Styrene-methyl Methacrylate Copolymers Research Articles

Hypochromic Effects in UV Spectra of Polymers in Solution

The hypochromic effect in the UV spectra of polystyrene and styrene copolymers in solution was investigated in detail. For this purpose, isotactic and syndiotactic-rich polystyrenes as well as their dimer model compounds, 2,4-diphenylpentanes, and styrene-methyl methacrylate copolymers were prepared. UV absorption measurements were carried out in dioxane and tetrahydrofuran at various temperatures. The extinction coefficients of phenyl rings depended not only on the solvent and the temperature but also on the microstructure of the polymers. A discontinuous temperature dependence of the extinction coefficients was observed between 40 and 50°C for homopolystyrenes as well as their dimer model compounds. It was suggested that this might be explained in terms of the rotation of phenyl rings. On the other hand, the hypochromicity in binary copolymers appeared to depend strongly on the sequential arrangement of monomers (the chain architecture and the chemical composition of copolymers). The measured average extinction coefficients were well interpreted by a simple treatment by using triad probability proposed by Harwood. The results were discussed in relation to the UV spectrometer which is being used as an auxiliary detector in gel-permeation chromatography and microcolumn chromatography.

Dilute solution properties of styrene–acrylonitrile and styrene–methyl methacrylate copolymers. II. Short‐range and long‐range interactions from intrinsic viscosity data

AbstractExperimental data on styrene–acrylonitrile (St–AN), and styrene–methyl methacrylate (St–MMA) copolymers reported in Part I of this series are tested by “two‐parameter” theoretical relations. The Fox–Flory (F–F) parameter K is estimated using the F–F, Stockmayer–Fixman (S–F), and Inagaki–Ptitsyn (I–P) equations. In general, the K values obtained by the F–F equation are low for the three St–AN copolymer samples in the systems studied while the values obtained from S–F and I–P equations agree within the limits of experimental error. Values of K obtained from Kurata–Stockmayer (K–S) equation for sample SA1 agree with values obtained by the S–F and I–P equations. The specific solvent effect on the K values is discussed. Values of the unperturbed dimension r̄02/M̄w, calculated from the K values estimated from the S–F equation and from the homopolymer data are compared. Except in one case, the calculated r̄02/M̄w values from homopolymer data are low in comparison with the values obtained from experimental data, which shows that the presence of the repulsive interactions between unlike monomer units brings about an expansion of copolymer molecule. The effect of composition on the steric factor σ values is discussed. The long‐range interaction parameter B, the excess interaction parameters ΔBAB, and χAB are calculated. The effects of composition and solvent on these parameters are discussed.

Dilute solution properties of styrene–acrylonitrile and styrene–methyl methacrylate copolymers. I. Intrinsic viscosity–molecular weight relations

AbstractStyrene–acrylonitrile (St–AN) copolymers of three compositions—27.4 mole‐% (SA1); 38.5 mole‐% (SA2); and 47.5 mole‐% (SA3) acrylonitrile—and styrene–methyl methacrylate (St–MMA) copolymer (SM) of 46.5 mole‐% methyl methacrylate were prepared by bulk polymerization at 60°C with benzoyl peroxide as the initiator, and were then fractionated. The molecular weights of unfractionated and fractionated samples were determined by light scattering in a number of solvents. The [η] versus M̄w relations at 30°C were established for SA1, SA2, SM, and polystyrene (PSt) in ethyl acetate (EAc), dimethyl formamide (DMF), and γ‐butyrolactone (γ‐BL), and for SA3 in methyl ethyl ketone (MEK), DMF, and γ‐BL. Second virial coefficients A2 and the Huggins constant were determined. From values of A2 and the exponent a of the Mark–Houwink relation it is seen that the solvent power for samples SA1, SA2, and PSt is in the order EAc < γ‐BL < DMF, while for sample SA3 the solvent power is in the order MEK < γ‐BL < DMF. The solvent power decreases with an increase in AN content. The solvent power of the three solvents used for SM copolymer sample is practically the same within experimental errors. From the a values it is concluded that in a given solvent the copolymer chains are more extended than the corresponding homopolymers.

