Solution properties of polyacrylic esters. II. Evaluation of unperturbed dimensions

According to existing well-known theories unperturbed dimensions can be calculated from light scattering and viscosity measurements. The statistical segment A_m proposed by Kuhn is a good measure for the flexibility of an unperturbed polymer coil. With the data reported in part I of the dependence of the radius of gyration and the Staudinger index, respectively, on the molecular weight, A_m was calculated for nine polyacrylic esters and poly(acrylic acid). Poly(acrylic acid) with A_m = 13,6 Å has the highest flexibility. The stiffness of the polymer chain is increased with growing C-number of the alcohol. Branching in the alcohol further increases the stiffness of the polymer chain.     

Solution properties of poly(fluorostyrene-co-chlorostyrene) copolymers. I. Light scattering,differential refractometry and viscometry

The weight-average molecular weights (M?_w) of nominally random, unfractionated copolymers of ortho- and para-fluorostyrene and ortho- and para-chlorostyrene were determined by light scattering measurements in tetrahydro-furan, toluene, carbon tetrachloride and chloroform. It was shown that there is no significant variation in measured M?_w in the various solvents, a finding indicating that the copolymers are not compositionally heterogeneous. Intrinsic viscosity measurements in the same solvents established a consistent relationship between [n] and M?_w despite the differences in copolymer compositions. It was not possible to establish a similar relationship between the second virial coefficient A₂ and M?_w. It was concluded that measurements of the specific refractive index increment could be used for determining copolymer composition if the measurements were performed in thermodynamically poorer solvents. The results established for the Mark-Houwink constant α, intrinsic viscosity, and A₂ values indicated that these solvated copolymer molecules are in a less expanded conformation than are polystyrene molecules of similar molecular weights in a given solvent.     

The dilute solution properties of maleic anhydride and maleic acid copolymers: 1. Light scattering, osmotic pressure and viscosity measurements

Dilute solution behaviour of poly(maleic anhydride-co-ethyl vinyl ether) and poly(maleic acid-co-ethyl vinyl ether) has been investigated by light scattering, osmotic pressure, and viscosity measurements. The molecular weights ($\text{M}\text{?}{}_{\mathrm{w}}$ and $\text{M}\text{?}{}_{\mathrm{n}}$), the second virial coefficients A₂, and the intrinsic viscosities [η] have been determined for three states of this copolymer: anhydride-form, H-form, and Na-salt independently. The constants in the Mark-Houwink relations were obtained for the above three states under different solvent conditions. The molecular weight of the anhydride-form is found to be higher than that of the acid-form or the Na-salt, suggesting the degradation in a process of hydrolysis. The second virial coefficient A₂ as well as the Mark-Houwink relation indicates that the anhydride-form and H-form behave as flexible polymer chains in good solvents. However, the polymer coil of Na-salt is highly expanded even at saturated NaCl concentration.     

Solution properties of xanthan. Light scattering and viscometry on dilute and moderately concentrated solutions

Elastic and quasi-elastic light-scattering, viscometric and rheological studies are given for solutions of the microbial polysaccharide Xanthomonas campestris (xanthan) in aqueous 0.62N NaCl for polymer concentrations from 0.03 to 2.2 g kg⁻¹. The observed negative ∂ln[η]/∂ln T is interpreted as a decrease of the persistence length with increasing T. The behaviour in moderately concentrated solutions (2<[η]c<25) reveals intermolecular association, leading to gel formation in the extreme case. The effect of the association on the viscometric and light-scattering data is discussed. It is concluded that the early stages of association involve structure with the chain axes nearly parallel, but that larger, particulate-like structures develop with increasing c, eventually leading to gel formation under certain conditions.     

Gradient dependence of viscosity of cellulose tricarbanilate in tetrahydrofuran

Summary The dependence of viscosity of cellulose tricarbanilate in tetrahydrofuran on the velocity gradient D <2500 s^–1 for molecular weights up to 1.2×10⁶ was determined, and an empirical equation for the determination of the limiting viscosity number for zero velocity gradient was derived. Errors involved in the viscosity determination from a single concentration using an approximate formula were also ascertained.     

Thermodynamic and hydrodynamic properties of the the systems polymer—tetrahydrofuran—water: 1. Solution properties of polystyrene

Tetrahydrofuran (THF) is a solvent widely applied in polymer science and technology. However, because of its hygroscopic nature THF may often contain water considerably influencing the properties of the corresponding polymer solutions. In the first part of a series devoted to this problem, cloud point titrations and viscosity measurements were performed in the system polystyrene (PS)-THF-water. The limiting viscosity numbers of polystyrene considerably depended on the water content already in the domain of azeotropic composition, i.e. at about 4.5 vol.% of water. The constants of the Mark—Houwink equation, K and a were determined in pure THF and in mixtures containing up to 8.2 vol.% of water and compared with those for PS-THF found in the literature. The corresponding unperturbed dimensions were determined by various extrapolation procedures and were found to depend on solvent composition. Simultaneously, polymer-mixed solvent interaction parameters B were determined and discussed. Two theta compositions were observed: at about 7.7 vol.% of water for second virial coefficient A₂ = 0, and about 8.12 vol.% for a = 0.5. This agrees with the hypothesis of Dondos and Benoit and indicates the presence of preferential solvation in the system.     

