bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Enzymatic Degradation of Microbial Polyesters by Plasma Modification
Authors: Ryou Jin‐Ho , Ha Chang‐Sik , Kim Jae‐Won , Lee Won‐Ki
Published: February 2003

The rate of enzymatic degradation of surface‐modified microbial polyesters, poly[(R)‐3‐hydroxybutyrate] and poly[(R)‐3‐hydroxybutyrate‐co‐3‐hydroxyvalerate], was studied. The plasma treatments were carried out in a CF3H or O2 environment. It was found that the CF3H plasma‐treated polyesters exhibited significant retardation of enzymatic erosion because of the surface fluorocarbon groups induced by CF3H plasma. These surface fluorocarbon groups act as retardants on enzymatic degradation due to increased hydrophobicity and of the inactivity of enzymes. However, the increased surface hydrophilicity of polyesters induced by O2 plasma results in no significant acceleration of the enzymatic erosion, which may be due to the thin modified layer.

Weight loss profiles of P(3HB) film exposed to CF3H plasma as a function of plasma exposure time.

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Weight loss profiles of P(3HB) film exposed to CF3H plasma as a function of plasma exposure time.
Synthesis and Characterization of Amphiphilic Biodegradable Copolymer, Poly(aspartic acid‐co‐lactic acid)
Authors: Shinoda Hosei , Asou Yukiko , Suetsugu Akio , Tanaka Kimiko
Published: February 2003

An amphiphilic biodegradable polymer, poly(aspartic acid‐co‐lactic acid) (PAL), was synthesized by simply heating a mixture of aspartic acid (Asp) and L‐lactide without additional catalysts or solvents. The unique branched architecture comprising succinimide units and lactic acid units was confirmed by IR and NMR spectroscopy. A copolymer of sodium aspartate and lactic acid (PALNa) was prepared by reacting PAL with an aqueous sodium hydroxide solution. The PAL was soluble in many organic solvents, while the PALNa was soluble in methanol and water. The hydrolytic degradation behavior of PAL varied with the copolymer composition. A higher Asp content resulted in a faster molecular weight decrease, and introducing glycolic acid units accelerated the degradation rate.

Microphotograph of microsphere of PAL‐1/5.

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Microphotograph of microsphere of PAL‐1/5.
Surface Hydrophilicities and Enzymatic Hydrolyzability of Biodegradable Polyesters, 2
Authors: Tsuji Hideto , Ishida Takuya
Published: February 2003

Control of the surface hydrophilicities and enzymatic hydrolyzability of hydrophobic aliphatic polyesters such as poly(ε‐caprolactone) (PCL) and poly(L‐lactide) [i.e. poly(L‐lactic acid) (PLLA)] was attempted by coating with hydrophilic poly(vinyl alcohol) (PVA). The PVA coating was carried out by immersion of the PCL and PLLA films in PVA solutions. The effects of PVA coating on the hydrophilicities were monitored by dynamic contact angle measurements, while the enzymatic hydrolyzability of the PVA‐coated PCL and PLLA films was evaluated by the weight losses after Rhizopus arrhizus lipase‐ and proteinase K‐catalyzed hydrolysis, respectively. It was found that the PVA coating successfully enhanced the hydrophilicities of the aliphatic polyester films and significantly suppressed enzymatic hydrolyzability of the aliphatic polyester films, excluding the PCL film coated at a very low concentration such as 0.01 g · dL−1 and the crystallized PLLA film coated at 1 g · dL−1, for which slight enhancement and no significant enhancement, respectively, were observed in the enzymatic hydrolyzability. Moreover, the hydrophilicities and enzymatic hydrolyzability of the aliphatic polyester films were controllable to some extent by varying the PVA solution concentration and the film crystallinity.

Advancing contact angle (θa) of PCL, PLLA‐C, and PLLA‐A films before and after the PVA coating by immersion in 1 g · dL−1 solution.

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Advancing contact angle (θa) of PCL, PLLA‐C, and PLLA‐A films before and after the PVA coating by immersion in 1 g · dL−1 solution.
Poly(amido‐amine)s Carrying Primary Amino Groups as Side Substituents
Authors: Malgesini Beatrice , Verpilio Ilario , Duncan Ruth , Ferruti Paolo
Published: February 2003

Poly(amido‐amine)s carrying primary amino groups as side substituents have been obtained by polyaddition of N‐triphenylmethyl‐monosubstituted 1,2‐diaminoethane (TPHMAE) to 2,2‐bisacrylamido acetic acid or 1,4‐bisacryloylpiperazine and subsequent removal of the protecting triphenylmethyl group by treating the resultant polymers with aqueous hydrochloric acid. Soluble polymers can be also obtained directly by the polyaddition of monoprotonated 1,2‐diaminoethane to 2,2‐bisacrylamido acetic acid in the presence of a limited amount of added acetic or hydrochloric acid. The resultant polymers are of a higher molecular weight than the corresponding ones prepared from TPHMAE. By adding a limited amount of N‐triphenylmethyl‐monosubstituted 1,2‐diaminoethane to the monomer mixtures leading to poly(amido‐amine)s with a recognised potential as nonviral vectors, such as ISA 23 and ISA 1, a controlled number of pendant primary amino groups have been introduced. By this procedure, ISA 23 and ISA 1 become suitable as polymer carriers for carboxylated drugs as well as amenable to the labelling techniques by fluorescent probes commonly employed for proteins.

Formation of monoprotected primary diamines.

