.42, r2 = 1.29; allyl butyrate (M1)–vinyl acetate (M2), r1 = 0.64, r2 = 0.97; allyl isobutyrate (M1)–vinyl acetate (M2), r1 = 0.51, r2 = 1.04; allyl valerate (M1)–vinyl acetate (M2), r1 = 0.58, r2 = 1.07; allyl trimethylacetate (M1)–vinyl acetate (M2), r1 = 0.34, r2 = 1.15. The Q‐e parameters were calculated from the allyl esters (M1)–vinyl acetate (M2) reactivity ratios. The e parameters of allyl ester monomers have been found to be nicely correlated with parameters such as dissociation constants of carboxylic acids, which are constituents of allyl ester monomers, and Taft σ* constants of the alkyl group in the acids. The molecular weights of copolymers were measured by GPC and ranged from (1.0–15.0) × 104.
Preparation and characterization of fluorine‐containing aromatic condensation polymers. I. Preparation and characterization of fluorine‐containing polycarbonate and copolycarbonates by two‐phase phase‐transfer‐catalyzed polycondensation of 2,2‐bis (4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane and/or 2,2‐bis (4‐hydroxyphenyl)propane with trichloromethyl chloroformate
Authors: Saegusa Yasuo , Kuriki Minoru , Kawai Akihiro , Nakamura Shigeo
Published: April 2003

A series of fluorine‐containing homopolycarbonate and copolycarbonates with a wide range of unit ratio were synthesized by the two‐phase phase‐transfer‐catalyzed plycondensation of 2,2‐bis (4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane (Bisphenol AF) and/or 2,2‐bis (4‐hydroxy‐phenyl) propane (Bisphenol A) with trichloromethyl chloroformate, and the effect of the fluorine substitution on the synthesis and properties of these polymers was investigated by comparing with those of Bishphenol A‐based homopolycarbonate without fluorine. Film‐forming moderate‐to high‐molecular‐weight fluorine‐containing polycarbonates with reduced viscosities up to 0.54 dL/g were obtained in high yields by using tetra‐n‐butylammonium bromide as a catalyst, sodium hydroxide as a base, and 1,2‐dichloroethane as a medium. The reduced viscosity, however, decreased markedly with increasing feed ratio of Bisphenol AF. Their solubility in common organic solvents was clearly improved by the introduction of fluorine atom. The pliability of the films also increased remarkably with increasing fluorine content. The contact angles formed by water were larger than 90°, regardless of their fluorine contents, at 25°C in air. The critical surface tension and refractive index of Bisphenol AF‐based homopolycarbonate were ca. 20 dyn/cm and 1.426, respectively. The glass transition temperatures and thermal stability increased monotonously with increasing fluorine content.
Chain‐Cleavage and hydrolysis of activated polyethylene glycol derivatives: Evidence for competitive processes
Authors: Mcmanus S. P. , Karaman R. M. , Sedaghat‐Herati M. R. , Shannon Thomas G. , Hovatter Thomas W. , Harris J. M.
Published: April 2003

Studies have been carried out with the tosylate of the monomethyl ether of polyethylene glycol (MeO–PEG–OTs) and with low molecular weight models to assess whether the neighboring oxygen at position 3 or 6 provides the driving force for hydrolytic cleavage of these activated derivatives. Our results reveal that MeO–PEG–OTs undergoes hydrolysis by competitive pathways. Water directly displaces the tosylate group to give the original PEG alcohol and the oxygen at position 6 nucleophilically displaces the tosylate group to give a cyclic oxonium ion as an intermediate. This intermediate can react by three pathways. First, it can lead to the production of the original PEG alcohol by attack of water on a ring carbon; second, dioxane and a lower molecular weight PEG alcohol is produced by water attack at the nonring carbon next to the charged oxygen; and third dioxane can be displaced by the oxygen atom at position 6 in the chain.
Synthesis and characterization of polyimides based on novel tricyclo[6,2,2,02,7] dianhydride
Authors: Su Ching‐Yie , Lee Yu‐Der
Published: April 2003

