Poly methyl methacrylate

Poly(methyl methacrylate) and its Maleimide and Glutarimide Copolymers 

This last section deals with linear polymers with side chains (as does Sect. 3). However, whereas in Sect. 3 the emphasis was on the ring motions involved in very low temperature transitions, the studies reported in this section exclusively concern the transition and, sometimes, its coupling with the a transition. In addition to assignment of the transition, the aim is a precise description of the involved motions as well as an analysis of the cooperativity that develops with increasing temperature. 

It is worth noticing that a molecular modelling approach is used to complement the experimental techniques of dynamic mechanical analysis, dielectric relaxation, solid-state and H NMR. 

Due to the relatively simple chemical structure of poly(methyl methacrylate) (PMMA)  

The a transition with its maximum at 116 °C, corresponding to the glass-rubber transition processes. 

In this section we first discuss two synthetic polymers, poly(methyl methacrylate) and polypropylene, to illustrate the proton and C NMR spectroscopy of macromolecules. The spectra of protein molecules will be discussed in later sections. We then describe deuterium NMR spectroscopy by illustrating the characteristic features of the motion in the polyethylene molecule. The motion is caused by a change in thermal energy. Finally, we describe polybenzyl-y-glutamate as an example of two-dimensional NMR spectroscopy. 

FIGURE 19.9 The 220-MHz P-methylene proton spectra of poly( methyl methacrylate) in chlorobenzene at 135 C (a) syndiotactic (b) isotactic. [Source Bovey (1972). By permission of Dr. Bovey and Academic Press.] 

The following is an example of the meso and racemic mixture of a triad  

As with other major tonnage polymers, the lUPAC-recommended name for PMMA is almost never used, partly no doubt because it is extremely cumbersome. It is poly[l-(methoxycarbonyl)-l-methylethene]. 

Commercially PMMA is becoming relatively less important as time passes. For example, in the mid-1960s sales of PMMA ran at 40% of the total level of sales of poly (styrene) by 1980, they had fallen to 12%. PMMA does, though, retain certain uses, including interestingly as the material from which plastic dentures are manufactured. 

PMMA is a transparent, glassy material, which is known from A-ray studies to be amorphous at the molecular level. It is clearly polar, as is shown by 

Other systems, the chemical shift calculated with the small atomic basis DZ is well correlated with the chemical shifts obtained with the larger basis IF. Only the absolute offset is not correctly predicted by the small basis. Thus, geometry-induced variations can be reliably obtained with a small atomic basis even for a system like PVC. Apparently, hetero atoms in themselves are no obstacle to the ab initio spectral simulation of polymer systems. 

Amorphous thermoplastics were some of the earliest plastics, excepting polycarbonate, to find general acceptance indeed, cellulose plastics were the first thermoplastics available commercially, and poly(methyl methacrylate), (PMMA), was a commercial product in the 1930s. Their continued application some 50 years later is a comment on their usefulness, and on their properties compared with those of polystyrene, since PMMA is almost twice the price of PS, and the cellulose plastics are significantly more expensive than PMMA. Polycarbonate, a development of the late 1950s, is some three times more expensive than PS, and so finds use in critical applications where performance rather than cost is the criterion of acceptability. There are other amorphous thermoplastics with yet more advantageous properties which have not reached the status of commodity materials a selection of these with elevated service temperatures is reviewed in a later chapter. 

In addition, one of the most versatile and widely used plastics, poly(vinyl chloride), (PVC), should also be included in this category. Since a small amount of crystallinity affects its behaviour, however, it will be considered separately in Chapter 8. 

Producing large shapings frequently involves thermoforming techniques 

The capabilities of the ESR technique for providing fundamental information about the mechanism of radiation degradation of polymers are shown in observations on gamma-irradiated poly(methyl methacrylate), polystyrene and their random copolymers. 

A variety of techniques can be used to analyse for the component radicals in an ESR spectrum. They include  

Figare 10.9 ESR spectrum of polyfa-methylstyrene) after y-irradiation in vacuum at 300K(dose6kGy) (a)oiiescanof200s (b) ISO scans 

C stage (2) C and D stage (3) E stage (4) propagating radical (F) is the only species present and is stable (5) F. 

The two neutral radicals are consistent with crosslinking being the major effect of radiation on polystyrene, in contrast to main-chain scission in poly(methyl methacrylate). 

