bluuebunny/crossref_metadata_2025 huggingface dataset:
Grafting onto carbon black by the reaction of reactive carbon black having epoxide groups with several polymers
Authors: Tsubokawa Norio , Kuroda Akio , Sone Yasuo
Published: April 2003

The grafting of functional polymers onto carbon black surface by the reaction of epoxide groups introduced onto the surface was investigated. The introduction of epoxide groups was achieved by the reaction of the phenolic hydroxyl and carboxyl groups on carbon black with chloromethyloxirane in the presence of sodium hydroxide. The amount of epoxide groups introduced onto the channel black Neospectra II was equal to 0.40 meq/g. The epoxide groups were reacted with polypropylene glycol, silicone diol (SDO), silicone diamine (SDA), and polyethyleneimine to give polymer‐grafted carbon blacks. For example, the percentage of grafting of SDO (Mn = 1.0 × 103) and SDA (Mn = 3.9 × 103) reached to 23.6 and 67.2%, respectively. The percentage of grafting increased with the molecular weight (Mn) of the polymers, while the number of grafted chain (Gn) decreased. In the case of SDO, the relationship between Mn and Gn was found to be Gn = 4.68 × 10−2 M. The carbon black obtained from the reaction gave stable colloidal dispersions in tetrahydrofuran and the stability of dispersion increased with an increase in the percentage of grafting.
Temperature dependence of unperturbed dimensions for isotactic poly(2‐hydroxyethyl methacrylate)
Authors: Oh Seok Heon , Jhon Mu Shik
Published: April 2003

The unperturbed dimensions of isotactic poly(2‐hydroxyethyl methacrylate) (PHEMA) were evaluated from intrinsic viscosity measurements in water, ethanol, 1‐propanol, 2‐propanol, and 2‐butanol under θ conditions over the temperature range of 3.7–32.1°C. The smallest value of unperturbed dimensions (Kθ) and the largest negative temperature dependence of unperturbed dimensions and the polymer–solvent interaction parameter (B) were obtained in aqueous θ solvent relative to the corresponding organic θ solvents. These results were interpreted by the hydrophobic interaction between the hydrophobic groups of isotactic PHEMA and water solvent. The temperature coefficient of the unperturbed dimensions, d ln〈r〉/dT, obtained in this study has a negative value of −1.44 × 10−3 deg−1 under chemically similar θ solvents such as ethanol, 1‐propanol, 2‐propanol, and 2‐butanol where specific solvent effects are eliminated or minimized. In order to obtain the thermodynamic parameters for mixing between isotactic PHEMA and solvents, the plots of the polymer–solvent interaction parameter versus reciprocal absolute temperature (1/T) were carried out. Both the entropy of dilution and enthalpy of dilution show the negative values for water, methanol, and t‐butanol, whereas the positive ones for ethanol, 1‐propanol, 2‐propanol, and 2‐butanol. This result indicates that the solution of isotactic PHEMA behave as exothermal systems in the former class of solvents and endothermal ones in the latter class of solvents.
Polymerization reactivity of unsaturated end group generated during the disproportionation in termination reaction of methyl methacrylate polymerization: A study using model compounds
Authors: Tanaka Hitoshi , Kawai Hirofumi , Sato Tsuneyuki , Ota Tadatoshi
Published: April 2003

Polymerizations of some vinyl monomers were carried out with 2,2′‐azobisisobutyronitrile at 60°C in the presence of a methyl methacrylate (MMA) dimer (I) or a MMA polymer (II) with a double bond at their ends to confirm the polymerization reactivity of unsaturated end group generated during the disproportionation in termination reaction of MMA polymerization. It was found that the polymerizations of α‐monosubstituted monomers have been much retarded than those of α,α‐disubstituted monomers by the addition of I. Kinetic study on MMA and methyl acrylate polymerizations showed that the rate constant for the reaction of a propagating radical with I was 5.4 and 29.2 L/mol s in their polymerizations, respectively. ESR study using I and II suggested that an addition reaction was a predominant mechanism for the reaction of an unsaturated end group with a radical rather than a hydrogen abstraction.
Stereoregularity of fractionally crystallized poly(propylene oxide) samples by 13C‐NMR spectroscopy
Authors: Uğur N. , Alyürük K.
Published: April 2003

Several stereoregular poly(propylene oxide) (PPO) samples were synthesized employing either trimethyl aluminum hydrolyzates or Pruitt–Baggett type catalysts. Dilute isooctane solutions of these samples were fractionally crystallized by stepwise cooling from 333 K down to 273 K. The fractions which dissolve at 273 K were noncrystallizable and were further fractionated by GFC. The isolated fractions were characterized by 13C‐NMR, DSC, and viscometry techniques. Both structural (head‐to‐head and tail‐to‐tail linkages) and steric (syndiotactic dyads) irregularities were found in otherwise isotactic chains and their abundance apparently increased as the melting point and the chain length of the fractions decreased.
Thermal behavior of amide substituted diacetylenes
Authors: Kato Jinichiro , Nakamura Katsuyuki , Yamazaki Satoru , Tokushige Kensaku , Amano Toshihiko
Published: April 2003

