Pressure-induced phase transitions of hydrophobically solvated block-copolymer solutions.
The structures of poly(2-(2-ethoxy)ethoxyethyl vinyl ether)-block-poly(2-methoxyethyl vinyl ether) in D2O have been investigated with small-angle neutron scattering (SANS) as a function of temperature T and pressure P. At ambient pressure, the solution underwent a two-step transition at 40 and 65 degrees C, both of which were convex-upward functions of P having a maximum around P0 approximately 150 MPa. The first transition was assigned to a microphase separation to form a bcc structure, and the second was to a macrophase separation. Pressurizing at 28 degrees C resulted in a macrophase separation with divergence at 350 MPa. At 45 degrees C, a reentrant microphase separation was observed by increasing P. Differences in the states of hydrophobic solvation in the low (P<P0) and high pressure regions (P>P0) are discussed based on the SANS structure factors.
Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, Tokai, Ibaraki 319-1106, Japan.
Noboru
N
Osaka
Mitsuhiro
M
Shibayama
D003903:Deuterium / Q000737:chemistry; D004987:Ethers / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D033363:Neutron Diffraction; D044367:Phase Transition; D011145:Polyvinyls / Q000737:chemistry*; D011312:Pressure; D012996:Solutions; D014867:Water / Q000737:chemistry
D004987:Ethers; D011145:Polyvinyls; D012996:Solutions; C510801:poly(2-(2-ethoxy)ethoxyethyl vinyl ether)-block-poly(2-methoxyethyl vinyl ether); D014867:Water; D003903:Deuterium