Poly Methyl Methacrylate Solutions Research Articles

Turbidity of critical solutions of polymethylmethacrylate in 3-octanone

We have measured the turbidity for a series of solutions of polymethylmethacrylate in 3-octanone (PMMA/3-OCT) with various polymer molecular weights. The obtained correlation length (ξ) and the osmotic compressibility (χ) show power law dependence on both the reduced temperature ε=(T−Tc)/Tc and the degree of polymerization N of the polymer chains, i.e., ξ∼N0.15ε−0.63 and χ∼N−0.06ε−1.23, with the associated scaling exponents in good agreement with theoretical predictions. When the results of the present experiment are combined with those from an earlier coexistence curve measurement [K.-Q. Xia, X.-Q. An, and W.-G. Shen, J. Chem. Phys. 105, 6018 (1996)], it is found that the concept of two-scale-factor universality applies to systems consist of the same polymer/solvent pair but with different molecular weights.

Measured coexistence curves of phase-separated polymer solutions

Measurements of the coexistence curves for phase-separated polymer solutions of polymethylmethacrylate in 3-octanone (PMMA/3-OCT) for six different molecular weights of PMMA have been carried out. We have tested the scaling behavior of the order parameter Δφ (the difference between polymer volume fractions in the two coexisting phases) for its dependence on the degree of polymerization N of the polymer chains and the reduced temperature ε=(Tc−T)/Tc. The experiments reveal that, in the asymptotic regime, the measured order parameter has power-law dependence on both N and ε, i.e., Δφ=3.8N−0.21ε0.34. Furthermore, when the symmerization procedure of Sanchez [J. Appl. Phys. 58, 2871 (1985)] is used to analyze the data, it suggests that εN0.46 may be used as a scaling variable for phase separated polymer solutions.

Phase separation in polymer solutions

Since the early work of Flory we have understood the causes and main features of the separation of dilute polymer solutions into coexisting phases below the theta point of the polymer-solvent pair. Some issues concerning corrections to the mean-field theory and the reconciliation of theory with experiment remain unresolved, and these are pointed out. In recent years attention has turned to questions about the structure and tension of the interface between those dilute polymer phases. The present status of the scaling theory is reviewed. The application of the theory to the interpretation of the pioneering measurements by Shinozaki et al. of the temperature and chain-length dependence of the interfacial tension in phase-separated solutions of polystyrene in methylcyclohexane, and a more recent test of the scaling theory through measurements of the capillary length of the interface in phase-separated solutions of polymethylmethacrylate in 3-octanone (Xia, Franck and Widom), are described.

Polymethylmethacrylate by XPS

X-ray photoelectron spectroscopy was used to analyze a thin film of polymethylmethacrylate (PMMA) which was spin cast from a 2% weight solution of PMMA in toluene onto a gold substrate. A Hewlett Packard 5950A ESCA spectrometer was used for this investigation.

Photographic measurements of propagation speeds of the conducting zone in polyaniline films during electrochemical switching

In order to observe the propagation of a conducting zone of a polyaniline film in response to anodic switching, propagation perpendicular to the film surface was simulated by propagation along the film by mounting the film on an insulated plate. A polyaniline film electrochemically deposited on an indium tin oxide (ITO) electrode was reinforced by casting polymethylmethacrylate solution on the film. It was peeled off the ITO, chemically reduced and then potentiostatically oxidized at one end in 1 mol dm −3 H 2SO 4 solution. Dynamic growth of the conducting zone was observed through an optical microscope. A well-defined boundary between the conducting zone and the insulating zone was seen. The contrast of the boundary did not vary with the electrolysis time, the growth length or the applied potential. The growth rate decreased slightly with the electrolysis time as a result of IR drop across the film. A differential equation for growth rate involving the effect of the IR drop was presented and solved to give more accurate values of the rate. The logarithmic growth ratio exhibited a linear relation with the applied potential, indicating a charge-transfer rate of the Tafel type. The anodic transfer coefficient was 0.2 and the rate constant was 5 × 10 −5 m s −1. The propagation on a molecular scale was discussed on the basis of the experimental results.

Polyfluoroalkyl derivatives of polyethers

The free radical addition of polyethers to fluoroalkenes, such as hexafluoropropene, is readily accomplished to afford materials with unusual properties. For instance, these materials will migrate to the interface of a polymethylmethacrylate solution to give a highly fluorinated surface. Polyfluoroalkyl derivatives of crown-ethers prepared by this technique have a surprisingly high affinity for alkali metal ions.

