Study of block copolymer interface by pulsed NMR

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Abstract
The polymer–polymer interface, i.e., the interface of the styrene-diene block copolymer, is detected by use of pulsed NMR, probably for the first time. The thickness of the interface estimated from NMR is about 20 Å in all the observed block copolymers, which is consistent with the results of the small angle x-ray scattering. The interface is detected by the NMR measurement through the two effects: (1) intramolecular effect and (2) intermolecular effect. The intramolecular effect is related to the restriction of the degree of molecular motion of the part of the chains bound to the phase with low mobility. This effect is characteristic in polymers because polymers have very large molecular weights and nuclei in polymers are correlated with each other on account of its connectivity. On the other hand, the intermolecular effect is directly related to the state of mixing of the two different polymers. The intramolecular effect seems to be mainly active for reducing the mobility of the part of the molecules in the interface in block copolymers.