bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer‐supported lewis acid catalysts. VII. Polystyrene‐bonded Ti(IV) chloride catalysts
Authors: Ran Ruicheng , Fu Diankui , Shen Ji , Wang Qingyang
Published: April 2003

A polystyrene‐bonded Ti(IV) chloride catalyst was synthesized by the reaction of a polystyryl lithium (catalystI, PS—TiCl2) or a polystyryl magnesium (catalystII, PS‐TiCl3) combined with titanium tetrachloride. The catalyst produced is a polymeric organometallic compound containing 0.479 mmol Ti/g catalyst, 0.986 mmol Cl/g catalyst (catalystI) and 0.281 mmol Ti/g catalyst, 0.766 mmol Cl/g catalyst (catalystII), depending on the method of synthesis. Both catalysts showed very good stability and good catalytic activity in such organic reactions as esterification, acetalation, and ketal formation. They can be reused many times without losing its catalytic activity. © 1993 John Wiley & Sons, Inc.
Functionalization and crosslinking reactions of ethyl‐α‐hydroxymethylacrylate
Authors: Avci Duygu , Küsefoğlu Selim H.
Published: April 2003

Ethyl‐α‐hydroxymethylacrylate (EHMA) was esterified with hexanoyl chloride in 80% yield. The homopolymer of the hexanoate ester was found to be a glassy thermoplastic and soluble polymer. Copolymerization of the hexanoate ester with EHMA in varying ratios gave polymers that were thermoplastic and more soluble as a result of internal lubrication of the long alkyl pendant groups. Copolymers with styrene were synthesized with relatively high conversion. Reaction of EHMA with adipoyl chloride gave a bis‐ester which served as crosslinking agent when copolymerized with different monomers including EHMA itself. In a separate synthesis EHMA was reacted with toluenediisocyanate (TDI). In the absence of catalyst a monourethane was formed. This monomer still contains one isocyanate function and is capable of further reactions subsequent to double bond addition polymerization. This reaction was also carried out on poly‐EHMA, with or without catalyst. The products were the mono and the crosslinked bisurethanes as expected. Thus, acyl chlorides and isocyanates were found to be excellent reagents for derivatization of EHMA. © 1993 John Wiley & Sons, Inc.
Microstructural analysis of methacrylonitrile‐styrene copolymers to obtain reactivity ratios
Authors: Hill David J. T. , Dong Limin , O'Donnell James H.
Published: April 2003

The copolymerization of methacrylonitrile (M) and Styrene (S) at 60°C in bulk has been studied at low conversion by the use of 1H‐ and 13C‐NMR to examine the copolymer microstructure for copolymer composition and sequence distribution. The penultimate model was found to provide the best description of the polymerization with rMM = 0.220, rSM = 0.519, rSS = 0.241, rMS = 0.570. These results have been compared with those found for the corresponding acrylonitrile‐styrene copolymerization. © 1993 John Wiley & Sons, Inc.
Polymeric aluminoxanes: A possible cocatalytic support material for Ziegler–Natta‐type metallocene catalysts
Authors: Janiak Christoph , Rieger Bernhard , Voelkel Rüdiger , Braun Hans‐Georg
Published: April 2003

The reaction of methylaluminoxane (MAO) with 1,6‐hexanediol or 1,10‐decanediol leads to white powdery materials which were studied by 13C and 27Al MAS NMR, scanning electron microscopy (SEM), and whose surface area and porosity was determined according to the BET method. The hydrolysis of trimethylaluminum with hydrogel was carried out and the product was investigated by SEM. © 1993 John Wiley & Sons, Inc.
Polymerization of mono‐substituted acetylenes with a liquid crystalline moiety by Ziegler–Natta and metathesis catalysts
Authors: Oh Se‐Young , Ezaki Ryuichi , Akagi Kazuo , Shirakawa Hideki
Published: April 2003

Polymerization of five monomers, 1‐[p‐(trans‐4′‐alkylcyclohexyl)phenoxy]alkyne (i.e., PCH001A, where PCH, 0, 01 and A represent phenylcyclohexyl mesogenic moiety, number of carbon in an alkyl group attached to cyclohexyl group, ether linkage + number of methylenic units in the spacer between phenoxy and acetylenic groups, and terminal acetylene, respectively) were carried out using Ziegler‐Natta and metathesis catalysts. All polymers were soluble in organic solvents such as benzene, chloroform, and THF. A liquid crystalline phase was observed in the polymers of PCH303A and PCH503A through the polarized optical microscope and DSC measurements. Polymerization of PCH003A by the Fe(acac)3‐AlEt3 catalyst yielded a high‐molecular‐weight polymer with Mw = ca. 3 × 106. © 1993 John Wiley & Sons, Inc.
Polymeric phosphonium salts as a novel class of cationic biocides. V. Synthesis and antibacterial activity of polyesters releasing phosphonium biocides
Authors: Kanazawa Akihiko , Ikeda Tomiki , Endo Takeshi
Published: April 2003

Polyesters were prepared which retained phosphonium biocides as counter ions of sodium sulfonate moieties incorporated into the polymers, and surface antibacterial activity of the polyester films against Staphylococcus aureus and Escherichia coli was explored. These films exhibited a high surface antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity was affected by the structure and the compositional ratio of the phosphonium salts. Amount of the released phosphonium salts was very small, so that liberation of the phosphonium biocides can be expected to occur over a long period. Morphological changes of the cells of S. aureus and E. coli in contact with the polyester films were evaluated by scanning electron microscopy. It was found that the surface antibacterial activity of the polyester films was rather bacteriostatic than bactericidal as evidenced by no morphological changes of the bacterial cells in contact with the phosphonium biocides © 1993 John Wiley & Sons, Inc.
Revisiting the design of experiments for copolymer reactivity ratio estimation
Authors: Burke A. L. , Duever T. A. , Penlidis A.
Published: April 2003