Fractionation of styrene-methyl methacrylate copolymer

Styrene-methyl methacrylate copolymer was fractionated by the column elution and coacervate extraction techniques. Different solvent-nonsolvent combinations were used; both batchwise and continuous column elution fractionations were carried out. Successful resolution of fractions according to molecular weight was achieved. The effect of the solvent-precipitant pair on the fractionation efficiency, as tested by gel permeation chromatography, is discussed. The results of continuous column elution depend significantly on the elution rate.

Role of Triad Concentration in Glass Transition Temperatures of Copolymers. II

Abstract Improved correlation between glass transition temperatures and copolymer composition was obtained in styrene-methyl methacrylate copolymers by assessing contributions of triad rather than diad concentrations. Contributions of ABA and BAB triads were found to be significantly different. Glass transition temperature minima as a function of copolymer composition were found to be related to the solubility parameters (and cohesive energy densities) of the parent homopolymers.

Factors influencing the creep behavior of poly(methyl methacrylate) cements.

Room temperature compression creep and recovery tests have been performed using samples of pure poly(methyl methacrylate) (PMMA), three commercially available poly(methyl methacrylate) cements, and several experimental cements. From these tests the influence of density, mixing procedure, particle size, methyl methacrylate-styrene copolymer, barium sulfate, aquenous storage environments, residual monomer, molecular weight of the continuous phase, benzoyl peroxide, and N,N-dimethyl-paratoluidine, upon the creep behavior of PMMA cements has been determined. The important results is that lowering the porosity or residual monomer content, increasing the powder size, or adding an MMA-styrene copolymer tends to increase the creep resistance of PMMA cement.

Preparation and characterisation of styrene—methyl methacrylate and styrene–methacrylic acid copolymer latices

AbstractSeries of styrene‐methyl methacrylate and styrene‐methacrylic acid copolymer latices have been prepared by emulsion polymerisation using polyoxyethylene nonyl phenyl ether as emulsifier and potassium persulphate as initiator. the effects of surfactant concentration and monomer composition on the ultimate particle size and conversion were investigated. The ultimate particle diameters decreased with increasing surfactant concentration, while the conversions were found to be almost independent of surfactant concentration. The ultimate particle diameters were notably decreased by increasing the content of methacrylic acid. Trace carboxyl groups were detected both in polystyrene latex and styrene‐methyl methacrylate copolymer latices. The number of sulphate groups on the polystyrene latex surface was about five times that of carboxyl groups.

Rheological Properties of Disperse Systems of Spherical Particles in Polystyrene Solution at Long Time-Scales. (III)

The dynamic and steady-flow properties of disperse systems of spherical particles of styrene-methyl methacrylate copolymer crosslinked by divinyl benzene in a polystyrene solution have been measured at long time-scale regions by means of a cone-and-plate type rheometer. The diameter of particles employed in the study was very uniform and found to be approximately 120 mμ. Four kinds of particles having different contents of methyl methacrylate (MMA) and ζ-potential were dispersed in a polystyrene solution at a content of about 10%. The rheological behavior observed for these different systems depend strongly not only upon the MMA content but also upon the ζ-potential. However, MMA content and ζ-potential are not deter-mining factors individually.Depending on the relative magnitude of attractive and repulsive forces between dispersed particles, the dispersion state can be classified into three different groups. When the methyl methacrylate content in the particles and the ζ-potential of electric double layer on the particle surface are assumed as the respective measure of the attractive and repulsive forces, the rheological behavior observed for the four different disperse systems can be explained without contradiction.