In this chapter, materials for fabricating POFs, especially their cores, are discussed. Section 4.1 describes the properties and problems of typical base polymer materials, namely poly(methyl methacrylate) (PMMA) and CYTOP . In Sections 4.2 and 4.3, recent material developments that have been attempted to solve the difficulties of conventional polymers are detailed. 

PMMA is a mass-produced, commercially available polymer that provides excellent resistance to both chemical and weather corrosion. The transmittance 

Fundamentals cf Plastic Optical Fibers, First Edition. Yasuhiro Koike. 

As mentioned in Section 2.3.2, there have been several reports on perdeuter-ated PMMA (PMMA-dg) as a base material for fabricating lower loss POPs. The replacement of hydrogen with deuterium in PMMA results in a considerable reduction in the C-H vibrational absorptions in the IR region and in its overtones in the visible to near-IR region. As a result, loss reductions to 20 and 63 dB/km at 670-680 nm for an SI POP [1] and a GI POP [2], respectively, were successfully achieved using PMMA-dg as the core base material. The refractive index profile of a GI POP was nearly optimized, and the —3-dB bandwidth was enhanced to 1.2 GHz over 300 m in an over-field-launch condition. 

However, the humidity resistance of these fibers is a problem. Because the substitution of hydrogen with deuterium does not seriously affect most physical properties of the polymer, PMMA-dg exhibits a relatively high water absorption rate, up to 2 wt%, similar to PMMA. Thus, despite the fairly low attenuation over a wide range of wavelengths, PMMA-dg-based POPs show high attenuations under 

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Mixtures of polymers at surfaces provide the interesting possibility of exploring polymer miscibility in two dimensions. Baglioni and co-workers [17] have shown that polymers having the same orientation at the interface are compatible while those having different orientations are not. Some polymers have their hydrophobic portions parallel to the surface, while others have a perpendicular disposition. The surface orientation effect is also present in mixtures of poly(methyl methacrylate), PMMA, and fatty acids. 

Figure Bl.19.30. Height and friction images of a spin-cast polystyrene-poly(methyl methacrylate) blend obtained with (a) gold and (b) silica probes under perfluorodecalin. Note the reversal of frictional contrast and the high spatial resolution. (Taken from [142], figure 7.)...

Lenk T J, Hallmark V M, Rabolt J F, Haussling L and Ringsdorf H 1993 Formation and characterization of self-assembled films of sulphur-derivatized poly(methyl methacrylates) on gold Macromolecules 26 1230-7... 

Polylmethyl Methacrylate). The monomer used for poly(methyl methacrylate), 2-hy-droxy-2-methylpropanenitrile, is prepared by the following reaction ... 

Hydroxy-2-methylpropanenitrile is then reacted with methanol (or other alcohol) to yield methacrylate ester. Free-radical polymerization is initiated by peroxide or azo catalysts and produce poly(methyl methacrylate) resins having the following formula ... 

Poly(methyl methacrylate) Cast sheet Impact- modified Heat- resistant ... 

At 25°C, the Mark-Houwink exponent for poly(methyl methacrylate) has the value 0.69 in acetone and 0.83 in chloroform. Calculate (retaining more significant figures than strictly warranted) the value of that would be obtained for a sample with the following molecular weight distribution if the sample were studied by viscometry in each of these solvents ... 

Figure 3.16 Some experimental dynamic components, (a) Storage and loss compliance of crystalline polytetrafluoroethylene measured at different frequencies. [Data from E. R. Fitzgerald, J. Chem. Phys. 27 1 180 (1957).] (b) Storage modulus and loss tangent of poly(methyl acrylate) and poly(methyl methacrylate) measured at different temperatures. (Reprinted with permission from J. Heijboer in D. J. Meier (Ed.), Molecular Basis of Transitions and Relaxations, Gordon and Breach, New York, 1978.)...

With T as the independent variable, the transition between glassy and rubbery behavior can be read directly at Tg. Note that Tg is about 100° lower for poly(methyl acrylate) than for poly(methyl methacrylate). 

Combination and disproportionation are competitive processes and do not occur to the same extent for all polymers. For example, at 60°C termination is virtually 100% by combination for polyacrylonitrile and 100% by disproportionation for poly (vinyl acetate). For polystyrene and poly (methyl methacrylate), both reactions contribute to termination, although each in different proportions. Each of the rate constants for termination individually follows the Arrhenius equation, so the relative amounts of termination by the two modes is given by... 