Tidwell and Mortimer used the D‐optimal criterion to design terminal model reactivity ratio estimation experiments. In this paper, two problems are investigated which were not addressed by Tidwell and Mortimer. The first problem is the design of reactivity ratio estimation experiments subject to composition constraints. It is shown that all the key information contained in the D‐optimal criterion can be summarized in two equations: one which is a function of r̂1, and one which in a function of r̂2. These two equations can be used to design reactivity ratio estimation experiments under composition constraints which are within 3 mol % of the D‐optimal feed compositions. The second problem is the design of penultimate reactivity ratio estimation experiments. The D‐optimal criterion for the penultimate model was derived and optimized for two existing systems as well as a large number of hypothetical systems. The D‐optimal criterion for the penultimate model was found to be much more complicated than the terminal model criterion. For this reason, the optimal penultimate reactivity ratio estimation experiments can not be approximated by simple equations. Anyone interested in designing such experiments must derive and optimize the D‐optimal criterion. © 1993 John Wiley & Sons, Inc.
Organized‐polymerization in micelle formed by diblock macromonomers
Authors: Ishizu Koji , Yukimasa Shinichi , Saito Reiko
Published: April 2003

Vinylbenzyl‐terminated poly[styrene(S)‐b‐isoprene(I)] AB type diblock macromonomers were prepared by the direct coupling of corresponding living diblock anions with a large excess of p‐chloromethylstyrene (CMS). The end group functionality of these diblock macromonomers was close to unity. Diblock macromonomers showed a narrow polydispersity (M̄w/M̄n = 1.04–1.09). Free radical polymerizations were carried out in micelle formed by diblock macromonomers. We also studied the formation of (AB)n type star block copolymers by means of micro‐gelation between diblock macromonomer and ethylene glycol dimethacrylate as a linking agent. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of poly[arylene ether (N‐arylenebenzimidazole)]s
Authors: Smith J. G. , Connell J. W. , Hergenrother P. M.
Published: April 2003

Poly(arylene ether)s containing N‐arylenebenzimidazole groups were prepared by the aromatic nucleophilic displacement reaction of two new bis(hydroxyphenyl‐N‐arylenebenzimidazole)s with activated aromatic difluorides in sulfolane at 200°C in the presence of anhydrous potassium carbonate. The bis(hydroxyphenyl‐N‐arylenebenzimidazole)s were prepared from bis(o‐aminoanilino) arylenes and phenyl‐4‐hydroxybenzoate. The polymers were soluble in N‐methyl‐2‐pyrrolidinone and m‐cresol and exhibited inherent viscosities from 0.37–0.86 dL/g and glass transition temperatures from 219–289°C. Thermogravimetric analyses showed 5% weight losses from 463–506°C in air and 467–522°C in nitrogen. Unoriented thin films exhibited tensile strengths, moduli, and break elongations at 23°C of 10.2–12.5 ksi, 318–365 ksi, and 4–7%, respectively, and at 177°C of 5.1–6.9 ksi, 256–296 ksi, and 1–5%, respectively. A 50 : 50 random copolymer prepared from 1,3‐bis(4‐fluorobenzoyl) benzene, 1,1'‐(4,4'‐biphenylene)‐bis[2‐(4‐hydroxyphenyl)benzimidazole], and 5,5'‐bis[2‐(4‐hydroxyphenyl)benzimidazole] exhibited higher moisture absorption and lower tensile properties than those predicted by a rule of mixtures relationship. The chemical, physical, and mechanical properties of these polymers are discussed. © 1993 John Wiley & Sons, Inc.‡
Preparation of micron‐size monodisperse polymer particles by dispersion copolymerization of styrene with poly(2‐oxazoline) macromonomer
Authors: Kobayashi Shiro , Uyama Hiroshi , Lee Seog Won , Matsumoto Yasuhiro
Published: April 2003

This article describes the preparation of micron‐size monodisperse polymer particles by dispersion copolymerization of styrene with a poly(2‐oxazoline) macromonomer in an aqueous ethanol solution. The macromonomer acted as a comonomer as well as a stabilizer. The diameter of the particles increased as the concentration of the macromonomer decreased. The higher the molecular weight of the macromonomer, the smaller the particle size. The copolymerization in the solvent containing higher water content gave smaller polymer particles. Under the condition giving the monodisperse particles, the particles volume increased linearly with the yield of the particles. From ESCA analysis of the particle surface, poly(2‐oxazoline) chains were enriched on the surface. © 1993 John Wiley & Sons, Inc.
Synthesis, characterization, and thermal studies of cardanol‐based polyphosphate esters
Authors: Antony Rosy
Published: April 2003

Polyphosphate esters were synthesized from derivatives of cardanol phosphorodichloridateates and dihydric phenols by interfacial polycondensation using a phase transfer catalyst. The polymers were characterized by IR, 1H‐, 13C‐, and 31P‐NMR spectroscopy, and GPC. The thermal stability and thermal degradation kinetics of the polymers were determined by thermogravimetry. The flammability of the polymers was evaluated by limiting oxygen index values. © 1993 John Wiley & Sons, Inc.
Anionic ring‐opening polymerization of several N‐substituted diphenimides
Authors: Pyriadi Thanun M. , Ahmad Abbas F.
Published: April 2003