3‐Phenyl‐tricyclo [6,2,2,02,7]dodeca‐2,11‐ene‐5,6,9,10‐tetracarboxylic dianhydride was prepared from 1,1‐diphenyl ethylene and maleic anhydride in 1 : 2 mole ratio by [4 + 2]π Diels‐Alder cycloaddition. The structure of the dianhydride was determined by mass spectroscopy, IR, 1H‐NMR, elemental analyses, and single crystal x‐ray diffraction. The monomer was condensed with several diamines in N‐methyl pyrrolidone or m‐cresol. The polyamic acids and the polyimides synthesized had inherent viscosities in the range of 0.19–0.31 and 0.17–0.25 dL/g, respectively, measured in N‐methyl pyrrolidone at 30°C. Both the polyamic acids and the polyimides were found to be soluble in m‐cresol, N‐methyl pyrrolidone, dimethylacetamide, dimethyl formamide, and dimethyl sulfoxide. The polymides showed a low degree of crystallinity from wide angle x‐ray diffraction. Thermal analysis of these polyimides revealed that their glass transition temperatures (Tg) were in the 215–237°C range and they decomposed in two stages. The first‐stage decomposition temperatures were almost the same in O2 or N2 atmospheres, but the polymers showed a better thermal stability in O2 rather than in N2 in the second stage. The mechanism of thermal degradation is discussed.
Membrane of epoxidized styrene–butadiene–styrene block copolymer complexing with (N,N′‐disalicylideneethylenediamine) cobalt (II) and use for oxygen permeation
Authors: Hsiue Ging‐Ho , Yang Jen‐Ming , Lee Pao‐Shun , Liaw Chin‐Yih
Published: April 2003

The complex formation reaction of epoxidized styrene‐butadiene‐styrene triblock copolymer (ESBS) with (N,N‐disalicylideneethylenediamine) cobalt(II) (CoS) in chloroform solution is studied. The coordination number and formation constant are determined by the Miller method. The membranes of ESBS complexing with CoS (ESBS–CoS) are made by solution casting method. The kinetics of oxygen binding to ESBS–CoS membrane is studied and the equilibrium constant, association, and dissociation constant are determined. The membrane of ESBS–CoS has the affinity to absorb oxygen with reversibility and that is confirmed by the studies of DSC. Due to the reversible absorption of oxygen to ESBS–CoS, the permeation of oxygen through ESBS–CoS membrane can be explained by dual mode.
The effect of power on the plasma‐assisted deposition of fluorinated monomers
Authors: d'Agostino R. , Favia P. , Fracassi F. , Illuzzi F.
Published: April 2003

The effect of power variation on the polymerization kinetics and on the polymer structure is reported for RF glow discharges fed with C2F6–H2 mixtures. Both deposition rate and polymer structure trends can be correlated to the variations of gas‐phase species density (atoms, radicals, and charged species) and can be explained by considering the competition of the deposition and etching process.
Rigid rod molecules as liquid crystal thermosets. II. Rigid rod esters
Authors: Hoyt Andrea E. , Benicewicz Brian C.
Published: April 2003

Nine rigid rod ester monomers endcapped with maleimide, nadimide, and methylnadimide groups were prepared and studied by DSC and hot stage polarized light microscopy. All of the monomers showed thermotropic nematic liquid crystalline phases and could be thermally crosslinked in the nematic phase. The nematic texture was maintained in the crosslinked solid state. The nematic phase range was enlarged by B‐staging the monomeric compounds. Heating the monomers for a short period of time in the nematic phase lowered the crystal to nematic transition temperatures and increased the nematic to isotropic transition temperatures. A nonequilibrium phase diagram was proposed to explain the melting behavior of these reactive liquid crystal thermoset materials.
Chemical structure of networks resulting from curing of N,N‐diglycidylaniline‐type resins with aromatic amines. IV. Characterization of TGDDM/DDS and TGDDM/DDM networks by high‐resolution solid‐state 13C‐NMR
Authors: Attias A. J. , Bloch B. , Laupretre F.
Published: April 2003

