Characterization of poly(1,4-phenyleneterephthalamide) in concentrated sulphuric acid: 1. Static and dynamic properties

Laser light scattering including angular dependence of total integrated scattered intensity and of the spectral distribution has been used to characterize five samples of poly(1,4-phenylene terephthalamide), PPTA (commercially known as Kevlar), of different molecular weights in 96% sulphuric acid and 0.1 NK₂SO₄. The data are supplemented by intrinsic viscosity measurements used to detect the possible effects of association, by differential refractometry providing a measure of the refractive index increments in mixed solvents (H₂O, H₂SO₄ and K₂SO₄) and by spectrophotometry for the extinction coefficient needed in the correction of attenuation in light scattering studies. The results show 〈D〉Z = 2.11 × 10^?5$\text{M}\text{?}{}_{\mathrm{<mtext>W</mtext>}}{}^{\mathrm{?0.75}}\text{cm}{}^{\mathrm{?2}}\text{s}{}^{\mathrm{?1}}$ in reasonable agreement with an average of many of the published intrinsic viscosity data obeying [η] = 1.09 × 10?3 M_w^1.25 ml g^?1 and _w expressed in g mol^?1.     

Molecular weight and chain conformation of amylopectin from rice starch

By using laser light scattering (LS) and size exclusion chromatography combined LS, we have investigated the molecular weight and chain conformation of amylopectin from rice of India (II‐b), japonica (IJ‐b), and glutinous (IG‐b) in dimethyl sulfoxide (DMSO) solution. The weight‐average molecular weight (M_w) and radius of gyration (〈S²〉^½) of amylopectin were determined to be 4.06 × 10⁷ and 128.5 nm for India rice, 7.41 × 10⁷ and 169.6 nm for japonica rice, 2.72 × 10⁸ and 252.3 nm for glutinous rice, respectively. The 〈S²〉^½ values were much lower than that of normal polymers, indicating a small molecular volume of amylopectin, as a result of highly branched structure. Ignoring the difference of degree of branching, approximated dependences of 〈S²〉^½ and intrinsic viscosity ([η]) on M_w for amylopectin in DMSO at 25°C were estimated to be 〈S²〉^½ = 0.30M_w^0.35 (nm) and [η] = 0.331M_w^0.41 (mL g^?1) in the M_w range studied. Moreover, from the 〈S²〉^½ values of numberless fractions obtained from many experimental points in the SEC chromatogram detected with LS, the dependence of 〈S²〉^½ on M_w for the II‐b sample was estimated also to be 〈S²〉^½ = 0.34 M_w^0.347, coinciding with the above results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Dependence of intrinsic viscosity and molecular size on molecular weight of partially hydrolyzed polyacrylamide

As a typical water-soluble polymer, ultra-high molecular weight (UHMW) partially hydrolyzed polyacrylamide (HPAM) has been widely used in various industries as thickeners or rheology modifiers. However, precise determination of its critical physical parameters such as molecular weight, radius of gyration (R_g) and hydrodynamic radius (R_h) were less documented due to their high viscosity in aqueous solution. In this work, the molecular structure of five UHMW-HPAM samples with different MW was elucidated by ¹H and ¹³C NMR spectroscopy, and their solution properties were characterized by both static and dynamic light scattering. It is found that all the second virial coefficient (A₂) values are positive and approaching zero, indicating of a good solvent of 0.5 M NaCl for UHMW-HPAM. The weight-average molecular weight (M_w) dependence of molecular size and intrinsic viscosity [η] for these series of HPAM polymers with MW ranging from 4.81 to 15.4 × 10⁶ g·mol⁻¹ can be correlated as R_g = 3.52 × 10⁻²M_w^0.51, R_h = 1.97 × 10⁻²M_w^0.51, and [η] = 6.98 × 10⁻⁴ M_w^0.91, respectively. These results are helpful in understanding the relationship between molecular weight and coil size of HPAM polymers in solution, and offer references for quick estimation of molecular weight and screening of commercial UHMW-HPAM polymers for specific end-users.     

