Water-soluble copolymers. VI. Dilute solution viscosity studies of random copolymers of acrylamide with sulfonated comonomers

Dilute solution viscosity of a series of random copolymers of acrylamide (AM) with sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS) and with sodium-2-sulfoethylmethacrylate (NaSEM) has been studied using a four-bulb shear dilution capillary viscometer. The hydrodynamic volume of the copolymers in aqueous media was determined as a function of salt concentration, temperature, shear rate, and time. A linear relationship was observed between the intrinsic viscosity [η]₀ and the reciprocal of the square root of ionic strength in sodium chloride solutions, with salt concentrations varying from 0.043M to 0.257M. Negative temperature coefficients for [η]₀ indicate a decrease in the hydrodynamic volume of the ionic polymer molecules with increasing temperature. The relative zero-shear-intrinsic-viscosity change in distilled water to 0.257M sodium chloride aqueous media is used to elucidate viscosity–structure relationships. A maximum value is reached for this parameter at a composition of about 30 mol % of ionic comonomers for AM–NaAMPS and AM–NaSEM copolymer series.     

Pyrolysis of random and block copolymers of ethyl acrylate and methyl methacrylate

Pyrolysis gas chromatography can distinguish random from block copolymers of ethylacrylate and methyl methacrylate. The pyrograms depend on the pyrolytic temperature, the ratio of copolymerized monomers, the degree of conversion, and the method of polymerization. Larger amounts of ethyl methacrylate and methyl acrylate are formed on pyrolysis of random copolymers than of block copolymers. The presence of mixed dimers indicates random copolymerization. The sum of the percent recovery of ethyl alcohol and ethyl acrylate is fairly constant over a range of compositions and monomer sequence. Random copolymers produce less ethyl alcohol than ethyl acrylate on pyrolysis, while homopolymers and block copolymers produce more ethyl alcohol and less ethyl acrylate. In a set of random copolymers with different EA/MMA ratios, there is an increasing per cent recovery of EA monomer with decreasing EA in the copolymer, while ethyl alcohol shows the opposite behavior. The characteristic degradation patterns are thought to be governed by the availability of the tertiary hydrogen for abstraction by the alkoxy oxygen of a neighboring acrylate unit, the availability depending on the sequence distribution of acrylate/methacrylate molecules.     

Application of random phase approximation to the dynamics of polymer blends and copolymers

The dynamics of melts of homopolymer mixtures and copolymers is studied with RPA. The first cumulant and the zeroth-order time moment of the measured dynamic scattering function S(q,t) are expressed-in terms of their counterparts in the non-interacting system of bare chains. The qualitative behaviour of these quantities as function of the wave number q and the interaction parameter χ_F are obtained using Rouse dynamics for bare chains, and the results are presented graphically as a guide to the interpretation of dynamic scattering experiments on such systems. The q-dependent threshold for spinodal decomposition in the case of copolymers, and the variation of the growth rate of the mean response with q in the unstable regime are also discussed qualitatively in both systems.     

Compositional analysis and infrared spectra of styrene–methyl methacrylate random copolymers

Compositional analysis of styrene–methyl methacrylate random copolymers by UV spectrophotometry at 260 nm, proton-NMR, and IR at 1730 cm^?1 have been accomplished and agreement between these three independent methods was excellent. IR spectra of the copolymers in the region of 1100 and 1300 cm^?1 are mainly characteristic absorption bands for the methyl methacrylate (MMA) component, but not the same for those of MMA homopolymer, that is, the IR spectra of the copolymers were not additive with those of polystyrene and PMMA. Information about the sequence distribution of copolymers of the same composition can be obtained by comparing the wavenumbers and absorption coefficients of the IR spectra in the region of 1100–1300 cm^?1     

Melt viscosity of acrylic copolymers

The melt flow behavior of methyl methacrylate (MMA) copolymerized with methyl acrylate (MA) was measured and analyzed in terms of the molecular structure of the copolymers. Measurement was done by using a capillary rheometer in the shear rate range from 6 × 10⁰ to 3 × 10³ s^?1 and in temperatures from 160°C to 280°C. The Newtonian flow pattern appeared in lower shear rate and higher temperature regions. However, with increasing shear rate at lower temperature, viscosity decreased to a constant slope on a logarithmic scale. The melt fracture arose at the critical shearing stress point S_c of 6 × 10⁶ dyn/cm². A die swell also appeared in the shear rate range larger than 1 × 10⁶ dyn/cm², and its maximum value was two times larger than that of the capillary diameter. The decrease in viscosity with increasing shear rate is explained in terms of the apparent energy of activation in flow E. E also decreases with increasing shear rate. The exponential relation of E to η is maintained in the higher shear rate. The lowering of viscosity in lower shear rate, however, is attributed to not only the change in E but also the change in the volume of flow unit. The melt viscosity increases in inverse proportion to the MA content in the copolymers which form more flexible chains. Syndiotactic form of MMA has increased viscosity, caused by the rigidifying of segmented chains, rather than the strengthening of intermolecular interaction.     