Diacetylenes substituted with various amide groups were prepared and their solid‐state polymerization behavior was studied. A calorimetric study of the isothermal polymerization of 1,6‐diacetylamino‐2,4‐hexadiyne was performed in detail. This compound has an extremely high reactivity. The reaction proceeded very quickly and the ultimate conversion reached over 40% slightly above room temperature. The feature of the reaction resembles those observed in the solid‐state polymerization of other diacetylene compounds, i.e., the reaction proceeds slowly in the initial stage, but the rate of reaction increases drastically at about 5% conversion to polymer. Quantitative conversion, however, was not attained at any temperature, and the reaction leveled off within 1.5 h. It is assumed that the reaction cannot continue owing to the distortions generated in the crystals during the polymerization process. The crystalline state of the polymer obtained was highly disordered.
Synthesis, surface accumulation, and micellar properties of amphiphilic block copolymers
Authors: Chujo Yoshiki , Kohno Kenji , Usami Noriyuki , Yamashita Yuya
Published: April 2003

Amphiphilic block copolymers, i.e., poly(methyl methacrylate)‐b‐poly(2‐dimethylethylammoniumethyl methacrylate), were synthesized by the reaction between two prepolymers. Carboxyl‐terminated poly(methyl methacrylate) and hydroxyl‐terminated poly(2‐dimethylaminoethyl methacrylate) were prepared by radical polymerization of the corresponding monomers in the presence of thioglycolic acid and 2‐mercaptoethanol as a chain transfer agent, respectively. Two condensation methods, i.e., DCC and the acid chloride method, were used for the reactions of these prepolymers. The subsequent quarternization produced the amphiphilic block copolymers. Surface property of poly(methyl methacrylate) films containing this amphiphilic block copolymer was examined by measuring contact angles for water. The addition of only 0.5 wt% of the block copolymer was sufficient to make poly(methyl methacrylate) surfaces hydrophilic. The block copolymer formed a polymeric micelle in acetone–water mixed solvent.
Molecular orbital calculations of poly(vinylidene fluoride) and its model compounds
Authors: Takakubo M. , Teramura K.
Published: April 2003

Calculations of dipole moments of poly(vinylidene fluoride)(PVDF) and its model compounds were performed by the MNDO method. 2,2‐difluoropropane as a model compound was found to have a dipole moment of 8.97 × 10−30C m (2.69 D). It was in satisfactory agreement with a previously obtained experimental value, 8.01 × 10−30C m. Dipole moments of two other model compounds, tetrafluoropentane and octafluorononane, were calculated to be 1.70 and 3.24 × 10−29C m, respectively. Ratios of repeat unit moments of the second and third compounds to the first compound moment were equal to 0.95 and 0.90, respectively. These were nearly identical with a theoretical ratio, 0.96, derived from the free rotation model of a polymer chain. The calculated dipole moments were considered to reflect the molecular structures in which free rotations of nearly tetrahedral bond angles might be allowed around C—C links. Dipole moments of each monomer unit for three polymorphs of PVDF, Form I, II, and III were calculated to be 7.64, 5.40, and 5.07 × 10−30C m, respectively. Ratios of the three moments to the first model compound moment were found to be 0.85, 0.60, and 0.57. The decreasing order of the three factors suggests that orientations of monomer unit dipoles are more and more interdependent, and free internal rotations around skeletal bonds are more and more hindered, when the conformation varies from Form I to III. Also it was confirmed that the atomic charge distributions of the three polymorphs were very similar, and that the difference in dipole moments were primarily caused by conformation changes of the polymer chain.
Synthesis of polyester by novel addition reaction of active di‐ester with di‐epoxy compound
Authors: Nishikubo Tadatomi , Iizawa Takashi , Matsumura Takahisa
Published: April 2003

Some polyesters having pendant ether groups were synthesized with high yield by polyaddition of active di‐esters such as di(S‐phenyl)thioisophthalate (PTIP) and di(S‐phenyl)thiosebacate with di‐epoxy compounds such as diglycidyl ether of bisphenol A (BPGE) and diglycidyl ether of ethylene glycol using some quaternary ammonium salts as a catalyst. The degree of polymerization in the reaction of PTIP with BPGE was strongly affected by the kind of reaction solvent, monomer concentration, the reaction temperature, and the kind of catalyst. As a result, it is found that tetrabutylammonium chloride has the highest catalytic activity for the polyaddition of PTIP with BPGE, and dimethylsulfoxide is a suitable solvent for the reaction system.
Synthesis of aliphatic–aromatic polyamides by palladium‐catalyzed polycondensation of aliphatic diamines, aromatic dibromides, and carbon monoxide
Authors: Yoneyama Masaru , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

Aliphatic–aromatic polyamides were synthesized by the palladium‐catalyzed polycondensation of aliphatic diamines, aromatic dibromides, and carbon monoxide. The effects of variables, such as the kind and amount of base, reaction temperature, and the kind of palladium catalyst were investigated in detail on the reaction of hexamethylenediamine and bis(4‐bromophenyl) ether with carbon monoxide. Inherent viscosities of the polyamides were between 0.13 and 1.21 dL/g and varied markedly with the structure of the diamine component. Solubility of the polyamides decreased with increase of chain length of aliphatic diamines, and the polyamides derived from p‐dibromobenzene was insoluble in organic solvents except for m‐cresol. Polyamides obtained from primary aliphatic diamines began to decompose at 210–250°C in air due to decomposition of the aliphatic chain.
Polymer drying. II. Replicated time‐studies of molecular desorption from liquid swollen poly(styrene‐co‐divinylbenzene) before and after transition from the gel‐state to the glass‐state
Authors: Errede L. A. , Van Bogart J. W. C.
Published: April 2003

