Solutions polystyrene, absorption

This value agrees with the lifetime of the excimer of polystyrene. The intensity of the excimer fluorescence decreased with increasing chloromethylation ratio. Electrons produced in cyclohexane, one of the precursors of the excimer, were scavenged by chloromethylated part of polystyrene. Absorption spectra of the excited states and the polymer radicals were measured by laser photolysis of the cyclohexane solutions. The results are summarized in Fig. 10 [67]. 

Polymer network samples were suspended over polystyrene solutions. Vapor absorption was measured by gravimetry and by monitoring the weight of the bottles, correction could be made for changes in solute concentration. 

Mercury is a highly toxic element and its removal and analytical detection are important. Dithiocarbamate-incorporated monosized polystyrene-based microspheres (2 pm) have been prepared (2043) and used for the selective removal of mercury(ll) from aqueous solutions. The absorption ability increases with pH (2044). Related to this, dithiocarbamate grafted onto dried silica gel have been shown to be highly effective for the removal of mercury from waste solutions containing various complexing agents (145). 

The electronic spectrum in DMF solution had absorption bands at 634 and 660 nm. The polymer contained 4.0 mol% Fe(III)-Pc rings that were covalently bonded to polystyrene. If the amount of Fe(III)-Pc attached to the polymer was less than 4 mol%, the polymer was soluble in DMF or benzene. A Fe(III)-Pc-containing film was obtained by casting from a benzene solution. Co(II), Ni(II), and Cu(II)-phthalocyanine were bonded covalently to polystyrene in a similar way. 

Barium and strontium salts of polystyrene with two active end-groups per chain were prepared by Francois et al.82). Direct electron transfer from tiny metal particles deposited on a filter through which a THF solution of the monomer was percolated yields the required polymers 82). The A.max of the resulting solution depends on the DPn of the formed oligomers, being identical with that of the salt of polymers with one active end-group per chain for DPn > 10, but is red-shifted at lower DPn. Moreover, for low DPn, (<5), the absorption peak splits due to chromophor-chromophor interaction caused by the vicinity of the reactive benzyl type anions. 

Thus the quantum yield for acid production from triphenylsulfonium salts is 0.8 in solution and about 0.3 in the polymer 2 matrix. The difference between acid generating efficiencies in solution and film may be due in part to the large component of resin absorption. Resin excited state energy may not be efficiently transferred to the sulfonium salt. Furthermore a reduction in quantum yield is generally expected for a radical process carried out in a polymer matrix due to cage effects which prevent the escape of initially formed radicals and result in recombination (IS). However there are cases where little or no difference in quantum efficiency is noted for radical reactions in various media. Photodissociation of diacylperoxides is nearly as efficient in polystyrene below the glass transition point as in fluid solution (12). This case is similar to that of the present study since the dissociation involves a small molecule dispersed in a glassy polymer. 

Recently, by using improved nanosecond pulse radiolysis with the monitoring wavelength region from 300 to 1600 nm [44], absorption spectra due to main reactive intermediates such as the intramolecular dimer cation radical in the near-IR wavelength region were clearly observed in the pulse radiolysis of polystyrene in various solutions [47]. For example. Fig. 1 shows the absorption spectra observed in the pulse radiolysis of polystyrene solutions in CH2CI2. 

Figure 1 Transient absorption spectra obtained in the pulse radiolysis in 200 mM (base mM unit) polystyrene solutions in CH2CI2 at the pulse end ( ) and 100 nsec after the pulse (A). Inset time-dependent behavior observed at 1200 nm.

The absorption spectrum observed in the pulse radiolysis of solid films of polystyrene is shown in Figure 5. The absorption spectrum around 540 nm is also very similar to the absorption spectrum of polystyrene excimer observed in irradiated polystyrene solutions in cyclohexane as reported previously (2,3). The absorption with the maximum at 410 nm was reported previously and was assigned to anionic species (13,14). The longer life absorptions, attributed to triplet excited polystyrene repeat units and nonidentifiable free radicals, were observed in a wave length region < 400 nm. The absorption spectrum of CMS films obtained in pulse radiolysis showed a peak around 320 nm and a very broad absorption around 500 nm as shown in Figure 6. 

