Methyl photoinitiated polymerization

The nematic LC is the original eutectic mixture of 35% (weight %) 4 (m-octyl oxy)-4-cyanobiphenyl (80CB) and 65% 4/-(n-pentyl)-4-cyanobiphenyl (5CB). The sample is doped with perylene and 2% (mol %) of NIAC, which is acrylate monomer containing the easily reduced l,4 5,8-naphthalenediimide moiety (see Scheme 3). Finally, 0.5% (mol %) of benzoin methyl ether (BME) is added to photoinitiate polymerization of the NIAC. 

In the first detailed study of benzoin photoinitiated polymerization of vinyl monomers (styrene, butyl acrylate, methyl acrylate and methyl... 

Kinetics and Mechanism of Methyl Methacrylate Polymerization Photoinitiated by Benzophenones in Tetrahydrofuran... 

In the benzophenone-photoinitiated polymerization of methyl methacrylate, interpretation (i) would tend to increase the order of reaction with respect to monomer concentration, whereas interpretation (ii) would tend to decrease this, assuming that the species formed as the result of quenching initiated polymerization less efficiently than the solvent-derived radicals. The data of Block et al. (46) give a value of 0.84 for the order in monomer, and it could be argued that this is significantly lower than the value of unity predicted by the suggested... 

Solvent effectiveness in the benzophenone-photoinitiated polymerization of methyl methacrylate was in the order tetrahydrofuran > isopropanol > toluene > benzene (46). In the case of TCMB, isopropanol gaw slightly higher polymerization rates than tetrahydrofuran, but both wore again considerably more effective than toluene and benzene. As might be expected, monomers which thonselves contain ether grouj , e.g. diethylene glycol diacrylate (7), do not require addition of a separate hydrogen-donor solvent for efficient photoinitiation by benzophenone. 

Benzil has frequently been used as a means of generating free radicals in polymerization systems subjected to ultra-violet irradiation 11, 16, 56—58). In studies of the benzil-photoinitiated polymerizations of methyl methacrylate, and vinyl acetate, Melville (16) assumed that initiation was brought about by fragmentation of photoexcited benzil into two benzoyl radicals. However a survey of the photochemistry of benzil 34) indicates that such a cleavage does not in fact take place in solution studies of the products formed on irradiation of benzil in cyclohexane (59), cumene and isopropanol (60) can be rationalised on the basis of initial hydrogen abstraction from solvent by photoexcit i benzil, e.g. 

As a photoinitiator for the polymerization of bulk methyl methacrylate, benzil was found to be considerably less efficient than benzoin or benzoin methyl ether (20), e,g. at photoinitiator concentrations of 10 M, the polymerization rate observed using benzoin was eight times that observed using benzil, despite the fact that the latter was found to absorb three times as much of the incident radiation (Fig. 1). The photo-initiating efficiency of benzil was improved by a factor of three on addition to the methyl methacrylate of 10% v/v tetrahydrofuran, whereas the same additive had no appreciable effect on rates of benzoin- and benzoin methyl ether-photoinitiated polymerizations direct evidence that photoinitiation by benzil proceeds by a hydrogen abstraction mechanism rather than by fragmentation. 

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. "... 

Table 23. Photoinitiated polymerization of methyl methacrylate (MMA) in benzene solution, using polymeric photoinitiators based on benzoin methyl ether and benzoin moieties (BE) as well as their low-molecular-weight analogues [111]...

Figure 6. Rate of heat evolution during argon-ion laser-photoinitiated polymerization of 1-methyl-2-pyrrolidinone (MP), 9 ML of 2-ethyl-2-(hydroxymethyl)-l,3-propanediol triacrylate (TMPTA), and the dyes at a concentration of 10 m. Initiators 1) 19, 2) 18, 3) 10, 4) 16, 5) RBAX (rose bengal derivative prepared from rose bengal, which is first decarboxylated and then acetylated [36]),...