Five N‐substituted diphenimides were prepared from the corresponding N‐substituted amic acids. Attempts to polymerize the prepared seven‐membered ring imides were partially successful. N‐phenyldiphenimide was relatively the best monomer that polymerized anionically using n‐butyl lithium or sodium metal as the initiater. The other N‐substituted imides were sluggish in anionic polymerization. The resistance of the seven‐membered ring imides toward ring‐opening polymerization was attributed to the stability of the rings caused by the two phenylene groups adjacent to the carbonyls. © 1993 John Wiley & Sons, Inc.
Effect of the poly(oxytetramethylene)diol spacer length on some properties of liquid crystalline polyurethanes
Authors: Szczepaniak Barbara , Frisch Kurt C. , Penczek Piotr , Mejsner Jerzy , Leszczyńska Irena , Rudnik Ewa
Published: April 2003

Previous studies on liquid crystalline polyurethanes prepared from 4,4′‐bis(2‐hydroxyethoxy)biphenyl (BHBP) and 2,4‐tolylene diisocyanate (TDI) were continued. In this article, a series of polyurethanes, which differ in the flexible spacer length and BHBP content is described. Poly(oxytetramethylene)diols of different molecular weights (PTMO, Mn = 250, 650, 1000, 2000) were used as flexible spacers. The polyurethanes were investigated by DSC, polarizing microscopy, x‐ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. The morphology of the polyurethanes was investigated by the SALS method. Partial replacement of BHBP by 25–75 mol % PTMO and the flexible spacer length influence the liquid crystalline properties, the phase transition temperatures, and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc.
Structural characterization of ethyl cellulose and its use for preparing polymers with viologen moieties
Authors: Liu Fu‐Tian , Yu Xian‐Da , Li Shu‐Ben
Published: April 2003

The characteristics of ethyl cellulose (EC) were studied by chemical reaction and the spectra method. EC was first tosylated with tosyl chloride, and then the tosylated EC (Ts‐EC) reacted with sodium iodide (NaI). By comparing the NMR spectra of EC and iodine‐substituted EC (EC‐I), a free hydroxyl group was proved to exist at the C‐6 of the D‐glucose unit of cellulose. Viologen moieties were introduced into the EC chain by the reaction of Ts‐EC with 4,4′‐bipyridine and n‐propyl bromide. The existence of viologen was confirmed by 1H‐NMR, IR, and ESR. © 1993 John Wiley & Sons, Inc.
Synthesis of monodisperse poly(divinylbenzene) microspheres
Authors: Li Kai , Stöver Harald D. H.
Published: April 2003

Highly crosslinked monodisperse poly(divinylbenzene) microspheres were produced by precipitation polymerization with acetonitrile as solvent. The radical initiators AIBN, BPO, and ADVN were used. The process does not require stabilizers of any type, and produces monodisperse particles with diameters between 2 and 5 μm, depending on the conditions. These microspheres do not swell or dissolve in any common solvent, and have clean, stabilizer‐free surfaces. The particle formation and growth mechanism is proposed to resemble that of dispersion polymerization, except that the particles are stabilized against coagulation by their rigid, crosslinked surfaces rather than by added stabilizers. Spherical particles were formed only at effective crosslinker/monomer or divinyl/monovinyl ratios larger than 1 : 2. © 1993 John Wiley & Sons, Inc.
Functionalization of polyethylene surface using plasma‐induced graft copolymerization of acrylic acid
Authors: Hsiue Ging‐Ho , Wang Chee‐Chan
Published: April 2003

Plasma‐induced graft copolymerization of acrylic acid onto PE films was investigated. The influence of plasma treatment power, pressure, time, graft copolymerization time, and monomer concentration on polymerization yield was determined. A chemical shift of the Cls signal of Ar plasma treated and untreated PE films was revealed by ESCA, which also verified the presence of grafted PAAc. An increase in graft polymerization yield with plasma treatment time and power was found. Both the plasma treated film and the subsequently grafted film were shown to be hydrophilic. Only the grafted film, however, shows an invariably low contact angle. The decomposition of peroxides upon heating was followed by a simple first‐order reaction. © 1993 John Wiley & Sons, Inc.
Synthesis of novel polysilylenes bearing phenol groups directly bonded to SiSi main chains for preparing Langmuir–blodgett thin films
Authors: Nakano Y. , Murai S. , Kani R. , Hayase S.
Published: April 2003

Polysilylenes with a phenol group directly bonded to the main chain Si atom were prepared by polymerizing dichlorosilane monomers bearing phenol groups protected by t‐butyldimethylsilyl ether, followed by deprotecting the silyl ether. These amphiphilic polysilanes were applied to provide oriented thin films by the Langmuir‐Blodgett technique. Stable monolayers were not obtained for polysilylenes having only alkyl and aryl substituents. However, all the polysilylenes with phenol moieties provided monolayers on a water surface. These polysilylene monolayers were transferred to hydrophobic substrates by applying the Langmuir‐Blodgett technique. Among these polysilylenes, only poly(n‐butyl‐3‐hydroxyphenylsilylene) provided multilayers in which the SiSi main chains oriented in the dipping direction. The orientation was determined by polarized UV absorption. The orientation ratio reached 0.45. © 1993 John Wiley & Sons, Inc.
Macrothiuram disulfide for the free radical synthesis of PDMS‐vinyl triblock copolymers. I. Syntheses and polymerization kinetics
Authors: Clouet G. , Kayser D.
Published: April 2003

