Hydrogenated amorphous polystyrene

The nature of the hard domains differs for the various block copolymers. The amorphous polystyrene blocks in the ABA block copolymers are hard because the glass transition temperature (100°C) is considerably above ambient temperature, i.e., the polystyrene blocks are in the glassy state. However, there is some controversy about the nature of the hard domains in the various multiblock copolymers. The polyurethane blocks in the polyester-polyurethane and polyether-polyurethane copolymers have a glass transition temperature above ambient temperature but also derive their hard behavior from hydrogen-bonding and low levels of crystallinity. The aromatic polyester (usually terephthalate) blocks in the polyether-polyester multiblock copolymer appear to derive their hardness entirely from crystallinity. 

For our experimental studies on polymer crystallization we used low molecular weight (Mw) poly(ethylene oxide) (PEO), either as a homopolymer or attached to an amorphous polystyrene or hydrogenated polybutadiene block. These block copolymers are abbreviated by PS-PEO and PB, -PEO, respectively. PEO is a weU-investigated polymer [5,19,36,37]. Molecular details of all investigated polymers are given in Table 1. 

WI2 Winoto, W., Radosz, M., Hong, K., and Mays, J.W., Amorphous polystyrene-6/ocA -polybutadiene and crystallizable polystyrene-Z>/ocA -(hydrogenated polybutadiene) solutions in compressible near critical propane and propylene Hydrogenation effects, J. Non-Crystal. Solids, 355, 1393, 2009. 

FIG. 18.3 Activation energy of diffusion as a function of Tg for 21 different polymers from low to high temperatures, ( ) odd numbers (O) even numbers 1. Silicone rubber 2. Butadiene rubber 3. Hydropol (hydrogenated polybutadiene = amorphous polyethylene) 4. Styrene/butadiene rubber 5. Natural rubber 6. Butadiene/acrylonitrile rubber (80/20) 7. Butyl rubber 8. Ethylene/propylene rubber 9. Chloro-prene rubber (neoprene) 10. Poly(oxy methylene) 11. Butadiene/acrylonitrile rubber (60/40) 12. Polypropylene 13. Methyl rubber 14. Poly(viny[ acetate) 15. Nylon-11 16. Poly(ethyl methacrylate) 17. Polyethylene terephthalate) 18. Poly(vinyl chloride) 19. Polystyrene 20. Poly (bisphenol A carbonate) 21. Poly(2,6 dimethyl-p.phenylene oxide). 

The symbols used are I for initiator, R for the radical derived from the initiator, S for styrene, and R for growing polystyrene radicals, XH for a source of hydrogen radical, and PS for polystyrene. Thus, polystyrene can be formed in the termination step by chain transfer, disproportionation, and combination. Temperature and chain transfer agents can be used to control molecular weight and molecular weight distribution. Polystyrene resulting from free-radical processes is amorphous. 

Polymeric optical fibers have been prepared from various amorphous polymers such as polycarbonate, poly(methyl methacrylate), polystyrene and diglycol diallylcarbonate resin [339,340]. In these cases, the light attenuation of the respective optical fibers is due to absorption by the higher harmonics of C—H vibrations. The substitution of hydrogen by deuterium, fluorine or chlorine results in a shift to higher wavelengths of the absorption due to overtone vibrations, and reduces the attenuation at key communication wavelengths (as shown in Table 3.37). 

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