Interpopulational variation in emitted pheromone blend of cabbage looper moth,Trichoplusia ni

Female cabbage looper moths,Trichoplusia ni, from laboratory colonies initiated from three locations across the United States emitted similar quantities and blend ratios of the six known pheromone components. In contrast, females from a long-established laboratory colony emitted a greater proportion of four of the five minor components relative to the major component, (Z)-7-dodecenyl acetate; only the relative proportion of 11-dodecenyl acetate was similar in all of the populations sampled. Females from this population emitted (Z)-7-dodecenyl acetate at a rate similar to that from females from field-collected colonies. Within each population there were highly significant correlations among the quantities of pheromone components of similar molecular weights. Correlations between components of different molecular weights were not as great, but often were significant. Similarities of blend ratios among field populations may indicate that the chemical signal in this species is conservative. The difference of the blend ratios in our laboratory population from the other populations may indicate a decrease in the intensity of selection pressure that usually would maintain these values.     

Isolation,Amino Acid composition and molecular weight distribution ofEucalyptus kirtoniana seed proteins

Proteins were extracted from the deoiled seeds ofEucalyptus kirtoniana in aqueous solutions of various pHs or by different concentrations of NaCl, Na₂SO₃, CaCl₂ and MgCl₂ at pH 8.0. Amino acid analysis of the isolated protein identified 16 amino acids, nine of which were essential. Gel permeation chromatography on Sephadex G-200 revealed the presence of four components in the protein fraction, and their molecular weights were determined by two comparable standard methods. SDS-PAG electrophoresis demonstrated that each protein isolate from different salt solutions was composed of six fractions whose molecular weights were estimated to be 131,800; 108,300; 93,300; 51,300; 38,000 and 25,700 daltons.     

Synthesis and characterization of poly(methyl methacrylate) star polymers

Star-branched poly(methyl methacrylate)s (PMMA) were synthesized by linking ‘living’ arms (produced by anionic polymerzation) with ethylene glycol dimethacrylate. Stars having arm molecular weights of 10000 and 40000 and between 4.9 and 18.7 branches were produced. The polymers were characterized using light scattering, size exclusion chromatography, and viscometry. It was found that well-defined PMMA stars were obtained only at the higher (40000) arm molecular weight. The stars prepared using the lower molecular weight (c. 10000) arms contained very high molecular weight gel components.     

Miscibility of polystyrene with poly(ethylene oxide) and poly(ethylene glycol)

The intrinsic viscosity of polystyrene–poly(ethylene oxide) (PS–PEO) and PS–poly(ethylene glycol) (PEG) blends have been measured in benzene as a function of blend composition for various molecular weights of PEO and PEG at 303.15 K. The compatibility of polymer pairs in solution were determined on the basis of the interaction parameter term, Δb, and the difference between the experimental and theoretical weight-average intrinsic viscosities of the two polymers, Δ[η]. The theoretical weight-average intrinsic viscosities were calculated by interpolation of the individual intrinsic viscosities of the blend components. The compatibility data based on [η] determined by a single specific viscosity measurement, as a quick method for the determination of the intrinsic viscosity, were compared with that obtained from [η] determined via the Huggins equation. The effect of molecular weights of the blend components and the polymer structure on the extent of compatibility was studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1471–1482, 1998     

Molecular weight distribution of PVC blends from resins with different K values

The molecular weight distribution (MWD) of blends of commercial suspension grade PVC resins with different molecular weights (MW) or K values is calculated. If the K‐value difference is not too high, the polydispersity of the blend is only slightly increased as compared to those of the components. It is not possible to get bimodal MWDs by blending. Additionally, a model calculation of mean molecular weights has been performed for temperature‐programmed polymerization. On the basis of the most realistic model, which takes into account the increasing polymerization reaction rate with increasing temperature and increasing conversion, it can be predicted that a linear temperature program will give a product corresponding to an isothermal resin polymerized at a temperature near the high end of the temperature program and showing only a slightly increased polydispersity.     

