Determination of Polyisoprene‐block‐poly(methyl methacrylate) Domain Sizes Using 1H Spin Diffusion

The microphase structure of polyisoprene‐block‐poly(methyl methacrylate) diblock copolymers was studied using solid‐state NMR techniques. Wideline separation spectroscopy reveals a narrow interphase between the two polymers. The domain sizes of a lamellar sample and a sample with hexagonally ordered cylinders were determined using ¹H spin diffusion. The lamellar sample shows a domain size of 16 ± 2 nm for the minor polyisoprene phase and a long period of 33 ± 4 nm. The cylindrical structure has a long period of 38 ± 7 nm, the diameter of the PMMA cylinders is 21 ± 4 nm. These results are about 20% below the estimates obtained from theoretical calculations according to Helfand and Wasserman.

Morphologies of an a) lamellar, and b) hexagonally ordered cylindrical sample (schematic). The triangle in (b) indicates the symmetry that can be used to calculate the d_L.