Gosh and Gosh [105] studied photoinitiated polymerization of methyl methacrylate initiated by the BP-TV,A-dimethylaniline couple, and Clarke and Shanks [106] tested the influence of a variety of amines on benzophenone-initiated polymerization. That amino radicals resulted during the initiation the polymerization by benzophenone-tertiary aromatic amines was shown by Li through the use of ESR and spin-trapping methods [107]. It was shown that the rate of photoinitiated polymerization depends on the structure of the amine. More recently [108] benzophenone-tertiary aromatic amines were studied as initiators of the free-radical polymerization of polyol acrylates. Illustrative kinetic curves recorded during photoinitiated polymerization of TMPTA are shown in Figure 23. 

For evaluating the influence of CD on the photoinitiated polymerization process, the polymerization of a water soluble monomer, AMsopropylacrylamide (NIPAAM), using complex of Me-P-CD and 2-hydroxy-2-methyl-1-phenylpropan-l-one (13) as... 

The polymerized acrylamide was completely bound in the graft since no homopolyacrylamide was found. Block polymers have been prepared by linear grafting 11). Eosin lactone was appended to poly (methyl methacrylate) chains by means of a terminal amino group to provide a polymeric initiator which was then used to photoinitiate polymerization of styrene and acrylamide. 

Naito et al. have examined the photopolymerization of methyl methacrylate initiated by poly(3-methyl-3-buten-2-one). Again a-cleavage was found to be the dominant initiating step. The photoinitiated polymerization of methyl methacrylate by benzophenone derivatives has been found to depend upon the nature of the substituent, which in turn influences the activity of the semipinacol radical. ... 

The role of sulphur-containing compounds in photopolymerization appears to have attracted some interest. Bis(j -methylpyridazinyl)-3,3 -disulphide has been found to initiate the photopolymerization of styrene but inhibits the thermal polymerization. The role of thiyl radicals (PhS-) in photoinitiated polymerization of vinyl monomers by aromatic thio-compounds has been postulated by several workers. In one study, flash photolysis was used to identify the nature of the radical. Sulphur-containing monomers such as 4-methyl-2-(vinylthio)thiazole and thiocyclanes have been photopolymerized and copolymerized with other vinyl monomers. Luca et al. have devised a mathematical model for the photopolymerization of 2,3-dimethylbutadiene and thiourea. 

Strongly redshifted fluorescence, as the solvent polarity was increased, demonstrated the formation of an intramolecular charge transfer state. Compounds under study were used as fluorescence probes for monitoring the kinetics of thermally initiated polymerization of methyl methacrylate and photoinitiated polymerization of 2-ethyl-2-(hydroxymethyl)propane-l,3-diol triacrylate. 

Photoinitiated polymerization of methyl methacrylate (1.0 M in benzene) is carried out using a photosensitizer and 3130 A light from a mercury lamp. If the quantum yield for radical production in this system is 0.50 and light is absorbed by the system at the rate of 10 ergs/L-s, calculate the rate of initiation. 

Waveguides consist of a thin layer of a high-refractive index material surrounded by/embedded in a low-refractive material. One way of making these layers uses of photolocking of a second component in a polymeric layer, followed by removal of this component from the unexposed area In this way, fiber optic sheet systems have been made as well as beam splitters, couplers, etc. In a typical example (Fig. 13) a dilute solution of polycarbonate, methyl acrylate and a photoinitiator in a solvent is spin-coated on a substrate, pattemwise exposed such that the methyl acrylate polymerizes in the exposed area and finally evaporation of unreacted monomer from the unexposed areas. 

KAS 03a] Kasapoglu F., Aydin M., Arsu N. et al, Photoinitiated polymerization of methyl methaciylate by phenacyl type salts . Journal of Photochemistiy Photobiology A, vol. 159, pp. 151-159,2003. 

The aqueous polymerization of methyl methacrylate initiated by the potassium trioxalate cobaltate (II) complex was studied by Guha and Palit [190]. At a relatively higher concentration (>0.001 mol L ), this compound can initiate aqueous polymerization of methyl methacrylate in the dark at room temperature. The complex is highly photosensitive, which can photoinitiate polymerization. A detailed end-group analysis of the obtained polymers indicated that carboxyl and hydroxyl radicals, which are from the decomposition of the photoexcited complex, are the initiating species. 

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