NMR studies of some styrene-based diblock copolymers

Abstract

A selection of styrene-based diblock copolymers were investigated using the technique known as Nuclear Magnetic Resonance spectroscopy (NMR) in both the solid- and solution-state. These diblock copolymers undergo phase separation due to the incompatibility of the glassy and rubbery blocks and this was to be detected using NMR. The microstructure of these copolymers was analysed using solution-state (^13)C and (^1)H NMR. An extensive study of the relaxation characteristics of these polymers was undertaken in the solid-state to try and understand the nature of molecular motions that occur in these polymers before and after phase separation. Due to the large number of variables involved a number of techniques were used to analyse the consistency of the data obtained. The Goldman-Shen experiment was used to monitor the process of spin- diffusion, which is an indicator of the distances that nuclear interactions can occur, and was to be used as an indicator of the degree of phase separation that can occur in these polymers. The WISE heteronuclear correlation experiment was used to try and correlate the mobilities of proton nuclei in differing blocks to individual resonances of chemically distinct carbon nuclei and ultimately to monitor the process of spin-diffusion whilst understanding the competing relaxation processes that occur during measurement.