Cured N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) based epoxy resins were investigated by high‐resolution solid‐state 13C‐NMR spectroscopy. Associated hardeners were the most commonly used low reactivity 4,4‐‐diaminodiphenylsulphone (DDS), as well as, for comparisons reasons, the higher reactivity 4,4′‐diaminodiphenylmethane (DDM) with, in each case, a1 to 1 or 1 to 0.6 epoxy/NH ratio. In order to interpret the spectra, the poorly resolved aliphatic region was decomposed into elementary lines, the structural assignments of which were made using solution 13C‐NMR data resulting from a previous model compound study. The main structural feature of all investigated systems is the predominance of small cyclic units resulting from intramolecular reactions of N,N‐diglycidylaniline groups. The resins are therefore far less crosslinked that it could be anticipated from the functionality of the reactants. Using the low reactivity DDS still increases this effect, due to a higher proportion of residual non reacted secondary amines. Reducing the initial ratio of hardener could on the contrary lead to a higher proportion of reacted amine function, and thus to a higher crosslinking degree. A qualitative picture of such networks is given at the end.
Synthesis, spectral, thermal, and flammability studies of phenolphthalein polyphosphate esters
Authors: Kishore K. , Kannan P.
Published: April 2003

Polyphosphate esters were synthesized from phenolphthalein and aryl phosphorodichloridates by interfacial polycondensation using a phase transfer catalyst. The polymers were characterized by IR, 1H‐, 13C‐, and 31P‐NMR spectroscopy. The molecular weights were calculated by end group analysis using 31P‐NMR spectral data. The thermal stability of the polymers was studied by thermogravimetry and the flammability was investigated by measuring limiting oxygen index values.
A novel synthetic procedure of vinylacetamide and its free radical polymerization
Authors: Akashi Mitsuru , Yashima Eiji , Yamashita Takanori , Miyauchi Noriyuki , Sugita Shuichi , Marumo Kuniomi
Published: April 2003

The pyrolysis of N‐(α‐methoxyethyl) acetamide, which was obtained by one‐step reaction of acetamide, acetaldehyde, and methanol, gave N‐vinylacetamide (NVA) in a good yield. The polymerizability and copolymerizability of NVA were studied. Free radical polymerization was carried out in the presence of radical initiator or by γ‐ray irradiation. The monomer reactivity ratios of NVA were estimated in the copolymerization with acrylamide, vinyl acetate, and methyl methacrylate. The solvents were found to influence the monomer reactivity ratio. NVA showed a typical copolymerizability as nonconjugated vinyl monomer, and Q and e values were obtained in DMF as 0.16 and −1.57, respectively.
Synthesis of soluble polymeric photosensitizers with the 4‐nitro‐1‐naphthyl‐carbamoyl as pendant group
Authors: Diaz F. R. , Tagle L. H. , Garcia F. , Sastre R. , Conde M. , Mateo J. L. , Catalina F.
Published: April 2003

Several models of monomers, homopolymers, and copolymers containing a photosensitizer group, 4‐nitro‐1‐naphthyl‐carbamoyl (NNC), have been synthesized. Synthetic methods are described, in addition to two routes for copolymers preparation. First, the radical copolymerization between monomers with the photosensitizer group built‐in and comercial monomers such as styrene and methyl acrylate and, second, polymer modification by nucleophilic reaction between carbonyl group polymer supported and nitro‐naphthyl amine. All products were characterized and one of the resulting soluble polymeric photosensitizer and its model compound, were tested as triplet energy donors against trans‐ stilbene and their Stern–Volmer constants were determined. Results show that the sensitizer efficiency is closer to that of the well known benzophenone sensitizer and higher than that of the acetophenone, while the sensitizer efficiency disminished when the chromophore is bonded to the polymer.
The preparation, characterization, and selected charge transfer properties of some anthracene functionalized polyesters
Authors: Gorda K. R. , Peiffer D. G. , Denney D. B.
Published: April 2003

