bluuebunny/crossref_metadata_2025 huggingface dataset:
Fully aromatic liquid crystalline homopolyesters and copolyesters of 1,1′‐binaphthyl‐4,4′‐diol
Authors: Bhowmik Pradip K. , Lenz Robert W.
Published: April 2003

A series of fully aromatic, thermotropic polyesters based on 1,1′‐binaphthyl‐4,4′‐diol, BND, was prepared by the melt polycondensation method and characterized for their thermotropic behavior by a variety of experimental techniques. The homopolymer of BND with terephthalic acid formed a nematic melt at 353°C. In contrast, the polyester from BND and 2,6‐naphthalenedicarboxylic acid had a melting transition, Tm, above 400°C, so it was not possible with the equipment available to determine whether it formed a nematic melt. All of the copolymers of BND formed nematic melts at much lower Tm values than those of its respective homopolymers, as expected, because of the copolymerization effect of the added monomer. Moreover, all of the copolymers had higher glass transition temperatures, Tg, than those of other liquid crystalline polyesters and higher thermal stabilities. © 1994 John Wiley & Sons, Inc.
Synthesis and thermal properties of liquid‐crystalline polyacrylates containing a carbazolyl group in the mesogen
Authors: Kosakasup Yozo , Kato Takashi , Uryu Toshiyuki
Published: April 2003

The new acrylate monomers 4‐(ω‐acryloyloxyalkyloxy)‐N‐(9‐methyl‐2‐carbazolylmethylene) anilines containing from 2 to 11 methylenic units in their alkyl group and a carbazolyl group in the mesogenic unit were synthesized and polymerized by azobisisobutyronitrile (AIBN) as radical initiator and by low‐energy electron beam (EB) initiation. The thermal properties of the resulting polymers were examined using differential scanning calorimetry and thermal optical polarizing microscopy. The polymer prepared by AIBN with a hexamethylene spacer exhibited a nematic phase from 73 to 170°C and with an undecamethylene spacer exhibited a smectic phase from 55 to 202°C. The isotropization temperature of the polyacrylates increased with increasing the number of carbons of the methylenic spacer. The yield of the resulting polymer was changed by EB irradiation temperature from 4.5 to 41%. The highest yield was obtained when the monomer was polymerized in a liquid‐crystalline phase. The same tendency was observed in the molecular weight of the resulting polymers. © 1994 John Wiley & Sons, Inc.
Mechanistic studies of carbonate macrocyclization
Authors: Aquino Eugene C. , Brittain William J. , Brunelle Daniel J.
Published: April 2003

The kinetics of phenylchloroformate (PCF) reactions have been used to model some of the key chemical events in carbonate macrocyclization. Three reactions have been studied using stopped‐flow FT‐IR spectroscopy: formation of acyl ammonium salt from PCF and three different trialkylamines, the conversion of acyl ammonium salt to urethane, and the condensation reaction between acyl ammonium salt and 4‐isopropylphenol. The rate dependence was studied for triethylamine (TEA), diethylmethylamine (DEMA) and tri‐n‐butylamine (TBA) at 0°C in anhydrous CH2Cl2. The reactivity order for acyl ammonium salt formation for TBA: TEA: DEMA is 1 : 2.7 : >444. By contrast, condensation and urethane formation are not sensitive to the structure of the amine. The rate of condensation is comparable to the rate of acyl ammonium salt formation for TEA and TBA, while the rate of urethane formation is the slowest process for all three amines. These results are consistent with the view that the yield of macrocyclic polycarbonates is related to the concentration of the acyl ammonium salt. The optimum amine concentration for obtaining high yields of cyclics varies with the amine structure and parallels the difference in the rates of acyl ammonium salt formation. © 1994 John & Sons, Inc.
Spectroscopic study of solid state photoreaction of di n‐propyl ester of dicyano p‐phenylenediacrylic acid
Authors: Ghosh Manash , Chakrabarti Subhasis , Sarkar Mamata , Misra T. N.
Published: April 2003

Photopolymerization reaction in di n‐propyl ester of dicyano p‐phenylene diacrylic acid crystal is shown to be mediated by exciton–phonon coupling. Raman phonon spectra suggest that at the initial stage of reaction progress, the reactant and the product form a solid solution. In the later stage, the reactant segregates out and forms its own lattice. The polymer lattice is shown to maintain a good degree of order. Infrared and Raman spectra confirm that the polymerization occurs by cyclobutane ring formation. © 1994 John Wiley & Sons, Inc.
Poly‐N,N‐diethylacrylamide prepared by group transfer polymerization: Synthesis, characterization, and solution properties
Authors: Eggert Martin , Freitag Ruth
Published: April 2003

The conditions for preparing poly‐N,N‐diethylacrylamide by group transfer polymerization (GTP) were investigated. While electrophiles did not catalyze the reaction, various nucleophilic substances could be used for that purpose. By using an appropriate initiator, either an ester or a carboxylic acid end group could be formed. The highest yields in the first case were obtained using tetrabutylammonium acetate and dimethylketene methyl trimethylsilyl acetal as catalyst and initiator, respectively, while the use of the corresponding bistrimethylsilyl compound as initiator gave polymers, albeit at lower yields, which carried the acidic end group. The 1H‐NMR, 13C‐NMR, and IR spectra of the polymers were taken and used together with information obtained with soft‐ionization mass spectrometric methods (MALDI‐MS, ESI‐MS, and FD‐MS) to elucidate molecule structure, apparent molecular weight distribution, polydispersity, and possible mechanisms of the termination reaction. The poly‐N,N‐diethylacrylamide prepared, showed an inverse temperature dependency in its water‐solubility, with a lower critical solution temperature between 29.8°C and 30°C. © 1994 John Wiley & Sons, Inc.
Trimethylsilyl‐group containing polyphenylacetylenes for oxygen and ethanol permselective membranes
Authors: Aoki Toshiki , Nakahara Hiroshi , Hayakawa Yoshio , Kokai Masayuki , Oikawa Eizo
Published: April 2003

