Molecular weight determination of 83% degree of decetylation chitosan with non‐Gaussian and wide range distribution by high‐performance size exclusion chromatography and capillary viscometry

Molecular weight determination of 83% degree of deacetylation (DD) chitosan with non‐Gaussian and broad molecular weight distribution by high‐performance size exclusion chromatography (HPSEC) and by capillary viscometry were proposed. The relationships between weight average retention volumes (RVw) of HPSEC and intrinsic viscosities ([η]) measured by capillary viscometer and the weight average molecular weight (Mw) measured by static light scattering were established for routine molecular weight determination of chitosans either by HPSEC or by the capillary viscometry method, respectively. These results showed: relationships of RVw and Mw for different Mw of 83.0% DD chitosans can be expressed by the equation Log Mw = −0.433 RVw + 11.66. The RVw of other DD chitosans do not correlate well with this equation. It indicated that DD of chitosan affected the relationship of RVw and Mw of chitosans studied. The Mark–Houwink constant a decreased from 0.715 to 0.521, as the solution ionic strength increased from 0.01M to 0.30M, whereas constant k increased from 5.48 × 10⁻⁴ to 2.04 × 10⁻³ over the same range of ionic strength solutions. The established RVw and Mw equation and [η] and Mw equation (Mark–Houwink equation) can be routinely used to determine the molecular weight from RVw or [η] of chitosan by HPSEC or by capillary viscometer, respectively, without the need of expensive instrumentation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1905–1913, 1999     

Urea‐induced conformational changes of chitosan molecules and the shift of break point of Mark–Houwink equation by increasing urea concentration

Chitosan solutions of the same 83% degree of deacetylation (DD) but different weight average molecular weights (M_ws) (78–914 kDa) in 0.01M HCl containing different concentrations of urea (0–6M) were prepared. Intrinsic viscosity ([η]) and weight average molecular weight (M_w) of chitosan were measured with a capillary viscometer and light scattering, respectively. Mark–Houwink exponent a was used as the parameter of conformational index. The Mark–Houwink exponent a increased with increasing concentrations of urea. When solutions contained 0, 2, 3, 4, and 6M urea, the value of a increased from 0.715 to 0.839, 0.894, 1.000, and 1.060, respectively. This indicates the occurrence of urea‐induced conformational transitions of chitosans. The break point shifted from 223 kDa in solutions containing no urea to 280 kDa in 2M urea solutions, to 362 kDa in 4M urea solutions and further to 481 kDa in 6M urea solutions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 452–457, 2000     

Molecular weight‐dependent antifungal activity and action mode of chitosan against Fulvia fulva (cooke) ciffrri

Antifungal activities of chitosans (CTS) with different molecular weights (M_w) and different concentrations against Fulvia fulva (cooke) ciffrri (F. fulva) causing leaf mold in tomato plants were studied in vitro and in vivo; the action mode and its inhibition at different stages during the life cycle of F. fulva were observed. The results showed that: (1) in vitro, CTS exhibited strong antifungal activity against F. fulva, especially for the medium M_w (213 and 499 KDa) CTS. Almost complete inhibition of F. fulva conidia germination and mycelia colony radial growth was found when CTS was at concentration of 0.5 and 2 mg mL^?1, respectively; however, inhibitory effect on sporulation was not very obvious for all CTSs tested in this experiment. In vivo, CTS of 213 KDa CTS at 6 mg mL^?1 concentration produced stronger antifungal effect than others. (2) The morphological study by scanning electron microscope (SEM) showed that CTS could induce the hyphal swelling, and the surface of hypha which was treated with low M_w (82 KDa) chitosan was smooth, but was rough treated with high M_w (1320 KDa) chitosan. The further study using a confocal laser scanning microscopy (CLSM) coupled with fluorescein isothiocyanate (FITC)‐fluorescence detection system showed fluorescence of the FITC‐labeled chitosans of which M_ws were below 500 KDa could enter into the inner of hypha; however, 1320 KDa chitosan was blocked off the outer of hypha. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Degradation and biodegradation of polyethylene with pro‐oxidant aditives under compost conditions establishing relationships between physicochemical and rheological parameters