Determination of solution viscosity characteristics of rubber seed oil based alkyds resins

Three medium oil alkyd samples of different oil length [(I) 45%, (II) 50%, and (III) 55%] were synthesized with rubber seed oil. Dilute solution viscosity measurements were carried out on the alkyd in acetone and in toluene. The parameters investigated include intrinsic viscosity [η], Huggins constant (k_H), and Mark‐Houwink Sakurada constants (κ and α). The [η] values for the alkyd samples were found to be larger in acetone than in toluene. The K_H values showed a regular order in acetone but not in toluene. The K_H values showed no regular order in their variation with the oil content of the alkyd samples and the solvent, but the values obtained are higher in acetone than in toluene. Correlation of molecular weight (M) with [η] was also examined. [η] was observed to increase with the increase in the molecular weight of the resins. The α values obtained are in reasonable agreement with the reported ranges of α values in good solvent. The characteristics examined suggest that acetone is a better solvent for rubber seed oil alkyd resin than toluene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3073–3075, 2006     

Free radical scavenging activity of cellulase‐treated chitosan

Partially N‐acetylated chitosan was hydrolyzed by the cheap, commercially available, and efficient cellulase. The products, with different molecular weight, were comparatively investigated by GPC, FT‐IR, XRD, and NMR. The results show that the decrease of molecular weight led to transformation of crystal structure and increase of water‐solubility, but the chemical structures of residues were not modified. Superoxide anion radical and hydroxyl radical quenching assay were used for the evaluation of free radical scavenging activity of cellulase‐treated chitosan in vitro. Low molecular weight chitosan (LMWC3, M_w 1.7 × 10³) exhibited high scavenging activity against free radical. It scavenged 79.3% superoxide radical at 0.1 mg mL^?1. At 2.0 mg mL^?1, scavenging percentage of initial chitiosan, LMWC1 (M_w 27.3 × 10³), LMWC2 (M_w 5.9 × 10³), and LMWC3 (M_w 1.7 × 10³) against hydroxyl radical was 14.3%, 33.1%, 47.4%, and 65.9%, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Study on conformational transition phenomena of poly(methyl methacrylate) in acetonitrile near theta conditions

The coil–globule transition for poly(methyl methacrylate) (PMMA) has been studied in a theta solvent, acetonitrile (Θ = 45 °C). The viscosity of PMMA was measured as a function of temperature in the range 26–55 °C. The contraction and expansion of the molecular chains are determined using the measured viscosity values. The temperature dependence of the intrinsic viscosity can be represented by a master curve in a versus |τ|M _w^1/2 (g^1/2 mol^−1/2) plot, where τ = |T − Θ|/T is the reduced temperature and M_w‐is the weight‐average molecular weight. A universal plot of reduced viscosity versus reduced blob parameter (N/N_c) shows the attainment of the collapsed state below the theta temperature. The dimensions of PMMA in acetonitrile (M_w = 3.15 × 10⁶ g mol⁻¹) decrease to 63 % at 26 °C of those in the unperturbed state. The results in this work are compared with those previously published. © 2000 Society of Chemical Industry     

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.     

Properties of aqueous salt solutions of poly(vinylpyrrolidone). II. Polymer dimensions and thermodynamic quantities

The unperturbed dimensions and thermodynamic parameters of poly(vinylpyrrolidone) (PVP) have been studied in aqueous salt solutions, e.g. phosphates, mono- and dihydrogen phosphates, carbonates, sulphates of sodium and potassium. Values of K₀ ( = [η]_ΘM^-1/2, where [η]_Θ is intrinsic viscosity at the theta temperature and M is molecular weight) with M_w = 78 000 g mol^-1 were found to range from 4·63×10^-4 to 5·56×10^-4 dl g^-1, and root-mean-square end-to-end distances, 〈r²〉₀^1/2, ranging from 1·61×10^-6 to 1·68×10^-6cm were evaluated. Values of the characteristic ratio, C_n, the steric parameter, σ, and the enthalpy and the entropy of dilution parameters, χ_H and χ_S, have also been calculated, and the interaction parameter was found to be χ-0·5<-0·001 for aqueous salt solutions of PVP. ©1997 SCI     