Phenylacetylenes having one or two trimethylsilyl groups at their benzene ring were synthesized, and polymerized by [Rh(cyclooctadiene) (PPh3)2]PF6, [Rh(norbornadiene)Cl]2, or WCl6 to afford high molecular‐weight polymers in high yields. These poly(phenylacetylene)s were soluble in many kinds of solvents and were fabricated to tough membranes by the solvent casting method. The oxygen permselectivities of these membranes were very good. The oxygen permeability coefficients (Po2) and oxygen separation factors (α = Po2/PN2) of poly[2,4‐(o,p)‐bis(trimethylsilyl)phenylacetylene] [poly (o‐1‐p‐1)] and poly[(4(p)‐trimethylsilyl)phenylacetylene] [poly(p‐1)] membranes were 4.73 × 10−8 cc(STP) cm/cm2 s cmHg and 2.65, and 1.52 × 10−8 cc(STP) cm/cm2 s cmHg and 3.39, respectively. In the case of poly(o‐1‐p‐1), Po2 was comparable to that of polydimethylsiloxane (PDMS) and α was higher than that of PDMS. However, the Po2 value reduced to 48% of its initial value in about 1 year. In the case of poly(p‐1), the Po2 value did not change in about 1 year. Ethanol permeated preferentially through these membranes (αEtOH > 1) in pervaporation of aqueous ethanol solution, whereas poly(phenylacetylene) [poly(PhA)] showed water permselectivity (αEtOH < 1). These favorable effects of trimethylsilyl groups on the oxygen and ethanol permselectivities were discussed on the basis of comparison with those of poly(PhA), other poly(substituted phenyl‐acetylene)s, and trimethylsilyl‐group containing polystyrenes. © 1994 John Wiley & Sons, Inc.
Block copolymers by polymer modification: Conversion of polyisoprene segment to hydroxylated polyisoprene
Authors: Kim Young H.
Published: April 2003

Polyisoprene (PIP) was found to react with trifluoroacetic acid (TFA) to give an adduct. Saponification of the ester gave a new alternating copolymer of ethylene and α‐methyl vinyl alcohol. TFA did not react with polybutadiene (PBD) under these conditions, thus providing a way to produce amphiphilic block copolymers from PBD‐b‐PIP. TFA addition to the PIP block took place cleanly at an ambient temperature with 2 equiv of the acid in toluene to give block copolymer of PBD and trifluoroacetated PIP. This polymer is very soluble in toluene regardless of molecular weight. Methanolysis with NaOMe cleaved the ester to give PDB‐b‐(ethylene‐alt‐α‐methyl vinyl alcohol) (PIPOH) in a MeOH/toluene mixture. Low molecular weight hydroxylated diblock copolymer is a viscous liquid when the ratio of PIP/PBD is 0.1 ( \documentclass{article}\pagestyle{empty}\begin{document}$\overline {M_n }$\end{document} = 4100, D = 1.3), but a solid with the ratio 0.5 (\documentclass{article}\pagestyle{empty}\begin{document}$\overline {M_n }$\end{document} = 7170, D = 1.6). High molecular weight polymer (\documentclass{article}\pagestyle{empty}\begin{document}$\overline {M_n }$\end{document} = 114,000, D = 1.4) with PIP/PBD ratio 0.1 is a hazy rubbery material. Block copolymers of PIPOH and poly(methacrylic acid) was also obtained from copolymers of PIP and poly(t‐butyl methacrylate). The hydroxylated copolymers showed surface activity by monolayer formation on a Langmuir–Blodgett trough. The transfer of the monolayer on a silicon wafer gave z‐type deposition, with the average ellipsometer thickness of the layer being about 40 Å thick per monolayer for \documentclass{article}\pagestyle{empty}\begin{document}$\overline {M_n }$\end{document} = 4100 copolymer. © 1994 John Wiley & Sons, Inc.
Carbenoid polycondensation with telechelic polyethers having dichloroacetic acid ester groups
Authors: Tezuka Yasuyuki , Hoshino Chisato
Published: April 2003

Poly(ethylene oxide) [poly(EO)], with number‐average molecular weights (Mns) of 1000 and 2000, and poly(tetrahydrofuran) [poly(THF)] with Mns of 1000 and 2000, possessing dichloroacetic acid ester end groups (1, and 2, respectively) were prepared from precursor diols by esterification with dichloroacetyl chloride in the presence of pyridine. 1 and 2 were subjected to the reaction with copper metal in DMSO to produce the corresponding segmented polyethers containing fumarate/maleate groups within the main chain (3 and 4, respectively), through a polycondensation of carbalkoxy carbenoid intermedlates generated via α, α‐dichloro elimination from the end groups of 1 and 2. The radical polymerization of styrene in the presence of 3 and 4 produced network copolymers consisting of poly (EO) or poly(THF) and polystyrene segments. © 1994 John Wiley & Sons, Inc.
A novel acrylate carrying a hindered phenol moiety as monomer and terminator in radical polymerization
Authors: Matsumoto Akikazu , Yamagishi Kenichi , Aoki Shuzo
Published: April 2003

Radical polymerizations of methyl methacrylate (MMA), styrene (St), and vinyl acetate (VAc) were carried out in the presence of a novel phenyl acrylate derivative bearing a hindered phenol moiety (HPA). It has been clarified that HPA acts as a retarder and inhibitor for the polymerizations of MMA and VAc, respectively, and that in the polymerization of St it behaves as a monomer to give a copolymer. These additive effects were interpreted in terms of intramolecular transfer of the phenolic hydrogen in competition with propagation of the HPA radical to monomers. © 1994 John Wiley & Sons, Inc.
Azeotropy in terpolymerization of N‐antipyryl acrylamide with different alkyl acrylates or styrene and acrylonitrile
Authors: El‐Hamouly S. H. , Azab M. M.
Published: April 2003

