Hydrogen bonding rubbery materials

For rubbery materials. Young s modulus is related to the number of cross-links in the system. In this case the cross-Unks are of a physical nature, caused by hydrogen bonding. Measurement of the modulus via ball indentation techniques allows a rapid, inexpensive method of counting these bonds. Table A9.1.2 shows that the number of these bonds is of the order of 10 mol/cm. The number of these bonds also was shown to increase Unearly with concentration, except at the highest concentrations. 

Trans-1,4 PHXD with 1,2-disubstituted trans double bonds and sterically hindered methyl branching adjacent to the double bonds appeared to be more difficult to hydrogenate than cis-PB and cis-PI. Under mild hydrogenation conditions, 1H-NMR showed that the hydrogenated polymer contained 20% unsaturated double bonds. The 80 percent hydrogenated material exhibited rubbery behavior with a glass transition temperature lower than that of the parent polymer (Table 15). 

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