Absorption of polymers at the solution–solid interface. XII. Stabilization of dispersed silica by absorbed styrene–methyl methacrylate copolymers

AbstractThe ability of styrene–methyl methacrylate copolymers to stabilize silica dispersions has been investigated. Random, block, and graft copolymers covering the entire composition range have been employed in carbon tetrachloride, trichloroethylene, and benzene solutions. Equilibrium sediment volumes and dispersion turbidities provide adequate and concordant estimates of stabilization efficiency. Polystyrene is not adsorbed by precipitated silica from trichloroethylene or benzene and does not stabilize dispersions in these liquids; although adsorbed from carbon tetrachloride, there is no stabilization. Poly(methyl methacrylate) is an efficient dispersion stabilizer, and its performance is independent of molecular weight over a wide range. Random copolymers having styrene contents in excess of ca. 60% do not stabilize in trichloroethylene but do so in carbon tetrachloride, although well adsorbed in both cases. With this major exception, and that of a low‐styrene graft copolymer in carbon tetrachloride, copolymers of all structures and compositions stabilize well, better than poly(methyl methacrylate) in the solvents examined. A substantial degree of surface coverage is necessary for optimum stabilization. Subsidiary solution adsorption and layer thickness measurements are also reported.

Carbon-13 nuclear magnetic resonance spectroscopy of polymers. Part III. Determination of tacticity in monomer sequence distribution triads in styrene–methyl methacrylate copolymer

In the 13C n.m.r. spectrum of styrene (S)–methyl methacrylate (M) the aromatic C-1 in the styrene units and the methyl carbon atom in the methyl methacrylate units are sensitive to tacticity in the various monomer sequence triads. Measurements of chemical shifts for MMM, SSS, SMS, and MSM tactic triads allow estimation of chemical shifts for SSM and MMS triads. Intensities for MMM, SSS, and MSM tactic triads show the distribution due to tacticity for such monomer sequence triads. The ten M-centred and ten S-centred tactic monomer sequence populations calculated over a whole range of styrene–methyl methacrylate copolymer allow computer simulation of peaks the results of which agree well with experimental observations. The copolymer is random with regard to monomer sequence and tacticity except that blocks of methyl methacrylate or styrene are predominantly syndiotactic.

Quantitative analysis of the microstructure of methyl methacrylate-styrene copolymers using PMR spectra of solutions

A comparative analysis was made of existing approaches to the quantitative study of the microstructure of methyl methacrylate-styrene copolymers according to PMR spectra of their solutions and new methods were proposed which are based on modelling the relation between integral intensities of signals of methoxyl protons. An attempt was made to apply algorithms of minimization to calculate microstructural parameters of these copolymers using the spectrum of phenyl protons.

Shape effects in graft copolymer macromolecules

A study is made of the concentration dependence of the shape effect for methyl methacrylate-styrene copolymers in dioxan, and the macro- and microshape effects are isolated. Despite the considerable length of the segment A for the main chain of the macromolecule, the macroshape effect is much greater than that of the microshape, owing to the considerable thickness of the molecule. The shape asymmetry of the macromolecule p=1·9 (coiling degrees), while that of the statistical segment ps is < 1·5. The latter finding agrees with the estimated value of A/ d≈1 based on measurement of the viscosity and dynamic birefringence in the absence of shape effects (bromoform).

Synthesis of copolymers with carboxyl groups in the side chains using the ?silylation-desilylation? principle

1. A new method is proposed for the synthesis of copolymers of vinyl monomers with acids of the acrylic series; it is based on the use of the “silylation-desilylation” principle, viz., silylation of the carboxyl groups in the monomeric acids, and desilylation of the side-chain, silicon-containing ester groups in the copolymers. 2. Carboxyl-containing styrene-methyl methacrylate copolymers with various percentages of unsaturated acid links were synthesized in high yields.

Chemiluminescence of benzoyl peroxide in polymer matrices

We have studied the dependence of the intensity of chemiluminescence on time for the decomposition of benzoyl peroxide in polymethyl methacrylate, polystyrene and styrene-methyl methacrylate copolymers, above and below Tg. There is a maximum which, with decreasing temperature, is shifted towards longer times. An attempt has been made to interpret the results.