A total of 90 time‐studies were monitored gravimetrically in order to establish the parameters that affect the reproducibility of the kinetic changes that occur sequentially when liquid‐saturated poly(styrene‐co‐divinylbenzene) [poly(Sty‐co‐DVB)] particles, enmeshed in a matrix of polytetrafluroethylene (PTFE) microfibers, are allowed to evaporate to apparent dryness at constant temperature. The test liquids were toluene, chloroform, and acetone. The absorbent samples were made from six different compositions of polymer particles, the DVB mode fractions, x, of which increased from 0.01 to 0.11. The weight, Wg, of residual sorbed molecules per gram of polymer at the glass‐transition composition was constant despite the large differences in x. Thereafter the weight of residual sorbed molecules was given by a linear combination of up to six exponential decay functions, which indicated that these molecules were “locked” into six different types of molecular environments (i.e., populations) created by the change from the gel‐state to the glass‐state. The fractions of Wg in the populations with the fastest (k1) and the slowest (kn) decay rates were usually less than those with intermediate decay rates. The logarithm of ki in a given time study was a linear function of i, the numerical sequence of decreasing k.
Depolymerization of poly(ethylene terephthalate) recycled from post‐consumer soft‐drink bottles
Authors: Baliga Satish , Wong Wing T.
Published: April 2003

Poly(ethylene terephthalate), recycled from post‐consumer soft‐drink bottles, is depolymerized by glycolysis in excess ethylene glycol at 190°C in the presence of a metal acetate catalyst. The glycolyzed products consist mostly of the PET monomer, bis(hydroxyethyl) terephthalate, and the dimer, and after long reaction time (up to and longer than 8 h), an equilibrium is attained between these two species. No other higher PET oligomers were detected in the study. Of the four metal acetates (lead, zinc, cobalt, and manganese) tested, zinc acetate is the best in terms of the extent of depolymerization, that is, the relative amount of monomer formed. The presence of green pigment in one type of recycled PET apparently has no effects on the glycolysis reaction.
MS and GC–MS studies on phthalocyanine monomers
Authors: Achar B. N. , Fohlen G. M. , Keshavayya J.
Published: April 2003

Phthalocyanines are a class of macrocyclic organic compounds known for their high tinctorial properties, thermal stability, chemical inertness, catalytic activity, and photoconductivity. A mass spectral study on metal phthalocyanines presented many difficulties because of their excellent thermal stability. The present work deals with MS and GC–MS studies of phthalocyanine, copper, and nickel phthalocyanine monomers at various temperatures. Tentative mechanism for the modes of fragmentation is proposed.
Graft copolymerization of acrylamide onto casein: A kinetic study
Authors: Mohan D. , Radhakrishnan Ganga , Rajadurai S. , Rao K. Venkata , Cameron Gordon G.
Published: April 2003

Polyacrylamide has been grafted onto casein in phosphate buffer medium using potassium peroxodisulfate as initiator. The influence of synthetic variables on percent grafting, grafting efficiency, rates of conversion of monomer, and the rates of graft copolymerization have been discussed. A possible kinetic scheme based on experimental results has been derived.
Solvent effect on the radical polymerization of di‐n‐butyl itaconate
Authors: Sato Tsuneyuki , Morita Naoki , Tanaka Hitoshi , Ota Tadatoshi
Published: April 2003

Solvent effect on the polymerization of di‐n‐butyl itaconate (DBI) with dimethyl azobisisobutyrate (MAIB) was investigated at 50 and 61°C. The solvents used were found to affect significantly the polymerization. The polymerization rate (Rp) and the molecular weight of the resulting polymer are lower in more polar solvents. The initiation rate (Ri) by MAIB, however, shows a trend of being rather higher in polar solvents. The stationary state concentration of propagating poly(DBI) radical was determined by ESR in seven solvents. The rate constants of propagation (kp) and termination (kt) were evaluated by using Rp, Ri, and the polymer radical concentration observed. The kp value decreases fairly with increasing polarity of the solvent used, whereas kt is not so influenced by the solvents. The solvent effect on kp is explained in terms of a difference in the environment around the terminal radical center of the growing chain. Copolymerization of DBI with styrene (St) was also examined in three solvents with different physical properties. The poly(DBI) radical shows a lower reactivity toward St in a more polar solvent.
Synthesis, characterization, and thermal stability of bismaleimides derived from maleimido benzoic acid
Authors: Rao B. S.
Published: April 2003

Bismaleimides containing ester, amide, urethane, and imide groups in the backbone were synthesized from maleimido benzoic acid via its acid chloride or isocyanate with 4,4′‐dihydroxy‐diphenyl‐2,2‐propane, 3,3′‐diamino diphenyl sulfone, and 3,3′,4,4′‐benzophenone tetracarboxylic acid anhydride by simple condensation or addition reaction. The new bismaleimides are characterized by IR, 1H‐NMR, and elemental analysis. DSC studies of these bismaleimides indicated a curing exotherm in the temperature range 150–270°C with heat of polymerization 30–50 J/g. Thermogravimetric analysis of the uncured resins showed high thermal stability and char yield for imide containing bismaleimide. The observed char yields of the bismaleimide resins are in accordance with the calculated C/H ratios.
Poly 4‐(3‐chloropropyl)styrene: Syntheses of monomer, polymerization, characterizations, and thermal degradation of polymer
Authors: Montheard J. P. , Boinon B. , Benayad B.
Published: April 2003

4‐(3‐Chloropropyl)styrene, a new functionalized styrene, has been synthesized in three steps from 3‐chloropropylbenzene or in two steps from 4‐chlorostyrene, and the polymerization has been carried out in bulk, with azobisisobutyronitrile as an initiator. The polymer has been characterized by its molecular weights, glass transition temperature, and NMR spectra. Thermal degradation has also been studied and volatile fractions characterized by GC‐MS. A mechanism of depolymerization, very similar to those of various polystyrenes, can be proposed.
Synthesis of nearly monodisperse poly(α‐methylstyrene)s containing two Si atoms and an allyl group and the application to resist
Authors: Saigo Kazuhide , Watanabe Fumitake
Published: April 2003