Novel anthracene backboned polyesters were successfully prepared by the melt condensation polymerization of anthracene 9,10‐diacetic acid dimethyl ester using titanium (IV) n‐butoxide as catalyst. Monomer and polymer structures were identified by a variety of methods. The melt polymerizations were carefully controlled to give low molecular weight polyesters soluble in chloroform. 1H‐NMR was used to determine the degree of polymerization
$ \[ {\rm (}\overline {{\rm DP}} ) \] $
and number‐average molecular weight
$ \[ {\rm (}\overline {\rm M} _n ) \] $ for each of the polyesters. Analysis of the 3‐5 ppm spectral region contained the necessary resonances for the interpretation. Spectral results show
$ \[ \overline {\rm M} _n = 7,000 - 10,000{g \mathord{\left/ {\vphantom {g {mol}}} \right. \kern-\nulldelimiterspace} {mol}} \] $.
Higher molecular weight polymers can also be prepared but chloroform solubility is lost. Thermal studies reveal the Tg of these materials varies from 50–60°C depending upon the aliphatic segment of the polymer. Decomposition temperatures in the range of 400–500°C were observed. Charge transfer complexes of these polymers were also studied. Ultraviolet absorption spectroscopy indicates these polyesters are good electron donating systems. Complexation with tetrachloro‐1,4‐benzoquinone (chloranil) have absorption maxima at approximately 662 nm. Absorption studies also reveal perturbations do exist in the polymer complexes suggesting the possibility of polymer effects. The emission spectra of these materials also confirms that fact.
Some aspects of stabilization and degradation of nigerian natural rubber. I. Photostabilization of natural rubber with bound di‐tert‐butyl‐4‐hydroxybenzyl thioglycollate (dbhbt)
Authors: Ebi Godwin Chukwu , Singh A.
Published: April 2003

3,5‐Di‐tert‐butyl‐4‐hydroxybenzyl thioglycollate (DBHBT) has been reacted with Nigerian Natural rubber latex at 65 ± 1°C using 4,4‐azobiscyanovaleric (AZBN) acid‐ferrous sulfate redox system to obtain a binding efficiency of 13%. The bound DBHBT was investigated as a UV stabilizer in unprocessed and unvulcanized rubber using spectroscopic method. With respect to the CO index, the masterbatch diluted to 56% gave the optimum activity and higher concentrations showed significant pro‐oxidant activity. The CC bonds in particular, showed greater stability which is a function of DBHBT concentration. The methylenic and the allylic hydrogen atoms, the most susceptible, and probably the sites of the primary attack, were not protected by DBHBT.
Chiral liquid‐crystalline polymers. XI. Thermotropic behavior and chiroptical properties in solution of a new series of optically active poly (ester β‐sulfide)s
Authors: Chiellini E. , Galli G. , Angeloni A. S. , Laus M.
Published: April 2003

The synthesis and characterization are described of a series of optically active semiflexible poly(ester β‐sulfide)s 6*Sn with repeating units constituted by two p‐oxybenzoyl diads spaced in an alternating fashion by a sulfide‐containing polymethylene segment of variable length (n = 2‐10) and a chiral (R)‐3‐methylhexanediyl segment of high enantiomeric purity. The polymers were prepared with good yields and relatively high molecular weights and narrow degrees of dispersity by a Michael‐type polyaddition reaction of bis‐thiols to the same chiral mesogenic bisacrylate monomer. Data are reported on the characterization of their chiroptical properties in dilute solution and thermal‐optical properties in the bulk, with attention being devoted to the distinct odd‐even alternations of the cholesteric‐isotropic melt transition parameters. A comparison of the mesomorphic behavior and relevant thermodynamic quantities is presented between the present series of polymers and the achiral analogues of series 6Sn as well as the chiral, positional isomers of series mS6*. The dependence of the overall properties and their trends on very subtle structural changes is stressed, thus highlighting the critical interconnection between mesogenic cores and spacer segments in semiflexible liquid‐crystalline polyesters.
Salt catalyzed heterogeneous dilute acid hydrolysis of the difficultly accessible portion of cellulose: Effect of nature of metal co‐ion
Authors: Zaranyika Mark F. , Moses Peter , Mavunganidze Taimos
Published: April 2003