Ternary copolymerization of N‐antipyryl acrylamide (NAA) with different alkyl acrylates [methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BuA)] or styrene (ST) and acrylonitrile (AN) were carried out in solution at 65°C in the presence of AIBN as a free radical initiator. Experimental terpolymerization daca agree well with calculations based on the Alfrey–Goldfinger equation. The determination of unitary, binary, and ternary azeotropes of various systems studied was easily handled by a computer program. Ternary azeotropic compositions for NAA–MA–AN, NAA–EA–AN, NAA–BuA–AN, and NAA–ST–AN system were 31.0 : 10.0 : 59.0, 37.0 : 09.0 : 54.0, 23.0 : 10.0 : 67.0, and 66.5 : 30.50 : 03.0 mol %, respectively. Selective unitary and binary azeotropic compositions were polymerized and the obtained results show good agreement between the theoretical and experimental terpolymer composition for each case. Also, pseudo‐azeotropic regions were identified where the deviation between feed and polymer composition is very small. The azeotropic points of the four systems were confirmed using Tarasov et al.'s equations and were found to have satisfactory results. © 1994 John Wiley & Sons, Inc.
Chemical preparation of conductive elastomeric blends: Polypyrrole/EPDM. I. Oxidant particle‐size effect
Authors: Zoppi Rita Aparecida , Felisberti Maria Isabel , De Paoli Marco‐Aurelio
Published: April 2003

This work describes the preparation of polypyrrole and EPDM rubber blends, PPy/EPDM, by the sorption of pyrrole (vapor phase) in an EPDM matrix containing CuCl2. We investigated the effect of the oxidant particle‐size on the sorption and polymerization equilibrium, electrical conductivity, and mechanical properties of the blends. Independently of the CuCl2 concentration and polymerization time, the polypyrrole weight fraction in the blend, Xppy, increases when the oxidant particle‐size in changed from 150–250 μm to smaller than 106 μm. For blends containing 50 phr of CuCl2, obtained following 72 h of exposure to pyrrole, an increase in the Young's Modulus (from 2.2 ± 0.2 to 3.9 ± 0.6 MPa) and an increase in the electrical conductivity (from 10−9 to 10−7 S cm−1) was observed when the oxidant particle‐size was decreased. Infrared spectroscopy, thermogravimetric analysis, scanning differential calorimetry, and scanning electron microscopy were used in sample characterization. © 1994 John Wiley & Sons, Inc.
Polymerization of ethylene at high temperature by vanadium‐based heterogeneous Ziegler—Natta catalysts. II. Study of the activation by halocarbons
Authors: Adisson E. , Deffieux A. , Fontanille M. , Bujadoux K.
Published: April 2003

The enhancement of the activity and productivity of heterogeneous V‐based catalysts in the presence of halogenated additives, has been investigated for high‐temperature ethylene homopolymerization (160°C). The influence of both the nature and structure of various organic halides on polymerization kinetics and on the oxidation state of vanadium derivatives has been examined in detail. Results suggest, as previously reported for lower temperature polymerizations, that the main role of the halogenated derivatives may be accounted for by their oxidizing character. It allows re‐oxidation of the reduced VII species formed during the polymerization process, to valence III. The various pathways able to lead to the formation of new active species from (re‐)formed VIII are examined and discussed. © 1994 John Wiley & Sons, Inc.
Preparation and properties of polyborosiloxanes as precursors for borosilicate formation of SiO2–B2O3 gel fibers and oxides by the sol‐gel method using tetraacetoxysilane and boron tri‐n‐butoxide
Authors: Kasgoz A. , Misono T. , Abe Y.
Published: April 2003

Formation of SiO2–B2O3 gel fibers and oxides was investigated by the sol‐gel method using tetraacetoxysilane (TAS) and boron tri‐n‐butoxide (BTB). Low molecular weight borosiloxanes (BS) were formed by the reaction of TAS with BTB in THF. Partial alkoxylation and hydrolysis of BS followed by further condensation of the resulting polymer (PBS) solutions led to the formation of highly polymerized polyborosiloxanes (HPBS) with good spinnability. Gel fibers were obtained by dry spinning of HPBS. The compositions of PBS and gels were not consistent with that in feed. Heat treatment of the gels, however, provided SiO2–B2O3 oxides with compositions almost compatible with those of the gels. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of novel polyarylates from 2,5‐bis(4‐hydroxyphenyl)‐3,4‐diphenylpyrrole and various aromatic dicarboxylic acids
Authors: Jeong Hwa‐Jin , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

A new tetraphenylated heterocylic diol, 2,5‐bis(4‐hydroxyphenyl)‐3,4‐diphenylpyrrole, was synthesized in three steps starting from 4‐methoxydeoxybenzoin. The tetraphenylpyrrole‐containing polyarylates having inherent viscosities of 0.28–0.88 dL/g were prepared from the diol and various aromatic dicarboxylic acid chlorides by both phase transfer catalyzed two‐phase polycondensation and high temperature solution polymerization methods. All the polyarylates were semi‐crystalline, and were readily soluble in a variety of solvents including N‐methyl‐2‐pyrrolidone, m cresol, pyridine, and 1,4‐dioxane. These polymers had glass transition temperatures in the range of 223–279°C, with no weight loss below 400°C in both air and nitrogen atmospheres. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of ran‐copoly (p‐phenylene sulfide sulfone/ketone)s
Authors: Senn Dwayne R.
Published: April 2003