Comparison of cellulolytic enzyme complexes of different fungal origin

The cellulolytic culture filtrates of Trichoderma reesei QM 9414, Aspergillus terreus OKI 16/5 and Penicillium verruculosum WA 30 were purified and separated into components by one-step preparative isoelectric focusing (IF). The culture filtrates, the mycelia and the separated components were investigated for cellulolytic (filter-paper degrading (FPA), carboxymethylcellulose degrading (C_x), cotton hydrolyzing (C₁), cellobiase) and proteinase B activities. The molecular weights of the cellulolytic fractions were determined by SDS-electrophoresis. The culture filtrates differed in the proportions of the various cellulolytic activities. The analytical IF separation of the enzyme complexes resulted in a total of 28–31 protein fractions, mostly glycoproteins. The complexes of the different culture filtrates were separated, by preparative IF, into 28 fractions each. The greatest part of the activities could be recovered in fractions 8–18. The activities in the fractions were recovered to different extents. The main protein components in the enzyme complexes were found to be endoglucanases (C_x) with pI values between 3 and 6. Most of the endoglucanases proved to be glycoproteins. FPA and cellobiase activities were recovered to various extents in the fractions of the three culture filtrates. Only small parts of the C₁ activities were recovered in the Trichoderma and Penicillium fractions. The originally low C₁ activity of the Aspergillus culture filtrate was recovered to 76% in the separated fractions. Most of the C_x activities were found to be lost. However, the separation losses were found to be reversible: on combining the fractions, the activities originally present in the culture filtrate were nearly entirely restored. The molecular weights of the fractions of the different culture filtrates covered the range 10 000 to 70 000 D. The IF fractions of similar activity patterns also showed similar molecular weight distributions. The relatively large number of isoenzymes is assumed to be the result of the endocellular proteinase activity present, which splits off the cellulase enzyme components from proenzymes of high molecular weight during the fermentation process.     

Effect of isotacticity distribution on crystallization kinetics of polypropylene

The crystallization kinetics of isotactic polypropylene (iPP) depends not only on the undercooling but also on its microstructure characteristics. In this paper the effect of isotacticity distribution on the isothermal kinetics of iPPs in the crystallization regime III was examined by differential scanning calorimetry. The microstructure features of two commercial film grade iPPs were characterized with temperature rising elution fractionation and size exclusion chromatography. The results indicated that, although the overall isotacticities and molecular weights of two iPPs were similar, their isothermal crystallization kinetics displayed marked differences due to the disparity in isotacticity distributions. With increasing molecular weight of components containing crystallizable units, the isothermal crystallization rate exhibited a higher temperature dependence. When the isotactic defects in polypropylene chains increase with the molecular weight of components, both the fold surface free energy σ_e and the work of chain folding q decreases, in spite of the higher molecular weight. © 2002 Society of Chemical Industry     

Synthesis and hydrophilicity of poly(butylene 2,6‐naphthalate)/poly(ethylene glycol) copolymers

Poly(butylene 2,6‐naphthalate) (PBN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two‐step melt copolymerization process of dimethyl‐2,6‐naphthalenedicarboxylate (2,6‐NDC) with 1,4‐butanediol (BD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structures, thermal properties, and hydrophilicities of these copolymers were studied by ¹H NMR, DSC, TGA, and by contact angle and moisture content measurements. In particular, the intrinsic viscosities of PBN/PEG copolymers increased with increasing PEG molecular weights, but the melting temperatures (T_m)_, the cold crystallization temperatures (T_cc)_, and the heat of fusion (ΔH_f) values of PBN/PEG copolymers decreased on increasing PEG contents or molecular weights. The thermal stabilities of the copolymers were unaffected by PEG content or molecular weight. Hydrophilicities as determined by contact angle and moisture content measurements were found to be significantly increased on increasing PEG contents and molecular weights. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2677–2683, 2006     

Molecular weight effect on antimicrobial activity of chitosan treated cotton fabrics

