Methyl methacrylate, from PMMA

Figure 4.20 First-order plots of the monomers formed in the thermal degradation at 500 °C of PMMA, PS and alternating PMMAS copolymer 1 O methyl methacrylate from PMMA, styrene from PS, methyl methacrylate from PMMAS, styrene from PMMAS.

Crystalline samples of syndiotactic poly(methyl methacrylate) (st-PMMA) may be obtained from chloroacetone 178). This guest could be completely replaced by a variety of other guest molecules such as acetone, 1,3-dichloroacetone, bromoacetone, pinacolone, cyclohexanone, acetophenone and benzene. The X-ray diffraction patterns for these inclusion compounds were similar. These data indicate that the st-PMMA chains adopt a helical conformation of radius about 8 A and pitch 8.85 A. The guest molecules are located both inside the helical canals and in interhelix interstitial sites. 

Hard contact lenses are composed of a polymer that repels water because the constituent repeating units (the monomers that link together to form the polymer) are nonpolar, hydrophobic segments. The first hard contact lens was constructed in 1948 from the monomer known as methyl methacrylate (MMA), yielding the polymer poly(methyl methacrylate) or PMMA. This material offers durability, optical transparency, and acceptable wettability for optimal comfort. Today the rigid lens material of hard contact lenses is often constructed by combining MMA with one or more additional hydrophobic monomers to provide better gas permeability. 

Propose a procedure for recovering monomeric methyl methacrylate from scrap PMMA. 

The 1930s saw the introduction of the poly generation and the first of many such thermoplastics was poly(vinyl chloride) or PVC which became commercial reality with the introduction of a plasticiser. At about the same time Du Pont Chemicals also launched the polyamide nylon 66 after studying the network structure of silk. A few years later German researchers developed nylon 6 from caprolactam. In the UK, ICI developed and produced polyethylene, a material vital to the success of radar technology during the Second World War. ICI also made a valuable wartime contribution with the development of poly(methyl methacrylate) or PMMA which was used to make shatterproof and protective screens. 

Commercial acrylic resins comprise a broad array of polymers and copolymers derived from esters of acrylic acid and methacrylic acid. They range from the homopolymer of methyl methacrylate to a variety of copolymers including both the thermoplastic and thermoset type and ranging from hard and stiff types to soft and elastomeric types. The most common of the thermoplastic acrylic resins are the poly(methyl methacrylate) homopolymer (PMMA) and the copolymers containing predominantly methyl methacrylate but with small amounts of methyl or ethyl acrylate, acrylonitrile, or styrene comonomers added for improved toughness. 

Another recipe from in the literature shall be given here in a shortened form to give an impression of the substantial similarity of practically all sufficient recipes with small differences to obtain particular effects A solution of 6.5 ml iron(III)-tosylate (40% in n-butanol), 2.0 ml water, 0.22 ml EDOT, and 0.15 ml p5n idine was applied by spin coating (250 to 4000 rpm for 30 s) on to a poly(methyl methacrylate), or PMMA, sheet. Then the PMMA sheet was baked for 10 min at 65°C. Afterward, the PEDOT layers were washed by applying 3 ml of a 1 1 mixture of n-butanol and anisole while spinning at 1000 rpm for 20 s, and the washed substrates were further dried for 5 min at 65°C. 

Polar monomers such as 2-vinylpyridine and methyl methacrylate are normally polymerized in polar solvents such as tetrahydrofuran and at low temperature (-78 °C). In addition, additives such as LiCl are often added to help lower the rates of termination reactions to levels insignificant in the time frame of the reaction. Block copolymers made with nonpolar and polar monomers start with the nonpolar monomer because of its greater reactivity. These active centers are then typically capped with 1,1-diphenylethylene to lower then-reactivity before the addition of the polar monomer. This helps eliminate side reactions resulting from addition of the active center to electrophilic sites in the polar monomers. The two polar polymers, polystyrene-2-vinylpyridine (PS-P2VP) and polystyrene-poly methyl methacrylate (PS-PMMA) have been extensively studied in thin films. 

Very few papers have been published on the preparation of polymer blend nanocomposite from organoclays and poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend by the solution blending method." In this section, we discuss how the blending sequence affects the microstructure of the ternary hybrid nanocomposites and especially the dispersion states of the organoclays in the polymer matrix. 

Figure 2 illustrates the molecular weight dependence of (S )/M for isotactic poly(methyl methacrylate) (i-PMMA) in acetonitrile, a-PMMA in acetonitrile, and atactic polystyrene (PS) in cyclohexane, all at the theta point. The curves represent the theoretical values calculated from eqn [12] with the HW chain parameters listed in Table 1. Their close fits to the data points for the respective polymers demonstrate the excellent applicability of the HW model to the flexible polymers. In particular, the peak of (S )/M around M = 1.2 x 10 for a-PMMA shows behavior typical of a chain with locally helical conformation. On the other hand, the monotonic rise of (S )/M with increasing M for PS indicates weak helical nature of the polymer. In this chapter, we often use the KP model for describing solution behavior of PS. 

The cadmium chalcogenide semiconductors (qv) have found numerous appHcations ranging from rectifiers to photoconductive detectors in smoke alarms. Many Cd compounds, eg, sulfide, tungstate, selenide, teUuride, and oxide, are used as phosphors in luminescent screens and scintiUation counters. Glass colored with cadmium sulfoselenides is used as a color filter in spectroscopy and has recently attracted attention as a third-order, nonlinear optical switching material (see Nonlinear optical materials). DiaLkylcadmium compounds are polymerization catalysts for production of poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVA), and poly(methyl methacrylate) (PMMA). Mixed with TiCl, they catalyze the polymerization of ethylene and propylene. 

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

In this stage of the investigation, poly(methyl methacrylates) (PMMAs) were selected as the polymeric probes of intermediate polarity. Polymers of medium broad molar mass distribution and of low tacticity (14) were a gift of Dr. W. Wunderlich of Rohm Co., Darmstadt, Germany. Their molar masses ranged from 1.6 X 10" to 6.13 X 10 g-mol. For some comparative tests, narrow polystyrene standards from Pressure Co. (Pittsburgh, PA) were used. 

Molecular weight calibration from a monomer to several million daltons can be carried out by a variety of techniques. Because narrow standards of p(methyl methacrylate) (pMMA) are available, these are often used. Narrow standards of p(styrene) (pSty) are also available and can be used. Using the Mark-Houwink-Sakurada equation and the parameters for pSty and pMMA, a system calibrated with pSty can give pMMA-equivalent values, and vice versa. 

An idea of the range of materials and applications for polymers in medicine can be gained from the information in Table 10.1. As can be seen from this table a number of polymers are used in medical applications. One particular such polymer is poly (methyl methacrylate), PMMA. Early on it was used as the material for fabricating dentures later other biomedical applications developed. For example, PMMA is now used as the cement in the majority of hip replacement operations worldwide. 

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