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Formation of monoprotected primary diamines.
Electrochemical studies on the effect of pyrazolo‐containing compounds on the corrosion of carbon steel in 1 M sulphuric acid
Authors: Abd El‐Maksoud S. A.
Published: February 2003

The effect of some synthesized pyrazolo containing compounds on the corrosion of carbon steel in 1 M H2SO4 was investigated. The investigation involved electrochemical polarization methods (potentiodynamic, Tafel extrapolation and the determination of the polarization resistance). A significant decrease in the corrosion rate of carbon steel was observed in the presence of the investigated compounds. The results show that these compounds act as mixed type inhibitors, but the cathode is more preferentially polarized. The relative inhibition efficiency of these compounds depends on both the nature and concentrations of the investigated compounds. Compounds are found to adsorb on the carbon steel surface according to the Langmuir adsorption isotherm.
Korrosionsschäden an Lagertanks für Salzlake
Authors: Burkert A. , Mietz J.
Published: February 2003

An einem Tankbehälter aus dem Werkstoff X2CrNiMo17‐12‐2, der zur Zwischenlagerung von Salzlake für die Käseherstellung dient, wurden trotz langjähriger positiver Erfahrungen an vergleichbaren Anlagen bereits kurze Zeit nach der Inbetriebnahme Lochkorrosionserscheinungen festgestellt. Durch entsprechende elektrochemische Laboruntersuchungen konnte gezeigt werden, dass die vorgefundene Lochkorrosion durch den Einsatz eines Oxidationsmittels zu Desinfektionszwecken verursacht wurde.
Combination of thermal activation and addition of H2O2 to improve cerium‐based immersion treatment of alloy AA5083
Authors: Bethencourt M. , Botana F. J. , Cano M. J. , Osuna R. M. , Marcos M.
Published: February 2003

Intensive research has been undertaken in recent years aimed at finding non‐contaminating alternatives to surface treatment processes based on the use of chromates. One of the alternatives proposed involves the use of lanthanide salts, and a variety of methods of protection have been described. In this study, the results of the treatment of samples of alloy AA5083 in a solution of Ce(III) at 323 K and incorporating small quantities of oxygenated water are presented. These results indicate that the application of this type of treatment gives a considerable reduction in the time required for this process and high levels of protection. This time reduction is associated with a combined effect caused, in part by the presence of oxygenated water, which facilitates the formation of islands of cerium, and in part by thermal activation, which facilitates a more rapid development of the alumina film over the metal matrix. Lastly, the results obtained indicate that these treatments provide increased resistance of the alloy against pitting corrosion.
Effect of ferric ions in AISI 316L stainless steel pickling using an environmentally‐friendly H2SO4‐HF‐H2O2 mixture
Authors: Narváez L. , Cano E. , Bastidas J. M.
Published: February 2003

A mixture of hydrogen peroxide, sulphuric and hydrofluoric acids has been used as pickling solution at pH 2.0 for AISI 316L austenitic stainless steel (SS). The stability of the H2SO4‐HF‐H2O2 mixture is assessed varying the ferric ions content from 0 to 40 g/L, the temperature from 25 to 60°C, and with and without stirring of the pickling solution. The AISI 316L SS pickling rate at 50°C was 2.6 and 0.2 mg/dm2 day (mdd) in the absence and presence of 40 g/L ferric ions, respectively. p‐toluene sulphonic acid (PTSA) has been used as stabiliser of hydrogen peroxide.
Corrosion resistance of Nd‐Fe‐B permanent magnetic alloys. Part 1: Role of alloying elements
Authors: El‐Aziz A. M.
Published: February 2003

The electrochemical behaviour of Nd‐Fe‐B magnetic alloys was investigated in acid and neutral solutions. The differences in the chemical composition of these materials have distinct influence on the corrosion rate and polarization behaviour. Small additions of cobalt, aluminium and gallium increase the corrosion resistance of the magnetic alloys at high cathodic potential. It was also observed that the increase of hydrogen evolution rate on the surface of the magnetic materials raises the rate of dissolution of these magnets. The electrostatic surface potential was examined by scanning probe microscopy. A relation between the electrostatic surface potential and electrochemical behaviour of these alloys was found. The high values of electrostatic surface potential of the intergranular phases reflect higher corrosion attack. Auger electron spectroscopy was used to analyse the surface layer which formed during anodic polarization of the magnet containing alloying additives. The result indicates the formation of (Nd,Fe)‐oxide with small amounts of cobalt and aluminium.
Fundamental investigation of the degradation laws of aluminide coatings during high‐temperature oxidation
Authors: Liu P. S.
Published: February 2003

During high‐temperature oxidation, the aluminide coating degrades by two mechanisms, one is the oxidation of the outer surface, and the other is Al diffusion into the substrate. The relevant laws are investigated for coatings on Co‐base superalloys oxidised in air at high temperatures. The driving force mainly comes from the oxidation reaction for the outer degradation layer, and the chemical potential for the inner degradation layer. By an approximation approach, it can be concluded that the life of the outward‐diffusion coating is roughly directly proportional to the second power of the main‐phase thickness of the coating.
Study of electronic‐ionic conducting transformation of temporarily protective oil coating in salt solution
Authors: Zhong Q. , Zhou G. , Xu N. , Rohwerder M.
Published: February 2003

