THE STRUCTURE OF POLY(ETHYLENE OXIDE)-POLY(DIMETHYLSILOXANE) TRIBLOCK COPOLYMERS IN SOLUTION

A series of triblock copolymers consisting of oligomeric segments of poly(ethylene oxide) (PEO) and poly(dimethylsiloxane) (PDMS) were synthesized. These amphiphilic polymers have the general structure (PEO)n-Z-(PDMS)m-Z-(PEO)n or inversely (PDMS)m-Z-(PEO)n-Z-(PDMS)m where "Z" is the group linking the chains of different polarity. n and m varied in the range m,n < 77. These polymers spontaneously form lyotropic mesphases if mixed with water. The phasediagrams and symmetry of the phases were determined. Moreover, photoreactive groups were attached at exactly and only the positions "Z" of the block copolymers. When photocrosslinking was induced in a particular lyotropic mesophase, the arrangement of the molecules in this phase structure was fixed. Although the phase structure collapsed when the systems were freed from water, the structure returned on reswelling. Some rules concerning the tendency of such molecules to self-organize as a function of the molecular structures are obtained.