PDMS‐based macrothiuram disulfides of different molecular weights capable of being used as macro‐thermal iniferters towards deriving PDMS‐containing triblock copolymers were synthesized and characterized. The synthesis of ω‐(secondary amine)‐terminated PDMS were accomplished by the hydrosilylation reaction of silyl hydride terminated PDMS with allyl‐N‐methylamine. Macroamines were eventually transformed to macroiniferters by the thiocarbamylation reaction and oxidative coupling. Kinetics of polymerization studied in the case of MMA and styrene in bulk, and as in toluene solution in case of MMA, revealed that the macroiniferters are as efficient as their microanalogues from the point of view of their initiating and chain‐terminating properties. The different kinetic parameters were determined and discussed. © 1993 John Wiley & Sons, Inc.
A kinetic study on grafting of maleic anhydride onto a thermoplastic elastomer
Authors: Wu Chung‐Jen , Chen Chuh‐Yung , Woo Eamor , Kuo Jen‐Feng
Published: April 2003

Maleation of a thermoplastic elastomer, styrene‐[ethylene‐butylene]‐styrene (SEBS) triblock copolymer, was carried out by a solution grafting reaction with maleic anhydride initiated by dicumyl peroxide. The reaction products from the graft reaction in xylene, commonly chosen as the solvent for maleation graft reactions, were identified using liquid chromatograph (LC), IR, and 13C‐NMR. Side products from the graft reaction were identified by the LC analysis and, it was concluded that xylene affected the graft reaction through its active methyl groups. Reaction mechanisms were investigated by performing free radical kinetics analysis. The reaction orders and the apparent rate constant were estimated. It was concluded that a proper choice of the solvent might favor better graft efficiency. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of new block copolymers based on polydimethylsiloxane and tetraphenylethylene‐containing polyimide
Authors: Nakata Shoichi , Kawata Masatoshi , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

New polydimethylsiloxane (PDMS)‐polyimide block copolymers were synthesized by the solution polycondensation of aminopropyl‐terminated polydimethylsiloxane, 1,1‐bis(4‐aminophenyl)‐2,2‐diphenylethylene, and 3,3′,4,4′‐benzophenonetetracarboxylic dithioanhydride in pyridine. New 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (BADS)‐based random copolyimides were also prepared. The inherent viscosities of all the random and block copolyimides were in the range of 0.13–0.90 dL/g in N‐methyl‐2‐pyrrolidone. These copolymers were soluble in N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone, and m‐cresol. All the BADS‐based random copolymers and PDMS‐containing copolymers with PDMS content above 42 wt % were soluble in tetrahydrofuran and chloroform. Transparent or somewhat cpaque films were prepared by casting from the reaction solutions. The BADS‐based random copolyimides had one glass transition temperature (Tg) in the whole composition ranges, which showed single phase nature of the copolymers. On the other hand, the PDMS‐polyimide block copolymers had double TgS, indicating phase‐separated morphology. The block copolymers containing PDMS content above 73 wt % behaved like a high temperature elastomer. © 1993 John Wiley & Sons, Inc.
Perfluorocyclobutane aromatic ether polymers
Authors: Babb David A. , Ezzell Bob R. , Clement Katherine S. , Richey W. Frank , Kennedy Alvin P.
Published: April 2003

Novel polymers containing alternating perfluorocyclobutane and aromatic ether subunits are prepared from aryl poly(trifluorovinyl ether) monomers via the thermal [2π + 2π] dimerization of the trifluorovinyl ether functionality. A model study is described, which probes the nature of the perfluorocyclobutane rings formed during the polymerization reaction. The bifunctional monomer 4,4′‐bis(trifluorovinyloxy) biphenyl and the trifunctional monomer 1,1,1‐tris(4‐trifluorovinyloxyphenyl)ethane are prepared and polymerized to provide thermoplastic and thermoset polymers, respectively. Characterization of the mechanical and dielectric properties of these new polymers is presented. © 1993 John Wiley & Sons, Inc.
PCILO and CNDO calculations on the specific interaction in two model analogs of BPA‐polycarbonate and a linear aliphatic polyster
Authors: Mora M. A. , Rubio M. , Cruz‐Ramos C. A.
Published: April 2003

Previous investigations have given evidence of the existence of specific chemical interactions between poly(bisphenol‐A carbonate) (PC) and a number of linear aliphatic polyesters, with the consequent formation of compatible polymer alloys. Here we address the particular kind of specific interaction that takes place in these systems by performing a quantum‐mechanical study of the apparently most reasonable types of molecular interactions occurring in model compounds of the above polymers. Complete neglect of diffential overlap, (CNDO), in its CNDMEX version, and perturbative configuration using localized orbitals (PCILO) were the calculation schemes used on diphenyl carbonate (DPC) and dimethyl succinate (DMS), selected as models. It was found that, on a one‐to‐one basis, the DPC‐DMS system is energetically more stable than the individual separate molecules; on examination of the possible interaction sites for the two chemical species, the interaction between the ester group oxygen in one DMS molecule with one of the phenyl rings in DPC appears to be the most favorable type of molecular interrelation, even though hydrogen bond formation is also possible between the oxygen atoms in DPC and the methylene hydrogens in DMS. (The former interaction decreases the total energy of the system by 0.12 kcal/mol, more than the latter.)
Rutherford backscattering spectrometry studies of iodine diffusion in polyimide
Authors: Romanelli J. F. , Mayer J. W. , Kramer E. J. , Russell T. P.
Published: April 2003