In this paper, a multiple microelectrode array was developed to study the electronic‐ionic conducting transition of temporarily protective oil coating in salt solution. It was pointed out that there existed electronic‐ionic transition of temporarily protective oil coating in salt solution varying with immersion time. At the early stage of immersion, the oil coating was an electronic conductor, which having very low conductivity. With increasing of immersion time, the oil coating transformed from electronic conductor to ionic conductor, where ionic diffusion in the coating was predominant. Based upon Bailey and Ritchie's general electrochemical theory for the oxidation of metals, an electrochemical analysis of potential inhomogeneity of the oil coating was presented. It was assumed that only one step could be rate‐determining in the overall reaction in the metal/oil film/solution system. It was predicted that there were two kinds of film in the temporarily protective oil coating, ionic and electronic conducting film. For the ionic conducting film, potentials of oil coated electrode were equal to equilibrium potential of metal oxidation at the metal/coating interface (Eaeq), and it had the most negative value. For the electronic conducting film, potentials obtained were equal to the equilibrium potential of the oxidant reduction at the coating/electrolyte interface (Eceq), and it had the most positive value. Potential measurements in this paper verified the results of Wormwell and Brasher's research in 1949; the distribution of potential on oil‐painted wire beam electrodes being heterogeneous and following a discontinuous binomial probability distribution were also elucidated.
An Analysis of the Concentration Effects on Elution Volumes by Using the Preferential Solvation Parameter in Two SEC Packings
Authors: García‐Lopera Rosa , Gómez Clara M. , Abad Concepción , Campos Agustín
Published: February 2003

Size exclusion chromatography (SEC) elution behavior of different solvent/polymer systems has been analyzed from chromatographic, thermodynamic, and hydrodynamic points of view in two organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, μ‐styragel and TSK‐Gel HHR. Although both packings present similar chromatographic properties, some differences arise when eluting the same systems. The values of the adsorption distribution coefficients, Kp, have been correlated with the preferential solvation coefficient, λ (see Figure), for both packings, showing that those systems with lower and negative λ values (denoting higher preferential solvation of the polymer by the gel packing) are those with Kp > 1. In addition, the main goal has been to make use of the λ values to adequately interpret the dependence of the elution volumes on injected polymer concentration. In this regard, the experimental concentration effects have been completely explained by taking into account not only the conventional hydrodynamic factors but also thermodynamic aspects such as the preferential solvation phenomenon.

Plot of the preferential solvation coefficient, λ, as a function of the volume fraction of polymer (2), ϕ2, at three hydrodynamic volumes, Vh = 106 (○ •); 107 (□ ▪), and 108 (▵ ▴) mL · mol−1 for the system THF/PBD/PS (μ‐styragel: empty symbols; TSK‐Gel HHR (solid symbols).

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Plot of the preferential solvation coefficient, λ, as a function of the volume fraction of polymer (2), ϕ2, at three hydrodynamic volumes, Vh = 106 (○ •); 107 (□ ▪), and 108 (▵ ▴) mL · mol−1 for the system THF/PBD/PS (μ‐styragel: empty symbols; TSK‐Gel HHR (solid symbols).
Synthesis of Poly(propylene oxide) with Strict Control of End Functionality, 1. Initiation with (4‐Methoxy)phenoxy Tetraphenylporphynatoaluminum
Authors: Lopitaux Garance , Ricart Guy , Faven Catherine , Coqueret Xavier
Published: February 2003

The polymerization of propylene oxide (PO) initiated by (4‐methoxy)phenoxy tetraphenylporphynatoaluminum (TPPAl‐O‐PMP) was studied with the aim of strictly controlling the end‐group functionality of the resulting poly(propylene oxide) (PPO), together with the molecular weight, in terms of average values and of narrow chain‐length distribution. The influence of the relative amount of reactants used for the preparation of the initiator on the nature and number of end groups was studied by various analytic methods including 1H NMR and UV spectroscopies and matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) spectrometry. In spite of apparent living behavior observed from size exclusion chromatograpy (SEC) measurements, large variations in the yield of polymerization, determined after several hours of reaction, indicated a strong dependence of the propagation rate on slight variations around the 1:1 stoichiometry of triethylaluminum to the unmetallated porphyrin and to the phenolic ligand. Associated with the anomalous kinetic behavior, differences in the nature of the end groups were unambiguously evidenced by MALDI‐TOF spectrometry for narrow molecular weight (MW) distributed PPOs obtained with a slight excess of triethylaluminum and a slight deficit in added phenol with regard to porphyrin. A mechanism involving side reactions is proposed to account for the observed kinetic and structural features. Immortal polymerization of PO with strict control of MW distribution and functionality is obtained under appropriate conditions and consistently supported by various methods of MW determination.

Principle of end‐group functionalization in porphyrin catalyzed PO polymerization.

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Principle of end‐group functionalization in porphyrin catalyzed PO polymerization.
Quantitative Aspects of the Dendronization of Dendronized Linear Polystyrenes
Authors: Shu Lijin , Göossl Illdiko , Rabe Jürgen P. , Dieter Schlüter A.
Published: February 2003

The paper describes in detail how amine‐terminated dendronized polystyrenes 1(G2), 2(G3), and 3(G1) of varying generations (first: G1, second: G2, third: G3) were reacted with the G1 (and G2) dendrons 4, 5c, and 6b carrying active esters at their focal point to furnish polymers 7(G4), 8(G2), 9(G3), and 10(G4). All these dendronization steps were monitored using UV absorbance measurements after labeling the unreacted amines with the Sanger reagent, 2,4‐dinitrofluorobenzene, providing a quantitative assessment of the overall structural integrity achievable for dendronized polymers synthesized according to this divergent growth scheme. Polymers 3(G1), 8(G2), 9(G3), and 10(G4) represent a quasi‐homologous series of high molar mass dendronized polymers whose lengths and length distributions, in their deprotected (and thus charged) state, was determined by contour‐length histograms using scanning force microscopy (SFM). Finally, the decoration of representatives of this series with long alkyl chains is also reported.