The effect of nature of metal co‐ion on the rate of hydrolysis, Vc, of the difficulty accessible portion of cellulose was investigated for Li+, Na+, K+, and Ca2+. For the univalent ions Vc decreases exponentially with an increase in ionic radius for a given concentration of co‐ion. For Ca2+, Vc is lower than would be predicted on the basis of ionic radius. This is attributed to the increased charge and/or increased degree of hydration. For the univalent ions the data presented suggest Vc increases sharply with concentration up to 0.25M, while for Ca2+, Vc increases more gradually up to 2.25M, before Vc begins to drop.
Ethylene polymerization catalysts from supported organotransition metal complexes. II. Chromium alkyls
Authors: Smith P. D. , Mcdaniel M. P.
Published: April 2003

Another class of organochromium compounds, beta‐stabilized chromium alkyls, has been synthesized and tested for catalytic activity in ethylene polymerization. Although not active alone, these compounds do exhibit remarkable activity when reacted with a partially dehydroxylated high surface area carrier. The best supports seem to be fluorided alumina or the aluminophosphates, depending on the particular chromium alkyl being tested. The worst was always silica. Both divalent and tetravalent chromium alkyls were tested and found to have high catalytic activity. Comparisons of activity and polymer structure were made between these compounds and previously studied organochromium compounds with pi‐bonded ligands.
Effects of coordinately unsaturated cobalt complexes on radical polymerization of vinyl monomers
Authors: Bhanu V. A. , Kishore K.
Published: April 2003

The tetrahedral cobalt(II) complexes A‐D are found to possess an unusual coordinately unsaturated nature. These additives significantly inhibit the thermal polymerization of acrylamide and further, they impart significant induction period during AIBN initiated polymerization of MMA and acrylamide. Some evidence has been obtained to show that the additives' effect plausibly results because of the reaction of the coordinately unsaturated cobalt complexes with radicals present in the system.
Radiation‐Induced degradation of polyethylene: Polymer structure and stability
Authors: Torikai Ayako , Geetha Ramarathnam , Nagaya Shigeo , Fueki Kenji
Published: April 2003

The radiation‐stability of annealed and quenched polyethylene (PE) was estimated by gel, FTIR, and mechanical property (elongation at break) measurements. Although both types of PE showed an equal probability in gel and carbonyl formation, the resistance to γ‐ray irradiation as probed by elongation at break (%) was superior in quenched PE compared to annealed PE. This difference is discussed from the viewpoint of polymer structure, especially the number of the tie molecules, of annealed and quenched PE.
Mechanism of photostabilization of polystyrene film by dihydroxyphenyl‐pirazoles
Authors: Sastre R. , Catalina F. , Mateo J. L. , Claramunt R. , Santa‐Maria M. D. , Catalán J.
Published: April 2003

A new family of ultraviolet absorbers, the dihydroxyphenyl‐pyrazoles, has shown to be able to act as photostabilizers of polymers. In the present work the efficiency of the derivative 2,5 bis(pyrazol‐1′‐yl)‐1,4‐dihydroxybenzene (BPHB) in preventing the photooxidative degradation of polystyrene films have been measured. The effect of light screening on polymer photostabilization was examined by using external filter solutions of BPHB and it was found that it does not function simply as a light screener. Phosphorescence quenching experiments show that BPHB behaves also as an efficient triplet‐state quencher of the polymer in‐chain carbonyl impurity groups, which play an important part in the overall mechanism of light stabilization.
Preparation and radical ring‐opening polymerization of exo‐methylene substituted cyclic ketene acetals
Authors: Yokozawa Tsutomu , Hayashi Ryoji , Endo Takeshi
Published: April 2003

Preparation and radical ring‐opening polymerization of the exo‐methylene substituted cyclic ketene acetals, 2,4‐dimethylene‐1,3‐dioxolane (I) and 2,5‐dimethylene‐1,3‐dioxane (II), were carried out. Ketene acetals I and II were prepared by dehydrohalogenation of the corresponding cyclic haloacetal with potassium tert‐butoxide in tetrahydrofuran at –78°C and ambient temperature, respectively. I underwent radical polymerization with essentially quantitative ring‐opening with di‐tert‐butyl peroxide in dimethylformamide at 120°C. On the other hand, II underwent both ring‐opening polymerization and vinyl polymerization under the same conditions of the polymerization of I. The differences of polymerization behavior between I and II were also discussed.
Epoxidation of styrene–butadiene–styrene block copolymer and use for gas permeation
Authors: Hsiue Ging‐Ho , Yang Jen‐Ming
Published: April 2003