In the present work, an analysis is carried out to provide a relationship between the Molecular Weight (M_w) of degraded LDPE films (containing Mn stearate as pro oxidant (MnSt‐LDPE) and changes in viscosity, elongation at break (EB %) and carbonyl index (CI) occurring during thermal degradation in the thermophilic phase of the compost process. The thermal treatment comprised various temperatures (50°C, 60°C, and 70°C) and exposure times, and was characterized through a so‐called Energy‐Time Factor (the product of thermal energy and exposure time). Changes in viscosity, EB %, and CI were correlated to this factor. A modified Mark‐Houwink equation was used to relate the zero shear‐rate viscosity and M_w of the degraded LDPE films. Results indicate that the EB %, M_w and viscosity decrease simultaneously with an increase in the CI as the Energy‐Time Factor augments, allowing the assessment of the variation of these properties with M_w. Calculations of the percentage abiotic degradation (%D) of LDPE films indicate that a M_w of 6 kg mol^?1 corresponds to a maximum abiotic degradation degree of 91.85%, which is henceforth susceptible to biodegradation. The film treated with Energy‐Time Factor of 2.79E+09 J s mol^?1 reached a 74% of biodegradation in 90 days (average time of the composting process). Results exhibit clearly the correlation between abiotic and biotic degradation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42721.     

Molecular weight distribution of commercial PVC

The molecular weight distribution (MWD) of commercial suspension grade poly(vinyl chloride) (PVC) resins with K values from 50 to 93 and mass grade PVC resins with K values from 58 to 68 has been determined by size exclusion chromatography (SEC), using literature Mark‐Houwink coefficients. The MWD is characterized by the number average molecular weight (M_n), the weight average molecular weight (M_w) and the polydispersity (M_w/M_n). Our results for M_w are consistent with recently published data, but we find different results for M_n and consequently for M_w/M_n. The polydispersity of PVC increases with increasing K value. This effect can be explained by two mechanisms. The first mechanism is a reduced terminating reaction rate between two growing polymer chains (disproportionation) at higher molecular weight owing to the reduced mobility of the polymer chains. The second mechanism is long‐chain branching of molecules with high molecular weight which lets the molecules grow at two ends. For two examples graphs of the measured MWD are compared with the theoretically expected MWD.     

Effects of the orientation of smectite particles and ionic strength on diffusion and activation enthalpies of I and Cs ions in compacted smectite

The apparent diffusion coefficients (D_a) for I⁻ and Cs⁺ ions in compacted Na-smectite which is a major constituent clay mineral of bentonite were studied as a function of smectite's dry density (0.9–1.4 Mg/m³), ionic strength ([NaCl] = 0.01, 0.51 M), temperature (22–60 °C) and diffusion direction to the orientated direction of smectite particles. The Na-smectite was prepared by ion-exchanging with Na⁺ ions a Na-bentonite, Kunipia-F®, of which smectite content is over 99 wt.%. The D_a-values for both ions showed a tendency to be higher in the parallel direction than in the perpendicular direction to the orientated direction of smectite particles at a low-ionic strength of [NaCl] = 0.01 M. The D_a-values for I⁻ ions showed different trends depending on diffusion direction and dry density at a high-ionic strength of [NaCl] = 0.51 M. Namely, although the D_a-values for I⁻ ions showed a tendency to be higher in the parallel direction than in the perpendicular direction to the orientated direction of smectite particles at a high-dry density of 1.4 Mg/m³, these showed a reciprocal tendency at dry densities of 0.9–1.0 Mg/m³. The D_a-values for Cs⁺ ions uniformly increased with an increase of ionic strength in both diffusion directions. Considering electrostatic effect from smectite surface and the change in tortuosity on dry density, ionic strength and diffusion direction to the orientated direction of smectite particles, I⁻ ions are considered to mainly diffuse in interstitial pores. While, Cs⁺ ions can diffuse in both interlayer and interstitial pores, and the D_a-values are considered to have elevated by competing with Na⁺ ions. The activation enthalpies (ΔE_a) for I⁻ ions, slightly higher (ΔE_a = 19.8−20.0 kJ/mol) than that of the diffusion coefficient in free water (D^o) for I⁻ ions (ΔE_a = 17.36 kJ/mol) at a low-ionic strength of [NaCl] = 0.01 M, decreased with an increase of ionic strength, became of similar level to that of the D^o at a high-ionic strength of [NaCl] = 0.51 M, increased with an increase of dry density. On the contrary, the ΔE_a-values for Cs⁺ ions, clearly higher (ΔE_a = 25.6−28.4 kJ/mol) than that of the D^o for Cs⁺ ions (ΔE_a = 16.47 kJ/mol) even in low-dry density over the ionic strength, increased with an increase of dry density. The ΔE_a-values for Cs⁺ ions are considered to be due to the decrease in the activity of porewater in addition to the effect of ion exchange enthalpy between Cs⁺ and Na⁺ ions in smectite.     