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Copolymers from Methacrylic Acid and Trimethylsilyl Methacrylate ‐ Synthesis, Reactivity Ratios and Thermal Properties
Authors: Mormann Werner , Ferbitz Jens
Published: February 2003

Copolymers from methacrylic acid (1) and trimethylsilyl methacrylate (2) have been synthesized by free radical copolymerisation and by controlled desilylation of poly(trimethylsilyl methacrylate) (3). The reactivity ratios were r1 = 2.75, r2 = 0.004. Differential scanning calorimetry showed a linear correlation between the peak temperature of the endotherm for the formation of cyclic anhydrides and the content of methacrylic acid in the copolymer. Obviously, the acid catalyses this reaction. The copolymers as well as poly(trimethylsilyl methacrylate) have a ceiling temperature. Sequence distributions were calculated and used to predict glass transition temperatures for comparison to the experimental results. The microstructure of the copolymers obtained by the different synthetic routes is different as shown from Tg and from their solubility. Those from desilylation are random with “reactivity ratios” of 1, those from copolymerisation seem to have longer sequences of methacrylic acid leading to formation of intermolecular aggregates.

Dependence of DSC peak temperature of anhydride formation on methacrylic acid content.

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Dependence of DSC peak temperature of anhydride formation on methacrylic acid content.
Cross‐Linked Poly(ε‐caprolactone/D,L‐lactide) Copolymers with Elastic Properties
Authors: Helminen Antti O. , Korhonen Harri , Seppälä Jukka V.
Published: February 2003

Cross‐linked ε‐caprolactone (CL) and D,L‐lactide (DLLA) copolymers with elastic properties were synthesized in three steps. First, the monomers were copolymerized in ring‐opening polymerization to obtain telechelic star‐shaped oligomers with almost completely random monomer distribution. The oligomers were methacrylated with methacrylic anhydride in the second step and cured in a third. Molar CL/DLLA compositions of 30/70, 50/50, 70/30, 90/10, and 100/0 were used to obtain elastic structures with a wide range of properties. The effect of the average length of the copolymer block on the properties of the networks was evaluated with three different co‐initiator contents (0.5, 1.0, and 2.0/100) in the oligomer synthesis. The oligomers were characterized by 13C NMR spectroscopy, size‐exclusion chromatography (SEC), and differential‐scanning calorimetry (DSC). The formation of elastic networks was confirmed by the absence of a flow region in dynamic mechanical analysis (DMA), the increase in Tg in DSC, and the full recovery of the sample dimensions after tensile testing. In addition, gel contents were high and the samples swelled in CH2Cl2. The networks possessed break stresses from 0.7–9.7 MPa with elongations from 80–350%. Networks with 100 or 90% of ε‐caprolactone retained their form in vitro for 12 weeks, but an increase in lactide content made the networks more vulnerable to hydrolysis.

Water absorption of the polymers during hydrolysis.

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Water absorption of the polymers during hydrolysis.
Nano‐Scale Molecular Shapes of Water‐Soluble Chitin Derivatives Having Monodisperse Poly(2‐alkyl‐2‐oxazoline) Side Chains
Authors: Aoi Keigo , Takasu Akinori , Okada Masahiko , Imae Toyoko
Published: February 2003

The molecular shapes and the sizes of structures formed by chitin derivatives with monodisperse poly(2‐alkyl‐2‐oxazoline) side chains were investigated using atomic force microscopy (AFM), cryo‐transmission electron microscopy (cryo‐TEM), and small‐angle neutron scattering (SANS) analyses. A ring structure with an outside diameter of 45–60 nm and a cross‐sectional diameter of 10–18 nm was observed in the AFM image for chitin‐graft‐poly(2‐methyl‐2‐oxazoline) 1d (DP of the side chain, 8.5; [side chain]/[glucosamine unit], 0.53). From the cryo‐TEM observation of the graft copolymer 1d in 0.5 wt.‐% D2O solution, an average diameter of 40 nm for the particles was determined, with a narrow size distribution. SANS measurements of the 0.5 wt.‐% D2O solution of 1d revealed that the outside diameter of the particles and the cross‐sectional diameter were 57 nm and 8 nm, respectively. The absolute weight average molecular weight of 1d was determined to be 5.4 × 105 by static light scattering. From these results it was concluded that 1d can form a unimolecular ring structure in aqueous solution. However, graft copolymers with fewer side chains (1c; [side chain]/[glucosamine unit], 0.30) and with more side chains (1e; [side chain]/[glucosamine unit], 0.96) did not form rings but instead formed monodisperse unimolecular spherical particles of diameters of 28–36 nm by AFM. A graft copolymer 1f with relatively long side chains (DP of side chain, 19.6; [side chain]/[glucosamine unit], 1.00) was also observed as a spherical particle by AFM (diameter: 30–40 nm by AFM; 40 nm by SANS). On the other hand, an intermolecular aggregate formation (diameter of the aggregate: 36–143 nm) was observed for graft copolymers 1a and 1b having short side chains (DP of side chains, 5.6; [side chain]/[glucosamine unit], 0.35 and 0.48, respectively), with a spherical molecular particle of diameter 36 nm by the AFM analysis. Chitin‐graft‐poly(2‐ethyl‐2‐oxazoline) (2) (DP of side chains, 21.7; [side chain]/[glucosamine unit], 0.95) generated larger aggregates of diameter 100–400 nm by AFM. The complexation behavior of graft copolymer 1d with magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS) and with N‐phenyl‐1‐naphthylamine (PNA) was also examined by fluorescence measurement in an aqueous solution. It was found that graft copolymer 1d complexed with both ANS and PNA, and the binding constants were calculated to be 7.5 × 104 M−1 and 5.3 × 104 M−1, respectively.