Random copoly(p‐phenylene sulfide sulfone/ketone)s (PPSS/K) are prepared in high yield by the polycondensation of sodium hydrosulfide (NaSH) with bis(4‐chlorophenyl) sulfone (BCPS) and 4,4′‐dichlorobenzophenone (DCBP). The polymerization is conducted between 200–220°C, depending on the composition of the copolymer, and in the presence of water without any detrimental effects to the molecular weight. The copolymers with sulfone/ketone mole ratios (S : K) > 25 : 75 are amorphous, while the copolymers with S : K ratios ≤ 25 : 75 are crystalline. These materials form tough, creaseable films and exhibit a linear increase in the glass transition temperature with increasing sulfone content. Sulfuric acid solutions of the copolymers are dark orange to red and display an increasing λmax in the uv‐visible spectra as the S:K ratio of the copolymers decreases. © 1994 John Wiley & Sons, Inc.
Swelling kinetics and release characteristic of crosslinked chitosan: Polyether polymer network (semi‐IPN) hydrogels
Authors: Yao Kang De , Peng Tao , Feng Han Bao , He Yu Ying
Published: April 2003

The aqueous swelling kinetics of a series of crosslinked chitosan (cr‐CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, the N‐deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi‐IPN were also investigated. © 1994 John Wiley & Sons, Inc.
Studies on the formation of PEN. II. Polymerization of bis(hydroxyethyl) naphthalate by various metallic catalysts
Authors: Wang Chun‐Shan , Sun Yih‐Min
Published: April 2003

Bis(hydroxyethyl) naphthalate (BHEN) was polymerized to polyethylenenaphthalate (PEN) in the presence of various metallic catalysts. The influence of the nature and concentration of these catalysts on the rate of polymerization has been investigated. The order of decreasing catalytic influence of various metal ions on the polymerization of BHEN was found to be: Ti > Sb > Zn > Co > Pb > Ni(Mg). The effect of the reaction temperature has also been studied. The optimal concentration of these catalyst and reaction temperature were found to be 30 × 10−5 (mol/mol BHEN) and 285–293°C, respectively. Because of its insolubility in ordinary solvent, the molecular weight of PEN was measured using the light scattering method. © 1994 John Wiley & Sons, Inc.
Polymerization of avidin and streptavidin with aromatic bisbiotin ligands
Authors: Morgan H. , Fukushima H. , Taylor D. M.
Published: April 2003

The synthesis of a range of aromatic bisbiotin ligands is described and their ability to polymerize the proteins avidin and streptavidin is investigated. The formation of protein polymers is confirmed by gel chromatography and transmission electron microscopy. It is shown that the degree of polymerization depends not only on the length of the ligand but also on the stereochemistry of the group linking the distal biotin moieties. © 1994 John Wiley & Sons, Inc.
High flow addition curing polyimides
Authors: Chuang Kathy C. , Vannucci Raymond D. , Ansari Irfan , Cerny Lawrence L. , Scheiman Daniel A.
Published: April 2003

A new series of high flow PMR‐type addition curing polyimides was developed, which employed the substitution of 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl (BTDB) for p‐phenylenediamine (p‐PDA) in a PMR‐II formulation. These thermoset polyimides, designated as 12F resins, were prepared from BTDB and the dimethyl ester of 4,4′‐(hexafluoroisopropylidene)‐diphthalic acid (HFDE) with either nadic ester (NE) or p‐aminostyrene (PAS) as the endcaps for addition curing. The 12F prepolymers displayed lower melting temperatures in DSC analysis, and higher melt flow in rheological studies than the corresponding PMR‐II polyimides. Long‐term isothermal aging studies showed that BTDB‐based 12F resins exhibited comparable thermo‐oxidative stability to p‐PDA based PMR‐II polyimides. The noncoplanar 2‐ and 2′‐disubstituted biphenyldiamine (BTDB) not only lowered the melt viscosities of 12F prepolymers, but also retained reasonable thermal stability of the cured resins. The 12F polyimide resin with p‐aminostyrene endcaps showed the best promise for long‐term, high‐temperature application at 343°C (650°F). © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of poly[4‐(4‐hydroxyphenoxy) benzoic acid]
Authors: Yonetake Koichiro , Maruyama Kunio , Sugiyama Jun‐Ichi , Masuko Toru , Ueda Mitsuru
Published: April 2003

Poly[4‐(4‐hydroxyphenoxy) benzoic acid] was prepared by the bulk polycondensation of 4‐(4‐acetoxyphenoxy) benzoic acid. Polycondensation was conducted at 350°C for 3 h under a reduced pressure of 0.1 mmHg and gave a polymer with X̄n of 255. The polymer was characterized by elemental analysis, IR spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray measurement. The crystal/nematic and nematic/isotropic phase transition temperatures of polymer, which depend on the molecular weight, were observed at about 300°C and 410°C, respectively. The polymers with low molecular weights showed nematic textures above 300°C. This nematic/isotropic phase transition temperature is lower than that of poly (4‐hydroxybenzoic acid). This thermal behavior of polymer comes from ether units, which increase the flexibility (the rotation or torsion of skeletal bonds) of the polymer chain. © 1994 John Wiley & Sons, Inc.
Synthesis of crosslinked poly(styrene‐co‐sodium styrenesulfonate) latexes
Authors: Sunkara Hari Babu , Jethmalani Jagdish M. , Ford Warren T.
Published: April 2003

Latexes of 100 nm diameter were synthesized by emulsifier‐free copolymerization of styrene, sodium styrenesulfonate, and 1–5 wt% divinylbenzene using persulfate initiator at 91°C. A shot growth method was used to incorporate a high density of sulfonate groups. Coefficients of variation of particle size were 0.04–0.08 without resort to seed growth polymerization. Redox initiation at 40–50°C produced larger, more polydisperse, and less colloidally stable crosslinked latexes. © 1994 John Wiley & Sons, Inc.
Role of N,N‐dimethyl‐para‐toluidine and saccharin in the radical polymerization of methyl methacrylate initiated by a redox system. I. Cumene hydroperoxide/copper saccharinate
Authors: Beaunez P. , Helary G. , Sauvet G.
Published: April 2003