Viscometric Behavior of Solution of Polyisobutylene in Hexane and Cyclohexane Solvents: Viscosity-Molecular Weight Relationships

The behavior of three different high molecular weight polyisobutylenes (PIB) in solutions of hexane and cyclohexane at 30°C has been investigated by viscometry. Mark–Houwink relations have been examined, the polymer–solvent interaction is discussed in terms of the calculated Huggins constant, k; parameter a of the Mark–Houwink equation; and equivalent hydrodynamic volumes V _e. The molecular weights of the three sample of polyisobutylene are remarkably well fitted with the intrinsic viscosity data.     

Glass transition temperature and chain flexibility of 1,2-polybutadiene

The solubility parameter and glass transition temperature of 1,2-polybutadiene with different 1,2-unit content have been measured. T_g increases with increasing 1,2-unit content, whereas no essential change of solubility parameter has been observed. So, it may be concluded that chain flexibility arising from internal rotation about single bond is the sole factor which determines glass transition. Chain flexibility was then studied by computation of energy of rotational isomerization ε and the steric factor ε characterizing hindrance to internal rotation. Finally, the potential barrier to internal rotation U was obtained by correlating δ and ε via T_g. The results are shown in Table VI. σ, ε and U all increase with increasing 1,2-unit content indicating rising of T_g is a result of increasing chain stiffness. Determination of the solubility parameter of 1,2-polybutadiene by viscometry with toluene–cyclohexane (similar molar volume) as mixed solvent was examined and proved to be reliable. The exponent α in the Mark–Houwink equation for 1,2-polybutadiene–toluene system was estimated from the solubility parameter of polymer and solvent according to the method of van Krevelen and Hoftzer¹⁶ and found to be 0.725. This value of α was used as a first approximation for the calculation of molecular weights from GPC data. The Mark–Houwink equations finally established for the system, 1,2-polybutadiene–toluene (30°C) with different 1,2-unit contents are given in eqs. (8)–(10).     

Polybenzimidazole (PBI) molecular weight and Mark‐Houwink equation

The molecular weight, and intrinsic viscosity of polybenzimidazole (PBI) and its phosphonylated derivatives are reported. The relationship between intrinsic viscosity [η] and weight average molecular weight (M_w) for PBI has been established in H₂SO₄ and DMF‐LiCl. The Mark Houwink constants K_w of 5.2 × 10^?3 mL/g, α of 0.92 for H₂SO₄ solvent systems and, K_w of 3.2 × 10^?2 mL/g, α of 0.754 for DMF‐LiCl solvent system have been determined at M_w < 65,000. The intrinsic viscosity of PBI determined by the Huggins–Kraemer method was compared with a single point method, and found that both methods fit well for PBI in relatively low concentration solvent system, giving ～ 99% accuracy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Moisture retention and antibacterial activity of modified chitosan by hydrogen peroxide