Chemical structure of chitin‐graft‐poly(2‐alkyl‐2‐oxazoline).

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Chemical structure of chitin‐graft‐poly(2‐alkyl‐2‐oxazoline).
Critically Evaluated Termination Rate Coefficients for Free‐Radical Polymerization, 1. The Current Situation
Authors: Buback Michael , Egorov Mark , Gilbert Robert G. , Kaminsky Vladimir , Olaj Oskar F. , Russell Gregory T. , Vana Philipp , Zifferer Gerhard
Published: February 2003

This is the first publication of an IUPAC‐sponsored Task Group on “Critically evaluated termination rate coefficients for free‐radical polymerization.” The paper summarizes the current situation with regard to the reliability of values of termination rate coefficients kt. It begins by illustrating the stark reality that there is large and unacceptable scatter in literature values of kt, and it is pointed out that some reasons for this are relatively easily remedied. However, the major reason for this situation is the inherent complexity of the phenomenon of termination in free‐radical polymerization. It is our impression that this complexity is only incompletely grasped by many workers in the field, and a consequence of this tendency to oversimplify is that misunderstanding of and disagreement about termination are rampant. Therefore this paper presents a full discussion of the intricacies of kt: sections deal with diffusion control, conversion dependence, chain‐length dependence, steady state and non‐steady state measurements, activation energies and activation volumes, combination and disproportionation, and theories. All the presented concepts are developed from first principles, and only rigorous, fully‐documented experimental results and theoretical investigations are cited as evidence. For this reason it can be said that this paper summarizes all that we, as a cross‐section of workers in the field, agree on about termination in free‐radical polymerization. Our discussion naturally leads to a series of recommendations regarding measurement of kt and reaching a more satisfactory understanding of this very important rate coefficient.

Variation of termination rate coefficient kt with inverse absolute temperature T−1 for bulk polymerization of methyl methacrylate at ambient pressure.[6] The plot contains all tabulated values[6] (including those categorized as “recalculated”) except ones from polymerizations noted as involving solvent or above‐ambient pressures.

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Variation of termination rate coefficient kt with inverse absolute temperature T−1 for bulk polymerization of methyl methacrylate at ambient pressure.[6] The plot contains all tabulated values[6] (including those categorized as “recalculated”) except ones from polymerizations noted as involving solvent or above‐ambient pressures.
Homo‐ and Copolymerization of ω‐Functional Polystyrene Macromonomers via Coordination Polymerization
Authors: Lahitte Jean‐François , Peruch Frédéric , Plentz‐Meneghetti Simoni , Isel François , Lutz Pierre J.
Published: February 2003

Macromonomers have been extensively used, as well defined building blocks for various macromolecular architectures via anionic, ROMP and free radical homo‐ or copolymerization processes. The purpose of the present work was to examine the homopolymerization and copolymerization of ω‐allyl, ω‐undecenyl and ω‐vinylbenzyl polystyrene (PS) macromonomers, in the presence of early or late transition metal catalysts. The influence of several parameters (type of catalytic system, nature of polymerizable end‐group and molar mass of the macromonomer) on the homopolymerization was first investigated. Whereas ω‐allyl or ω‐undecenyl PS macromonomers were not very reactive in homopolymerization whatever the catalyst, ω‐vinylbenzyl PS macromonomers gave interesting results with CpTiCl3/MAO and Cp*TiCl3/MAO. The copolymerization of these macromonomers with ethylene was also studied in the presence of the following palladium catalyst: [(ArNC(Me)C(Me)NAr)Pd(CH2)3(COOMe)]+BAr4′−(VERSIPOL™) (Ar = 2,6‐iPr2–C6H3 and Ar′ = 3,5‐(CF3)2C6H3). ω‐vinylbenzyl PS macromonomers could not be incorporated into poly(ethylene) chains. On the contrary, the incorporation of ω‐allyl PS macromonomers was achieved. Moreover, for macromonomers containing an alkyl spacer between the allylic unit and the PS chain, the incorporation rate, the copolymerization yield and the molar masses of the copolymers were increased, giving access to a new type of graft copolymer structure.

Synthesis of polystyrene macromonomers.

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Synthesis of polystyrene macromonomers.
Controlled Ring‐Opening Polymerization of Lactones and Lactide Initiated by Lanthanum Isopropoxide, 2. Mechanistic Studies
Authors: Save Maud , Soum Alain
Published: February 2003

The mechanism of ring‐opening polymerization of some lactones and lactide initiated by lanthanum isopropoxide has been comprehensively investigated. NMR and viscosity analyses demonstrated that three active polymer chains grow per lanthanum atom and that, depending on the coordinating ability of the monomer, propagation proceeds on aggregated or unaggregated active species. It is also demonstrated that inter‐ and intramolecular side reactions are limited and that lanthanum‐based initiator selectivity in ring‐opening polymerization is analogous to that of aluminum ones.

Part of the proposed mechanism for the lanthanum alkoxide initiated polymerization of ε‐caprolactone.

