Methyl methacrylate plasma polymerization

A number of typical polymer-forming monomers have been polymerized using plasma polymerization including tetrafluoroethylene, styrene, acrylic acid, methyl methacrylate, isoprene, and ethylene. Polymerization of many nontypical monomers has also occurred including toluene, benzene, and simple hydrocarbons. 

Monomers Polymerizable by Plasma Initiation. Polymerization data for all of the vinyl monomers utilized in this study are summarized in Table 1. As shown previously, methyl methacrylate is readily polymerizable (, ). Methacrylic acid (MAA) and acrylic acid (AA) are polymerized immediately upon exposure to the plasma. Because the resulting polymers are insoluble in their monomers, the products are precipitated out and conversion is low despite prolonged post-polymerization. However, if water is now added as solvent, polymerization becomes homogeneous and high conversions can be readily achieved with post-polymerization. For example, after a 15 second plasma initiation period more than 80% yield was obtained for a 75% aqueous solution of MAA. The molecular weight, determined by intrinsic viscosity measurements, was found to be 4.5 X 10 gm/mole. 

We note in Table 1 that although methyl methacrylate polymerizes readily upon plasma initiation, ethyl methacrylate (EMA) and n-butyl methacrylate (BMP) gave only low yields (1- ) of polymer regardless of the length of post-polymerization period. Apparently a small amount of polymer was formed during the plasma initiation period (up to 60 seconds), and no further polymerization took place when plasma was turned off. Parallel experiments of dark polymerization (no plasma initiation) under the same conditions also resulted in no polymer formation. 

Figure 1. Monomer—copolymer composition relationship for the plasma-initiated copolymerization of methyl methacrylate with styrene. Plasma-initiated polymerization (%) NMR, (x) elemental analysis. Thermal polymerization (O) NMR, (Aj elemental analysis, (—) theoretical curve, tmma = 0.46 =...

Figure 3. NMR spectra of poly(methyl methacrylate-co-methacrylic acid) obtained by (1) plasma-initiated polymerization and (2) thermal polymerization in 0.2% deuterated pyridine.

Plasma-Initiated Chain Polymerization Mechanisms of Plasma Polymerization of Methyl Methacrylate... 

Non-thermal plasma can be applied not only for the stepwise polymerization discussed earlier, but also for effective stimulation of more conventional chain polymerization processes. Plasma-initiated polymerization of methyl methacrylate (MMA) with production of practically important polymer poly methyl methacrylate (PMMA) is a good example of such... 

The structures that have evolved for ablative-mode optical discs make use of interference effects to minimize the reflectance (R) of the disc in the absence of a hole. A typical ablative-mode optical disc has the structure shown in Figure 5.51. The substrate is an optically transparent material such as polycarbonate, poly(methyl methacrylate), poly(ethylene terephthalate), or poly(vinyl chloride), topped by a subbing layer to provide an optically smooth (to within a fi-action of a nanometer) surface for the recording layer. A metal reflector (typically aluminum) is then incorporated next to a transparent dielectric medium such as spin-coated poly(a-methyl styrene) or plasma-polymerized fluoropolymers. This dielectric spacing layer serves both to satisfy the quarter-wave (2/4) antireflection conditions and to insulate thermally the A1 reflector from the top absorbing layer where the information pits are created. 

Plasma polymerization was also applied to obtain an RO membrane, taking as a support a microflltration PP membrane or a UF PSU membrane. All used monomers (AAc, acrylonitrile, allylamine, ethylenediamine, n-propylamine, and methyl methacrylate) in proper plasma conditions improved the RO performance and the membrane resistance of chlorine (Kim and Kim 2001,2006). 

Johnson, D. R., Osada, Y, Bell, A. T., and Shen, M., Studies of the mechanism and kinetics of plasma-initiated polymerization of methyl methacrylate. Macromolecules, 14, 118-124 (1981). 

Several polymethacrylates, primarily alkyl esters, were compared with a novolac resist in terms of etch rates in CF4 and Ar plasmas. The alkyl groups examined included methyl, terf-butyl, cyclohexyl, norbonyl, adamantyl, and benzyl [226]. The polymerization of alicyclic methacrylates was pioneered by Otsu, who has demonstrated facile polymerization of bulky methacrylates and reported high Tg of this class of polymethacrylates [230]. It has been found that alicyclic polymers exhibit better dry etch resistance than acyclic esters and that the dry etch durability is increased by an increase in the number of rings. Thus, poly(adamantyl methacrylate) is as stable as a novolac resist under dry etch conditions. A 30/70 copolymer of adamantyl methacrylate with ter/-butyl... 

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