Pulsed NMR studies on the interfacial structure of the block copolymers of styrene and isoprene with variable interface

摘要

Three kinds of block copolymers of styrene and isoprene with differnet interface structure were prepared by using step anionic copolymerization method. A diblock copolymer (SI), tapered block copolymer (TBSI) and poly(isoprene-b(isoprene-co-styrene)-b-styreen) triblock copolymers (INA) were used for hte following studies. Information about content, composition and thickness of the interface, as well as molecualr motion differences in the three phases were obtained by using proton solid state NMR. In addition, complementary studies usign dynamic mechanic analysis, TEM and solution NMR were performed. The order of the interface content of the samples is TBSI>INA>SI. This is consistent with the sequence length resutls from solution NMR. The spin-spin relaxation time T_2, which is a function of the system mobility of the rigid PS block of TBSI, is longer than that of SI and INA, while the T_2 of the mobile PI block of TBSI is shorter than that of SI and INA. This indicates that there is a substantial mixing of the incompatible componetns within the PS and PI domain. The interfaces detected yb NMR seem to be mainly by the intramolecular effect because the interface consists of 70