Dilute solution properties of cationic poly(dimethyl sulfate quaternized dimethylaminoethyl methacrylate)

The dilute solution properties of a cationic polyelectrolyte, poly(dimethyl sulfate quaternized dimethylaminoethyl methacrylate) [poly(DMAEM · C₂H₆SO₄)], are studied by measurements of intrinsic viscosity, degree of binding, and flocculation application. The intrinsic viscosity of this polyelectrolyte is related to the type and concentration of added salt. The intrinsic viscosity behavior for cationic polyelectrolyte resulting from the electrostatic repulsive force of the polymer chain is contrasted with polyampholyte. The polyelectrolyte in the presence of KCl has a lower degree of binding, indicating that the proton ion (H⁺) is relatively difficult to bind to the CH₃SO₄^? at the polymer end. The polymerization of DMAEM · C₂H₆SO₄ in 0.5M KCl aqueous solution proceeded more easily than that of DMAEM · C₂H₆SO₄ in pure water. The polymerization rate of DMAEM · C₂H₆SO₄ is found to pass through an extreme value as a function of pH. Optimum flocculation, corresponding to the complete removal of turbidity in the supernatant, is achieved. Beyond the optimum flocculation, high polymer dosages redisperse the bentonite suspensions.     

Preparation and properties of polyurethane/benzyl amylose semi‐interpenetrating networks

A series of semi‐interpenetrating polymer networks (semi‐IPNs) films were prepared from 20 wt % of benzyl amylose (BA) of different M_w and castor oil‐based polyurethane (PU) in N,N‐dimethylformamide (DMF). The weight‐average molecular weight (M_w), and radii of gyration (<S²>_z^1/2) of benzyl amylose were determined by laser scattering measurement, and the results suggested BA was in a compact coil conformation in DMF. Furthermore, the properties and miscibility of the polyurethane/benzyl amylose (PUBA) films were studied by scanning electronic microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, ultraviolet–visible spectrophotometer, and tensile testing. The PUBA films possessed much higher optical transmittance and tensile strength than the pure PU film regardless of the molecular weight of BA, but lower values of elongation at break were observed. With decreasing of the BA M_w from 9.24 × 10⁵ to 2.69 × 10⁵, interestingly, the elongation at break of the films increased from 135 to 326%. This might be ascribed to the decrease of crosslinking density of PU networks and the enhancement in freedom of the molecular motion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of novel photoactive polyamide derived from substituted fluorene by copper (I) catalyst

A novel polyamide has been successfully prepared through the reaction of 2,7‐dibromo‐9,9‐dioctylfluorene with 2,5‐dipiperazinedione in the presence of CuI, N,N′‐dimethylethylene diamine (DMEDA) and K₂CO₃ as base mixture and as catalyst. The structures of the monomer and the resulting model compound, as well as the structure, solution viscosity, solubility, molecular weights, thermal behavior, thermal stability, and light absorption and emission spectra of the resulting polyamide were characterized by means of FTIR, elemental analysis, ¹H‐NMR, ¹³C‐NMR, DSC, TGA, GPC and UV–visible absorption, and fluorescence emission spectrophotometers. The polyamide possesses excellent solubility in organic solvents such as tetrahydrofuran (THF), N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), ethylacetate, acetone, ethanol, pyridine, chloroform, and toluene at room temperature. The polyamide had inherent viscosity of 0.65 dL/g, and molecular weights of M_n= 4.25 × 10⁴ and M_w= 5.99 × 10⁴ g/mol. The polyamide had glass transition temperature (T_g) of 138°C, and 10% weight loss at 350°C in nitrogen. The polyamide showed strong UV absorption and blue emission in solution and in solid state. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Behaviour of poly(β-hydroxybutyric acid) in dilute solution

The refractive indices of poly(β-hydroxybutyric acid) (PHB) at four wavelengths have been determined via different procedures. Viscometric and light scattering measurements have been made on solutions of eight samples of PHB (M_w = 20·9 × 10³?929 × 10³ g mol^?1) in 2,2,2-trifluoroethanol. From the dependences of intrinsic viscosity and of radius of gyration on molar mass, the conformation of PHB in dilute solution is shown to be that of a random coil. The findings are discussed in relation to existing conflicting evidence on the conformation of this polymer.     