The anionic polymerizations of 4‐allyldimethylsilyldimethylsilyl‐α‐methylstyrene (1), 4‐allyldimethylsilylmethyldimethylsilyl‐α‐methylstyrene (2), and 4‐allyldimethylsilylethyldimethylsilyl‐α‐methylstyrene (3) have been conducted. Nearly monodisperse poly(4‐allyldimethylsilyldimethylsilyl‐α‐methylstyrene) (4), poly(4‐allyldimethylsilylmethyldimethylsilyl‐α‐methylstyrene) (5), and poly(4‐allyldimethylsilylethyldimethylsilyl‐α‐methylstyrene) (6) were obtained. The Tgs of 4, 5, and 6 are 100.5, 39.0, and 30.5°C, respectively. Among these, 4 has attracted most interest because of a high Tg (100.5°C) and a high Si content (20.5%, w/w). Therefore, a near‐UV resist (DMAS‐A) composed of 4 and a bisazide has been developed as a top resist layer for a bilayer system.
Ethylene polymerization catalysts from supported organotransition metal complexes: I. Pentadienyl derivatives of Ti, V, and Cr
Authors: Smith P. D. , McDaniel M. P.
Published: April 2003

A new class of ethylene polymerization catalysts, namely the bis‐(2,4‐dimethyl pentadienyl) derivatives of titanium, vanadium, and chromium, have been synthesized and tested. When supported on a variety of inorganic carriers, these compounds yielded 0.2–1.0 million g polymer/g metal/h under typical slurry conditions. Sensitivity to H2 as a molecular weight regulator varied among the three metals, but in the absence of H2 all produced ultrahigh‐molecular‐weight polyethylene. The molecular weight distribution varied from moderately narrow to very broad (bimodal) depending on the metal and the carrier. Catalyst synthesis and polymer properties are discussed.
Description of oxygen permeability in various high polymers using a graph theoretical approach
Authors: Surgi Marion R. , Polak A. J. , Sundahl R. C.
Published: April 2003

Graph theory methods are shown to complement group additivity methods of predicting oxygen permeability in certain types of polymers. Graph theory is a topological approach that assigns a set of indices to a molecule to describe its structure. Since many physical properties of molecules depend upon their structure, graph theory indices can be used to describe important properties of molecules. In this work a set of graph theory indices are used to describe the property of a polymer based on a modified representation of the monomer unit. More specifically, Randic indices are used to describe the log of the oxygen permeability with 3.2% average relative error. Polymers comprising the basis set contain backbones of sp2, sp3, or aromatic carbons, oxygen, or silicon and have substituents that contain chloride, fluoride, alkyl groups, hydrogen, oxygen, aromatic carbons, or chloro and/or fluoro substituted alkyl groups. The correlation coefficient (R2) (0 ≤ R2 ≤ 1) of a nonlinear model is 0.91. The graph theory method for describing the oxygen permeability of these selected groups of polymers is in good agreement with that predicted by the permachor model. The permachor method makes oxygen permeability predictions based upon group additivity and distinguishes the degree of crystallinity of a polymer by empirically assigning different permachor (π) values to identical groups based upon the polymer crystallinity. The inability of graph theory to explain the remaining 9% of the scatter in the data is probably due to failure to incorporate into the graph theory model terms which quantify crystallinity.
Kinetics of polyesterification: Adipic acid with ethylene glycol, 1,4‐butanediol, and 1,6‐hexanediol
Authors: Kuo Chin‐Tsou , Chen Show‐An
Published: April 2003

Polyesterifications of adipic acid with ethylene glycol, 1,4‐butanediol, and 1,6‐hexanediol in the absence and presence of the foreign acid (p‐toluene sulfonic acid) as catalyst were carried out under constant reaction temperatures of 140–180°C (rather than at constant oil‐bath temperatures) and at ratios of diol to diacid of 0.9867–3.5880. The experimental data fit the rate equations proposed by Chen and Wu: d(RCOOR′)/dt = kaeαp(RCOOH)2(R′OH) – kh(H2O)(RCOOR′) and d(RCOOR′)/dt = kac(AH)eαp(RCOOH)(RO′H) – kh(H2O)(RCOOR′) for self‐catalyzed and acid‐catalyzed reactions, respectively; the data did not fit the other equations appearing in the literature. Here p is the conversion of acid, and α is the constant related to dielectric constants. The reaction rate constants and activation energies for self‐catalyzed and acid‐catalyzed reactions are calculated. The activation energy is found to decrease with chain length of the alkyl group of the diol. This result is consistent with that observed by Brauman and Blair using ion cyclotron resonance spectroscopy for the variation of acidity of alcohols with chain length of the alkyl group.
Synthesis and properties of high strength high modulus ABA block copolymers
Authors: Tsai Tsu T. , Arnold Fred E. , Hwang Wen F.
Published: April 2003

A series of novel ABA block copolymers were synthesized containing a rigid‐rod (B) block for reinforcement and a flexible coil (A) block as the matrix. Poly[(benzo[1, 2d: 4, 5d′]bisthiazole‐2,6‐diyl)‐1,4‐phenylene] (PBT) was the rigid‐rod (B) block utilized in this study and was polymerized in such a way as to provide carboxylic acid end‐groups. The carboxy‐terminated PBT was copolymerized with the AB monomers, 3,4‐diaminobenzoic acid and 4‐amino‐3‐mercaptobenzoic acid, which generates a benzimidazole or benzthiazole (A) block, as well as grafts the blocks together. Composition of the blocks could be varied by the weight of AB monomer used in the copolymerizations. Solution behavior of the copolymers in methanesulfonic acid was determined, and fibers were obtained by wet spinning techniques. The block copolymers exhibited typical tenacities of 200 ksi, 16 Msi modulus, and an elongation to break of 1.4%. Critical concentration values for fabrication increased approximately 3% over mechanical mixtures of the same heterocyclic components.
Organosilane polymers: Formable polymers containing methylsilylene units
Authors: Qiu Huayu , Du Zuodong
Published: April 2003