Rutherford backscattering spectrometry with a 2.1‐meV He2+ion beam is used to measure the diffusion of iodine into polyamic acid and polyimide films. The iodine diffusion coefficient D decreases from its initial value of about 2X10−13cm2/s in polyamic acid to approximately 1.4 × 10−15cm2/s in partially cured polyimide, but then increases to a value of nearly 1.5 × 10−14 cm2/s in fully cured polyimide. This dramatic increase in D cannot be attributed to the “in‐plane” biaxial orientation of the polyimide molecules since indential D's were found with isotropic specimens. Microvoids less than 2 nm in size caused by water and carbon dioxide formation during imidization may, however, give rise to the observed behavior. The results demonstrate that Rutherford backscattering spectrometry with its excellent depth resolution (better than 30 nm) and good sensitivity (50 ppm iodine can be detected) is very useful for measuring the diffusion of slowly diffusing species in glassy polymers.
Light‐scattering studies on the sol–gel transition in aqueous solutions of poly(vinyl alcohol)
Authors: Komatsu Motoko , Inoue Takashi , Miyasaka Keizo
Published: April 2003

The dynamics of the sol–gel transition in aqueous solutions of poly(vinyl alcohol) was investigated by light scattering. The dynamical studies confirmed that this system has an upper critical solution temperature. In the phase diagram, the spinodal curve crosses the sol–gel transition curve. Essentially this is nothing but the situation predicted by Coniglio et al. as a result of the site‐bond correlated‐percolation problem. The gelation takes place both above and below the spinodal curve, suggesting two modes of gelation: one is accompanied by a spinodal decomposition and the other takes place without liquid–liquid phase separation. In the former case, the dynamics of phase separation at an early stage of gelation is well described within the framework of Cahn's linearized spinodal decomposition theory. The wavelength of the concentration fluctuation at the highest rate of phase separation is about 300 nm.
A dielectric study of poly(ethylene‐co‐vinyl acetate)–poly(vinyl chloride) blends. II. Loss curve broadening and correlation parameters
Authors: Rellick G. S. , Runt J.
Published: April 2003

Normalized dielectric loss curves for blends of PVC with an EVA copolymer containing 70% vinyl acetate showed significant broadening with increasing PVC content. In conjunction with phase separation studies it was concluded that increasing loss curve broadness correlated with increasing tendency toward phase separation. Calculation of correlation parameters for the blends revealed differences in intermolecular correlations with blend composition.
Influence of static strain on dynamic mechanical behavior of amorphous networks prepared from aromatic polyesters
Authors: Diaz‐Calleja R. , Riande E. , Guzman J.
Published: April 2003

Dynamic mechanical experiments were performed between −140 and 50°C on both poly(diethylene glycol isophthalate) and poly(triethylene glycol terephthalate) networks. Plots of loss tangent versus temperature show a well‐defined α peak, associated with the transition from glasslike to rubberlike consistency, and two overlapping peaks (β1 and β2) in the glassy region. Dynamic deformations of small amplitude were superimposed on large static deformations. It was found that the position of the β1 and β2 peaks as well as their intensities are independent of the static elongation ratio. However, the intensity of the loss tangent associated with the glass–rubber transition tends to decrease with increasing static deformation. Moreover, the position of the maximum of the α peaks shifts to lower temperatures as the elongation ratio increases. This behavior suggests that for both networks the volume effects (shifting the α peaks to lower temperatures with increasing elongation ratio) overcome the entropic effects (shifting the α peaks to higher temperatures with decreasing entropy).
Axial force fluctuations in long‐chain molecules
Authors: Weiner J. H. , Berman D. H.
Published: April 2003

The fluctuations Δf in the axial force f acting on a long‐chain molecule whose end‐to‐end displacement r is fixed are computed for a freely jointed model in which the covalent bonds are represented by stiff linear springs. It is found that the relative fluctuation Δf/f remains large regardless of the length of the chain. A time‐dependent computer simulation of the model serves both to verify the theoretical calculation of Delta;f and to provide physical insight. The result helps to clarify the difference in behavior of the strain ensemble (r is fixed and f fluctuates) and the stress ensemble (f is fixed and r fluctuates) for which, in the absence of excluded volume, the strain ensemble predicts that f = 0 for r = 0, while for the stress ensemble with f = 0 it is found that 〈r2〉0 > 0.
Solute and penetrant diffusion in swellable polymers. I. Mathematical modeling
Authors: Korsmeyer Richard W. , Lustig Steven R. , Peppas Nikolaos A.
Published: April 2003

A mathematical model was developed to describe diffusion of a penetrant and a solute in a swellable polymer slab. The model was applied to the case of a hydrophilic polymer loaded with a soluble bioactive agent, in which the penetrant (water) is sorbed and solute is desorbed. The model allows the incorporation of any appropriate form of the diffusion coefficients. A Fujita‐type exponential dependence on penetrant concentration was chosen and shown to be adequate for prediction of a range of transport behavior. Dimensional changes in the sample were predicted by allowing each spatial increment to expand according to the amount of penetrant sorbed. During the initial period of release, the swelling was restricted to one dimension by the glassy core of the sample. At a later point in the process, the center of the sample had sorbed enough penetrant to plasticize it, and the sample relaxed to an isotropically swollen state; thereafter swelling was three‐dimensional.
Concurrent chain extension and crosslinking of hydroxyl‐terminated poly(dimethyl siloxane): Possible formation of catenate structures
Authors: Rigbi Z. , Mark J. E.
Published: April 2003

