Diffusion of probe polystyrenes with different molecular weights in poly(methyl methacrylate) gels and inhomogeneity of the network structure as studied by time-dependent diffusion NMR spectroscopy

Poly(methyl methacrylate) (PMMA) gels have been prepared with radical polymerization by cross-linking methyl methacrylate monomer using ethylene glycol dimethacrylate as cross-linking monomer in toluene containing polystyrenes (PSs) with Mw from 4000 to 400,000. The diffusion coefficients of the PSs in the PMMA gels swollen in deuterated chloroform have been measured by pulsed field-gradient (PFG) 1H NMR method with the diffusing time Δ varied. From the experimental results, it is found that the network structure of PMMA gels prepared in the presence of PSs with Mw=4000 and 400,000 are relatively homogeneous and inhomogeneous, respectively, within the Δ range from 40 to 500 ms.