TEMPERATURE AND PRESSURE-DEPENDENCE OF THE ORDER-PARAMETER FLUCTUATIONS, CONFORMATIONAL COMPRESSIBILITY, AND THE PHASE-DIAGRAM OF THE PEP-PDMS DIBLOCK COPOLYMER
D. Schwahn et al., TEMPERATURE AND PRESSURE-DEPENDENCE OF THE ORDER-PARAMETER FLUCTUATIONS, CONFORMATIONAL COMPRESSIBILITY, AND THE PHASE-DIAGRAM OF THE PEP-PDMS DIBLOCK COPOLYMER, Physical review letters, 77(15), 1996, pp. 3153-3156
The structure factor of a poly(ethylene-propylene)-poly(dimethylsiloxa
ne) diblock copolymer has been measured by small-angle neutron scatter
ing as a function of temperature and pressure. The conformational comp
ressibility exhibits a pronounced maximum at the order-disorder phase
transition. The phase boundary shows an unusual shape. With increasing
pressure it first decreases and then increases. Its origin is an incr
ease, respectively, of the entropic and of the enthalpic part of the F
lory-Huggins interaction parameter. The Ginzburg parameter describing
the limit of the mean-field approximation is not influenced by pressur
e.