Photopolymerization methyl methacrylate

Similar observations were made in the photopolymerization of methyl methacrylate by a dimethylaniline-nitrobenzene complex. Remaining with methyl methacrylate photopolymerization by A -benzylpyridinium chloride in methylene dichloride is believed to be initiated by a chlorine atom formed from the decomposition of a charge-transfer complex. The presence of the halogen-... 

Other functional moieties, such as phenolphthalein and benzodifuran, when incorporated in to CMP networks showed effective photocatalytic activity towards heterogeneous photosensitization for methyl methacrylate photopolymerization and the photocoupling of primary amines, respectively. The... 

Fig. 7 Topographic images, SFM scan lines, and schematic cross-sectional representation of glass slides with chromium patterns and the formation of the polymer and copolymer layer A cleaned sample, B sample modified with SBDC, C after photopolymerization of styrene for 5h, D after photopolymerization of styrene for 15 h, and E after photopolymerization of styrene for 15 h and subsequently methyl methacrylate for 10 h. (Reproduced with permission from [45] American Chemical Society)...

Various metal nitrates, represented by silver nitrate, sensitize photopolymerization of AN, methaciylonitrile, a-chloroacrylonitrile, croto-nitrile and methyl methacrylate. The efficiency of photosensitization runs nearly parallel to the ease of reduction of the metal ion. Although there is little doubt that the monomer plays some role in the photochemical process, it is rather difficult to decide whether the primary act is direct oxidation of the monomer or electron transfer between metal ion and nitrate anion. 

A more conventional mechanism appears to be operative in the photopolymerization of ethyl acrylate [178] and methyl methacrylate [179] in aqueous solution, sensitized by fluorescein and Erythrosin, respectively. Ascorbic acid is the reducing agent in both cases and it is observed that the reaction does not proceed in the absence of buffer, usually phosphate buffer pH 6. Polymer formation starts after an induction period but its dependence on light intensity and ascorbic acid concentration has not been determined. The rate of photopolymerization is proportional to the monomer concentration and to the square root of the light intensity, dye, and ascorbic acid concentration. The authors report the order with respect to the monomer as 3/2. However, from our analysis of the data for fluorescein, which are more... 

However, no independent evidence is presented for the existence of this complex. In our view a simpler explanation for the lack of reaction in unbuffered solution is that the nondissociated form of ascorbic acid is a chain terminator. At the typical concentrations employed, 1-10 mM, more than 90% of ascorbic acid (pK = 4.1) is not dissociated when dissolved in pure water. At pH 6.0 only 1% is present as the protonated form. Furthermore, in their study of the photopolymerization of methyl methacrylate initiated by acriflavine-ascorbic acid, Lenka and Mohanty [180] report the rate of polymerization reaches a maximum when the ascorbic acid concentration is approximately 10 mM. The decrease in polymerization rate at higher concentrations suggests ascorbic acid participates in chain transfer and/or termination reactions. 

Recently Fouassier and Chesneau [219] studied the photochemistry of the system Eosin-PDO-MDEA in aqueous acetonitrile using steady-state irradiation and laser flash photolysis. The photopolymerization of methyl methacrylate (MMA) sensitized by the photoreduction of Eosin is investigated in acetronitrile to understand the mechanism of initiation and the enhancement in the rate of polymerization caused by the presence of PDO, 3. Rates, quantum yields of photopolymerization, and number average molecular weights of the polymer are determined with MMA (7 M), Eosin (3 x 10 5 M), and MDEA (0.1 M) in the presence and in the absence of 2 x 10-3 M PDO. 

The photopolymerization of 7 M methyl methacrylate in acetonitrile was studied. Measurements of the quantum yield of photopolymerization and the molecular weight of the formed polymer indicate PDO increases the quantum yield of initiation and decreases the rate of termination. The data are shown in Table 9 with the quantum yield of initiation, i5 and k, /kt reported in arbitrary units. 

TABLE 9 Photopolymerization of Methyl Methacrylate Sensitized by Eosin"... 

A more efficient photoinitiator has been designed by combining the Eosin-MDEA system with diphenyliodonium salt. The quantum yield of photopolymerization of methyl methacrylate (7 M) in acetonitrile is 30 with MDEA (0.1 M) and diphenyliodonium (0.05 M). The molecular weight of the isolated polymer is 55,000. In the absence of quantum yield and molecular weight, respectively. Thus, the presence of diphenyliodonium decreases the quantum yield of initiation by approximately 40% and increases the value of k3/kt by a factor of 6. 

In feet this method is similar to the synthesis of block copolymers using trapped radicals produced by polymerization of a monomer in a non-solvent. The existence of occluded radicals with a relatively long life-time was already postulated several years ago by Melville, in the photopolymerization of gazeous methyl methacrylate (149). The polymer deposited on the walls of the vessel was able to initiate the polymerization of chloroprene and of methylisopropenylketon (44,150). 

Photopolymerization using polysilanes can also be carried out to yield block copolymers containing runs of silicon atoms, for instance polysilane-methyl methacrylate. The resulting copolymer can then be used as a macro-photoinitiator for further free-radical polymerizations.144145... 

Kargin, V. A., V. A. Kabanov i V. P. Zubov Formation of Isotactic polymethyl-methacrylate by photopolymerization of the system methyl methacrylate zinc chloride. Vysokomolekulyarnye Soedineniya 2, 765 (1960). 

Table Z Data of the photopolymerization of methyl methacrylate with ketone-amine initiator systems (IE = ionisation potential, 3k H = quenching constant of ketone triplet state with amine in benzene, AV/At = dilatometric contraction) [1]...