The effect of the molecular weight of chitosan on antimicrobial activity was investigated using three chitosans of different molecular weights [1800 (water soluble), 100,000, and 210,000] and similar degrees of deacetylation (86–89%). Cotton fabrics were treated with chitosan by the pad–dry–cure method. The molecular weight dependence of the antimicrobial activity of chitosan was more pronounced at a low treatment concentration. Chitosans with molecular weight of 100,000 and 210,000 effectively inhibited Staphylococcus aureus at a 0.5% treatment concentration. Chitosan with a molecular weight of 1800 was effective against S. aureus at a 1.0% treatment concentration. Escherichia coli was effectively inhibited by chitosan with a molecular weight of 210,000 at a 0.3% treatment concentration and by chitosans with a molecular weight of 1800 and 100,000 at a 1.0% treatment concentration. Proteus vulgaris was effectively inhibited by chitosans with molecular weight of 100,000 and 210,000 at a 0.3% treatment concentration and by chitosan with a molecular weight of 1800 at a 0.5% treatment concentration. None of the chitosans significantly inhibited Klebsiella pneumoniae and Pseudomonas aeruginosa below a 1.0% treatment concentration. Chitosans with high molecular weights were more effective in inhibiting bacterial growth than chitosans with low molecular weights. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2495–2501, 2001     

Nitroxide‐Controlled Grafting by an Insertion Mechanism using a Polymerizable N‐Oxyl

Summary: The polymerizable nitroxide 4‐acryloyloxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (AOTEMPO) was utilized in a two step polymerization to prepare alkoxyamine‐functionalized backbone polymers. These backbones were then used as initiators for stable free‐radical graft polymerizations in bulk at 125 °C. The products were cleaved into their linear components by reaction with L ‐(+)‐ascorbic acid allowing a reproducible analysis of the molecular weights. The influences of the backbone concentration and the graft density on the polymerization were investigated. Graft polymers purely consisting of styrene were produced as well as polymers with a backbone based on 2‐ethoxyethyl acrylate (EOEA). In addition a graft polymer with block copolymer side chains was prepared by extending a preformed graft polymer. In all cases the controlled course of the reaction was confirmed by the linear increase of the molecular weights over conversion and the low polydispersities of the products.

Structure of an extended graft copolymer.     

Factors influencing molecular weights of methylcelluloses prepared from annual plants and juvenile eucalyptus

We studied the factors that influenced the molecular weights (M_w) of water‐soluble methylcelluloses prepared from annual plants and juvenile eucalyptus. Miscanthus and cardoon stalks, and bleached pulps of abaca, jute, sisal, hemp, and flax were the annual plant materials studied. A higher concentration of NaOH solution during the impregnation led to a spring cardoon methylcellulose having a lower molecular weight. As the impregnation times increased, so did the molecular weights of the water‐soluble methylcelluloses of spring cardoon. The impregnation conditions had less influence on the methylcelluloses of summer cardoon than on the methylcelluloses of spring cardoon. As the cooking times increased, so did the molecular weights of miscanthus methylcelluloses. A lower pulping severity increased the molecular weight of eucalyptus methylcellulose. The preliminary treatments (water soaking, premercerization, mercerization under pressure, and steam explosion) improved the molecular weights of water‐soluble abaca methylcelluloses. The steam explosion method was the best of the preliminary treatments for the abaca pulp. Different species led to different molecular weights for methylcelluloses synthesized from ECF bleached pulps, and these were further improved by preliminary mercerization. The molecular weight of α‐cellulose methylcellulose changed as the ratio of the methylation reagent was varied. To synthesize an optimum M_w of methylcellulose, the different raw materials can be chosen, the pulping parameters adjusted (including impregnation and cooking), the cellulose pretreated, and the methylcellulose conditions changed. The plant species is the decisive factor for the M_w of methylcellulose. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1785–1793, 2006     

Synthesis of PLLA‐PEOMA comb‐block‐comb type molecular brushes based on AGET ATRP and ring‐opening polymerization