Difunctional and tetrafunctional ethoxysilanes in varying proportions were used to simultaneously chain‐extend and crosslink dihydroxyl‐terminated poly(dimethyl siloxane). When only dimethyl deithoxysilane was used an insoluble product, possibly a catenate, was formed. Its swelling behavior was equivalent to that of a tetrafunctional network obtained by end‐linking chains approximately twice as long as those actually used.
Studies on the β‐crystalline form of isotactic polypropylene
Authors: Jacoby P. , Bersted B. H. , Kissel W. J. , Smith C. E.
Published: April 2003

A study has been made of the mechanical, thermal, and morpholigical characteristics of melt‐crystallized isotactic polypropylene containing high levels of the β or pseudohexagonal crystalline form. Different levels of β‐form crystallinity were produced in the polymer by blending in low levels of quinacridone dye nucleating agent. Microscopical studies of the crystallization process revealed that both α‐form (monoclinic), and β‐form spherulites nucleated on the dye particles, with α‐spherulite growth commencing at a higher temperature. These observations were able to qualitatively explain the dependence of β‐form level on both the nucleant concentration and its state of dispersion in the polymer. Improving the dispersion of the nucleant was found to reduce the level of β‐form crystallinity if the nucleant concentration exceeded an optimum level. A new procedure for quantifying the volume fraction of β spherulites in a sample was developed which utilized the technique of selective solvent extraction. From volume‐fraction, x‐ray, and density data, the pure α and β crystal densities were obtained. Dynamic mechanical measurements‐obtained on unoriented specimens containing varying levels of β‐form crystallinity showed an increase in the magnitude of the damping in the post‐Tg region with increasing β content. High levels of the β form lead to lower values of the modulus and yield stress, and higher values of the elongation at break and impact strength.
On the theory of dilute polyelectrolyte solutions: Extensions, refinements, and experimental tests
Authors: Davis R. M. , Russel W. B.
Published: April 2003

We synthesize a quantitative theory for the radius of gyration, second virial coefficient, intrinsic viscosity, and friction coefficient for polyelectroytes in dilute solution from existing treatments of electrostatic and hydrodynamic interactions within and among wormlike chains. Comparison with data for K‐PSS demonstrates the importance of accounting for nonlinearities in the electrostatics and the finite diameter of the polymer backbone.
Molecular segregation and nucleation of poly(ethylene oxide) crystallized from the melt. I. Calorimetric study
Authors: Cheng Stephen Z. D. , Wunderlich Bernhard
Published: April 2003

Thermal analysis is used to elucidate the fusion of fractions of poly(ethylene oxide) of from 3500 to 5000000 molecular weight. In addition, the equilibrium and nonequilibrium phase diagrams of binary mixtures of these fractions have been studied. Complete segregation from high‐molecular‐weight polymer is possible up to at leat 20000 molecular weight. This segregation is not governed by the melting/crystallization equilibrium, but rather by molecular nucleation. Over a broader crystallization temperature range three regions can be identified. At low crystallization temperature, solid solutions result, at higher temperature one finds an intermediate type of crystallization, and ultimately one reaches complete, eutectic segregation. This work will be followed by analysis of the kinetics of crystallization.
Molecular segregation and nucleation of poly(ethylene oxide) crystallized from the melt. II. Kinetic study
Authors: Cheng Stephen Z. D. , Wunderlich Bernhard
Published: April 2003

A kinetic study of crystallization of fractions of poly(ethylene oxide)s between 3500 and 5,000,000 MW and their mixtures from the melt by differential scanning calorimetry and optical microscopy is reported. For the fractions the crystal growth rate is inversely dependent on the logarithmic molecular weight. Binary mixtures of widely different molecular weights show mixed‐crystal formation at low crystallization temperature described by a single Avrami equation with exponent 3. At higher temperature, increasing segregation takes place despite higher deposition probabilities of the low molecular weight. Two consecutive Avrami equations describe the crystallization. Before the equilibrium melting temperature of the low molecular weight component is reached, complete segregation occurs. This segregation is possible up to at least 20,000 MW. Classical crystallization theory is unable to describe the process. Molecular nucleation seems a viable alternative for the description of crystallization of both fractions and mixtures. Reversibility of crystallization is on a one‐molecule scale and reaches thermodynamic reversibility as the molecular length approaches monomer size.
Equation of state of copolymer melts: The poly(vinyl acetate)–polyethylene pair
Authors: Zoller Paul , Jain R. K. , Simha R.
Published: April 2003

The pressure—volume—temperature properties of a series of copolymers ranging in content from 18 to 40 wt % of vinyl acetate, and up to a maximum pressure of 1800 kg/cm2 are studied. The results for the melt state can be satisfactorily fitted by the scaled equation of state, developed previously and applied to single‐component systems and to mixtures. The dependence of the scaling parameters for the copolymers on composition deviates from that expected for a mixture, where volumes at elevated pressures can be predicted without further recourse to experiment. These differences are discussed in terms of the sequential structure of the copolymer chain and its series of interfaces between the two species.
Effect of doping on thermoluminescence in polymers. I. 9,10‐phenanthrenequinone‐doped polydiancarbonate
Authors: Vanderschueren J. , Linkens A. , Niezette J.
Published: April 2003

