Functionalized Nanochannels from Self‐Assembled and Photomodified Poly(Styrene‐b‐Butadiene‐b‐Styrene)

Abstract

Membranes are prepared by self-assembly and casting of 5 and 13 wt% poly(styrene-b-butadiene-b-styrene) (PS-b-PB-b-PS) copolymers solutions in different solvents, followed by immersion in water or ethanol. By controlling the solution-casting gap, porous films of 50 and 1 µm thickness are obtained. A gradient of increasing pore size is generated as the distance from the surface increased. An ordered porous surface layer with continuous nanochannels can be observed. Its formation is investigated, by using time-resolved grazing incident small angle X-ray scattering, electron microscopy, and rheology, suggesting a strong effect of the air-solution interface on the morphology formation. The thin PS-b-PB-b-PS ordered films are modified, by promoting the photolytic addition of thioglycolic acid to the polybutadiene groups, adding chemical functionality and specific transport characteristics on the preformed nanochannels, without sacrificing the membrane morphology. Photomodification increases fivefold the water permeance to around 2 L m h bar , compared to that of the unmodified one. A rejection of 74% is measured for methyl orange in water. The membranes fabrication with tailored nanochannels and chemical functionalities can be demonstrated using relatively lower cost block copolymers. Casting on porous polyacrylonitrile supports makes the membranes even more scalable and competitive in large scale.

Block Copolymer Membranes

“…Another recent example is a membrane prepared from polystyrene-b-polybutadiene-bpolystyrene (SBS) prepared also by anionic polymerization. [106] SBS is commercially available in large scale and low cost with a block ratio different than that used for the membrane preparation. This is important to mention because it indicates that the cost of block copolymers can be considerably reduced if produced in the technical scale and should not be seen as an obstacle for membrane manufacture.…”

“…Block copolymers recently used for SNIPS membranes. [105][106][107] Advantages, drawbacks, and perspectives…”

3D Analysis of Ordered Porous Polymeric Particles using Complementary Electron Microscopy Methods

“…The particles were then embedded in epoxy resin and cured at 60 °C for 24 h. Slices of 100 nm or thinner were cut with diamond knife using an ultramicrotome Leica EM UC6 and collected on 200–300 mesh copper grids. The TEM tomography was conducted on a FEI Titan CT microscope, operating at 300 kV, equipped with a 4 k × 4 k CCD camera (Gatan, Pleasanton, CA, USA) 47 . The sample was tilted from −65 to +65° and the images were taken at 2° intervals, following a Saxton scheme.…”

Self-Assembled Membranes with Featherlike and Lamellar Morphologies Containing α-Helical Polypeptides

“…Our group also reported membranes with a selective transport for proteins and improved water permeance using a block copolymer containing hydrogen bond forming groups (polystyrene-bpolyhydroxstyrene-b-polystyrene) 27 , and photochemically modifying self-assembled block copolymers containing double bonds (polystyrene-b-polybutadiene-b-polystyrene) 29 .…”