BACKGROUND: Molecular brushes are types of macromolecules with densely grafted side chains on a linear backbone. The synthesis of macromolecular brushes has stimulated much interest due to their great potential in applications in various fields. Poly(L ‐lactide)–poly(ethylene glycol) methyl ether methacrylate (PLLA‐PEOMA) comb‐block‐comb molecular brushes with controlled molecular weights and narrow molecular weight distributions were successfully synthesized based on a combination of activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) and ring‐opening polymerization. The synthetic route is a combination of the ‘grafting through’ method for AGET ATRP of the PEOMA comb block and the ‘grafting from’ method for the synthesis of the PLLA comb block. Poly(2‐hydroxyethyl methacrylate) (PHEMA) was synthesized by ATRP, and PLLA side chains and PEOMA side chains were grown from the backbones and the terminal sites of PHEMA, respectively. RESULTS: The number‐average degrees of polymerization of PLLA chains and poly[poly(ethylene glycol) methyl ether methacrylate] (PPEOMA) comb blocks were determined using ¹H NMR spectroscopy, and the apparent molecular weights and molecular weight distributions of the brush molecules were measured using gel permeation chromatography. The crystallization of the components in the comb‐block‐comb copolymers was also investigated. The crystallization of PLLA side chains is influenced by PLLA chain length and the content of PPEOMA in the molecular brushes. The comb‐block‐comb copolymer composed of hydrophobic PLLA and hydrophilic PEOMA can self‐assemble into a micellar structure in aqueous solution. CONCLUSION: A combination of AGET ATRP and ring‐opening polymerization is an efficient method to prepare well‐defined comb‐block‐comb molecular brushes. The physical properties of the molecular brushes are closely related to their structures. Copyright © 2009 Society of Chemical Industry     

Reactions of unsaturated fatty alcohols. III. Viscosity and molecular weight studies on some vinyl ether polymers

Summary Molecular weights of the polymers of the vinyl ethers of stearyl, soybean, and linseed fatty alcohols were measured cryoscopically in cyclohexane at three different concentrations. Corrected number-average molecular weights were obtained by extrapolation to zero cocentration. For each family of polymers a series of preparations varying in degree of polymerization were studied with number-average molecular weights ranging from 1,500 to 15,000 or higher. Reduced viscosity measurements at 25°C. were made on benzene solutions of each polymer preparation at three different concentrations. Intrinsic viscosities were obtained by extrapolating to zero concentration. Intrinsic viscosities for the polymers range from 0.05 to 0.20. Logarithmic plots of molecular weightvs. intrinsic viscosity gave linear relationships for stearyl, soybean, and linseed polymers. Values forK′ anda in the equation of Mark and Houwink were obtained from these plots. Presented at fall meeting. American Oil Chemists' Society, September 23–26, 1956, Chicago, Ill.     

Solution blending of polystyrene and poly(methyl methacrylate)

Blends of poly(methyl methacrylate) (PMMA) and polystyrene (PS) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were made of a low molecular weight PS with three PMMAs having number-average molecular weights of (1) 18,300, (2) 37,000, and (3) 211,000, The blend was found to be partially miscible. The composition-dependent values of the polymer-polymer interaction parameter (g₁₂) were determined and found to be from 0.015 to 0.029 for solution casting at 25°C. The interaction parameter (g₁₂) increases with increasing PMMA molecular weights in the PMMA/PS blend systems. This result is consistent with the behavior of the glass transition temperatures and with the microscopy study which indicate that compatibility is greater in the PMMA-1/PS blends having the low molecular weight of PMMA than in the PMMA-3/PS blends having the higher molecular weights of PMMA.     

A simple strategy for the separation and purification of water-soluble polysaccharides from the fresh Spirulina platensis

A novel and industrially applicable strategy for separating and purifying the water-soluble polysaccharides from the fresh Spirulina platensis is introduced in this study. After hot water extraction, using chitosan flocculation treatment, 86.0% of the particles and 85.9% of the pigments in the crude extract were removed. The purity of polysaccharides could be increased to 94.6% and 96.1% by applying the macroporous resin ADS-7 to remove the impurities in the mode of static adsorption and in a dynamic mode of operation, respectively. The polysaccharides obtained were composed of three major components having molecular weights of 1400, 420 and 2 kDa.     