Prediction of melt viscosity flow curves at various temperatures for some olefin polymers and copolymers

A knowledge of the variation of melt viscosity of thermoplastic polymers with both shear rate and temperature is of considerable importance to plastics engineers as well as to polymer rheologists. The actual measurement of melt viscosity at a large number of temperatures and shear rates is frequently a tedious and time-consuming task. A technique has been developed, based upon the applicability of shear rate-temperature superposition, for predicting the flow curves of a number of olefin polymers and copolymers at various temperatures from experimental data obtained at one temperature for the material in question. The experimental validity for superimposing log shear stress—log shear rate curves at different temperatures along the log shear rate axis has been established for both high and low density polyethylenes, polypropylene, polybutene-1, and poly (ethylene vinyl acetate) copolymers. The temperature dependence of the resultant shift factors has been determined for each system, and the method of utilizing this information to predict viscosities as a function of temperature and shear rate is discussed.     

Glass‐transition temperatures and rheological behavior of methyl methacrylate–styrene random copolymers

Poly(methyl methacrylate‐ran‐styrene) copolymers were synthesized under monomer‐starved conditions by emulsion copolymerization. The glass‐transition temperatures (T_g's) of the copolymers were measured by differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The results showed that the methyl methacrylate–styrene random copolymers produced an asymmetric T_g versus composition curve, which could not even be interpreted by the Johnston equation with different contributions of dyads to the T_g of the copolymer considered. A new sequence distribution equation concerning different contributions of triads was introduced to predict the copolymer's T_g. The new equation fit the experimental data exactly. Also, the T_g determined by TBA (T_gTBA) was higher than the one determined by DSC (T_gDSC) and the difference was not constant. The rheological behavior of the copolymers was also studied. T_gTBA ? T_gDSC increased with increasing flow index of the melt of the copolymer, and the reason was interpreted. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2891–2896, 2003     

Properties of block versus random copolymers

Physical and mechanical properties of block copolymers are compared and correlated with the corresponding random copolymers. The important properties of melting point, transition temperatures, tensile strength, modulus, and elastic properties depend upon the structural arrangement of the molecular units comprising the polymer strecture. All available data suggest overwhelmingly that properties of block copolymers are superior to those of random copolymers. A block copolymer can have properties characteristic of each of the homopolymers from which it is derived as well as a set of properties due to the polymer strcture as a whole. Block copolymers have an advantage over random copolymers in that a crystalline polymer can be modified without significant reduction of its melting point, modulus, tensile strength, and elastic properties, and by suitable selection of a second component it affords a means of “building in” a particular property.     

Approach to the glass transition temperature of random copolymers using the Gibbs-Dimarzio theory

Summary It is supposed that the molecular parameters of the Gibbs-DiMarzio (GD) theory (hole energy, flex energy and coordination number) of random copolymer vary linearly with the molar composition from the molecular parameters of one parent homopolymer to those of the other. This assumption enables us to calculate,according to the GD theory, the configurational entropy of a random copolymer S_c,cop and thus (if S_c,cop at the glass transition temperature of the random copolymer, T_g,cop, is again a linear function of the composition) also T_g,cop. The theoretical prediction has been compared with the experimental data obtained on the system butyl methacrylate — methyl methacrylate, and a good agreement between the theory and experiment has been found. On leave from the Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences, CS-162 06 Prague 6, Czechoslovakia     

Synthesis of novel random and block copolymers of tert-butyldimethylsilyl methacrylate and methyl methacrylate by RAFT polymerization

Hydrophobic-hydrolysable copolymers consisting of methyl methacrylate (MMA) and tert-butyldimethylsilyl methacrylate (TBDMSMA) have been synthesized for the first time by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization technique using cumyl dithiobenzoate (CDB) and cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents (CTAs). The monomer reactivity ratios for TBDMSMA (r₁ = 1.40 ± 0.03) and MMA (r₂ = 1.08 ± 0.03) have been determined using a non-linear least-squares fitting method. Well-defined random copolymers PMMA-co-PTBDMSMA have been prepared. Then, the versatility of the RAFT process to synthesize silylated block copolymers with controlled molecular weights and low polydispersities has been demonstrated using two strategies: the synthesis of PMMA-SC(S)Ph or PTBDMSMA-SC(S)Ph as macro-chain transfer agent (macro-CTA) for use in a two step method or an one-pot method which consists in the successive addition of the two monomers. Diblock copolymers with narrow molecular weight distributions (PDI < 1.2) were obtained from the one-pot method with number-average molecular weight values within the range 10,000-22,000 g mol⁻¹.     