Kinetics of methyl methacrylate polymerization initiated by a redox system [cumene hydroperoxide (CHP)/copper saccharinate] were studied in bulk at 20°C in the presence of accelerators such as N,N‐dimethyl‐p‐toluidine (DMPT) and o‐benzoic sulphimide (saccharin). Assuming a steady‐state concentration of propagating radicals, the polymerization rate depends on the square root of the initiation rate and the kinetic orders with respect to each compound in the initiation step may be deduced. Initiation is first‐order in CHP, copper saccharinate, and saccharin and second‐order in DMPT. A reaction scheme consistent with these orders is proposed. The main features are the following: (1) CHP reduces rapidly Cu(II) to Cu(I); (2) a small fraction of Cu(I) is complexed with DMPT; (3) the complexed ions (Cu+, DMPT2) are strong reductants with respect to CHP whereas uncomplexed Cu+ are almost inactive; (4) the decomposition of CHP is strongly catalyzed by saccharin (protonated CHP is 13000 times more reactive than free CHP). Thus both accelerators are necessary to get high polymerization rates. © 1994 John Wiley & Sons, Inc.
Role of N,N‐dimethyl‐para‐toluidine and saccharin in the radical polymerization of methyl methacrylate initiated by a redox system. II. Cumene hydroperoxide/iron saccharinate
Authors: Beaunez P. , Helary G. , Sauvet G.
Published: April 2003

The role of N,N‐dimethyl‐p‐toluidine (DMPT) and saccharin as accelerators in the polymerization of methyl methacrylate initiated by the redox decomposition of cumene hydroperoxide (CHP) in the presence of iron saccharinate has been kinetically investigated. DMPT reduces ferric ions to ferrous ions, so that an equilibrium is established between the two oxidation states. With the assumption of a steady‐state concentration of propagating radicals, the rate of initiation was deduced from the rate of polymerization and the kinetic orders with respect to each compound involved in the initiation step have been determined. The reaction is first‐order in CHP, iron saccharinate, and saccharine and second‐order in DMPT. In a proposed scheme, Fe2+ ions, complexed by two DMPT molecules, are much more reactive than uncomplexed Fe2+ and saccharin activates the decomposition of CHP by protonation of the OO bond. This mechanism, similar to that proposed in the case of copper saccharinate, explains the synergistic effect of both accelerators. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of poly(amide‐imide)s derived from trimellitic anhydride, ω‐amino acids, and aromatic diamines
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping , Wu Feng‐Yueh
Published: April 2003

Seven imidodicarboxylic acids II‐1 to 5, II‐10, and II‐11 were prepared from trimellitic anhydride and ω‐amino acids, such as glycine, β‐alanine, 4‐aminobutyric acid, 5‐aminopentanoic acid, 6‐aminohexanoic acid, 11‐aminoundecanoic acid, and 12‐aminododecanoic acid. Several aliphatic‐aromatic poly(amide‐imide)s were prepared by triphenyl phosphite promoted polycondensation reaction from the combination of 3‐(4‐carboxyphthalimido)propionic acid (II‐2) or 6‐(4‐carboxyphtalimido)hexanoic acid (II‐5) with various aromatic diamines and of all the imidodiacids with p‐phenylenediamine or 4,4′‐oxydianiline. All poly(amide‐imide)s were characterized by inherent viscosity, gel permeation chromatography (GPC) measurements, solubility, tensile test, wide‐angle X‐ray scatting patterns, differential scanning calorimetry (DSC) measurements, and thermogravimetric (TGA) analyses. Effects of structural changes such as polymethylene length and diamine moieties on the properties of poly(amide‐imide)s were studied. © 1994 John Wiley & Sons, Inc.
Use of V and V–Cr catalysts interchanged in “Y” zeolites for the polymerization of ethylene
Authors: Ismayel A. , Arribas G. , Celta D. , Sanchez G.
Published: April 2003

Ethylene polymerization has been studied in the presence of catalyst based on vanadium or vanadium‐chromium supported on a zeolite HY. The effect of vanadium over chromium has been investigated as a function of the sequence of exchange of metals on the support and metal contents. Both effects were investigated in relation to the characteristics of the polyethylene (PE) obtained. Low activity has been found for the V (II) zeolite HY catalyst. Moreover, vanadium acts either as an inhibitor or as a promoter for the polymerizing activity of the Cr (III)/zeolite catalyst, depending on the preparation method. © 1994 John Wiley & Sons, Inc.
Preparation and characterization of functional group gradient surfaces
Authors: Lee Jin Ho , Kim Heoung Woo , Pak Pyong Ki , Lee Hai Bang
Published: April 2003

Functional group gradient surfaces where the density of functional groups changes gradually along the sample length were prepared. The functional group ( COOH,  CONH2, and  OH group) gradient surfaces were produced by the treatment of low‐density PE sheets using a corona with gradually increasing power, followed by the graft copolymerization of acrylic acid and subsequent substitution reaction of carboxylic acid groups to amide or hydroxyl groups. The prepared gradient surfaces were characterized by the measurement of water contact angle, FTIR‐ATR, and ESCA. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of the surface functional groups and their density of polymeric materials. © 1994 John Wiley & Sons, Inc.
Biodegradable and pH‐sensitive hydrogels: Synthesis by crosslinking of N,N‐dimethylacrylamide copolymer precursors
Authors: Yeh Ping‐Yang , Kopec̆ková Pavla , Kopec̆ek Jindr̆ich
Published: April 2003

Novel pH‐sensitive hydrogels containing azoaromatic crosslinks were synthesized by the crosslinking of polymeric precursors. First, a reactive polymeric precursor was synthesized by copolymerization of N,N‐dimethylacrylamide, N‐tert‐butylacrylamide, acrylic acid, and N‐methacryloylglycylglycine p‐nitrophenyl ester. The hydrogel was prepared in the second step by the reaction of the polymeric precursor with N,N′‐(ω‐aminocaproyl)‐4,4′‐diaminoazobenzene. The hydrogels were characterized by the network structure, (that is, content of crosslinks, unreacted pendent groups, and cycles), the equilibrium swelling ratio as a function of pH, modulus of elasticity in compression, and the degradability in vitro. The results obtained indicated that the hydrogel network structure strongly depends on the reaction conditions such as polymer concentration, and the ratio of the reactive groups during the crosslinking reaction. The swelling and mechanical properties of hydrogels can be controlled by the modification of polymer backbone structure and/or the crosslinking density. The rates of hydrogel degradation depended on their degree of swelling. The higher the degree of swelling, the higher the degradability. The properties of the hydrogels suggest that they have a potential as carriers for colon‐specific drug delivery. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of bismaleimides derived from polyurethanes
Authors: Liao D. C. , Hsieh K. H.
Published: April 2003