The epoxidation of styrene–butadiene–styrene triblock copolymer (SBS) by an in situ generated peracid method is discussed. The presence of an acid acting as catalyst led to side reaction. The reactivities of internal double bonds (the 1, 4‐structure) were higher than those of the vinyl bonds (the 1, 2‐structure). In the 1, 4‐structure, the reactivities of cis‐structure were higher than those of trans‐structure. The oxirane weight content and total oxygen weight content were determined by titration and element analysis, respectively. The cohesive energy, solubility parameter, and the glass transition temperature of epoxidized SBS increased with increasing total oxygen weight content. But the molecular weight between crosslinking points decreased resulting in an increase of crosslinking density with increasing total oxygen weight content. The changes of properties of epoxidized SBS reduced the gas permeability of oxygen and nitrogen through epoxidized SBS membrane, but increased the gas selectivity between oxygen and nitrogen. When the operating temperature of gas permeation was increased, the permeability of oxygen and nitrogen increased but the selectivity decreased. For epoxidized SBS containing 7.35 wt % oxygen content, the activation energy was 9 and 12.2 kcal/mol for oxygen and nitrogen, respectively.
Electron spin resonance studies of plasma‐induced polystyrene radicals
Authors: Kuzuya Masayuki , Noguchi Akihiro , Ito Hideki , Kondo Shin‐Ichi , Noda Nahoko
Published: April 2003

Plasma‐induced polystyrene radicals were first studied by electron spin resonance (ESR). The room temperature ESR spectrum was compared with those obtained by γ‐irradiation, UV‐irradiation, and mechanical fracture. It was found that even less than a few seconds of plasma‐irradiation gave rise to a large amount of polystyrene radicals and the ESR spectrum consisted of two types of spectra, a triplet and a single broad line. The spectral feature of the triplet was nearly identical with that of γ‐irradiated polystyrene. Thus, it was assigned to the structure of a cyclohexadienyl‐type radical formed by a nearly random addition of a hydrogen atom to the aromatic ring. The single broad line, thought to be an outline of multicomponent spectrum, was assigned to an immobilized dangling‐bond sites at the plasma‐induced crosslinked portion of the polystyrene surface.
Influence of allyl ethers on free radical polymerization of styrene
Authors: Johansson Mats , Hult Anders
Published: April 2003

The effect of allyl ethers on the free radical polymerization of styrene has been studied with respect to chain transfer, copolymerization, and conversion. The studies have been performed in an inert atmosphere or in air. Six different allyl ethers have been used as model substances in order to show the effect of structural differences of the ethers on the polymerization. Contrary to what was expected, no chain transfer through hydrogen abstraction was found. Nor did any copolymerization occur. When the polymerization was performed in air, the allyl ethers had a retarding effect on the polymerization rate, due to oxidation of the allyl ethers. The oxidation rate of the allyl ethers was found to be related to their structure, where the functionality and presence of intramolecular hydrogen bonding are the main factors.
Synthesis and characterization of aromatic polyamides from 1,1‐bis(4‐aminophenyl)‐2,2‐diphenylethylene and aromatic diacid chlorides
Authors: Xie Mei‐Li , Oishi Yoshiyuki , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

Novel, soluble aromatic polyamides and copolyamides containing tetraphenylethylene units were prepared by the low temperature solution polycondensation of 1,1‐bis(4‐aminophenyl)‐2,2‐diphenylethylene and aromatic diamines with various aromatic diacid chlorides. Highmolecular‐weight polyamides having inherent viscosities of 0.6–1.5 dL/g and number‐average molecular weight above 21000 were obtained quantitatively. These polymers were readily soluble in various solvents such as N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide (DMAc), and dimethyl sulfoxide and gave pale yellow, transparent, flexible films by casting from DMAc solution. The polymers had glass transition temperatures between 290 and 340°C, and started to lose weight around 400°C, with 10% weight loss being recorded at about 470°C in air.
Phase transfer catalyzed polymerization of 4‐bromo‐2,6‐dimethylphenol in the presence of either 2,4,6‐trimethylphenol or 4‐tert‐butyl‐2,6‐dimethylphenol
Authors: Percec Virgil , Wang James H.
Published: April 2003