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Part of the proposed mechanism for the lanthanum alkoxide initiated polymerization of ε‐caprolactone.
Stereochemical Pseudohexad 13C NMR Resonances and Regioregular Propylene/Ethylene‐1‐13C Copolymers
Authors: Sessa Irene , Ferro Dino Romano , Grisi Fabia , Liguori Dario , Milano Giuseppe , Zambelli Adolfo
Published: February 2003

This paper reports the assignment of the 13C NMR resonances of the Sββ and Sαγ methylenes observed in the spectra of copolymers of propylene with trace amounts of enriched ethylene‐1‐13C. The assignment is achieved by comparing the chemical shifts calculated by an empirical method (at the CH2 stereochemical pseudohexad level), with the experimental spectra of regioregular copolymers with different stereochemical structure. The implications of the observed Sββ and Sαγ resonances on the stereochemical polymerization mechanisms are also discussed.

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Change of Tacticity during Thermal Degradation of PMMA
Authors: Wondraczek Katrin , Adams Jörg , Fuhrmann Jürgen
Published: February 2003

The change of tacticity during thermal treatment of commercial poly(methyl methacrylate) (PMMA) at 200 °C in air was studied in detail. The coupling between de‐ and repolymerization is contrasted by NMR analysis. The parameter of tacticity opens up a new perspective in describing the consequences of degradation. The analysis of the configuration of the residue was performed by 1H NMR spectroscopy. The ratios of the three characteristic triads – of isotactic (I), syndiotactic (S), and heterotactic (H) sequences – depend on degradation time and approach a constant value of S/H/I = 0.3:0.4:0.3 at about 80% of mass loss when starting with an initial ratio of S/H/I = 0.5:0.4:0.1. A two‐parameter two‐state model is proposed to calculate the transition from the initial to the final stereo‐sequence distribution generated by de‐ and repolymerization. The correlation between the evaluated parameters and the degradation processes leads to information on repolymerization, which is dominant after about 50% weight loss, i.e., from about 20 h on, and afterwards in two consecutive steps with a rapid change in tacticity, when 50% of the residual material is converted into a new sequence distribution. This type of tacticity conversion has its maximum speed at about 80% weight loss in the second of the consecutive steps.

Triad portions during degradation determined by 1H NMR spectroscopy: • syndio‐, ♦ hetero‐, ▴ isotactic triads.

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Triad portions during degradation determined by 1H NMR spectroscopy: • syndio‐, ♦ hetero‐, ▴ isotactic triads.
Grafting of Vinyl‐Type Polynorbornene on Polybutadiene and Polyisoprene
Authors: Schroers Michael , Demeter Jürgen , Dehnicke Kurt , Greiner Andreas
Published: February 2003

High molecular weight vinyl‐type polynorbornene was obtained by polymerization of norbornene initiated by [NiBr(NPMe3)]4/B(C6F5)3. Polymerization in the presence of olefins resulted in termination of polynorbornene chains by olefinic moieties. Molecular weights of polynorbornenes terminated by vinylidene compounds are lower than those terminated by vinyl and vinylene compounds. Corresponding polymerizations with polybutadiene and polyisoprene yielded graft copolymers with polynorbornene as grafts without contamination by homopolymerized polynorbornene. Grafting reactions were proved by spectroscopy, GPC, and degradation experiments using OsO4.

GPC traces (refractometer detector) of PN obtained for the polymerizations of 2 in the presence of 4d.

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GPC traces (refractometer detector) of PN obtained for the polymerizations of 2 in the presence of 4d.
Synthesis, Characterization, and Thermal Properties of Block Copolymers Containing Poly(styrene‐co‐4‐vinylpyridine) and Poly(styrene‐co‐butyl acrylate) by Controlled Radical Polymerization
Authors: Taube Carsten , Fernández García Marta , Schmidt‐Naake Gudrun , Fischer Hartmut
Published: February 2003

Radical polymerization of styrene and mixtures of styrene and 4‐vinylpyridine was performed in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) producing polymers with controlled molecular weights and molecular weight distributions. The living nature of these polymers was confirmed by using them as macroinitiators in the block copolymerization of styrene and butyl acrylate. The thermal properties of the synthesized statistical diblock copolymers measured by differential scanning calorimetry indicated that a phase‐separated morphology was exhibited in most of the block copolymers. The results were confirmed by transmission electron microscopy (TEM) and small angle X‐ray scattering (SAXS) showing microphase‐separated morphology as is known for homo A‐B diblock polymers.

SAXS of a block copolymer synthesized from S/V 70:30 macroinitiators (03) with one detected Tg.

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SAXS of a block copolymer synthesized from S/V 70:30 macroinitiators (03) with one detected Tg.
Ethene/Norbornene Copolymerization using the Catalyst System Pri[(3‐Pri‐Cp)Flu]ZrCl2: Determination of the Copolymerization Parameters and Mechanistic Considerations
Authors: Wendt Ralf A. , Mynott Richard , Fink Gerhard
Published: February 2003

The 13C NMR spectra of ethene/norbornene copolymers in which there are no norbornene microblocks are much simpler than those of copolymers in which norbornene microblocks are present, making it possible to completely assign all the 13C resonances to the corresponding pentads in the copolymer chain. However, there is disagreement in the literature over several assignments of the ethene 13C NMR signals. In this paper these discrepancies are summarized and discussed. This contribution also reports ethene/norbornene copolymerizations carried out at various temperatures using the homogeneous catalyst system Pri[(3‐Pri‐Cp)Flu]ZrCl2. The 13C NMR spectra of the copolymers were analyzed in the light of the discussion above and the triad distributions were used to determine the copolymerization parameters by Markov first‐ and second‐order statistical models. On the basis of these results, the mechanism generating such an alternating microstructure in these copolymers is discussed and compared with the mechanism previously proposed in the literature.

The 13C NMR spectrum with signal assignments of an ethene/norbornene copolymer without norbornene microblocks.