Organosilane polymers containing methylsilylene units were prepared by sodium condensation of MeHSiCl2alone or with R1R2SiCl2(R1and R2= alkyl, aryl, or aralkyl) in a blend of toluene and dioxane followed by fast filtration under N2. These polymers are readily soluble in common solvents and can be drawn into fibers or formed into films by molding, casting, or potting. They can be crosslinked by oxidation, irradiation, or hydrosilylation of vinylsilane in the presence of platinum complexes. The effect of the quantity of MeHSiCl2on molecular weights of copolymers was also discussed.
Organosilane polymers: Formable polymers containing reactive side groups
Authors: Qiu Huayu , Du Zuodong
Published: April 2003

Formable organosilane polymers containing various reactive side groups were synthesized by hydrosilylation of unsaturated compounds containing reactive groups with poly(methylsilane) in the presence of platinum complexes. These polymers have appreciable solubility in common solvents, can be molded or cast into films or drawn into fibers, and are photoactive.
Functionalization of crosslinked poly(4‐vinylpyridine) and poly(4‐vinylpyridine‐co‐styrene) with permanganate species: Preparation of poly(4‐vinylpyridinium permanganate)s and their use as oxidizing reagents
Authors: John K. J. , Pillai V. N. Rajasekharan
Published: April 2003

Crosslinked poly(4‐vinylpyridine) and poly(4‐vinylpyridine‐co‐styrene) were functionalized with permanganate group to afford the corresponding poly[4‐vinyl(pyridinium permanganate)] resin. These resins were found to selectively oxidize alcohols to corresponding carbonyl compounds. These insoluble functionalized polymers possess the desired characteristics of the polymeric reagents, including operational simplicity, filterability, and regenerability. The influence of solvent, duration of reaction, and molar excess of the reagent in these oxidation reactions was investigated to find out the optimum conditions for effective oxidation reactions. The reactions were found to be more facilitated in nonpolar solvents, and a large excess of the polymeric reagent did not have any significant effect on the extent of reactions. The poly[4‐vinyl(pyridinium permanganate)] resin bears a contrast to KMnO4 and other polymer‐supported oxidizing agents like poly[4‐vinyl(pyridinium chlorochromate)] in that it does not bring about the oxidation of the alcohol group directly attached to the ring structure.
Alternating copolymerization of 2,4‐dicyanobut‐1‐ene and isoprene: Structural analysis
Authors: Cowie J. M. G. , Cree S. H.
Published: April 2003

The two monomers 2,4‐dicyanobut‐1‐ene and isoprene undergo spontaneous copolymerization when mixed together. A more controlled set of solution copolymerizations have been carried out in toluene to low conversions (< 4%), and analysis of the data gave monomer reactivity ratios ofr1, (DCB) = 0.016 andr2(IP) = 0.109. Alternating copolymers are formed over a wide feed range, and the copolymer structure has been analyzed using1H,13C‐NMR and IR spectroscopy. This shows that the isoprene units are predominantly in thetrans‐1,4 conformation and are attached to the DCB through the 1 position when adding onto the chain. The presence of a 1:1 donor–acceptor complex has been identified in CCl4, solutions of the monomers with an equilibrium quotient ofK= 0.055 dm3mol−1at 333 K. The frontier orbital approach has been used in an attempt to elucidate the most likely structure of the D‐A complex.
Polyethylene and elastomeric polypropylene using alumina‐supported bis(arene) titanium, zirconium, and hafnium catalysts
Authors: Tullock Charles W. , Tebbe Frederick N. , Mulhaupt Rolf , Ovenall Derick W. , Setterquist Robert A. , Ittel Steven D.
Published: April 2003

Bis(arene) complexes of zerovalent titanium, zirconium, and hafnium supported on partially dehydroxylated, fumed alumina are effective catalysts for the polymerization of olefins. The zerovalent complexes react with surface hydroxyls with loss of one equivalent of arene to yield the active species. The polyethylenes derived from these catalysts are very high molecular weight. Polymerization of propylene yields elastomeric stereoblock polymers which are composed of isotactic and stereoirregular sequences. The polymers are stiffer than polypropylenes obtained with similar catalysts derived from tetra(neophyl)zirconium. The chain microstructures of the various components of the whole polymers have been characterized by 13C‐NMR and solvent extraction studies. The ether soluble component of these polymers is of a relatively high molecular weight and the microstructure of the backbone is largely stereoirregular. It is the cocrystallization of this fraction of the polymer with the crystalline, isotactic fractions which is critical to the observed elastomeric properties.
Poly(3‐hydroxyoxetane)—an analog of poly(vinyl alcohol): Synthesis, characterization, and properties
Authors: Vandenberg E. J. , Mullis J. C. , Juvet R. S. , Miller T. , Nieman R. A.
Published: April 2003