The thermoluminescence (TL) and thermally stimulated depolarization currents (TSDC) observed in polycarbonate doped with 9,10‐phenanthrenequinone (PhQ) have been compared in order to test to what extent the TL phenomenon can be correlated with intrinsic relaxation properties of the macromolecular chains. Good qualitative agreement has been found between the two types of curves, showing that the two TL peaks appearing at about 140 and 185 K are attributable to untrapping of electrons induced by the onset of local motions. However, the values and distribution of the activation energies determined by the two techniques differ markedly. The apparent activation energy deduced from TL data presumably reflects the energy level of traps decreased by molecular motions rather than the thermal energy of these relaxations. The primary process responsible for light emission is related to a transition of the n‐π type occurring in PhQ at 420 nm, while the trapping sites are probably formed by carbonate groups of the polymeric matrix. The same trapping mechanism has been postulated for the two TL peaks on the basis of their parallel evolutions as a function of dose and dopant concentration.
Composition dependence of glass transition temperature of sulfonated‐polystrene ionomers
Authors: Mattera Vincent D. , Risen William M.
Published: April 2003

The glass transition temperatures of alkali (Na, K, Rb, Cs) and alkaline‐earth (Ba, Sr, Ca, Mg) ionomers of sulfonated polystyrenes (PSSA) with 3.4, 6.9, 12.7, and 16.7% of the styrene moieties sulfonated are reported. For the alkali‐metal PSSA ionomers, Tg depends on the degree of sulfonation, at least up to 13%, but not strongly on the nature of the cation. For the alkaline‐earth analogs Tg does not depend strongly on either the cation or the degree of sulfonation until the 16.7% level is reached. These and other reported data are discussed in terms of the role of cations in determining morphology.
Dual‐mode analysis of subatomspheric‐pressure CO2 sorption and transport in Kapton H polyimide film
Authors: Uragami T. , Hopfenberg H. B. , Koros W. J. , Yang D. K. , Stannett V. T. , Chern R. T.
Published: April 2003

Sorption kinetics and equilibria as well as permeabilities and diffusion time lags for CO2 in Kapton polyimide film have been studied at temperatures from 35 to 55°C and pressures up to 0.78 atm. The sorption/desorption cycles indicate that the diffusivity of CO2 increases with increasing local penetrant concentration in the polymer. Both the permeability and time lag decrease with increasing upstream CO2 pressure. All of these results are described well by theoretical expression based on the dual‐mode theory of sorption and transport in glassy polymers.
Demixing and gelation behavior of ternary cellulose acetate solutions
Authors: Reuvers A. J. , Altena F. W. , Smolders C. A.
Published: April 2003

The demixing behavior on cooling of ternary systems of cellulose acetate/solvent/water has been examined for CA concentrations up to 40 wt% CA in several solvents. Cloud points have been measured as a function of cooling rate. The rapid process of liquid—liquid demixing can be discriminated from the slow process of aggregate formation by examining the dependence of the cloud point on the cooling rate and by structure analysis of quenched solutions with scanning electron microscopy. The appearance of aggregate formation depends strongly on the type of solvent. Slow cooling of ternary solutions in which acetone is the solvent leads to aggregate formation long before liquid—liquid demixing occurs.

In addition, isothermal sol—gel transitions have been measured for quenched solutions at varying gelation times. It is concluded that gelation is not always preceded by aggregate formation.
Reversible and irreversible variation of the superstructure of highly oriented low‐density polyethylene during heat treatment
Authors: Fronk W. , Wilke W.
Published: April 2003

The small‐angle x‐ray scattering (SAXS) intensity of highly‐oriented, low‐density polyethylene (LDPE) with fixed draw ratio has been investigated during several heating and cooling cycles. Using a three‐dimensional, monoclinic, paracrystalline superlattice to describe the superstructure of the sample, it has been possible to calculate the SAXS patterns completely. A very large irreversible variation of the superstructure during the first heating cycle, and a smaller reversible variation of the average size and distance of the crystallites during subsequent temperature cycles, could be obtained. These results can be explained using the thermodynamic theory of crystallization of polymer multicomponent systems of Kilian.
Small‐angle x‐ray scattering studies of thermally‐induced morphological changes in segmented polyurethane elastomers
Authors: Gibson P. E. , Van Bogart John W. C. , Cooper Stuart L.
Published: April 2003

The effect of temperature on the morphology of a series of polyether and polyester polyurethanes has been studied using small‐angle x‐ray scattering. Scattering curves were obtained in situ at high temperature (90 and 150°C) and also later at room temperature to study the effects of thermal history on the materials. In general, annealing improves the degree of phase separation and increases the hard domain size in the materials studied. Annealing improves the degree of phase separation in more compatible systems to a greater degree than in less compatible systems. Increased interfacial mixing is apparent in the materials studied in situ at high temperatures. Thicker interfacial regions are also present in the annealed material relative to the control.
Ferroelectric switching characteristics of 73/27 copolymer of vinylidene fluoride and trifluoroethylene
Authors: Jimbo Masashi , Fukada Tomohiro , Takeda Hiromi , Suzuki Fuminao , Horino Kaoru , Koyama Kiyohito , Ikeda Susumu , Wada Yasaku
Published: April 2003

Ferroelectric polarization‐reversal switching of vinylidene fluoride—trifluoroethylene copolymer with 73 mol % of vinylidene fluoride is investigated under a variety of conditions in an attempt to derive detailed information on the polarization reversal of the polymer. The electric‐field dependence of switching time ts obeys an exponential law. The temporal change of switching current density J is presented in the form J/(Ps − P) versus time (P is the polarization, and Ps is its saturation value), which is free of the depolarization‐field effect and discriminates in a straightforward manner between acceleration and deceleration of switching. Effects of the annealing of samples upon ts are observed together with changes in the degree of crystallinity. Effects of space charge distribution upon ts are investigated by applying two successive pulses, positive and negative, with varied intervals tw between the two. The dynamics of space charge redistribution is elucidated from the tw dependence of the ts of the second pulse. The temperature dependence of ts indicates that the switching becomes critically fast as the phase‐transition temperature is approached.
Block copolymers of poly(ethylene terephthalate–polybutylene terephthalate). I. Preparation and crystallization behavior
Authors: Misra A. , Garg S. N.
Published: April 2003