Interfacial tensions of phase-separated polymer solutions

Measurements of the capillary length in phase-separated solutions of polymethylmethacrylate in 3-octanone (PMMA/3-OCT) for each of five different molecular weights of PMMA, and in phase-separated solutions of polystyrene in methylcyclohexane (PS/MCH) for a single molecular weight of polymer, are reported. Measurements on PMMA/3-OCT were by the sessile-drop method; those on PS/MCH were by both the sessile-drop and capillary-rise methods. Interfacial tensions are estimated from estimated density differences and the measured capillary lengths. A theoretically predicted scaling law for the dependence of capillary length on polymer molecular weight and temperature is tested and at least semiquantitatively verified. As by-products of the sample preparation, the molecular-weight dependences of the critical composition and critical solution temperature of PMMA/3-OCT were also determined. The volume fraction of polymer at the critical point, φc, is found to be proportional to the −0.37±0.01 power of the molecular weight, in agreement with values of this exponent found by others for polystyrene solutions.

Thin-Film Formation on a Rotating Disk.

Thin-film formation on a rotating disk during the spin-coating process is analyzed. In the experiments for a solution of PMMA (polymethyl methacrylate) solute and chlorobenzene solvent, the final film thickness of dry film formed on silicon wafers for integrated circuits is measured with an ellipse thickness meter. Also, the transient film thickness during the entire film formation process on a rotating optical glass is measured using a laser displacement meter. A numerical calculation considering heat and mass transfer such as solvent evaporation is performed using a one-dimensional complete model proposed by the authors for each phase of liquid film and adjacent gas phase. Satisfactory agreement is obtained between these numerical and experimental results and the effect of various process parameters, e.g., spinning speed and initial film thickness, is clarified by this study.

Characterization of gamma-irradiated polymethyl methacrylate by viscometry

Characterization of dilute solution of gamma-irradiated polymethyl methacrylate (PMMA) in acetone has been carried out. The polymer sample in form of natural beads was administered a gamma-ray dose of 30 kGy by a cobalt-60 radiationsource. Various types of viscosities, viscosity average molecular weight, shape and size of irradiated PMMA and its two fractions were calculated. The results were compared with those for unirradiated PMMA. Degradation of PMMA as a result of irradiation has been observed.

Spin-lattice relaxation and chain dynamics in polymer solutions

Abstract Proton spin-lattice and spin-spin relaxation in polymer solutions of polymethylmethacrylate in deuterated chloroform and polystyrene in carbontetracloride are reported. Measurements were performed with pulsed NMR as a function of concentration and molecular weight and for different measuring frequency υ vL . The experimental results are analysed in terms of segmental dynamics for polymer chains, on the basis of the q and ξ dependence of the decay rate of the excitations as predicted by the “blob” model of de Gennes. The relation between the NMR data and light scattering quantities is discussed and it is shown how NMR can be complementary to light scattering.

Preparation of gelatin microspheres of bleomycin

A new method for preparing hydrophilic, cross-linked, solid gelatin microspheres of 15–28 μm size has been developed. Two main advantages of this method are the addition of the cross-linking agent in an organic medium to the aqueous gelatin medium and the use of concentrated high polymer solutions as the organic phase for polymeric dispersions. Gelatin microspheres containing bleomycin were prepared by this novel method using concentrated solutions of polymethylmethacrylate.

Adsorption-entanglement layers in flowing high molecular weight polymer solutions II. The effect of the nature of the surface

Adsorption-entanglement layers are thick, i.e. multimolecular, layers formed at solid surfaces from solutions of high molecular weight polymers in a state of flow. This publication, the second part of a series of four, is concerned with the effect that the chemical nature of the surface has on formation of these layers. It is shown that for the solutions of polyethylene (PE) and polymethylmethacrylate (PMMA) the layers form most readily on carbon surfaces. Further it is shown that in the case of PE, addition of aluminium stearate can prevent formation of the layers along steel surfaces.These and other effects reported in the paper all bear on actual situations encountered in rheological practice and in particular on the measurement of viscosities. It is concluded that the marked dependence of layer formation on the chemical nature and treatment of the surface is responsible for the differences in viscosity measurements featuring in earlier works by different authors.

Primary Normal Stress Coefficient Predictions

This paper deals with the problem of evaluating material elasticity through measurements of a material function such as the non‐Newtonian viscosity. A brief summary is provided between relations involving several material functions. In particular, two methods for predicting the primary normal stress coefficient from the steady shear viscosity are examined in detail. These methods are due to Bird, Hassager, and Abdel‐Khalik and to Wagner. Experimental data are presented involving test fluids such as polymethyl methacrylate solutions, polystyrene solutions, and polyacrylamide solutions. Finally, a relation between the shear viscosity and the primary normal stress coefficient is discussed using the concept of the finitely extensible bead‐spring chain model.

Film Thickness Determination of PMMA on InP by Ellipsometry

The thickness of polymethylmethacrylate (PMMA) films deposited in solution on is measured by ellipsometry to determine its dependence on terminal spin speed. The PMMA solution behaves as a steady‐state Newtonian fluid. Film thickness in excess of the periodic thickness is measured by combining data taken at three angles of incidence; a procedure for applying this technique is discussed. The main feature consists of assigning the film index from data taken at the incident angle where the ellipsometer readings are most sensitive to film index, and using this index in determining the film thickness at the other two angles. The basis supporting this procedure is presented, and the dependence of the ellipsometric model on uncertainties in the assignment of film and substrate optical constants is discussed specifically in terms of its effect on the three‐angle technique.