The spontaneous polymer formed from 3‐hydroxyoxetane (HO), as first reported by Wojtowicz and Polak, is linear, low molecular weight, water‐soluble, atactic, poly(3‐hydroxyoxetane) (PHO) of high crystallinity with OCH2CH(OH)CH2OH end units. The highly crystalline nature of this atactic polymer may be related to the crystalline nature of atactic poly(vinyl alcohol) since PHO can be considered a copolymer of vinyl alcohol and formaldehyde. Spontaneous PHO apparently is formed in a cationic polymerization by the carboxylic acids produced by the air oxidation of HO on standing at room temperature for several months. The polymerization can be duplicated by the addition of 2% hydroxyacetic acid to HO. The rate of this unusual cationic polymerization increases greatly with acid strength, e.g., trifluoromethanesulfonic acid reacts explosively with pure HO. A mechanism is proposed for this cationic polymerization. High molecular weight, water‐soluble, linear atactic, and highly crystalline PHO (mp = 155°C) was made by polymerizing the trimethylsilyl ether of HO with the i‐Bu3Al–0.7 H2O cationic catalyst followed by hydrolysis. Two 1H‐NMR methods for measuring the tacticity of PHO were developed based on finding two different types of methylene units at 400 MHz with the methine protons decoupled. Also, an 1H‐NMR method was developed for measuring branching in HO polymers. High molecular weight, linear PHO with enhanced isotacticity (80%) has been obtained in low yield as a water‐insoluble fraction with Tm = 223°C. The low molecular weight PHO prepared previously by the base‐catalyzed, rearrangement polymerization of glycidol is highly branched.
Thermal stability of poly(methyl methacrylate) as polymerized in aqueous media by using redox systems as initiators
Authors: Fernández M. D. , Fernández M. J. , Guzmán G. M.
Published: April 2003

The thermal degradation of poly(methyl methacrylate) as polymerized in aqueous nitric acid solution using Ce(IV) alone and in combination with isobutyl alcohol, isopropyl alcohol, glucose, maltose, and cellobiose as initiator systems has been investigated using differential thermal analysis (DTA) and thermogravimetry (TGA) in dynamic nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analysis. The most stable material was found to be the PMMA sample obtained with Ce(IV), and the Ce(IV)–IBA and Ce(IV)–maltose polymerized samples were the least stable. In the pyrolysis of Ce(IV)–IBA and Ce(IV)–maltose polymerized samples it was found that two reactions occurred, while in the case of the PMMA polymerized with Ce(IV), Ce(IV)–IPA, Ce(IV)–glucose, and Ce(IV)–cellobiose three reactions took place.
Thermal stability of copolymers of vinyl acetate and methyl acrylate
Authors: Fernández M. J. , Fernández M. D. , Casinos I. , Guzmán G. M.
Published: April 2003

The thermal degradation of a series of copolymers of vinyl acetate and methyl acrylate and the two homopolymers poly(vinyl acetate) and poly(methyl acrylate) obtained using Ce(IV) as initiator has been investigated using differential thermal analysis (DTA) and thermogravimetry (TGA) in dynamic nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The stability increases as the methyl acrylate content in the copolymer composition increases. The incorporation of 5 mol % of vinyl acetate in the copolymer produces a marked decrease in stability compared to the homopolymer poly(methyl acrylate). There is evidence for an intramolecular lactonization process in vinyl acetate—methyl acrylate copolymers.
Preparation of highly sulfonated polystyrene model colloids
Authors: Kim J. H. , Chainey M. , El‐Aasser M. S. , Vanderhoff J. W.
Published: April 2003

Previous attempts to prepare monodisperse styrene/sodium styrene sulfonate copolymer latexes by batch, seeded, and semicontinuous emulsion polymerization were unsuccessful at high concentrations of the functional comonomer. Broad, and sometimes bimodal, size distributions, and large amounts of water soluble homopolymer were obtained. After removal of free monomer, solute and adsorbed homopolymer and copolymer, the overall incorporation of the functional comonomer was found to be low. To overcome these problems, a two stage “shot‐growth” or in situ seeding technique was developed. A first stage copolymerization was carried out with a low concentration of sodium styrene sulfonate: the purpose of the functional comonomer was to enhance the stability and regulate the size of the seed particles. When this reaction had reached high conversion (> 90%), a second stage monomer mixture was added. The ratio of styrene to sodium styrene sulfonate in this mixture determined the final surface charge density. The mechanism by which the NaSS is incorporated in the polymer particles is considered to be by solution copolymerization with solute styrene monomer to form surface active oligoradicals. These radicals adsorb on the particle surface, initiate polymerization and become inextricably bound, preventing their transfer back to the aqueous phase. By this means, it was possible to vary independently the particle size and surface charge density. High concentrations of functional comonomer could be polymerized without undue wastage (incorporations were only slightly less than 100%) or loss of monodispersity. In extreme cases, the area per functional group fell below the theoretical minimum, indicating considerable hydration of the surface layers.
Synthesis and characterization of 9‐anthrylmethyl propiolate polymers
Authors: Simionescu Cristofor I. , Grigoras Mircea
Published: April 2003

The polymerization of 9‐anthrylmethyl propiolate using various initiating methods was studied with particular emphasis on the elucidation of the structure of the polymers. A polymer having a pure polyene structure was synthesized by anionic or anionic‐coordination mechanism only. Thermal or transition metal halides polymerization led to a polymer possessing anthrylene methylene groups into the main polymer chain. A plausible mechanism for the obtention of this structure was proposed.
Copolymerization of α‐methylstyrene and N‐phenylmaleimide
Authors: Fleš D. D. , Vuković R. , Ranogajec F.
Published: April 2003