A series of novel bismaleimides (BMIs) were prepared from maleic anhydride and polyurethane prepolymers based on MDI (4,4′‐diphenylmethane diisocyanate) and polyether and polyester diols with various chain lengths. All the BMIs were characterized by IR, 1H‐NMR, and elemental analysis. DSC studies indicated that the thermal polymerization of the BMIs could be carried out in the temperature range of 102–245°C, and that curing behavior was significantly affected by the molecular weight of the BMIs. The crosslinked BMI elastomers showed good mechanical properties and much better thermal stability than that of the traditional polyurethane elastomers. The glass transition temperatures, mechanical, and dynamic mechanical properties were dependent on the types of polyols used and the resultant crosslink densities due to various chain lengths of the BMIs. © 1994 John Wiley & Sons, Inc.
Living cationic polymerization of isobutyl vinyl ether by EtAlCl2 in the presence of ether additives: Cyclic ethers, cyclic formals, and acyclic ethers with oxyethylene units
Authors: Aoshima Sadahito , Fujisawa Takashi , Kobayashi Eiichi
Published: April 2003

The living cationic polymerization of isobutyl vinyl ether (IBVE) was investigated in the presence of various cyclic and acyclic ethers with 1‐(isobutoxy)ethyl acetate [CH3CH(OiBu)OCOCH3, 1]/EtAlCl2 initiating system in hexane at 0°C. In particular, the effect of the basicity and steric hindrance of the ethers on the living nature and the polymerization rate was studied. The polymerization in the presence of a wide variety of cyclic ethers [tetrahydrofuran (THF), tetrahydropyran (THP), oxepane, 1,4‐dioxane] and cyclic formals (1,3‐dioxolane, 1,3‐dioxane) gave living polymers with a very narrow molecular weight distribution (MWD) (M̄ω/M̄n ≤ 1.1). On the other hand, propylene oxide and oxetane additives resulted in no polymerization, whereas 1,3,5‐trioxane gave the nonliving polymer with a broader MWD. The polymerization rates were dependent on the number of oxygen and ring sizes, which were related to the basicity and the steric hindrance. The order of the apparent polymerization rates in the presence of cyclic ether and formal additives was as follows: nonadditive ∼ 1,3,5‐trioxane ≫ 1,3‐dioxane > 1,3‐dioxolane ≫ 1,4‐dioxane ≫ THP > oxepane ≫ THF ≫ oxetane, propylene oxide ≫ 0. The polymerization in the presence of the cyclic formals was much faster than that of the cyclic ethers: for example, the apparent propagation rate constant k in the presence of 1,3‐dioxolane was 103 times larger than that in the presence of THF. Another series of experiments showed that acyclic ethers with oxyethylene units were effective as additives for the living polymerization with 1/EtAlCl2 initiating system in hexane at 0°C. The polymers obtained in the presence of ethylene glycol diethyl ether and diethylene glycol diethyle ether had very narrow molecular weight distribution (M̄ω/M̄n ≤ 1.1), and the M̄n was directly proportional to the monomer conversion. The polymerization behavior was quite different in the polymerization rates and the MWD of the obtained polymers from that in the presence of diethyl ether. These results suggested the polydentate‐type interaction or the alternate interaction of two or three ether oxygens in oxyethylene units with the propagating carbocation, to permit the living polymerization of IBVE. © 1994 John Wiley & Sons, Inc.
Styrene polymerization with some new macro or macromonomeric azoinitiators having peg units
Authors: Hazer Baki , Erdem Bedri , Lenz Robert W.
Published: April 2003

Several new macroinitiators and macromerinitiators (macroinimers) were synthesized and evaluated for the bulk polymerization of sytrene at 60°C. Macroinitiators were prepared from the reaction of 4,4′‐dicyano‐4,4′ azovaleryl chloride (1) with poly(ethylene glycol) (PEG) with a Mω of 400 and with either benzoyl chloride, acetyl chloride, phenyl isocyanate, or poly(ethylene glycol) oleyl ether. Macromer initiators were also prepared from the reaction of 1 with PEG having Mω values of 200, 400, 600, 1000, or 1500 and with 4‐vinylbenzyl chloride. The bulk polymerization of styrene by macroinimers gave crosslinked styrene‐PEG block copolymers, while the polymerization by macroinitiators gave soluble copolymers. The molecular weights of the styrene‐PEG block copolymers obtained with macroinitiators having either oleyl, benzoyl, or phenyl urethane end groups were 22000–29000 g/mol. DSC measurements showed that the crosslinked block copolymers had crystalline PEG units with melting transitions ranging from 11–37°C. © 1994 John Wiley & Sons, Inc.
High solids content emulsion terpolymerization of vinyl acetate, methyl methacrylate, and butyl acrylate. I. Kinetics
Authors: Urretabizkaia Agustín , Asua José M.
Published: April 2003

The kinetics of the high solids content emulsion terpolymerization of vinyl acetate, methyl methacrylate, and butyl acrylate were investigated. The effect of feed flow rate, total amount of emulsifier, distribution of emulsifier between the initial charge and the feed, concentration of initiator, and solids content on the time evolution of the conversion, terpolymer composition, and total number of polymer particles were investigated. The experimental results were analyzed by means of a mathematical model that incorporated the main features of the system. © 1994 John Wiley & Sons, Inc.
High solids content emulsion terpolymerization of vinyl acetate, methyl methacrylate and butyl acrylate. II. Open loop composition control
Authors: Urretabizkaia Agustín , Arzamendi Gurutze , Unzué María J. , Asua José M.
Published: April 2003