A study of the interaction between macromolecular links in concentrated solutions of polymethylmethacrylate by fluorescence quenching

Fluorescence quenching has been used to investigate the inter- and intramolecular interactions of polymethylmethacrylate macromolecules in the range of polymer concentrations from 0·5 to 16%. For this purpose, the fluorescent fragment (the anthracene group) and the quenching agent (a tertiary amino group) were included either with both in the same polymer chain or in different polymer chains. The results showed that the efficiency is essentially different for intramolecular interactions between the links from that for intermolecular interactions.

Polymethyl methacrylate dissolved in chloroform as treatment for superficial digital injuries

The application of a solution of polymethyl methacrylate dissolved in chloroform is advocated as treatment for superficial digital injuries. This method has the distinct advantage over sealing with benzoin tincture in that the fingers can be freely used in the presence of water.

A simple method for sealing surgical skin wounds in young or new-born mice.

To close skin incisions in albino mice, a solution of polymethyl methacrylate in chloroform is recommended to be smeared over the wound, a procedure which virtually eliminates the incidence of maternal cannibalism.

A Study on the Applications of the Enamel Disk

Extracted teeth are not suitable for many experiments, for example, regarding enamel solubility and plaque adhesion, because they have no reproducibility. So it is necessary to make a test piece that closely resembles enamel, is uniform, and applicable to such experimentation.The enamel disk molding method is as follows.1) Thoroughly mix 325 mesh enamel powder refined from many extracted teeth with polymer solution.2) Dry and pulverise it to 250 mesh.3) Take 200 mg of 250 mesh powder and fill a metal mold with it.4) Press it with a pressure of 18 ton/cm2.The enamel powder is reduced to an enamel disk which is from 0.7 to 1.0 mm in thickness and 13 mm in diameter.Polymer solution of polymethyl methacrylate (PMMA), epoxy (EP), or polystyrene (PS) can be used to mold an enamel disk. The concentration of polymer solution can be 10%, 20%, or 30%.A 10% PMMA-enamel disk is better than any others judging from its handling and attributes. It specific gravity of 2.27±0.07, a Vickers hardness number of 79.80±4.47 and a strength of rupture in bending of 0.928±0.059. The coefficients of variation of the Vickers hardness number and strength of rupture in bending are relatively small, 5.60% and 6.36%, respectively, in five-time repetitive tests.The purpose of this study, to get a uniform test piece, was achieved.

Effect of molecular weight on the viscosity of moderately concentrated solutions of polymethylmethacrylate and of methyl methacrylate-methacrylic acid copolymers

The viscosities of solutions in dimethylformamide of polymethylmethacrylate and of methyl methacrylate-methacrylic acid copolymers with M>10 5 have been measured over a wide range of temperatures and shear stresses. The properties of solutions of methyl methacrylate-methacrylic acid copolymers prepared by radical copolymerization and by hydrolysis have been compared. It is shown that the concentration of methyl methacrylate links in the copolymer has almost no effect on the solutions' viscosity. The ways in which the viscosity and activation parameters for the viscous flow of the systems depend on molecular weight have been studied. It has been found that the value of α in the relationship ν ∼ M α is greater than the figure of 3·4 associated with melts and solutions of flexible-chain non-polar polymers.

The connection between structure formation and the kinetics of the methyl methacrylate radical polymerization over ZnCl 2 at high conversions

The structural-rheological features of the polymer and of model systems were compared in this study with the kinetic parameters of the methyl methacrylate (MMA) radical polymerization over ZnCl 2 at high conversion and in the presence of a chain transfer agent. From the intensity of the light scattered by the reaction systems during polymerization it was established that the characteristic conversion q 1, associated with the change from a dilute polymethylmethacrylate (PMMA) solution in its monomer to a moderately concentrated solution, in which a fluctuating structural network starts to form, q 2, which coincides with the onset of spontaneous acceleration of the polymerization, q a , will shift towards smaller polymer concentrations in the reaction system when the ZnCl 2 content is increased. The rheological measurements carried out on model systems containing the hydrogenated monomer analogue, namely methyl isobutyrate (MIB) indicated a considerable increase in viscosity of the PMMA concentrate as a result of increase in ZnCl 2 concentration. The change from a slightly structurated system to a planar, steric, fluctuating network, observed during these rheological determinations as a kink on the log η = f (log c 2) plot and the effect of the ZnCl 2 additions on the position of this kink, correlated well with the q 2 and q a values determined from light scattering and the polymerization kinetics. The results are explained by the structuring effect of the ZnCl 2 on the PMMA macromolecules. The two coordination bonds of ZnCl 2 are saturated by reaction with the carbonyl groups in a single or in two adjacent macromolecules, which increases the PMMA chain rigidity, or they form ligands between the chains. Both these factors will give rise to the formation of supermolecular structures and of a bulky steric network in the polymerizing and in model systems.