In
this study, we prepared ultrafiltration membranes with a decoupled responses of
filtration property to temperature and pH. The membrane preparation method was
developed based on our previous work. We utilized methanol-supercritical carbon dioxide (methanol-scCO<sub>2</sub>)
selective swelling method to introduce nanopores to block copolymers containing poly(diethylene glycol) methyl
ether methacrylate (PMEO<sub>2</sub>MA), poly(N,N-dimethylaminoethyl methacrylate)
(PDMAEMA) and polystyrene (PS) blocks. Formation of the mesoporous barrier layer with PS being the
mechanically stable part of the matrix was driven by selective swelling of the
PMEO<sub>2</sub>MA-b-PDMAEMA domains. Due to the selective swelling of PMEO<sub>2</sub>MA or PDMAEMA domains to introduce
pores, the interior of the pores are covered with PMEO<sub>2</sub>MA or PDMAEMA blocks after pore
formation. The PMEO<sub>2</sub>MA-b-PDMAEMA polymer brushes are naturally attached on the pore walls and worked
as functional gates. PMEO<sub>2</sub>MA is a non-toxic, neutral thermo-responsive polymer with LCST at 26 ᴼC. PDMAEMA is a typical weak polyelectrolyte with pK<sub>a</sub> value
at 7.0-7.5 and also a thermo-responsive polymer revealed a LCST of 20-80 °C in
aqueous solution. Therefore, these membranes were expected to have multi dimensions as
function of the combination of temperature and pH. Moreover, to understand the
detail of the temperature and pH depended conformation transitions of PMEO<sub>2</sub>MA-b-PDMAEMA brushes, those diblock
copolymers were end-tethered on flat substrates and analyzed via neutron
reflectivity (NR).