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The 13C NMR spectrum with signal assignments of an ethene/norbornene copolymer without norbornene microblocks.
New Poly(sodium carboxylate)s Based on Saccharides, 1. Synthesis and Characterization of Ionic Allyl Glycoside Polymers
Authors: Mahrholz Thorsten , Klein Joachim , Klein Thomas
Published: February 2003

New poly(sodium carboxylate)s, containing monosaccharide side groups with ether linkages to the main chain, are presented as substitutes for water‐soluble homo‐ and copolymers of acrylic acid. Neutral and ionic allyl glycoside monomers, namely allyl‐α‐D‐galactopyranoside and allyl‐β‐D‐glucofuranosidurono‐6,3‐lactone, were synthesized by Fischer glycosidation. These monomers were copolymerized with maleic anhydride and itaconic acid in aqueous and nonaqueous solution. The corresponding copolymers with different structures, degrees of functionalization, and charge densities were characterized by 13C NMR spectroscopy, molecular‐weight measurements, and intrinsic viscosity [η] determination. From these, the monomer reactivity ratios and Mark–Houwink relations were established (see Figure).

Copolymerization curves of maleic acid copolymers 6 and 10. M1: mole fraction of allyl monomer 2β and 5α in the feed; m1: mole fraction of allyl monomer in the copolymer. The dashed line shows the course of an ideal alternating copolymerization (excepted: M1 = 0 mol‐%, M1 = 100 mol‐%).

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Copolymerization curves of maleic acid copolymers 6 and 10. M1: mole fraction of allyl monomer 2β and 5α in the feed; m1: mole fraction of allyl monomer in the copolymer. The dashed line shows the course of an ideal alternating copolymerization (excepted: M1 = 0 mol‐%, M1 = 100 mol‐%).
Impact of Molecular Weight on Miscibility and Interdiffusion between Poly(N‐vinyl pyrrolidone) and Poly(ethylene glycol)
Authors: Bairamov Danir F. , Chalykh Anatoly E. , Feldstein Mikhail M. , Siegel Ronald A.
Published: February 2003

Miscibility and mutual diffusion between poly(N‐vinylpyrrolidone) (PVP) and short‐chain poly(ethylene glycol)s (PEGs) of different molecular weight were studied by optical wedge microinterferometry (WMI). The PVP Mn varied from 1 300 to 360 000 g · mol−1, whereas that of PEG ranged from 200 to 6 000 g · mol−1. Photographs of interference patterns measured at λ = 546 nm with an optical microscope were used to observe the PVP/PEG interface. PVP blends with short‐chain PEG fractions, ranging in molecular weight from 200 to 1 500 g · mol−1, were found to be fully miscible above the temperatures of PEG fusion, whereas an increase in the molecular weight of up to 3 000 g · mol−1 renders the two polymers completely immiscible. Successive photographs of interference patterns (the interferogram of the contact interface between PEG6000 (left) and PVP is shown in the Figure) were used to determine composition‐distance profiles and to calculate the composition‐dependent mutual diffusion coefficient in miscible PVP/PEG blends. It was shown that the effects of PVP molecular weight are in reasonable agreement with those observed for other compatible polymer systems. In contrast to PVP behavior, the effects of PEG molecular weight indicate appreciable contribution of hydrogen bonding of terminal hydroxyl groups in short PEG chains to the miscibility and diffusivity behavior in the PVP/PEG system. The difference in the effects of PEG and PVP chain lengths is ascribed to hydrogen bonding between PEG terminal hydroxyl groups with carbonyl side groups of repeat units in PVP macromolecules and ether oxygens in the PEG chains.

Interferogram of the contact interface between PEG 6000 (left) and PVP. Magnification: 60‐fold.

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Interferogram of the contact interface between PEG 6000 (left) and PVP. Magnification: 60‐fold.
A Novel Impact Modifier for Nylon 6
Authors: Peng Jing , Qiao Jinliang , Zhang Shijun , Wei Genshuan
Published: February 2003

A new carboxylated styrene‐butadiene rubber (CSBR) in ultrafine powder form was used to modify the properties of nylon 6. The nylon 6/CSBR blends possessed higher toughness than nylon 6/maleic anhydride‐grafted polyethylene‐octene elastomer (POE‐g‐MAH) system. TEM micrographs revealed the fine dispersion of CSBR particles with a diameter of 150 nm. The effective toughening of nylon 6 with CSBR was attributed to the good interface, fine dispersion, and shear yielding.

TEM photograph of undeformed Nylon 6/CSBR (80/20) blend (×40 000).

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TEM photograph of undeformed Nylon 6/CSBR (80/20) blend (×40 000).
EVA Copolymer Based Nanocomposites
Authors: La Mantia F. P. , Lo Verso S. , Tzankova Dintcheva N.
Published: February 2003

Nanocomposites are a new class of polymer material with an ultrafine phase dispersion of the order of a few nanometers that shows very interesting properties often very different from those of conventional filled polymers. In this work the mechanical and optical properties of Poly[ethylene‐co‐(vinyl acetate)] (EVA copolymer) based nanocomposites have been investigated to evaluate its possible use in several applications. For example, films for covering greenhouses made by EVA copolymer are appealing because of their interesting optical properties and for the so‐called greenhouse effect. Mechanical properties, and the rigidity in particular, are, on the contrary, quite low. Nanocomposites should avoid this shortcoming if optical properties and processability are not unfavorably effected. EVA copolymer based nanocomposites have been prepared by compounding polymer matrix and two different functionalized silicates (0–10 wt.‐%) in molten state. X‐Ray diffractograms show that the in the adopted experimental conditions no exfoliation of the filler is obtained, but an intercalated morphology is observed. Rheological behavior both in shear and in non‐isothermal elongational flow is only slightly influenced by the presence of the filler. As for the mechanical properties, the elastic modulus strongly increases without any worsening of the elongation at break. The permeability in the UV region is not influenced by adding even relatively high contents of the silicates. The improved mechanical and optical properties and the unmodified processability suggest then the use of these new polymeric systems in many applications and in particular as films for covering greenhouses.