The absorption band around 520 nm is very similar to that of polystyrene excimer (2,3,5). The decay follows first order kinetics with a lifetime of 20 ns. The decay rate agrees with that of the excimer fluorescence and excimer absorption. The longer life absorptions, attributed to the triplet states and free radicals (2,5), were observed at wave lengths <400 nm, although the anionic species of polystyrene with the absorption maximum at 410 nm as seen in solid films (cf. Figure 5) was not observed. Figure 9 shows the absorption spectrum observed in the pulse radiolysis of CMS solution in cyclohexane. 

Figure 8. Transient absorption spectrum obtained by pulse radiolysis of 200 mM polystyrene solution in cyclohexane.

Polystyrene Solution in CHClj and CCl. In the laser photolysis and pulse radiolysis of polystyrene solution in CHC13 one observes an absorption spectra with maxima at 320 nm and around 500 nm (2,4,17). as shown in Figure 12. 

The absorptions at both 500 nm and 320 nm follow first order kinetics with a lifetime of 420 ns. This absorption species is neither the excimer of polystyrene nor free cationic species of polystyrene. Although the excimer of polystyrene has an absorption band around 500 nm, the lifetime is only 20 ns. Further the free cationic species of polystyrene should live for a longer time in this solution, and the absorption band should exist in a longer wavelength region (6). These considerations of lifetime and absorption spectrum lead us to conclude that the absorption spectrum shown in Figure 12 is due to the charge transfer-radical complex between polystyrene and Cl radical (2,4,17). A very similar... 

The transient absorption spectrum obtained in the pulse radiolysis of polystyrene solution in CC1 is shown in Figure 13. The spectrum is very similar to the charge transfer radical complex (PS4+C14-) species. The lifetime is about 200 ns. Consideration of the absorption spectrum and the lifetime suggest that this species is (PS4+C14-)-. The processes leading to formation of this species in liquid CC14 can be written as follows (4,7). 

Reaction Scheme of CMS Resists. The transient absorption spectrum shown in Figure 6 and observed for irradiated CMS films is mainly composed of two components as based on pulse radiolysis data of solid films of CMS and polystyrene, and CMS and polystyrene solutions in cyclohexane, chloroform, and carbon tetrachloride. An absorption with a maxima at 320 nm and 500 nm as due to the charge transfer radical-complex of the phenyl ring of CMS and chlorine atom (see Figure 14) and an absorption with maxima at 312 and 324 nm is due to benzyl type radicals (see Figure 11). 

Figure 3 shows the effect on the viscosity of polystyrene samples irradiated (X > 305 nm) in benzene solution in the presence of initiator I-III. The degradation of the polymer is caused by free radicals generated from the initiators. There is also a significant difference between the three initiators. Initiator I has a stronger absorption band between 300 and 400 nm than the... 

This coupling methodology was subsequently utilized to prepare zwitterionic-PPy 64 that possessed a remarkably low solution band gap of 1.1 eV [272]. Their strategy, depicted in Scheme 62, included a copper-bronze-promoted polymerization to afford polymer 64, exhibiting an Mn of ca. 5000 g/mol relative to polystyrene. While this material was reported to be an intrinsic semiconductor, it showed interesting pH-dependent changes in the electronic absorption spectra. 

In cyclohexane geminate recombination occurs very efficiently and the observation of polymer ions is rather difficult [57, 58]. However, when the electron scavenger such as chloroform and carbon tetrachloride was added to the solution of polystyrene in cyclohexane, a weak, broad absorption band with a maximum at lOOOnm due to dimer cation of benzene was observed. The dimer cation radical might be produced by the hole migration, along the polymer chain, from a radical cation to a site suitable for the dimer-cation formation [59]. 

In benzene and toluene solutions, electrons produced by ionizing radiation also recombined with parent cations very quickly. Excited states are mostly originated through this reaction. The transient absorption obtained in the solution of chloromethylated polystyrene showed a band due to benzyl type... 

The infrared spectrum of the precipitated polystyrene at this stage exhibited no absorption using thermally polymerized polystyrene in the reference beam. A 3.5% solution of dried Triton X-405 in chloroform showed intense adsorption at about 1100 cm. 1, characteristic of the ether linkage. 

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