Side Chain Molecular Weight Research Articles

Dynamic mechanical properties and creep of poly-2-ethyl butyl methacrylate

The real ( J′) and imaginary ( J″) components of the complex compliance have been measured between 0.05 and 3600 cycles/sec. in the temperature range from 20° to 151 °C. for a fractionated poly-2-ethyl butyl methacyrlate with molecular weight 2.20 × 10 6. The creep compliance, J(t), and creep recovery were measured from 101° to 151°. The glass transition temperature was determined to be 11°C. The method of reduced variables gave superposed curves in the transition zone with shift factors following the WLF form of equation; the WLF parameters were f g = 0.021, α f = 1.8 × 10 −4 deg. −1. In the plateau zone (including the creep) an additional f-reduction for temperature dependence of entanglement was necessary, with ΔH = 4.4 kcal. The retardation and relaxation spectra were calculated; the latter is almost identical in shape throughout with that of the n-butyl polymer. The logarithm of the monomeric friction coefficient is −3.69 at 100°C. and 4.79 at T g . The average degree of polymerization between the entanglement coupling points is calculated to be 83, 115, and 178, respectively, from the plateau in the spectra, from the height of the maximum in J″, and from the position of the latter on the frequency scale. In general, the viscoelastic behavior of the 2-ethyl butyl polymer resembles that of the n-butyl much more closely than that of the n-hexyl which has the same side chain molecular weight.