The synthesis of poly(2,6‐dimethyl‐1,4‐phenylene oxide) with one 2,6‐dimethylphenol chain end (PPO–OH) and with well‐defined molecular weight by phase transfer catalyzed polymerization of 4‐bromo‐2,6‐dimethylphenol (20) in the presence of either 2,4,6‐trimethylphenol (1) or 4‐t‐butyl‐2,6‐dimethylphenol (1′) as chain initiators is described. The range of controllable molecular weights and the mechanism of molecular weight control are discussed based on the differences between the reactivities of 20, 1, and 1′ and of the corresponding reactive species. The PPO–OH synthesized from 20/1′ has structural units derived from 1′ attached only at the chain end. PPO–OH synthesized from 20/1 contains structural units derived from 1 both internally and at the chain ends. Structural units derived from side reactions were identified by 1H‐NMR spectroscopy. A reaction mechanism is proposed to account for their formation.
Complexing effect in the reaction of graft polymerization proceeding by the coordination‐radical mechanism with the participation of copper ions
Authors: Smirnova N. V. , Gabrielyan G. A. , Gal'braikh L. S.
Published: April 2003

A new phenomenon in graft polymerization has been investigated: the complexing of growing radicals with copper ions. Graft polymerization of methacrylic acid to polycaproamide, initiated by the reversible K2S2O8–Na2S2O3 redox system in the presence of copper ions, is used as an illustration to show that the complexing of growing radicals with copper ions significantly enhances their activity. The concepts of the graft polymerization mechanism have been formulated.
Estimation of reactivity ratios using emulsion copolymerization data
Authors: De La Cal José C. , Leiza José R. , Asua José M.
Published: April 2003

An approach for the estimation of reactivity ratios using cumulative copolymer composition–overall conversion data obtained in batch emulsion copolymerization is presented. The approach is based on an algorithm for parameter estimation in ordinary differential equations and takes into account the partition of the comonomers between the different phases present in the system. Both copolymer composition and conversion were considered to be affected by experimental errors. The method was first checked by using simulated data that included random errors. The effect of the initial guess and level of errors on the values of the estimated reactivity ratios was investigated. Once the approach was checked, it was used to estimate the reactivity ratios of the styrene–acrylonitrile system based on data obtained in unseeded batch emulsion copolymerizations of these monomers.
On some regularities of grafting of vinylpyridine derivatives onto acetyle cellulose
Authors: Mateva Roza , Nikolov Krasimir
Published: April 2003

The radical graft copolymerization of vinylpyridine derivatives onto acetyl cellulose was investigated using Fe2+/H2O2 redox system as an initiator. It was proved that the addition of hydrazine hydrate increased the degree of grafting many times. The reaction mechanism of hydrazine hydrate was also investigated. A. correlation between nitrogen content and the total anion exchange capacity was established. The vinylpyridine derivatives were ordered according to their reactivity. The effects of reaction conditions on the total anion‐exchange capacity, the total conversion, the degree of grafting, and the grafting efficiency of the copolymers obtained were examined. The copolymers were characterized by IR and H‐NMR spectra, thermogravimetric analysis, elemental analysis, and total anion‐exchange capacity.
Synthesis and properties of polyethersulphone–polydimethyisiloxane block copolymers
Authors: Collyer A. A. , Clegg D. W. , Morris M. , Parker D. G. , Wheatley G. W. , Corfield G. C.
Published: April 2003

High molecular weight alternating block copolymers of polyethesulphone (PES) and polydimethylsiloxane (PDMS) were prepared by the condensation of dimethylamino‐terminated PDMS oligomers and hydroxy‐terminated PES oligomers in 1,2‐dichlorobenzene. Microphase separation of the block copolymers at exceptionally short block lengths was observed by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The SiOC intersegment linkage in these materials appeared to display poor hydrolytic stability which is contrary to results obtained for other block copolymers.
Photochemical synthesis of nitroxyl free radicals in the presence of vinyl monomers
Authors: Van Den Broeck Hilde , Schmitz‐Smets Maria , Smets Georges
Published: April 2003