A method for the calculation of the optimal monomer addition policies for polymer composition control in emulsion terpolymerization is developed. The method is applied to reactors with and without limited heat removal capacity. A mathematical model that incorporates the main features of the vinyl acetate/methyl methacrylate/butyl acrylate high solids content emulsion terpolymerization system allows the calculation of the composition of the initial charge of the reactor and the time‐dependent monomer addition rates required. © 1994 John Wiley & Sons, Inc.
Preparation and photoreaction of copolymers derived from N‐(1‐phenylethyl)acrylamide and 7‐acryloyloxy‐4‐methyl coumarin
Authors: Chen Yun , Wu Jehng‐Daugh
Published: April 2003

The copolymers containing photoreactive 4‐methyl coumarin pendant groups have been prepared by radical copolymerization of N‐(1‐phenylethyl)acrylamide (M1) and 7‐acryloyloxy‐4‐methyl coumarin (M2) in DMF at 70°C. The monomer reactivity ratios (MRR) of M1 and M2 are estimated by Finenam‐Ross, Kelen‐Tüdos, Mayo‐Lewis, and YBR methods to be about r1 = 0.12–0.16 and r2 = 1.13–1.28. Dilute dioxane solutions of the copolymers (10−4‐10−5 M of 4‐methyl coumarin chromophores) are first photocrosslinked intramolecularly by irradiating 350 nm light (dimerization of 4‐methyl coumarin) and then photo‐cleaved at 254 nm (symmetric cleavage of cyclobutane). Tracing by an UV‐visible spectrophotometer, it is found that photocrosslinking and photocleavage proceed simultaneously when 254 nm is the light source and finally reaches to a dynamic equilibrium. However, only photocrosslinking can be observed under 350 nm light. Kinetic results show that both photocrosslinking and photocleavage are first‐order reactions. Moreover, photocrosslinking rate constant increases with mole fraction of M2 in the copolymer (F2). On the contrary, rate constant of photocleavage decreases with increasing F2. © 1994 John Wiley & Sons, Inc.
Phase‐Transfer catalyzed free‐radical polymerization of acrylonitrile
Authors: Balakrishnan T. , Arivalagan K.
Published: April 2003

The kinetics of phase‐transfer catalyzed free‐radical polymerization of acrylonitrile (AN) was carried out with water‐soluble initiator peroxomonosulphate (PMS) with phase‐transfer catalysts (tetrabutylammonium chloride and benzyltributylammonium chloride (TBAC and BTBAC) in tolune/water two‐phase systems in the temperature range of 45–55°C at fixed pH (4) and ionic strength. The rates of polymerization (Rp) were evaluated at various values of [PMS], [PTC], and [AN]. It has been observed that the rates of polymerization increase with an increase of [AN], [PMS], and [PTC]. A kinetic scheme has been proposed to account for the experimental observations. © 1994 John Wiley & Sons, Inc.
Analysis of 1H‐NMR spectra of various end‐functionalized polyisobutylenes
Authors: Si Jiaoshi , Kennedy Joseph P.
Published: April 2003

1H‐NMR spectra of various telechelic (i.e., ∼ CH2C(CH3)2Cl, ∼ CH2C(CH3)CH2, ∼ CHC(CH3)2, and ∼ CH2CH(CH3)CH2OH capped) polyisobutylenes (PIB) have been analyzed. The products were prepared by living carbocationic polymerization followed by end‐group functionalization. Shielding and deshielding effects strongly influence the 1H‐NMR spectra of these products. Inductive effects (chlorine‐ended PIBs), magnetically anisotropic end‐groups (olefin groups and phenyl rings), allylic coupling (olefin end‐groups), chirality (hydroxyl end‐groups), and the interaction of these effects on the 1H‐NMR spectra are discussed. Numerous heretofore unidentified resonances have been assigned and better insight into the detailed structure of end‐functionalized PIBs has been obtained. © 1994 John Wiley & Sons, Inc.
Polymer‐supported Ziegler–Natta catalysts. I. A preliminary study of catalyst synthesis
Authors: Sun L. , Hsu C. C. , Bacon D. W.
Published: April 2003

Polymer‐supported Ziegler–Natta catalysts based on various polymer carriers were synthesized by different methods, including (1) loading TiCl4 directly onto the polymer supports; (2) loading TiCl4 onto the polymer supports modified by magnesium chloride (MgCl2); (3) loading TiCl4 onto the polymer supports modified by Grignard reagent (RMgCl); and (4) loading TiCl4 onto the polymer supports modified by magnesium alkyls (MgR2). The activity and kinetic features of the catalysts for ethylene polymerization were examined. Among the combinations tested, the best was found to be TiCl4/n‐Bu2Mg.Et3Al/poly(ethylene‐co‐acrylic acid) (92:8), which produced a catalyst of very high activity for ethylene polymerization. © 1994 John Wiley & Sons, Inc.
Triblock copolymers based on cyclic ethers: Preparation and properties of tetrahydrofuran and 3,3‐bis(azidomethyl) oxetane triblock copolymers
Authors: Hsiue Ging‐ho , Liu Ying‐Ling , Chiu Yie‐Shun
Published: April 2003

Novel energetic thermoplastic elastomers (TPEs) based on tetrahydrofuran (THF) and 3,3‐bis (azidomethyl) oxetane (BAMO) were prepared in this present study by cationic living polymerization. A bifunctional catalyst, triflic anhydride [(CF3SO2)2)O] was selected to be an initiator for the polymerization THF and BAMO. The resulting polymers were characterized by IR, NMR, and DSC, which demonstrated that triblock copolymers with A‐B‐A type were formed. The polymers were indicated from thermogravimetric analysis (TGA) to have decomposed at approximately 243°C. The decomposition enthalpies were determined by DSC. These enthalpies were varied with the poly‐BAMO contents of the copolymers. The synthesized polymers exhibited relatively good mechanical properties and thermoplastic characteristics at room temperature. © 1994 John Wiley & Sons, Inc.
Model prediction of batch emulsion copolymerization as a function of conversion: A sensitivity analysis
Authors: Noël Lilian F. J. , Maxwell Ian A. , Well Willy J. M. Van , German Anton L.
Published: April 2003