Adsorption of polymers at the solution–solid interface. V. Styrene–methyl methacrylate copolymers on carbon

AbstractThe adsorption of a series of block and random styrene–methyl methacrylate copolymers on an animal charcoal and on Graphon has been studied. On charcoal, adsorption decreases with increase of molecular weight because of the inability of larger coils to penetrate into the adsorbent. An analysis is presented which requires that coils undergo considerable distortion on adsorption in pores. The adsorption of random copolymers on Graphon is also in reverse order of molecular weight; this effect may be due to particle bridging leading to the formation of interparticle “pores.” The relative affinity of the styrene and methyl methacrylate residues is different on charcoal and Graphon, respectively; on both surfaces, however, relatively few of the more active residues are required for adsorption. Block and random copolymers are adsorbed to different extents which depend on the nature of the adsorbent surface.

Radical Polymerizations of Methyl Methacrylate and of Related Monomers with a Ruthenium Complex–Triphenylphosphine Catalyst

Methyl methacrylate, methyl acrylatelate, and dimethyl itaconate are polymerized in homogeneous solutions with a catalyst derived from dichloro(dodeca-2,6,10-triene-1,12-diyl)ruthenium(IV) 1 and triphenylphosphine. The polymer yields of these three monomers increase with the increasing molar ratio of triphenylphosphine to 1. 1 itself has stable π-allylic bonds and yields no polymer. With addition of triphenylphosphine to 1, the π-allylic bonds are converted into active σ-allylic ones, which are considered to participate in the initiation of these polymerizations. On the basis of the tacticity of the resulting poly(methyl methacrylate), of the kinetic investigations on the polymerization of methyl methacrylate, and of the composition of methyl methacrylate–styrene copolymer, it is concluded that the polymerization proceeds through a radical mechanism. The mechanism of the formation of the radical species in the initiation is discussed on the ground of the specificity of the activity for the polymerizations of typical vinyl monomers.

Phase separated droplets: Light scattering and size distribution

Abstract Light scattering properties and particle size distributions for phase separated droplets in a polymer matrix are investigated. The matrix materials are polyethyl methacrylate and a styrene-methyl methacrylate copolymer. Precipitated phases are polystyrene and docosane. Effects of molecular weight, concentration, and kinetics of phase separation are investigated. A theory is developed which predicts the droplet size distribution to be an exponentially decreasing function with increasing droplet radius. The scattering intensity varies as 1 sin 4 ( θ 2 ) at large θ. It is found that the data can be represented by the theory.

Dilute Solution Properties of Styrene-Methyl Methacrylate Copolymers with Different Architecture

The results of an extensive study on solution properties of alternating, statistical and block copolymers of styrene and methyl methacrylate with nearly equimolar composition are described, by placing emphasis upon their dependence on the sequential arrangement of monomers. The θ temperatures are determined in cyclohexanol by a phase-equilibrium method. Measurements of intrinsic viscosity are made in six different solvents, which are chosen to differ in their behavior toward the parent homopolymers. All data are examined on the basis of current two parameter theories.The short-range interactions, as given by the characteristic ratios, are expressed for the block copolymers as a composition average of those of the parent homopolymers, whereas for the alternating and statistical copolymers they show a positive deviation from the average. The deviation is roughly proportional to the population of the dyads of unlike monomers in the copolymer chain, i.e., to the run number. The long-range interactions are interpreted by assuming dyads as copolymer segments. Thus, the interaction parameters of the statistical and block copolymers may be expressed as a function of composition and run number in terms of the three parameters each characterizing the interaction of the parent homopolymers and the alternating copolymer with the pure solvent.

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. III. NMR study of methyl methacrylate–styrene copolymer

AbstractThe copolymer composition curve of the methyl methacrylate–styrene copolymer obtained by the copolymerization in the presence of ZnCl2 has more alternating tendency than that of ordinary methyl methacrylate–styrene copolymer obtained by radical copolymerization. The fine structure of the copolymer was examined by NMR, and the mechanism of the propagation step of the copolymerization in the presence of ZnCl2, which was proposed in the first report of this series, was verified.

Pyrolytic gas chromatography of styrene-methyl methacrylate copolymers

Pyrolytic gas chromatography of styrene-methyl methacrylate copolymers