Limits of the chemical composition heterogeneity of random copolymers

One of the characteristic features of copolymers is their chemical heterogeneity. Examples are given of the dependence of conversion heterogeneity in the chemical composition of random copolymers on the initial composition of the monomer mixture, along with typical examples of the differential distribution functions of chemical composition. The maximum attainable values of the conversion heterogeneity parameter have been calculated depending on the copolymerization parameters. The conditions are discussed under which copolymers may acquire chemical heterogeneities high enough to be perceived or determined by fractionation or light scattering. Limits are estimated beyond which the chemical heterogeneity becomes undetectably low and the copolymers can be regarded as chemically homogeneous.     

无规共聚聚丙烯的结构与性能

利用博里叶变换红外光谱仪与差示扫描量热仪分析了五种无规共聚聚丙烯(PP)的组成和结构,测试了五种PP产品的力学与光学性能.五种无规共聚PP都是由乙烯与丙烯无规共聚合而成,在高分子链中没有乙烯结晶.PP树脂的拉伸屈服应力随着共聚单体乙烯含量的升高而降低,Izod缺口冲击强度、光学性能随着乙烯含量的增加而提高.加入乙烯的质量分数控制在2％～3％为宜.     

Melt viscosity characteristics of methacrylate–styrene copolymers

The activation energies of flow E_A of methacrylate–styrene copolymers containing n-butyl, n-hexyl, n-heptyl, n-octyl, n-decyl, n-dodecyl, n-tridecyl, n-octadecyl, and cyclohexyl methacrylate have been investigated as a function of molecular weight, composition, and methacrylate monomer. Below a critical pendent group molar volume per chain unit (120 ± 10 ml Le Bas units), E_A was found to increase with molar volume; and above this value, a decrease in E_A was observed, reflecting a decrease in copolymer density. Copolymers with pendent group molar volumes per average chain unit of between 96 and 140 ml (Le Bas units) were found to exhibit sufficiently high E_A values to render them suitable for use in thermoplastic and photothermoplastic devices with superior development and erasure rates, at temperatures which enabled the attainment of the development and erasure viscosities with a low expenditure of heat energy. Methacrylate–styrene copolymers with long-chain ester methacrylates (viz., n-decyl and n-dodecyl methacrylate) were found to exhibit critical molecular weights M_c below 3000; and M_c was found to decrease with increasing methacrylate tail length and methacrylate concentration. These M_c values correspond to critical chain lengths Z_c below 45. Similar Z_c values have been previously reported for acrylonitrile–methyl methacrylate copolymers³⁰ and ethylene–propylene copolymers.²⁸     

Kinematic viscosity of fatty acid methyl esters: Prediction, calculated viscosity contribution of esters with unavailable data, and carbon–oxygen equivalents

Many properties of biodiesel, the mono-alkyl esters of vegetable oils, animal fats or other triacylglycerol-containing feedstocks, are largely determined by its major components, the fatty acid alkyl esters. Therefore, information on the properties of individual components and their interaction is essential to understanding and predicting the properties of biodiesel fuels. Viscosity, which affects flow and combustion of a fuel, is such a property. In previous literature, the effect of the structure of fatty esters on viscosity was discussed. However, these data are largely confined to esters with an even number of carbon atoms in the chain and that are liquid at 40 °C. To gain a better understanding of kinematic viscosity, this work additionally reports data on esters with an odd number of carbons in the fatty acid chain and some unsaturated fatty esters. Furthermore, the kinematic viscosity of some biodiesel fuels is affected by components that are solids at 40 °C. A method based on polynomial regression for determining the calculated viscosity contribution (CVC) of esters that are solid at 40 °C (saturated esters in the C₂₀–C₂₄ range) or esters that are liquids but not available in pure form is presented as these values are essential for predicting the kinematic viscosity of mixtures containing such esters. The kinematic viscosity data of esters are compared to those of aliphatic hydrocarbons in the C₆–C₁₈ range and those of dimethyl diesters. The increase of kinematic viscosity with increasing number of CH₂ groups in the chain is non-linear and depends on the terminal functional groups, chain length and double bonds. To illustrate this effect, carbon–oxygen equivalents (COE) are used in which the numbers of carbon and oxygen atoms are added. A straightforward equation, taking into account only the amounts and kinematic viscosity values of the individual neat components, suffices to predict the viscosity of mixtures of fatty esters (biodiesel) at a given temperature.     