Recently a model has been developed capable of predicting absolute monomer concentrations and their ratios in the polymer, aqueous, and monomer droplet phases as a function of conversion in batch emulsion copolymerizations without using any adjustable parameters. In this article the sensitivity of model predictions of composition drift toward deviations of 10% in all model parameters (maximum swellabilities of monomer in the polymer phase, water solubilities, reactivity ratios, and monomer and polymer densities) was estimated using the monomer combination methyl methacrylate‐styrene as an example. From the sensitivity analysis it can be concluded that the reactivity ratios are the most important parameters affecting composition drift. The effects of deviations in maximum swellabilities and monomer and polymer densities on composition drift can be neglected, while the water solubility is important only in those cases where the amount of monomer in the aqueous phase cannot be neglected as compared with the total monomer amount. © 1994 John Wiley & Sons, Inc.
Monodisperse polymer beads as packing material for high‐performance liquid chromotography: Effect of divinylbenzene content on the porous and chromatographic properties of poly(styrene‐co‐divinylbenzene) beads prepared in presence of linear polystyrene as a porogen
Authors: Galia Marina , Svec Frantisek , Frechet Jean M. J.
Published: April 2003

The effect of concentration of divinylbenzene on pore size distribution and surface areas of micropores, mesopores, and macropores in uniformly sized porous poly(styrene‐co‐divinylbenzene) beads prepared in the presence of linear polystyrene as a component of the porogenic mixture has been studied. While the total specific surface area was clearly determined by the content of divinylbenzene, the sum of pore volumes for mesopores and macropores as well as their size distribution does not change within a broad range of DVB concentrations. Consequently, the size exclusion chromatography calibration curves are almost identical for all the beads prepared with different percentages of crosslinking monomer. However, the more crosslinked beads have better mechanical and hydrodynamic properties. © 1994 John Wiley & Sons, Inc.
NMR investigations of the possible cross reactions between cyanate and epoxy resins
Authors: Fyee C. A. , Niu J. , Retting S. J. , Wang D. W. , Poliks M. D.
Published: April 2003

The possible cross reactions indicated by solid‐state NMR between cyanate functionalized resin and epoxy functionalized resin have been investigated by using both natural abundance and labeled monofunctional model compounds. These soluble products were isolated and purified by silica gel adsorption chromatography and gel permeation chromatography. They were fully characterized by high resolution 1H‐, 13C‐, 15N‐NMR spectroscopy and by mass spectrometry. The major cross‐reaction product is a racemic mixture of enantiomers, which contain an oxazolidinone ring formed by one cyanate molecule and two epoxy molecules. However, epoxy consumption lags cyanate consumption in the overall reaction as triazine formation from the cyanate is much faster than the two competing reactions, the cross reaction between cyanate and epoxy, and the self‐polymerization of epoxy, under the conditions investigated. The cross reaction between cyanate and epoxy is limited. Approximately 12% of cross reaction between cyanate and epoxy was found in the overall reaction. In addition to the cross reactions of epoxy and cyanate, the reactions of epoxy and the carbamate, which is the major side product for the curing reaction of cyanate resin in solution, have also been investigated, and the mechanism of these reactions discussed. From the reactions of epoxy and carbamate, several products related to cross reaction between epoxy and cyanate have been isolated and identified. It is suggested that the reaction of epoxy and carbamate is one of the pathways in the overall cross reaction between epoxy and cranate resins. Finally, the mechanism of the overall cross‐curing reaction between the diepoxy and dicyanate mixed resins is discussed. © 1994 John Wiley & Sons, Inc.
Elucidation of mechanism for living radical polymerization of styrene with N,N‐diethyldithiocarbamate derivatives as iniferters by the use of spin trapping technique
Authors: Doi Toru , Matsumoto Akikazu , Otsu Takayuki
Published: April 2003

The photodissociation of several N,N‐diethyldithiocarbamate derivatives (RDC), i.e., benzyl, 1‐phenylethyl, 2‐phenylethyl, n‐butyl, sec‐, and tert‐butyl N,N‐diethyldithiocarbamates, was investigated by the spin trapping technique to elucidate the polymerization mechanism of styrene (St) with RDC as iniferters. The scission of RDC occured at two different CS bonds depending on the structure of the alkyl groups of RDC and the cleavage manner was dominated by both resonance and steric effects. It has been confirmed that RDC generating an N,N‐diethyldithiocarbamyl radical acts as an effective iniferter and induces the living radical polymerization of St in homogeneous system. The polymerizations of St with tetraethylthiuram disulfide and p‐xylylene bis(N,N‐diethyldithiocarbamate) were also discussed on the basis of the results of the spin trapping for RDC as the model compounds of the poly(St) chain ends. © 1994 John Wiley & Sons, Inc.
Determining the chromophore in the amylopectin–iodine complex by theoretical and experimental studies
Authors: Davis Heather , Khan Arshad
Published: April 2003

A partial hydrolysis of amylose followed by the addition of iodine provides a spectrum almost identical to that of the amylopectin–iodine (API) complex suggesting the involvement of smaller “amylose‐like” units in the API complex. Our theoretical studies on different polyiodine and polyiodide species suggest that a nearly linear I4 unit stabilized within the cavity of a small “amylose‐like” helix is responsible for the characteristic API spectrum. Since there are 2.75 anhydroglucose residues (AGU) for every iodine atom in the amylose–iodine (AI) complex and a structural similarity exists between the API and the AI (amylose–iodine) complexes, we identify (C6H10O5)11I4 to be the chromophore in the API complex. © 1994 John Wiley & Sons, Inc.