Methylated poly , photolysis

Photolysis of the unsubstituted poly(ethylene sebacamide) (A), methylated poly(l,2-propylene sebacamide) (B), and poly(l,l-dimethylethylene sebacamide) (C) resulted in mostly chain fragmentation as indicated by the decreases in intrinsic viscosities of the polymer samples, Table 1. The same decrease in intrinsic viscosity was also observed for polyurea D. Polymer A and D remained bio-inert under the testing condition whereas the abilities for polymers B and C to support the growth of Apergillus niger were improved by photolysis. 

Phosphorescence studies in isobutylene-methyl methacrylate-1-naphthyl-methyl methacrylate co-polymer provided evidence to show that in very dilute solution the chain collapses into more compact structures, and intramolecular excimer formation in poly-(2-vinylnaphthalene) has been shown to exhibit non-Stokes-Einstein behaviour. Laser photolysis of polymers containing phenanthryl groups, such as poly-(9-vinylphenanthrene), indicates the presence of plural dimer sites having different geometries owing to the stacking effect of phenanthrene chromophores. In poly-(2-naphthyl methacrylate). 

A reversed sequence of the same procedure has also been followed [151] by using ABME in conjunction with EMP+PF and CHO in order to obtain, under UV irradiation, poly(CHO) containing an azo linkage in the main chain. As the photolysis of the az group at 350 nm irradiation is not achievable due to the higher absorption coefficient of the residual benzoin methyl ether end groups, poly(CHO) is thermally decomposed in the presence of styrene, to give mainly three-block copolymers (Scheme 46). 

Photolysis of Blends of Poly(Methyl Methacrylate) and Polypropylene... 

Poly(alkyl and aromatic ethers) - Using laser flash photolysis poly(2,6-dimethyl-l,4-phenylene oxide) undergoes scission at the phenolic link to give phenoxy radicals . Poly(vinyl methyl ether) has been shown to undergo a complex series of photoprocesses as shown in Scheme 2. ... 

There was a strong possibility that initiation occurred via photosensitized formation of hydrogen peroxide on the metal oxide surface followed by desorption and subsequent photolysis of hydrogen peroxide to form free radicals. Radicals formed by this means would lead to abstraction of hydrogen from the fiber surface and subsequent grafting of poly(methyl acrylate) at these sites. 

Volatile product evolution has been observed in the photolysis of many vinyl polymers as a consequence of side-group scission. The nature of these volatile products is therefore related to the side group. Carbon dioxide, carbon monoxide and methyl formate are produced from polymethylmethacrylate [12], carbon dioxide, carbon monoxide, methane and acetic acid in the photolysis of poly vinylacetate [13], and hydrogen chloride in the photolysis of polyvinylchloride [14]. 

Hydrogen is evolved in the photolysis of poly-a-methylstyrene with a quantum yield of 1.7 x 10-2, together with some carbon dioxide and carbon monoxide. This indicates that there are some bonded oxygen atoms in the polymer and it has been suggested that degradation could be due to the scission of a few weak bonds situated at random in the polymer chain [10]. No mention is made of the evolution of methane as a consequence of methyl group abstraction. It has been noticed that a yellow colour is produced on long exposure and that this remains even when the polymer has been reprecipitated [10]. 

Poly (styrene-afo-methyl methacrylate) undergoes yellowing more rapidly in vacuum than in air. The major yellowing moiety is a species related to l,5-diphenyl-l,3,5-hexatriene. Simultaneous photolysis of the triene results in a reduction in the rate of yellowing with increasing time of irradiation oxidative reactions of the triene appear to reduce the rate of yellowing in air. Fluorescence quenching takes place by processes that are the same in air and vacuum. 

Other studies on ketone containing polymers include copolymers of unsaturated ketones with styrene and methyl methacrylate and poly(methylisoprenyl ketones) for use as photoresists. A review has appeared on the laser flash photolysis of vinyl ketones. ... 

Poly(methyl methacrylate) (PMMA) and Related Polymers.—The photolysis of PMMA in methyl acetate, chloroform, CH2C12, and benzene solution has been shown to be consistent with scission resulting from random absorption directly by the polymer without participation of the solvent.199 The photolysis of thin films of PMMA in 02 has been shown to produce methanol, formaldehyde, methyl acetate, methyl formate, water, formic acid, carbon dioxide, and methane.200 The reactions caused by light in PMMA in the presence of atomic... 

The products of photolysis of poly(ethyl acrylate) and po y(n-butyl acrylate) in vacuo and in oxygen have been reported.800 The photolysis of copolymers of MMA and methyl acrylate 207 and of MMA and p-methoxyacrylophenone208 has been described. 

Another group of positive UV resists operating on the principle of radiation-induced main chain scission utilizes the efficient photochemistry of polymeric ketones, exemplified hy poly(methyl isopropenyl ketone) PMIPK, to effect image discrimination. Scheme 7.21 shows the photolysis of this resist. ... 

Further confirmation of the important effect of solid-phase transitions in polymer photochemistry was reported by Dan and Guillet (29). They studied the quantum yields of chain scission, c >s, as a function of temperature in thin solid films of vinyl ketone homo- and copolymers. For polymers where the Norrish type-II mechanism was possibici large increases in n were observed at and above the glass transition T. Figure 8 shows this effect in a styrene copolymer containing about 5% phenyl vinyl ketone (PVK). Below Tg, )s is about 0.07, but at Tg it rises to about 0.3, a value similar to that observed for photolysis in solution at 2S°C. A similar effect was observed with poly (methyl methacrylate-co-methylvinyl ketone) (PMMA-MVK) and PVK homopolymer. 

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