On the plastic and viscoelastic behavior of methylmethacrylate-based random copolymers

Both plastic and Viscoelastic properties were investigated on neat polymethyl-methacrylate (PMMA) and methylmethacrylatc-based random copolymers including N-substituted maleimide units. A strong coupling was evidenced between the glass transition motions and the secondary transition motions for PMMA samples rapidly quenched from the molten state. This coupling was shown to diminish markedly in the case of aged PMMA and to disappear almost completely in the case of MMA-maleimide copolymers having a maleimide content as small as 5 mol%. Thus, it strongly suggests tnat a greater compacity of the glassy PMMA matrix and (or) the presence of stiff maleimide units in the copolymers are sufficient to hinder the early occurrence of large scale conformational motions in the secondary transition region. In addition, it was shown that the strain softening that follows the yield point is also important for aged PMMA and maleimide-rich copolymers, but tends to vanish in the other samples. Therefore, the probable origin, at least in this series of materials, of the strain softening would be the different nature of the molecular motions that occur in the secondary relaxation region and in the glass transition region.     

Hot air aging behavior of polypropylene random copolymers

This article deals with the global aging behavior of three polypropylene random copolymer (PP-R) materials with varying primary structure and morphology. Hot air aging experiments at elevated temperatures from 95 to 135 °C were carried out using micro-sized specimens with a thickness of 100 μm. Technological and analytical aging indicators were monitored for an exposure time of up to 750 days. Independent of comonomer type (ethylene vs. butylene) and morphology (α vs. β crystal form) a critical molar mass of 300 kg mol⁻¹ was obtained. The consumption of antioxidants was slower for the β-nucleated PP-R grade with finer spherulitic structure. The β-grade outperformed the α-crystal PP-R grades resulting in about 20% higher time-to-embrittlement values. © 2018 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47350.     

Behaviour of methylmethacrylate-acrylonitrile random copolymers in dilute solution

Studies on the dilute solution properties of methylmethacrylate-acrylonitrile random copolymers of three different compositions, 0.236, 0.5 and 0.74 mole fraction (m.f.) of acrylonitrile (AN) designated as MAa, MAb and MAc, respectively, have been made in good solvents and theta solvents. MAa has been studied in benzene (Bz) and ethylacetate (EAc). MAb in acetonitrile (MeCN), dimethyl sulphoxide (DMSO) and a binary solvent mixture of Bz and dimentyl formamide (DMF) in the volume ratio 6.5:1 designated as BM1 and MAc in MeCN, DMSO and Bz + DMF in the volume ratio 1.667:1 designated as BM2. The Mark-Houwink exponent ‘a’ reveals that Bz is a theta solvent for MAa at 20°C. For MAb and MAc, BM1 and BM2, respectively have ‘a’ values of 0.5 at all three temperatures studied (30°, 40° and 50°C). It is not clear whether they represent theta states or preferential adsorption plays a role complicating the behaviour in solution. The values of A₂ are very low in MeCN considering that it is a very good solvent for the copolymer, ‘a’ values for MAb and MAc being 0.75 and 0.7, respectively.     

Synthesis of methyl methacrylate-n-butylacrylate copolymers: Study of the paint properties

A series of acrylic copolymer solutions were prepared by copolymerizing methyl methacrylate (MMA) with n-butylacrylate monomers in toluene to high conversion using dibenzoyl peroxide (0.5 wt %) as initiator. The various reaction parameters, such as MMA concentration and mode of addition of reactants to the reaction vessel, were changed to obtain an acceptable quality of the resins for the paint. The properties of the resins and the effect of MMA concentration on these properties (such as viscosity, drying time, hardness, and adhesion) were measured according to ASTM standard tests. A linear relation between final percentages of conversion and MMA concentration was observed. Drying time, hardness, and glass transition temperature of the samples were increased with MMA concentration; adhesion of the samples remained constant up to 50 wt % of MMA and then decreased significantly with a further increase in MMA concentration. These results led to the selection of resins with the properties that fulfill the requirement of a good quality traffic paint. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 367–372, 1998