Methyl ethers molecular shape

The kinetics of the bimolecular decay of poly(vinyl alcohol) (Ulanski et al. 1994) and poly(vinyl methyl ether) radicals (Janik et al. 2000b) have been studied in some detail (cf. Fig. 9.2). The OH radicals formed during the pulse generate on the (coil-shaped) polymer a non-random distribution of radicals. First, the radicals which are very close to one another recombine. The intrinsic bimolecular rate constant for such a process can be much faster than that of the decay of an equal concentration of randomly distributed low molecular weight radicals. As the number of close-by radicals decreases, the intrinsic rate constant drops, and the lifetime of the polymer radicals increases considerably. Now, the bimolecular decay of the polymer radicals becomes much slower than that of the corresponding low molecular weight radicals. While in the case of low molecular weight radicals the bimolecular rate constant is independent of the... 

The samples used are the polystyrene (PS) and poly(vinyl methyl-ether) (PVME) blends whose mechanical properties can be freely changed by controlling the blend ratio. In this case, in order to make the sample the measurement standard, the molecular weight of the polystyrene used is relatively low to avoid phase separation at room temperature. Ordinarily, the modulus of PS is on the order of GPa and PVME is on the order of MPa the moduli of blends can vary continuously in the range of these values as a function of the blend ratio. This is why this blend system was chosen as the standard of mechanical properties. The cantilever used is a V-shaped lever with thickness of 0.8 pm and length of 100 pm. At the tip, a very small Si3N4 scanning needle is fixed. The modulus of the cantilever is 0.68 N/m, which is stiffer than the one for ordinary contact measurement. Two different measurements were conducted. The first is the... 

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