In the copolymerization of α‐methylstyrene (α‐MeSt) and N‐phenylmaleimide (NPMI), the resulting copolymers were found to have a high alternating structure regardless of the ratio of comonomers in the feed. The monomer reactivity ratios were r1 = 0.21 (NPMI) and r2 = 0.03 (α‐MeSt) (Kelen–Tüdös method), the equilibrium constant of CT complex K was 0.02 L mol−1, and the energy of activation EA was 73 kJ mol−1. From the equation Rp = Rp(f) + Rp(CT) proposed by Shirota and coworkers, Rp(f) and Rp(CT) were calculated, and it was found that in toluene the copolymerization proceeds predominantly by the addition of free monomers. Copolymers prepared at an equimolar ratio of comonomers in the feed have a glass transition temperature Tg of 539 K (DSC method).
Synthesis of diblock copolymers containing both polydiene and polyalcohol blocks
Authors: Chung T. C.
Published: April 2003

A wide range of functional diblock copolymers containing both functional polymer and hydrocarbon polymer, have been prepared by the combination of anionic polymerization and borane chemistry. The distinctive hydroboration reactivity between various polydienes enables us to selectively functionalize one polydiene segment in diblock copolymers which contain two different polydiene segments. In turn, the hydroborated polymers are valuable intermediate compounds which can be converted to a whole family of functional polymers with a variety of other functionalities under mild reaction conditions. The hydroxylated diblock copolymer is used as an example to demonstrate the chemistry. The two‐phase nature of these copolymers is also shown by the observation of two distinctive glass transition temperatures associated with the individual polymer segments.
Biocatalytic synthesis of polymers. II. Preparation of [AA–BB]x polyesters by porcine pancreatic lipase catalyzed transesterification in anhydrous, low polarity organic solvents
Authors: Wallace J. Shield , Morrow Cary J.
Published: April 2003

Enzyme‐catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures. (1) Such polymerizations may allow the polymer to retain functionality that would be destroyed under normal polymerization conditions. (2) The selectivity provided by enzyme catalysts may permit polymers, including optically active polymers, to be prepared that are either not accessible or accessible only with difficulty by other methods. (3) The characteristics of the enzyme and the mild polymerization conditions may permit formation of polymers having highly regular sizes and backbone structures. This report describes the first successful use of an enzyme‐catalyzed polycondensation to prepare a chiral (AA–BB)x polyesters of more than a few repeat units. Polymerization of bis(2,2,2‐trichloroethyl) alkanedioates (BB) with diols (AA) using the enzyme porcine pancreatic lipase (PPL) as a catalyst is detailed. The polycondensations were carried out at ambient temperature in anhydrous, low polarity organic solvents such as ether, THF, and methylene chloride. End group analysis by NMR provided Mn values of 1300–8200 daltons while GPC provided Mw values of 2800–14900 daltons for the polymers. Based on proton NMR spectra obtained during the polymerization, relatively rapid formation of an AA–BB “dimer” and an AA–BB–AA “trimer,” slower formation of a BB–AA–BB “trimer,” and subsequent condensation of these to give higher polymers are suggested to be components of the polymerization mechanism.
Polymerization and characterization of nitrile‐terminated diacetylene materials
Authors: Grasso Robert P. , Lando Jerome B.
Published: April 2003

A family of nitrile‐terminated diacetylene materials were synthesized. Samples were prepared in various forms and polymerization was performed photochemically and thermally. The resulting materials exhibited low molecular weights and were obtained in low yields. Although the diacetylene group had oligomerized, no evidence was found in support of CN chain formation. Thermochromism was exhibited by the irradiated 8‐nitrile sample and a molecular interpretation of this chromic transition was discussed. Diffraction data implied that strong intermolecular interactions were present between adjacent nitrile groups in the low temperature phase. It is suggested that stresses are built up during polymerization which cause the low degree of polymerization and yield.
Polymeric formamides as liquid–liquid phase transfer catalysts
Authors: Kondo Shuji , Inagaki Yasuhito , Ozeki Masashi , Tsuda Kazuichi
Published: April 2003

Polymeric formamides were prepared by free radical polymerization of N‐methyl‐N‐vinyl‐formamide or N‐methyl‐N‐(4‐vinylbenzyl)formamide, and copolymerization of these monomers with styrene. These soluble polymers serve as phase transfer catalysts for several reactions under liquid–liquid biphase conditions. The catalytic activity of copolymers containing styrene unit is affected remarkably by composition, and there are maxima at certain composition in both polymers. However, copolymers with an acrylonitrile co‐unit scarcely exhibit catalytic activity. Furthermore, it was found that these polymers can extract all alkali metal ions employed here, and that the extraction ability increases with increasing the density of active sites. From these results, it is demonstrated that catalytic activity strongly depends on both cation extraction ability of polymers and lipophilicity around the active sites in the polymer.
Surface modification of polymers. IV. UV initiated degradation of polymers with stabilizers grafted onto the surface
Authors: Allmér K. , Hult A. , Rånby B.
Published: April 2003

Polypropylene (PP), Polyethylene (PE), and polystyrene (PS) films were grafted with glycidylmethacrylate in thin surface layers. To the oxiran groups thus grafted onto the surface three UV stabilizers were attached, 4‐amino‐2,2,6,6‐tetramethylpiperidine (AP), 2,4‐dihydroxybenzophenone (DHBP), and phenyl 4‐aminosalicylate (PAS). The amount of stabilizer grafted onto the surface varied between 25 and 40 nmol/cm2 depending on the polymer substrate. The samples were exposed to UV radiation in air, and the degradation and oxidation of the polymers were studied with IR, UV, and ESCA spectroscopy and by stress–strain measurements. PP grafted with AP exhibited a near 20‐fold increase in lifetime compared with the unprotected PP, AP did not stabilize the PE or PS samples. DHBP was an efficient stabilizer of PE, the oxidation rate of the grafted sample being 1/2 to 1/3 of the ungrafted. A similar effect was observed when DHBP was grafted onto PP and PS. PAS underwent a rearrangement reaction when irradiated with UV light, and had only a slight stabilizing effect.
A 1H magnetic resonance imaging study of porosity in polyurethane foams
Authors: Perry B. C. , Koenig J. L.
Published: April 2003