Some radical initiators decomposing by heat can also be decomposed by UV radiation. Photopolymerization of acrylonitrile in the presence of AIBN or hydrogen peroxide, or of other initiators [75-78] has been reported. The quantum yield of AIBN decomposition is 0.4 at 298 K and 0.6 at 318 K. Photopolymerization of methyl methacrylate, styrene, and vinyl acetate can be initiated by tetramethylsilane, methylchlorosilanes, and halides of Group IV metals [79]. We assume that the radicals are formed by homolytic splitting of the covalent bond... 

The accelaration of styrene photopolymerization by oxygen is also explained by excitation of the DA complex of these two substances [82], A copolymer is produced which decomposes upon illumination [83]. Polymerization of methyl methacrylate is initiated by the photoexcited complex of the monomer with triethylaluminium [84]. Methyl methacrylate, acrylonitrile and acrylates in general readily produce unstable DA complexes which decompose to products quite different from the initial components. Methyl methacrylate, for example, polymerizes in the presence of quinoline and bromine. With the monomer, these pairs yield a DA complex which is unstable upon illumination [85a]... 

The Inifer technique enables us to fulfil some requirements of polymer architecture even in some radical processes. An amplified form may be applied, the Iniferter variant, where the radical initiator simultaneously acts as a transfer and terminating agent. Otsu et al. used sulphides and disulphides (tetraethylthiuram disulphide, PhSSPh, Ph2S, PhCH2SSCH2Ph) [96] and carbamates (benzyl-A,A-diethyldithiocarbamate, p-xylylene-A,7V-diethyl-dithiocarbamate) [97] in the photopolymerization of methyl methacrylate and styrene, and phenylazotriphenylmethane in the polymerization of methyl methacrylate [98]. Living radical polymerizations yield polymers with defined end groups or the required block copolymers. 

Benzophenone per-esters are apparently highly efficient photoinitiators for the photopolymerization of methyl methacrylate, and Neckers and coworkers have compared the efficiencies of several compounds (1) of this... 

Table 1 Rate of photopolymerization, of methyl methacrylate (bulk) in-...

In the photopolymerization of methacrylamide by benzoin methyl ether, chain-transfer to monomer has been found to be important, and benzalde-hyde is reported to be an inefficient photoinitiator of methyl methacrylate polymerization unless benzophenone and triethylamine are present. Acetophenone has been found to sensitize the cycloaddition of maleic anhydride to 7-oxabicyclo[2.2.1]heptan-5-one-2,3-dicarboxylic anhydride, , a-hydroxy-acetophenone derivatives have been found to be non-yellowing initiators, and h.p.l.c. has been used to determine residual carbonyl photoinitiators in u.v.-cured resins. In the emulsion-polymerization of methyl methacrylate using an aromatic ketone and a continuous or intermittent laser, the former conditions were found to be similar to those under continuous u.v. irradiation. The dependence of the polymerization rate and average chain-length on the absorbance of the initiator used in the photoinitiated polymerization of vinyl monomers has been studied. Interestingly, irrespective of all conditions, maximum conversion is observed when initiator absorbance is 2.51. "... 

New photoreactive polymers with dimethylmaleimide side groups have been prepared, "" and co-polymers of methyl methacrylate with oligourethanes have tensile properties superior to those of the separate homopolymer systems."" New monomers have been prepared for fire-retardant u.v.-curable polymers " and trimethylolpropane has been photopolymerized in the vapour phase. Diphenylsulphoniumbis(methoxycarbonyl)methylide photoinitiates the polymerization of styrene and methyl methacrylate through the formation of... 

Cp2TiCl2 has been assessed as additive that controls polymer chain growth in the polymerization of methyl methacrylate.1224 Methyl methacrylate is easily polymerized in the photopolymerization with Cp2TiCl2 in a water-methanol mixture under irradiation of a 15 W fluorescent room lamp. The polymerization proceeded heterogeneously.1225 This process in the presence of 2,2 -bipyridyl, 1,10-phenanthroline, or sparteine as the chelating reagent has been studied.1226 Similar studies on the polymerization of methacrylate monomers such as methyl methacrylate, ethyl methacrylate, phenyl methacrylate, and benzyl methacrylate at 40 °C have also been performed.1227 The results of co-polymerization of methyl methacrylate and acrylonitrile indicate that this process proceeds through a radical mechanism.1228 The mechanism of the controlled radical polymerization of styrene and methyl methacrylate in the... 

Other synthetic approaches to the kinetic problem have been taken. Variations in catalyst concentration for the formation of each component network from linear polyurethanes and acrylic copolymers have been used along with a rough measure of gelation time (5) to confirm the earlier (2-3.) results. Kim and coworkers have investigated IPNs formed from a polyurethane and poly(methyl methacrylate) (6) or polystyrene (7) by simultaneous thermal polymerization under varied pressure increasing pressure resulted in greater interpenetration and changes in phase continuity. In a polyurethane-polystyrene system in which the polyurethane was thermally polymerized followed by photopolymerization of the polystyrene at temperatures from 0 to 40 C, it was found (8.) that as the temperature decreased, the phase-... 

The second type of initiation mechanism is exemplified by the photopolymerization of styrene or methyl methacrylate. Absorption of light in this case does not result in decomposition of monomer molecules. Instead, it has been suggested [26] that radicals are produced by a complex initiation mechanism, illustrated for styrene by the following equations ... 

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