Block copolymers of two crystallizable compounds, poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), were developed with PET as the major component and the amount of PBT varying from 1.0 to 20.0 wt %. These block copolymers were prepared by end‐group coupling of preformed oligomers. All polymers prepared were of equivalent molecular weight as determined by the intrinsic viscosity method. Thermal properties were determined by differential thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). With increasing PBT content, the block copolymers showed a general decrease in the values of glass transition temperature, melting temperature, initial decomposition temperature, and maximum decomposition temperature. The heat of fusion and heat of crystallization first increased and then decreased slightly. Rates of crystallization were determined by measuring density as a function of time of isothermal crystallization carried out at 95°C. It was found that small amounts of PBT increased the crystallization rate considerably over that of PET. Random copolymers did not show this phenomenon and behaved more like pure PET. The crystallization behavior of block copolymers was analyzed by the Avrami equation and Avrami exponents were determined. Results were explained on the basis that the faster‐crystallizing PBT blocks crystallized first and provided built‐in nucleation sites for the subsequent crystallization of PET, thus resulting in a relatively fast‐crystallizing copolyester.
Infrared and raman spectroscopy of stressed polyethylene
Authors: Wool R. P. , Bretzlaff R. S. , Li B. Y. , Wang C. H. , Boyd R. H.
Published: April 2003

Polyethylene films were stressed in uniaxial tension at room temperature while the infrared (FTIR) or Raman spectra were simultaneously measured. The purpose of these experiments was to gain an understanding of the molecular origins of the stress‐induced vibrational frequency shifts Δν and determine the mechanisms of molecular deformation and fracture of PE molecules with stress σ. The PE samples consisted of ultradrawn, high‐density, ultrahigh‐molecular‐weight, solid‐state‐extruded films and the stress was applied parallel to the nearly perfectly oriented orthorhombic crystal c‐axis direction. The experimental frequency shifting coefficients α = (∂ν/∂σ)σ→0 were compared with calculated α values determined from a vibrational analysis of an isolated PE chain using conformational energy minimization methods in which both harmonic and anharmonic (Morse) potential energy functions were used for the CC stretching modes in the valence force field. The following α values were obtained and are compared with theory (anharmonic case in parentheses, in cm−1/GPa): CC symmetric stretch, α(1127) = −5.9 (−5.3); CC asymmetric stretch, α(1059) = −11.2 to −5.7 (−5.8); CH2 rock, α(730/720) = −2.0 to −3.0 (−2.2); CH2 scissors, α(1472/1462) = −1.0 to −1.2 (−1.1); CH2 twist, α(1295) ≃ 0(0.8); CH2 wag, α(1370) undetermined owing to weak bands (−4.6); CH2 stretch α(3000) ≈ 0. The largest negative frequency shifts were observed for the CC stretching modes, in agreement with the calculations using the Morse potential. The harmonic potential for CC stretching resulted in small positive α values for both the CC stretching and CH2 wagging modes, while the other modes were unaffected by this choice of potential. The relative contribution of CC bond stretching and CĈC valence angle bending to the c‐axis strain was about 1:1, in agreement with experiment. The Young's tensile modulus of a PE chain was calculated as Ec = 267 GPa.
Molecular analysis of the crystallization behavior of poly(aryl‐ether‐ether‐ketone)
Authors: Nguyen Huy X. , Ishida Hatsuo
Published: April 2003

The crystallization behavior, via annealing, of PEEK was investigated using FTIR spectroscopy. It was found that predominantly amorphous PEEK (e.g., quenched polymer) follows two distinct mechanisms when it is annealed. One is a lower energy relaxation process that involves the partial rotation of the ether linkages, allowing the molecular chains in the disordered phase to become better packed, and occurs from 50 to 140°C (slightly belowTg). This relaxation process is also observed by dynamic mechanical analyses. The other process is a crystallization that takes place above the glass transition, with its onset characterized by the rotation of the benzophenone linkages nearTg. Isothermal crystallization kinetics data on PEEK can be described by an Avrami equation with an Avrami constantnof about 1.
The physical properties of bisphenol‐A‐based epoxy resins during and after curing
Authors: Choy In‐Chul , Plazek Donald J.
Published: April 2003

A series of epoxy resins derived from diglycidyl ethers of bisphenol A with differing initial linear molecular chain lengths have been studied during and after curing with the diamines MDA (4,4′‐methylene dianiline) and DDS (4,4′‐diamino diphenyl sulfone). The properties that were measured during curing were the volume, the fictive temperature Tf, the gel fraction, the viscosity, and the equilibrium compliance. Graphs of Tf as a function the time of curing tc obtained at four curing temperatures between 40 and 100°C have been reduced to a common curve. After curing, creep compliance curves J(t) were determined which characterize the viscoelastic response from the glassy compliance level to a rubbery equilibrium compliance level. The change in properties that occurs during the time‐dependent spontaneous densification below the glass temperature Tg was monitored with repeated measurements of J(t). Time‐scale shift factors as a function of volume contraction obtained during this physical aging below Tg were reduced to a common curve.