The photochemical formation of an inhibitor in the presence of monomers and a photoinitiator offers the possibility of producing positive two‐step photoresists. As inhibitor precursor sterically hindred amines have been used in the presence of air oxygen and Rose Bengal as oxidation photosensitizer. On irradiation with visible light (546 nm). stable nitroxyle radicals are formed, which act as strong inhibitors of free radical polymerization. Hexanediol diacrylate and 2‐acryloxy‐2′‐propionyl oxydiethylether were used as monomers. The photoinitiator required for the second step polymerization is benzoin isopropyl ether, which photolyzes on irradiation at 340 n,. The quantum yield of nitroxyl radical formation has been determined in solution and in polymeric films. Polymerization inhibition experiments were carried out with methyl methacrylate in solution and with neat monomers. Though the quantum yield ΦNO° is low, especially in the last case, the experiments confirm the possibilities of this two‐step procedure.
Reactions in aminosilane–epoxy prepolymer systems I. Kinetics of epoxy–amine reactions
Authors: Serier Aicha , Pascault Jean Pierre , My Lam Thanh
Published: April 2003

The reactions of an epoxy prepolymer based on bisphenol A diglycidylether (DGEBA) with γ‐aminopropyltriethoxysilane (γ‐APS) are studied. The results of different techniques are compared: size exclusion chromatography, differential scanning calorimetry, chemical titration, and Fourier Transform Infrared absorption. Epoxy amine reactions are shown to be faster than the crosslinking reactions between alkoxysilane and hydroxy groups, and thus, can be studied seprately. The reactivity of the epoxy group in DGEBA is compared with that of phenylglycidylether (PGE). And the reactivity of the amine group of γ‐APS is compared with that of hexylamine. The kinetic constants are calculated with a mechanism which takes into account both the catalytic and noncatalytic reactions. The ratior=k2/k1of the reactivity of the secondary to the primary amino‐hydrogens was also determined. The values ofrare 1.4 for hexylamine and 1.2 for γ‐APS. The reactivity of the epoxy groups are the same for both PGE and DGEBA.
Electronitiated polymerization of maleic anhydride by direct electron transfer
Authors: Akbulut Ural , Hacioǧlu Bi̇lge
Published: April 2003

Controlled potential electrolysis was employed to accomplish homopolymerization of maleic anhydride, by direct electron transfer. The solvent used in the polymerization studies was acetonitrile–dimethylformamide mixture (1 : 1) with the supporting electrolyte tetrabutylammonium tetra fluroborate, A brown paramagnetic polymer was obtained from the catholyte, upon electroreduction of monomer.
Polypyrrole/dodecylsulfate: Effects of different synthesis conditions
Authors: Peres Rosa C. D. , Pernaut J. M. , De Paoli Marco‐A.
Published: April 2003

We have studied in detail the effects of synthesis conditions, such as current density and sodium dodecylsulfate electrolyte concentration, on the electrical and mechanical properties of polypyrrole. Flexible and self‐supported films were electrochemically obtained using an aqueous solution containing pyrrole and sodium dodecylsulfate. The conductivity (2–20 S/cm) of the films increases with increases in either the current density or the electrolyte concentration. This behavior is caused by the structural changes induced by the different kinetics of film formation. Result indicate that the dodecylsulfate anion, incorporated as dopant in the polymer, randers it flexible with tensile strength in the order of MPa.
A facile synthesis for functional perfluoropolyether oligomers, diacids, diesters, and surfactants
Authors: Persico Daniel F. , Lagow Richard J.
Published: April 2003

Linear polyester precursors provide a convenient low cost synthesis for flurocarbon surfactants, diacids, diesters, and intermediates. A reaction scheme starting with hydrocarbon linear polysters followed by conversion of the ester to a perfluoro ester by direct fluorination and subsequent treatment with nonstoichiometric amount of sulfur tetrafluoride produce upon hydrolysis of ester units remaining in the polymer, low molecular weight perfluropolyether diacids. Alternatively, this technique can be altered slightly to produce diesters and other functional perfluorocarbon intermediates.