Molecular architectures of four‐arm star‐shaped styrene‐butadiene copolymer

To understand the molecular architectures of styrene‐butadiene four‐arm star (SBS) copolymers, a size exclusion chromatography combined with laser light scattering (SEC‐LLS) has been used to determine their weight‐average molecular weight (M_w) and radius of gyration (〈S²〉^1/2), and a new method for the establishment of the Mark‐Houwink equation from one sample has been developed. Based on the Flory viscosity theory, we successfully have reduced the 〈S²〉^1/2 values of numberless fractions estimated from many experimental points in the SEC chromatogram to intrinsic viscosities ([η]). For the first time, the dependences of 〈S²〉^1/2 and [η] on M_w for the four‐arm star SBS in tetrahydrofuran at 25°C were found, respectively, to be 〈S²〉^1/2 = 2.62 × 10^?2 M (nm) and [η] = 3.68 × 10^?2 M (mL/g) in the M_w range from 1.4 × 10⁵ to 3.0 × 10⁵. From data of [η] and 〈S²〉^1/2 for linear and star SBS, we have obtained the information about the branching, namely, the ratios (g and g′) of 〈S²〉 and [η] for star SBS to that of the linear SBS of the same molecular weight, which agree with theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 961–965, 2005     

Estimation of Mw from dilute solution viscosity

The viscosity-average molecular weight, M_v, of a polymer is given operationally through its limiting viscosity number [η] and the Mark-Houwink equation [η] = KM_v^α, where K and α are empirical constants. If [η] is measured under different conditions, α and M_v will vary for the same sample. M_v^α is the α-order moment about the origin of the differential weight distribution of the polymer. Practically, the results of a series of M_v measurements on the same polymer are equivalent to a cluster of fractional moments of the weight distribution, with orders between 0.55 and 0.80. It is shown that the first moment of this distribution, M_w, may be estimated reliably by a straightline plot of M_v against α-extrapolated to α equals 1. This simple expedient is effective although there are probably no molecular weight distributions in which the relation is strictly linear and there are no mathematical distributions for which the αth root of the αth moment is a linear function of α for all α. The deviation from linearity is small enough, however, that the real curve can be represented by a straight line over a short range of α. Thus, M_w can be measured accurately, but M_n, M_z, or the breadth of the distribution is not accessible by this method. Experimental and literature examples show that the precision of M_w estimated by this method compares well with that of primary methods for measuring this molecular weight average. If a linear relationship is observed with reliable α values, this appears to be a sufficient condition for estimation of a valid M_w.     

Light‐scattering study of poly(hydroxy ester ether) in N,N‐dimethylacetamide solution

Static and dynamic light‐scattering techniques were used to study biodegradable thermoplastic poly(hydroxy ester ether) in N,N‐dimethylacetamide (DMAc). A weight‐average molecular weight M_W = 6.4 × 10⁴ g/mol, radius of gyration R_G = 9.4 nm, second‐virial coefficient A₂ = 1.05 × 10^?3 mol mL/g², translational diffusion coefficient D = 1.34 × 10^?7 cm²/s, and hydrodynamic radius R_H = 8.3 nm are reported. In addition, the effect of H₂O on the polymer chain's conformation and architecture in a DMAc/H₂O solution is evaluated. Results suggest that H₂O makes the mixed solvent poorer as well as promotes polymer chain branching via intramolecular transesterification. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1737–1745, 2001     

Viscosity behavior and chain conformation of a (1→3)-α-glucan from Ganoderma lucidum

