Poly olefins

C. Poly( olefin sulfonejs Molecular Weight Changes.920... 

TABLE 3. G values of volatile products from poly(olefin sulfone)s... 

The most radiation-stable poly(olefin sulfone) is polyethylene sulfone) and the most radiation-sensitive is poly(cyclohexene sulfone). In the case of poly(3-methyl-l-butene sulfone) there is very much isomerization of the olefin formed by radiolysis and only 58.5% of the olefin formed is 3-methyl-l-butene. The main isomerization product is 2-methyl-2-butene (37.3% of the olefin). Similar isomerization, though to a smaller extent, occurs in poly(l-butene sulfone) where about 10% of 2-butene is formed. The formation of the olefin isomer may occur partly by radiation-induced isomerization of the initial olefin, but studies with added scavengers73 do not support this as the major source of the isomers. The presence of a cation scavenger, triethylamine, eliminates the formation of the isomer of the parent olefin in both cases of poly(l-butene sulfone) and poly(3-methyl-1-butene sulfone)73 indicating that the isomerization of the olefin occurred mainly by a cationic mechanism, as suggested previously72. 

Hydrogen, which is a major product in the radiolysis of most hydrocarbon polymers, is only a minor product in the radiolysis of poly(olefin sulfone)s, although it is of the largest yield between the minor products. Hydrogen is formed by H atoms combination or by an H atom abstracting hydrogen... 

The effect of the temperature is an exponential increase in the radiolytic yield of the volatile products for each poly(olefin sulfone). If the logarithm of G(volatile products) is... 

FIGURE 8. Overall reactions scheme for radiation degradation of poly(olefin sulfone)s. Reproduced by permission of the authors from Reference 74. 

C. Poly(olefin sulfone)s Molecular Weight Changes... 

The high sensitivity of poly(olefin sulfone)s to chain scission by radiation was first discovered for poly(l-butene sulfone) and poly( 1-hexene sulfone) by Brown and O Donnell79,80. 

Bowden and Thompson83 studied the degradation of thin films of various poly(olefin sulfone)s of low olefins due to radiolysis by electron beams at 20 °C. All samples decreased in thickness, indicating scission and depropagation. 

Polychloromethylsulphonylbiphenyls, mass spectra of 154, 155 Polyenes, synthesis of 771 Polymerization, of sulphoxides 846 Polymer-supported reagents 928 Polymorphonuclear leukocytes 854 Poly(olefin sulphonejs, radiolysis of 916-922 Polysulphones, radiolysis of 913 Population analysis 14, 15, 21, 22 Propargylic sulphenates, rearrangement of 736-739... 

Sulphones - see also Acetoxysulphones, /1-Acyloxysulphones, a-Alkoxysulphones, a-Aminosulphones, Azidosulphones, Azosulphones, Azoxysulphones, co-Cyanosulphones, Dialkoxysulphones, a-Diazosulphones, Disulphones, Episulphones, Epoxysulphones, a-Halosulphones, Hydroxysulphones, / -Iminosulphones, Ketosulphones, a-Lithiosulphones, a-Nitrosulphones, /1-Oxosulphones, Poly(olefin suphonejs, Polysulphones, y-Siloxysulphones, Tetrahalosulphones, Trisulphones addition reactions of 642-649, 774-809 alkadienyl - see Alkadienyl sulphones alkenyl - see Alkenyl sulphones alkyl aryl - see Alkyl aryl sulphones alkylthiomethyl - see Alkylthiomethyl sulphones... 

This sequence of formation of radical cation which is followed by a C—S bond scission into alkyl radical and alkyl sulfonyl cation was previously suggested by the same authors for the radiolysis of poly(olefin sulfone)s in the solid state and was confirmed by scavenger studies . Seavengers are ineffeetive in erystalline solids such as dialkyl sulfones and hence eould not be used in this study. 

Membrane banners are applied to the exterior of the foundation and also beneath the floor slab during construction. Materials used for the membrane barriers range from coextruded poly olefin to polyvinyl chloride to foil sheets with many other materials in between. All membrane barriers must have the edges sealed to prevent radon from migrating around the edges and back into the building. 

Figure 19 A comparison of the experimental and calculated arrival time distributions for T4FC, T4R-Na and P4FC poly(olefins). Reproduced with permission from Bushnell et al. [117], Figure 6. Copyright (2004) American Chemical Society.

Another class of "chain scission" positive resists is the poly(olefin sulfones). These polymers are alternating copolymers of an olefin and sulfur dioxide. The relatively weak C-S bond is readily cleaved upon irradiation and several sensitive resists have been developed based on this chemistry (49,50). One of these materials, poly(butene-l sulfone) (PBS) has been made commercially available for mask making. PBS exhibits an e-beam sensitivity of 1.6 pC cm-2 at 20 kV and 0.25 pm resolution. 

While "conventional positive photoresists" are sensitive, high-resolution materials, they are essentially opaque to radiation below 300 nm. This has led researchers to examine alternate chemistry for deep-UV applications. Examples of deep-UV sensitive dissolution inhibitors include aliphatic diazoketones (61-64) and nitrobenzyl esters (65). Certain onium salts have also recently been shown to be effective inhibitors for phenolic resins (66). A novel e-beam sensitive dissolution inhibition resist was designed by Bowden, et al a (67) based on the use of a novolac resin with a poly(olefin sulfone) dissolution inhibitor. The aqueous, base-soluble novolac is rendered less soluble via addition of -10 wt % poly(2-methyl pentene-1 sulfone)(PMPS). Irradiation causes main chain scission of PMPS followed by depolymerization to volatile monomers (68). The dissolution inhibitor is thus effectively "vaporized", restoring solubility in aqueous base to the irradiated portions of the resist. Alternate resist systems based on this chemistry have also been reported (69,70). 

Recent studies on LET effects In 2 mm thick samples of polymers have shown no difference between fast neutron and Co60 gamma irradiations for poly(olefIns) (32), a small difference for... 

In poly(olefines) the metastable allyl radical is often observed by ESR techniques following irradiation ... 

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