NETWORKS OF GEL-FORMING TRIBLOCK COPOLYMER SOLUTIONS - IN-SITU SANS AND RHEOLOGICAL MEASUREMENTS

Triblock copolymers in a solvent, selective for their middle blocks pr ovide the basis for the formation of novel physical networks where cro ss-links are formed by self-assembled domains of the end-blocks. Tribl ock copolymers of oly(styrene)-poly(ethylene,butylene)-poly(styrene) ( SEBS) dissolved in a mixture of aliphatic and alicyclic compounds cons titute such a network system. Using a Rheometrics RSA-2 instrument mod ified for in situ measurements of small-angle neutron scattering and r heology provides a unique possibility far detailed understanding therm odynamics of such a gel. The self-association of the PS-blocks do not only promote formation of highly inter-connected end-block domains, bu t within a narrow temperature range these domains furthermore constitu te a network with body-centered cubic (BCC) microstructure. Upon large amplitude oscillating shear the polycrystalline soft gel can be align ed into a twinned BCC monodomain. (C) 1998 Elsevier Science B.V. All r ights reserved.