1H magnetic resonance imaging (MRI) is used to study the distribution of water in polyurethane foams. Flexible open‐celled foams are easily distinguished from the closed‐cell foams as the latter does not absorb any detectable amounts of water. Flexible foams degassed in vacuo revealed no structural detail due to the resolution limitation of approximately 100 μm. Incompletely degassed foams revealed considerable areas of trapped gas which were recorded as a function of distance beneath the water. Samples injected with water indicated that a tortuous flow pathway is taken due to the presence of cell windows. Samples with lower porosity had a higher resistance to flow.
Thermal behavior of polytriazole films: A thermal analysis study
Authors: Gebben B. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

The thermal behavior of poly(1,3‐phenyl‐1,4‐phenyl)‐4‐phenyl‐1,2,4‐triazole has been investigated using different scanning calorimetry (DSC) and thermogravimetry (TG). Processes are studied for this thermally stable polymer that take place between 200 and 500°C. While the polycondensation reaction product in powder from appeared to be partially crystalline, films prepared by casting from a formic acid solution appeared to be completely amorphous. A thermal treatment between Tg(∼ 270°C) and Tm(∼ 430°C) can introduce crystallinity in the films because of the polymer's ability to cold crystallize. The cold crystallization temperature Tc seems to be dependent on the preparation history of the solid polymer phase. Thermal annealing of the films just below Tg does not introduce crystallinity but inhibits subsequent cold crystallization at higher temperatures. Crystallization upon cooling from the crystalline melt has not been observed either. At temperatures just above the crystalline melting point the polymer starts to decompose in an exothermic reaction.
Nafion‐like thin film plasma‐polymerized from perfluorobenzene/SO2 mixture
Authors: Inagaki N. , Tasaka S. , Horikawa Y.
Published: April 2003

Plasma polymerization of perfluorobenzene/sulfur dioxide (PFB/SO2) mixture was investigated by elemental analysis, infrared spectroscopy, and XPS. Plasma polymer films like Nafion were obtained from the plasma polymerization of PFB/SO2 mixture. The plasma polymerization deposited fluoropolymers with sulfur moieties including sulfonate and sulfonic acid groups. The elemental composition, F/C, and S/C atomic ratio of the formed plasma polymers were 0.65–0.67 and 0.24–0.27, respectively, which were independent of the starting mixture composition. The polymers showed cation‐exchange ability of which the capacity was 0.49 meq/g polymer, and initiated the polymerization of pyrrole.
Ring‐opening polymerization of α,β‐disubstituted oxiranes by α‐methoxyphenylmethylium hexachloroantimonate
Authors: Iijima Takao , Sashida Nobuyuki , Kakiuchi Hiroshi
Published: April 2003

α‐Methoxyphenylmethylium hexachloroantimonate was used as a novel initiator for the polymerization of α,β‐disubstituted oxiranes such as cyclohexene oxide (CHO) and 2‐butene oxide (trans and cis) (2‐BO) at −78°C with dichloromethane or dichloromethane‐toluene mixtures as solvents. The CHO polymerization mixture became turbid and the polymer precipitated in dichloromethane. The CHO polymerization proceed quantitatively in dichloromethane–toluene mixtures. The molecular weight distribution of polyCHO obtained was bimodal regardless of the solvent used. The polymerization of trans‐2‐BO was heterogeneous in both dichloromethane and dichloromethane–toluene mixture. The polymerization mixtures of cis‐2‐BO were transparent but reached a limit yield which was less than the polymer yield of trans‐2‐BO. Furthermore, the microstructure of the poly2‐BOs were analyzed by Vandenberg's method and the results confirmed Vandenberg's finding that inversion of configuration occurs in the propagation step.
Miniemulsion copolymerization of styrene–methyl methacrylate
Authors: Rodriguez Valmore S. , El‐Aasser Mohamed S. , Asua Jose M. , Silebi Cesar A.
Published: April 2003

Miniemulsion copolymerization of 50 : 50 weight fraction of styrene–methyl methacrylate monomer, using hexadecane as the cosurfactant, was carried out in both unseeded and seeded polymerizations. Effects of the hexadecane concentration and the ultrasonification time on the conversion–time curves and particle size of the final latex were investigated for unseeded polymerization. The kinetic and particle size distribution results showed that an increase in hexadecane concentration and ultrasonification time cause faster polymerization rate and smaller particle size. The mechanism of mass transport from miniemulsion droplets to polymer particles was also investigated for seeded polymerization. For this purpose a monomer miniemulsion was mixed with a fraction of a previously prepared miniemulsion latex particles prior to initiation of polymerization, using residual oil‐soluble initiator in the seed latex. The concentration of hexadecane and a water‐insoluble inhibitor (2,5 di‐tert‐butyl hydroquinone) in the miniemulsions were the main variables. Seeded polymerizations were also carried out in the presence of miniemulsion droplets containing a water‐insoluble inhibitor and water‐soluble initiator. The inhibitor concentration and the agitation speed during the course of polymerization were the experimental variables. The kinetic and particle size results from these seeded experiments suggested that collision between miniemulsion droplets and polymer particles may play a major role in the transport of highly water‐insoluble compounds.