A series of chitosans with various molecular weights from 1.2 × 10³ to 30.0 × 10⁴ were prepared by oxidative degradation with H₂O₂ and characterized by IR, ¹³C‐NMR, and gel permeation chromatography. Their carboxylic contents increased with a decrease in molecular weight (M_w). The moisture‐absorption and moisture‐retention capacities of resulting chitosans were dependent on both the molecular weight and the degree of deacetylation (DD). Microcalorimetry was first used to study the kinetics of action of the chitosans on a strain of Staphylococcus aureus at pH 7. The antibacterial activity of the water‐soluble chitosan against S. aureus, Escherichia coli, and Salmonella typhi was evaluated by the conventional agar plate method at pH 7. The water‐soluble product with M_w of 0.45 × 10⁴ from initial chitosan of DD of 90% showed high moisture‐absorption and moisture‐retention capacities, and <2% concentration can completely inhibit the growth of these bacteria. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1724–1730, 2002     

Synthesis of star‐shaped poly(ϵ‐caprolactone) by samarium‐based tetrafunctional initiator and its dilute‐solution properties

An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1‐tetra(2‐bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh₂)₂ and SmI₂] in tetrahydrofuran has proven to initiate the ring‐opening polymerization of ?‐caprolactone (CL) giving star‐shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four‐armed poly(?‐caprolactone) (PCL) was fractionated, and the dilute‐solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10^?2M_w^0.74 and [η] = 1.97 × 10^?2M_w^0.75, respectively. In addition, the unperturbed dimensions of the star‐shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006     

Preparation and characterization of a foam regulator with ultra‐high molecular weight

Multistage emulsion polymerization was used to prepare ultra‐high molecular weight foam regulator of low cost, with methyl methacrylate (MMA), butyl acrylate (BA), styrene (St) as main raw materials. Ubbelohde viscometer, dynamic light scattering, infrared and raman spectra, TEM, DSC, TGA, and GPC were all used to characterize constituent and structure, morphology, and molecular weight. As a result, when the ratio of soft monomer (BA) and hard monomer (St + MMA) is 1:3, MMA:St = 4:1, potassium persulfate (KPS): 0.15%, sodium hydrogen sulfite (SHS): 0.05%, azodiisobutyronitrile (AIBN): 0.15%, divinyl benzene (DVB): 0.3%, the final product terpolymer has obvious core‐shell structure and ultra‐high molecular weight (M_w = 1,400,000). This kind of foam regulator showed improvements in the melt strength, prevention of bubble coalescence and reduction on cost when compared with the traditional. Finally, the coefficients of poly (methyl methacrylate‐butyl acrylate‐styrene) terpolymer's Mark‐Houwink equation were calculated with tetrahydrofuran (THF) solvent at 25 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44479.     

Characterization of poly[di(carboxylatophenoxy)-phosphazene] by an aqueous gel permeation chromatography

A water-soluble phosphazene polyelectrolyte, poly[di(carboxylatophenoxy)phosphazene] (PCPP), was characterized using aqueous gel-permeation chromatography (GPC) with concentration (UV and RI) and molecular weight sensitive (multiangle laser light-scattering) detectors. Agreement was observed between the weight-average molecular weights determined by GPC with a light-scattering detector, conventional GPC using fractionated narrow PCPP standards, and also by static light-scattering measurements. The effect of chromatography conditions, such as ionic strength of the mobile phase, column resolution, and injection volume was investigated. Mark–Houwink constants of PCPP in aqueous solution (phosphate buffer, pH 7.4, 0.42MNaCl) were determined. The validity of the universal calibration curve and the occurrence of a secondary nonexclusion mechanism of separation in aqueous GPC of phosphazene polyelectrolytes are discussed. © 1996 John Wiley & Sons, Inc.     