Light scattering properties of acacia catechuic acid. Effects of urea and temperature

Association of acacia catechuic acid (ACA) molecules was established in ethanol–water medium². This association was further tested in pure aqueous medium as well as by using urea in increasing amounts in aqueous solutions. The 5M urea depressed the molecular weight to 2.82 × 10⁶, as against 5.04 × 10⁶ in aqueous solution of NaCl or KCl. This reduction has been explained as due either to rupture of the molecule itself or dissociation of molecules which normally remain associated in water. The diminution of root-mean-square end-to-end distance in urea from 323 mμ in water³ to 290 mμ has also been attributed to the disaggregation of the associated molecules. To test this point further, the effect of increasing the temperature was next studied. The molecular weight was observed to be lower at higher temperature (actual value at 47°C was nearly half the original value at 28°C). This considerable reduction positively points to a dissociation of the molecule which was first suspected in our study with urea. The root-mean-square end-to-end distance also diminished to a certain extent, but not so much as the molecular weight. This has been explained as due to the stretching of the molecule when the solvent behaves as a better solvent at higher temperature.     

Light scattering Rayleigh linewidth measurements on some solutions of cellulose trinitrate

Light scattering Rayleigh linewidth measurements have been made upon three cellulose trinitrate samples in ethyl acetate by obtaining the autocorrelation function of fluctuations in scattered intensity. The weight average degrees of polymerization (DP_w) were in the range 2400 to 3300 and $\text{DP}{}_{\mathrm{w}}\text{DP}{}_{\mathrm{n}}\text{～ 1.3}$. Measurements were made at concentrations below 2 × 10^?3 g/ml and no concentration dependence was detected within experimental error (±7%). No effects due to internal motion of the polymer chains were observed even though current theories predict that these effects should be quite large. Reasons for this are discussed and it is suggested that the effects of internal motion are diminished when the second virial coefficient is large and positive. Absolute values of translational diffusion constant calculated from the results lie well within the range of those obtained by other authors using conventional techniques. Over the limited range of degrees of polymerization investigated the equivalent hydrodynamic diameter per monomer unit was found to be $\text{0.45 ± 0.03}\text{A}\text{?}$. The effects of polydispersity on the results are discussed.     

Physical properties of fatty acid methyl esters. I. density and molar volume

Saturated fatty acid methyl esters from acetate to arachidate, methyl oleate, linoleate, linolenate, and erucate have been prepared in high purity. Densities, refractive indices, dispersions, ultrasonic sound velocities, and dielectric constants have been measured in the liquid state at 20 and 40C. In this first communication, the densities of the saturated compounds have been correlated with the Smittenberg relation. The following relations were derived: d ₂₀ ⁴ = 0.85407 + 0.18494/ (n + 0.096) and d ₄₀ ⁴ = 0.84225 + 0.12904/(n-0.408). Molar volumes have been computed and checked for additivity.     

Light scattering characterisation of polymers I. An extension of the zimm plot

A new method is proposed for extrapolating light-scattering data to the zero angle of scattering. Essentially the method consists of iterative extrapolations by use of the regression method as a subroutine, and it applies in general to the data obtained at low polymer concentrations and at low angles of scattering. Light-scattering results on high molecular weight linear polystyrene in benzene were successfully analysed with the method. In comparison with other published methods, the strong points and limitations of the method are discussed.     

Lubricants. I. Preparation and properties of benzyl and substituted benzyl esters of dilinoleic acid

Benzyl and substituted benzyl esters of dilinoleic acid and of hydrogenated dilinoleic acid have been prepared in good yield. Some of the chemical characteristics and physical properties of the resulting products have been measured including a study of their thermal stability by thermogravimetry. Also, they have been examined by several of the bench tests used in laboratory evaluation of lubricants. Several of them compare favorably with control materials used in the study. E. Utiliz. Res. Devel. Div., ARS, USDA.     

Size exclusion chromatography with multiple detectors: Solution properties of linear chains of varying flexibility in tetrahydrofuran

Narrow molecular weight distribution polyisoprenes (PI), polybutadienes (PBD), poly(isobuty1enes) (PIB), poly(methylmethacry1ates) (PMMA), polystyrenes (PS), and poly(octadecy1 methacrylates) (PODMA) have been studied by size exclusion chromatography (SEC) in tetrahydrofuran (THF) with light scattering and viscometric detectors. The molecular weight (M) dependence of the intrinsic viscosity, [η], and radius of gyration, R_g, is reported for THF solutions of these polymers, in many instances for the first time. The availability of these data for a series of chains of varying flexibility allows a test of the universal calibration principle in SEC. Furthermore, an apparent dependence of the hydrodynamic parameter in good solvents, Φ, on chain stiffness is observed. All chains appear to exhibit hydrodynamic draining in THF. © 1996 John Wiley & Sons, Inc.     