UV spectra of the EVA/Nanofil system.

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UV spectra of the EVA/Nanofil system.
The Effects of Copper Oxides on the Curing Behaviors of Bismaleimide Triazine Prepreg
Authors: Hong Shinn‐Gwo , Yeh Chin‐Sen
Published: February 2003

The effect of copper oxides on the curing behaviors of the bismaleimide triazine (BT) prepreg is studied with infrared spectroscopy (IR), attenuated total reflection infrared spectroscopy (ATR), and X‐ray photoelectron spectroscopy (XPS). The result of IR analyses indicates that there is a concentration distribution present in the prepreg surface layer and the outer surface layer contains less cyanate, imide, and epoxide but more triazine groups than the inner layer. From ATR, it is concluded that the cuprous oxide attracts more cyanate ester resins but less bismaleimide resins from the prepreg to its surface than the cupric oxide. The copper surface affects the curing extent of the BT resin in contact and the cupric oxide has a more pronounced effect than the cuprous oxide, and this surface effect can extend to at least two microns deep into the BT prepreg from the contacted interface. The XPS results confirm that the BT/CuO interface contains more thermally stable and polar functional groups than the BT/Cu2O interface, and both two copper oxides attract only a small amount of brominated epoxy resin onto their surfaces. These results are attributed to the difference in preferential adsorptions and catalytic curing effects of two copper oxides on the BT prepreg in contact.

The intensity changes of IR bands obtained from BT prepreg during cure.

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The intensity changes of IR bands obtained from BT prepreg during cure.
Microcomposites of Poly(ε‐caprolactone) and Poly(methyl methacrylate) Prepared by Suspension Polymerization in the Presence of Poly(ε‐caprolactone) Macromonomer
Authors: Abraham Gustavo A. , Kesenci Kemal , Fambri Luca , Migliaresi Claudio , Gallardo Alberto , Román Julio San
Published: February 2003

Poly(methyl methacrylate)‐poly(ε‐caprolactone) (PMMA/PCL) microparticles were synthesized by suspension polymerization of methyl methacrylate in the presence of PCL. The incorporation of a small amount of a macromonomer, methacryloyl‐terminated PCL (M‐PCL), into the reaction mixture, led to the formation of grafted systems, namely PMMA‐g‐PCL/PCL. The synthesis of the macromonomer and its characterization by nuclear magnetic spectroscopy (1H NMR) is described. The role of M‐PCL as an effective compatibilizing agent in the composite was investigated. PMMA/PCL and PMMA‐g‐PCL/PCL composites were fully characterized by 1H NMR, gel permeation chromatography (GPC) and thermal analysis, including thermogravimetric analysis (TGA), conventional differential scanning calorimetry (DSC), modulated DSC (MDSC) and dynamic mechanical thermal analysis (DMTA). Finally, the morphology of the prepared systems was investigated by scanning electron microscopy (SEM). The addition of compatibilizing agent led the formation of a more homogeneous microcomposite with improved mechanical properties.

SEM picture of PMMA‐g‐PCL/PCL composite surface.

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SEM picture of PMMA‐g‐PCL/PCL composite surface.
Dry Processes for Surface Modification of a Biopolymer: Chitosan
Authors: Matienzo Luis J. , Winnacker Sarah K.
Published: February 2003

Standard dry surface modification reactions have been applied to partially deacetylated chitosan without affecting its bulk properties. Chitin, extracted from shells of Penaeus vannamei, yielded chitosan with a degree of acetylation of 70% and molecular weight of 250 000 D. The copolymer consists of (β‐(1‐4)‐2‐2‐acetamido‐D‐glucose) units linked to (β‐(1‐4)‐2‐amino‐D‐glucose) units. Since the main interest of this work was to study the surface properties of films on substrates, a method to cast this material onto Al‐coated silicon wafers had to be developed. X ray photoelectron spectroscopy (XPS) has been used to determine the surface composition of the unmodified films and to follow modification changes. The films were treated in either an oxygen plasma environment or under UV/ozone irradiation. Water advancing contact angle measurements and infrared spectroscopy (FTIR) were used to complement XPS measurements. The films appeared to orient on the silicon wafer surface in the type II chitin structure. The rates of oxidation are faster for the plasma process but they result in similar changes to those induced by UV/ozone treatment. Atomic force microscopy (AFM) clearly shows the advantage of the milder modification reaction without much change in surface morphology. The oxidation processes, as detected by XPS, proceed without much alteration of the amine nitrogen atoms but carbonyl containing moieties are formed as a function of treatment time. Specific reactions with a fluorosilane to measure the activity of hydroxyl groups indicate that at short treatment times, these groups are essentially inactive. The resulting surfaces can also serve as a potential way to induce silica‐like domains that can function as diffusion barriers. Irradiation of chitosan solutions shows that UV/ozone induces depolymerization. In both cases, i.e., plasma and UV/ozone reactions, the main active component to surface modification appears to be UV irradiation with a wavelength below 360 nm.

AFM surface profile for oxygen plasma treated film in barrel etcher for 1 min.

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AFM surface profile for oxygen plasma treated film in barrel etcher for 1 min.