Improved accuracy and precision in the light-scattering characterization of homo- and copolymers in THF

A one-point method was developed for the estimation of weight-averaged molecular weights from light-scattering data. The method is based on the calculation of the second virial coefficient from theoretical predictions of the dependence of A₂ on the molecular weight. The second virial coefficient is then regressed for a particular polymer—solvent combination from a series of preexisting measurements over a range of molecular weights. The one-point method is found to yield as accurate molecular weight estimates as obtained from a Debye plot using the conventional dilution technique. The variance in the estimation of the Rayleigh factor has also been found to be highly dependent on the measurement concentration. Therefore, the precision in the estimation of molecular weight can be improved by calculating molecular weights at or near the optimal concentration, which is itself molecular weight-dependent. The one-point method is demonstrated for poly(methyl methacrylate)s of various polydispersities in tetrahydrofuran. The molecular weight of polystyrene and polystyrene-co-acrylic acid were also estimated by the one-point method in THF. In the case of the polystyrene-co-acrylic acid, THF becomes a poorer solvent with increasing levels of acrylic acid in the copolymer, and the parameter (A₂M^0.5) is found to vary with the copolymer composition, as is theoretically predicted. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1303–1316, 1997     

Gel permeation chromatography of ethylene–propylene copolymerization products

A simple method to calculate average molecular weights and D (≡M _w/M _n) value from the GPC chromatogram of copolymerization products, especially for ethylene–propylene copolymerization products, was investigated by simulation technique. The method is based on the use of the calibration curve determined by the average ethylene content of the products. In addition to this method, the calibration curve prepared for polypropylene was also applied to determined the D value. Average molecular weights and D values were determined, with small errors, for narrow distribution samples with respect to molecular weight and chemical composition.     

Solution properties of lignin. Thermodynamic properties and molecular weight determinations

Number-average molecular weights and the thermodynamic parameters ΔF?₁, ΔH?₁, and ΔS?₁ have been obtained for lignin in the solvents dimethylsulfoxide, dimethyl-formamide, and dioxane. Widely different molecular weights were found in the different solvents and at the different temperatures as a consequences of molecular association. Analysis of the thermodynamic parameters revealed that these quantities are dominated by the change in solvent structure accompanying the solution process. A correlation between the “goodness” of a lignin solvent and the Hildebrand solubility parameter is consequently misleading in such systems.     

Heterogeneous bulk polymerization of styrene in the presence of polybutadiene: Calculation of the macromolecular structure

A mathematical model is presented that simulates the polymerization of styrene in the presence of polybutadiene (PB) for producing high‐impact polystyrene (HIPS) via the heterogeneous bulk process. The model follows the polymerization in two phases; and calculates in each phase the main reaction variables and the molecular structure of the three polymeric components: free polystyrene (PS), unreacted PB, and graft copolymer. Two polymerizations (at 90 and 120°C) were carried out and simulated. The model was validated with measurements of the monomer conversion, the grafting efficiencies, and the average molecular weights. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3023–3039, 2006     

Graft copolymers of nylon 6 and polyphenylene oxide: Syntheses and their role in compatibilizing nylon 6/polyphenylene oxide blends

Poly(2,6-dimethyl-p-phenylene) oxides (PPO) grafted with nylon 6 were prepared by first quantitatively brominating the PPO, followed by reacting the brominated products with nylon 6 of different molecular weights. The molecular weights of PPOs were kept intact during bromination. These graft copolymers with well-defined structures were used as compatibilizers for nylon 6/PPO blends. Some compatibilization phenomena were observed, as indicated by the mechanical properties of the blends. The best compatibilization was achieved when the graft copolymer is most block-copolymer-like. © 1994 John Wiley & Sons, Inc.