It is not the purpose of this book to discuss in detail the contributions of NMR spectroscopy to the determination of molecular structure. This is a specialized field in itself and a great deal has been written on the subject. In this section we shall consider only the application of NMR to the elucidation of stereoregularity in polymers. Numerous other applications of this powerful technique have also been made in polymer chemistry, including the study of positional and geometrical isomerism (Sec. 1.6), copolymers (Sec. 7.7), and helix-coil transitions (Sec. 1.11). We shall also make no attempt to compare the NMR spectra of various different polymers instead, we shall examine only the NMR spectra of different poly (methyl methacrylate) preparations to illustrate the capabilities of the method, using the first system that was investigated by this technique as the example. 

Figure 7.10 shows the 60-MHz spectra of poly (methyl methacrylate) prepared with different catalysts so that predominately isotactic, syndiotactic, and atactic products are formed. The three spectra in Fig. 7.10 are identified in terms of this predominant character. It is apparent that the spectra are quite different, especially in the range of 5 values between about 1 and 2 ppm. Since the atactic polymer has the least regular structure, we concentrate on the other two to make the assignment of the spectral features to the various protons. 

The hydrogens of the methylene group in the backbone of the poly (methyl methacrylate) produce a single peak in a racemic dyad, as illustrated by structure [XVI]. 

Figure 7.10 Nuclear magnetic resonance spectra of three poly(methyl methacrylate samples. Curves are labeled according to the preominant tacticity of samples. [From D. W. McCall and W. P. Slichter, in Newer Methods of Polymer Characterization, B. Ke (Ed.), Interscience, New York, 1964, used with permission.]...

Figure 7.11 Methylene proton portion of the 220-MHz NMR spectrum of poly(methyl methacrylate) (a) predominately syndiotactic and (b) predominately isotactic. [From F. A. Bovey, High Resolution NMR of Macro molecules, Academic, New York, 1972, used with permission.]...

Figure 9.17 Plot of log [i ]M versus retention volume for various polymers, showing how different systems are represented by a single calibration curve when data are represented in this manner. The polymers used include linear and branched polystyrene, poly(methyl methacrylate), poly(vinyl chloride), poly(phenyl siloxane), polybutadiene, and branched, block, and graft copolymers of styrene and methyl methacrylate. [From Z. Grubisec, P. Rempp, and H. Benoit, Polym. Lett. 5 753 (1967), used with permission of Wiley.]...

The sedimentation and diffusion coefficients for three different preparations of poly(methyl methacrylate) were measuredf in /i-butyl chloride at 35.6 C (= 0) and in acetone at 20 C (> 0) and the following results were obtained ... 

Bhatnagar and Biswast measured the turbidity at 436 nm of 2l single sample of poly(methyl methacrylate) in several solvents, including acetone and methyl ethyl ketone (MEK) ... 

Another type of synthetic polymer-based chiral stationary phase is formed when chiral catalyst are used to initiate the polymerisation. In the case of poly(methyl methacrylate) polymers, introduced by Okamoto, the chiraUty of the polymer arises from the heUcity of the polymer and not from any inherent chirahty of the individual monomeric subunits (109). Columns of this type (eg, Chiralpak OT) are available from Chiral Technologies, Inc., or J. T. Baker Inc. 

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

Suspension Polymerization. Suspension polymerisation yields polymer in the form of tiny beads, which ate primarily used as mol ding powders and ion-exchange resins. Most suspension polymers prepared as mol ding powders are poly(methyl methacrylate) copolymers containing up to 20% acrylate for reduced btittieness and improved processibiUty are also common. 

The cured polymers are hard, clear, and glassy thermoplastic resins with high tensile strengths. The polymers, because of their highly polar stmcture, exhibit excellent adhesion to a wide variety of substrate combinations. They tend to be somewhat britde and have only low to moderate impact and peel strengths. The addition of fillers such as poly (methyl methacrylate) (PMMA) reduces the brittleness somewhat. Newer formulations are now available that contain dissolved elastomeric materials of various types. These mbber-modifted products have been found to offer adhesive bonds of considerably improved toughness (3,4). 

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