Solution properties and molecular-weight distribution of nylon 11

Molecular, hydrodynamic, and thermodynamic properties of nylon 11 in meta cresol and 1,1,1,2,2,2-hexafluor-2-propanol (HFIP) solutions, as well as its distribution of molecular weights were investigated by means of viscosimetry, conductimetric titration of end groups, light scattering, and fractionation by successive precipitation. The studies were carried out on commercial samples as such (M _n = 14,900, M _w = 29,400) and on specimens prepared by solid-state postpolymerization of the former (M _n = 35,000–43,000, M _w = 91,000–104,000). The results show the expected normal or Flory–Schulz distribution of molecular weights on the commercial sample (U = 1.03), and a broadened distribution on the postpolymerized one (U = 1.42), in agreement with previous observations on solid-state postpolymerization of other polyamides. The intrinsic viscosity of the individual fractions was determined experimentally and the weight-average molecular weights were calculated from the data of the fractionation (number-average molecular weight and the mass fraction of polymer on each individual fraction) by means of an iterative numerical procedure. The parameters of the Mark–Houwink equation were, then, derived from the data of a large number of samples, including that corresponding to the whole, unfractionated polymers, spanning a range of about 100,000 units of molecular weight. The value of the exponent (a = 0.69) for solutions in meta cresol corresponds to the behavior of a linear, flexible macromolecule in a good-solvent medium. The solutions in HFIP employed for the light-scattering studies, on the other hand, display high values of the second virial coefficient (A₂ = 7.8 × 10^?3 ? 5.6 × 10^?3 mol mL/g), suggesting that HFIP is a good solvent for nylon 11.     

Evaluation of GPC methods for estimation of Mark–Houwink–Sakurada constants

Constants for the Mark–Houwink–Sakurada relation can be established in principle from GPC measurements on broad distribution polymers. The method requires use of two samples with different intrinsic viscosities or a single polymer for which [η] and M ⁿ M ^w are known. The [η]–M ^w combination is not reliable because M ^v and M ^w are often very similar in magnitude. The [η]M _n method is likewise not recommended because of the influence of skewing and axial dispersion effects on the GPC measurement of M _n. The simplest and safest way to use GPC data to estimate the MHS constants involves the measurement of GPC chromatograms of two polymer samples with different intrinsic viscosities. The method is not confined to the solvent used as the GPC eluant. The MHS constants derived from GPC appear to reflect the molecular weight range of the calibration samples and may not be as widely applicable as those from the more tedious classical methods which employ a series of fractionated samples.     

High-pressure viscosity and density of polyethylene solutions in n-pentane

Viscosity and density of homogeneous one-phase solutions (1 wt %) of polyethylenes with narrow molecular weight distributions (M_w = 2150, 15,520, 108,000, and 420,000) in n-pentane were determined at 398, 413, and 428 K over a pressure range from 20 to 60 MPa. Measurements were done with a special falling cylinder type viscometer that permits simultaneous determination of viscosity, density, and phase state of the solutions. It is shown that the viscosities of these solutions can be correlated with density (p) using the exponential relationships μ ? A exp {B/(1 ? V_oρ)} or μ = C₁ exp (C_2ρ), which are based on free-volume considerations. Analysis of the temperature dependence of viscosity at fixed pressures, and its pressure dependence at fixed temperatures show that the flow-activation energies for these solutions are in the range 8–12 kJ/mol, and the apparent activation volumes are in the range 30–45 cm³/mol. Evaluation of the specific viscosity and analysis of the molecular weight dependence of intrinsic viscosity in accordance with Mark–Houwink type relationship μ = KM^a suggest a value of 0.5 for the exponent a, which is typical of poor or theta solvents. © 1995 John Wiley & Sons, Inc.     