Studies of cyclic and linear poly(dimethyl siloxanes): 8. Light scattering measurements in good and poor solvents

Weight average molar masses (M_w) and second virial coefficients (A₂) have been measured for linear and cyclic poly(dimethyl siloxane) (PDMS) fractions in toluene at 298K and for linear PDMS in bromocyclohexane at 301K. The values of M_w are compared with those deduced previously using gel permeation chromatography, broadly confirming the values already assigned to the fractions. The values of A₂ for linear PDMS in toluene are shown to be consistent with previously published values for oligomeric linear PDMS. The values of A₂ for cyclic PDMS approach those of linear PDMS for M_w<～1000 g mol^?1 and decrease more rapidly as M_w increases in approximate agreement with theoretical predictions. In addition, the conventional relations between A₂ and the expansion factor α_s are shown to be inapplicable at low molar mass.     

聚丙烯酸系增稠剂的合成及性能研究

以丙烯酸单体为原料,N-马来酰化壳聚糖为交联剂,过硫酸铵为引发剂,采用溶液聚合法制备聚丙烯酸系增稠剂。研究了交联剂浓度、中和度、温度、不同电解质对聚丙烯酸系增稠剂粘度的影响。实验结果表明:交联剂为0.4wt%,中和度为80mol%,0.5wt%该增稠剂凝胶溶液粘度可达54 200 mPa.s,但在温度升高或电解质存在的情况下,体系粘度降低。     

Estimation of the content of fatty acid methyl esters (FAME) in biodiesel samples from dynamic viscosity measurements

In order for biodiesel to be commercialized as pure biofuel or blending stock for diesel fuels, it must meet a set of requirements defined in standard specifications for a safe and satisfactory engine operation, one of these specifications is the content of fatty acid methyl esters (FAME). Besides, this parameter indicates the performance of the transesterification reaction for biofuel production from vegetable oils. There are several methods to determinate FAME content in biodiesel samples (chromatography, nuclear magnetic resonance spectroscopy and FTIR spectroscopy); however, they take long times and high cost for FAME content determination. From a practical point of view, in industrial biodiesel production is usually necessary to estimate the FAME value quickly. This paper presents correlations experimentally obtained from different oil feedstocks in order to estimate the biodiesel FAME content from the biodiesel dynamic viscosity, a fast determination parameter.     

Suspension polymerization of vinyl chloride. I. Influence of viscosity of suspension medium on resin properties

The suspension polymerization of vinyl chloride is studied in a bench-scale reactor adequately reproducing reaction conditions and resin properties of industrial relevance. The evolution of particle morphology is analyzed at different stages of conversion, and a model for particle formation is verified. The influence of viscosity of the suspension medium is analyzed in relation to molecular weight distribution and particle morphology.     

Anomalous viscosity behavior of fatty acid esters in solution

Solution viscosity of oils of melonseed(Colocynthis vulgaris Schrad.), soyabean [Glycine max (L). Merr], and rubberseed [Hevea brasiliensis (Kunth) Muell.] were determined in different solvents at various concentrations. Reduced viscosity(_{η red}) vs concentration (C) plots showed three types of behavior:_{η red} increased linearly with C (2–30 g/dl);_{η red} levelled off with C (2–1.2 g/dl); and_{η red} rose steeply with decrease in C (below 1.2 g/dl), the latter behavior is anomalous. Similar viscosity behavior was observed for the methyl ester of melonseed oil, methyl palmitate and n-butyl acetate. Molecular cluster formation was believed to cause the observed anomalous viscosity behavior, the extent of which varied, depending on the nature of the fatty acid ester and the solvent.     

Physico-chemical characterization of poly(vinyl chloride). I. Solution properties

Poly(vinyl chloride) was fractionated and its solution properties were studied. Calibration of the gel permeation chromatograph was carried out using poly(vinyl chloride) and polystyrene. Empirical correlations were established for the calibration plots.     

Surface active block copolymers: I. The preparation and some surface active properties of block copolymers of tetrahydrofuran and ethylene oxide

A new type of surface active block copolymer (TE type) having the general formula HO(C₂H₄O)_x(CH₂. CH₂CH₂CH₂O)_y-(C₂H₄O)_zH, was obtained by addition of ethylene oxide to polyoxytetramethylene glycols with molecular weight of 1000-3400. TE types in which the polyoxyethylene sections comprised more than 20–25% of the total weight are soluble in water, and the relation between cloud point and oxyethylene content for TE types was similar to that for propylene oxide-ethylene oxide block copolymers (Pluronics). Some surface active properties of TE types were examined in comparison with those of Pluronics and some other surfactants. The surface tension, foaming and antifoaming properties of TE types were comparable to those of Pluronics. Although the wetting power of TE types was poor, their suspending power (for carbon black) was superior to that of Pluronics in both aqueous and nonaqeuous media. The addition of TE types to some conventional detergents enhanced significantly their detergency. TE types showed a remarkable demulsifying action, on addition to some W/O emulsions.