Chain dynamics of polyisoprene confined in porous media. A dielectric spectroscopy study

The global dynamics of polyisoprene (PI) in the controlled porous glass (CPG) Bioran have been studied with dielectric spectroscopy by varying the end-to-end vector (⟨ r 2 ⟩ 1/2 ) of the chain from dimensions smaller to much larger compared to the pore radius. Pulsed-field gradient NMR is used for the same systems and shows that all polymer chains are localized within the pores—no free PI exists. We find that the effect of confinement on the length scale of the chain relaxation shows both in the breadth and in the dynamics. In all cases the PI normal mode within the pores is significantly broadened with respect to bulk PI. The effect on the dynamics was found to depend on the size of the chain with respect to the pore radius. Silinization of the CPG has a pronounced effect on the amplitude and dynamics of the segmental and chain relaxations.