Styrene–butyl acrylate–N,N-dimethyl N-butyl N-methacrylamidino propyl ammonium bromide emulsifier–free emulsion copolymerization

Emulsifier-free emulsion copolymerization of styrene (St) and butyl acrylate (BA) in the presence of cationic functional comonomer N,N-dimethyl N-butyl N-methacrylamidino propyl ammonium bromide (DBMPAB) was carried out using azobis(isobutylamidine hydrochloride) (AIBA) as initiator. The surface properties of particles were studied by testing the actual value of -N⁺ and -C⁺(NH₂)₂ (Publisher's note: for graphical representations please see printed journal or the Acrobat PDF version on this website.) on the surface of particles and the surface charge density. The copolymer particles were characterized by transmission electron microscopy (TEM). The effects of reaction temperature, DBMPAB content, AIBA content, and ionic strength on conversion of monomer, average diameter D _w) and number (N_p) of copolymer particles were investigated. Under constant ionic strength the average diameter of copolymer particles (D_w) decreased with increasing AIBA and DBMPAB concentration, and decreased with rising reaction temperature. At constant concentration of comonomer and initiator and constant monomer composition, D_w showed an increase–decrease–increase with ionic strength plot. The polymerization rate increased with increasing DBMPAB content, AIBA content and rising temperature. The surface charge properties of particles were mainly decided by DBMPAB content, AIBA content, and ionic strength. ©1997 SCI     

The influence of molar mass on rheological and dilute solution properties of poly(butylene succinate)

The fundamental rheological properties of a wide molar mass M_w range of poly(butylene succinate)s (PBSs) are investigated. For entangled samples and a reference temperature of 140°C, the shear viscosity is described by the Carreau–Yasuda model. The plateau modulus is estimated at 1.5 × 10⁵ Pa, the average activation energy of PBS melt is , and the critical molar mass for entanglement M_c is found to be 16,000 g mol^?1 (PS equivalent). The dilute solution properties of PBS are also studied. A size exclusion chromatography equipped with a triple detection system is used to estimate the Mark–Houwink–Sakurada (MHS) parameters of PBS in solution in chloroform at 30°C. The exponent a and the coefficient K of the MHS relationship are found to be 0.71 ± 0.1 and 39.94 × 10^?5 ± 6.31 × 10^?5 dL g^?1(g mol^?1)^?a, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40887.     

Studies on bulk diffusion and local diffusion of polystyrene in melt

Results of bulk viscosity (η) and local viscosity (ξ) of various molecular weights of polystyrene (PS) have been reported. In this paper the relationship between η and bulk diffusion coefficient (D_B), and that between ξ and local diffusion coeffizient (D_L) are presented. Data obtained lead to several conclusions. From the results of unperturbed dimensions and a universal constant (Φ), it was found that F. Bueche's equation D_B · η = const. is valid for polystyrenes with molecular weights over 600. Temperature and component concentration dependence of bulk diffusion coefficient for the two-component blend system may be interpreted in terms of the free volume theory. At an iso-free volume state, molecular weight dependences of bulk diffusion coefficients for both PS of narrow distribution of molecular weight and blend PS can be composed to a single curve, which is composed of two straight lines in a double logarithmic presentation with intersection at M_w = 1.78 × 10⁴ g/mol. The slopes of these two lines were ? 1.0 and ? 3.3, respectively. The product D_L · ξ was determined to be 1.10 × 10^?7 (c.g.s) for n-paraffines from the data of self-diffusion coefficient and ξ. This made it possible to determine D_L from ξ. For higher molecular weights of PS, log D_B is a linear function of log M_w while log D_L stays almost constant.     

溶剂对壳聚糖粘度及Mark-Houwink方程参数的影响

采用粘度法分析了不同溶剂对壳聚糖粘度的影响 ,用光散射法测定了超声波分级的壳聚糖的相对分子质量。实验结果表明 :四种溶剂体系分别溶解壳聚糖 ,其粘度行为不同 ,溶剂的离子强度越大 ,壳聚糖的比浓粘度越小。在 0 .3mol/ L乙酸 + 0 .3mol/ L乙酸钠溶剂的条件下 ,应用 Mark-Houwink方程测得 K=0 .1 81 cm3 / g、α=0 .62 ,说明离子强度越大 ,壳聚糖分子的聚集态越大 ,α越小。为了获得准确的 K、α值和壳聚糖的相对分子质量 ,必须选择合适的溶剂体系来消除这种聚集态的影响。