Summary Seven fractions of a (1→3)-α-D-glucan from Ganoderma lucidum have been studied by light scattering, sedimentation equilibrium, and viscometry in dimethylsulfoxide (DMSO) containing 0.25 M lithium chloride at 25°C. The intrinsic viscosity [η] - molecular weight relation for this glucan in the mixed solvent is found to be represented approximately by [η] = 0.071 M _w ^0.60 cm³ g⁻¹ in the range of weight-average molecular weight M _w studied, i.e., from 8 × 10³ to 4.4 × 10⁵. Its analysis based on current theories for wormlike chains shows that, without excluded volume effect, the (1→3)-α-D-glucan chain is characterized by a linear mass density of 380 nm⁻¹, a Kuhn segment length of about 3 nm, and a diameter of 1.2 nm and is somewhat more extended but more flexible than amylose, a (1→4)-α-glucan, in DMSO. Received: 28 July 1998/Accepted: 18 August 1998     

Solubility properties of poly(1,1-difluoroethylene) in dipolar aprotic solvents

A screening study of the solubility of poly(1,1-difluoroethylene) (PVF₂, M?_w = 2 × 10⁵) at room temperature in a wide variety of dipolar aprotic species has facilitated the discovery of a series of new solvents (N-methyloxazolidone, cyclic-substituted ureas) and rationalization of the data in a two-dimensional solubility map involving their dipole moment, μ, and their hydrogenx-bond-accepting (HBA) power β (Taft solvatochromic parameter). This map may be used as a predictive tool for the research of new functional classes of solvents, such as N-substituted mixed amideester of phosphoric acid or N-substituted sulfurous diamides. The variations of the intrinsic viscosity of the polymer with solvent polarity may be quantitatively analyzed using a linear multiparametric correlation which emphasizes the two opposite contributions of cavitation effects (Hildebrand solubility parameter δ) and of polymer–solvent interactions (β) on the coil expansion: [η] (dL.g^?1) = 0.792 - 1.2 × 10^?3δ2(J.cm^?3) + 1.59 β. Finally, 1,3-dimethyl-2-oxo-hexahydropyrimidine (N,N′-dimethylpropylene urea) leads to the highest value of the refractive index increment (dn/dc = ?0.065 mL.g^?1 at λ = 632 nm), and thus appears as the best solvent for light-scattering measurements.     

Continuous fractionation and solution properties of PIB. I. Search for the best mixed solvent and first results of the continuous polymer fractionation

To adopt a recently developed method for large scale fractionation (CPF = continuous polymer fractionation, a special kind of counter current extraction) to polyisobutylene (PIB), a systematic search for the best mixed solvent was performed. For this purpose, the essential parts of the phase diagrams solvent/nonsolvent/PIB were determined for 21 mixed solvents by cloud-point measurements; with eight systems of special interest, the molecular weight distributions of the polymers contained in the coexisting phases were also studied. On the basis of these experiments and of considerations concerning additional criteria for the performance of the continuous counter current extraction, the mixed solvent toluene/methyl ethyl ketone was chosen. First experiments with a PIB sample of M_w = 420,000 g/mol and a molecular nonuniformity U = (M_w/M_n) ? 1 of 2.3 yielded two high molecular weight fractions M_w = 1.1 × 10⁶ and 0.6 × 10⁶ resp., with U = 0.3 on a 100 g scale upon the application of four CPF steps.     

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     

Aspects of the kinetics of the radiation-induced polymerization of acrylonitrile in dimethylformamide

The radiation-induced homopolymerization of acrylonitrile (AN) in dimethylformamide (DMF) has been followed in detail over a range of monomer concentrations. In all cases a short induction period was observed which was equivalent to 1.6 × 10⁴ rad. The initial rates of polymerization for solutions of AN in DMF of mole fraction (×) of 0.33, 0.20, and 0.10 are 1.44 × 10^?5, 7.23 × 10^?6, and 2.79 × 10^?6 mole/dm³rad, respectively. Deviations of the polymerization pathway from the standard unity in monomer dependence are examined in terms of radical production ratios to the monomer and the solvent (Φ_M/Φ_S) and the polymer together with the solvent (Φ_p/Φ_s), for various mole fractions of AN in DMF. Thus, an indirect route to G_radical(events) is provided together with the corresponding k/k_t values.