Preparation of cellulose-based filtration membranes with stimuli-responsive properties

TY - THES

T1 - Preparation of cellulose-based filtration membranes with stimuli-responsive properties

T2 - Master's thesis

AU - Hakalahti, Minna

N1 - BA3155 64 p. + app. 7 p.

PY - 2013

Y1 - 2013

N2 - Membranes are major components of many water-intensive industrial processes. Fouling, one of membrane technology's main challenges, decreases permeability and increases the need for cleaning. Anti-fouling properties of membranes can be enhanced for example by surface treatment by chemical modification. Additionally, smart cleaning behaviour can be achieved by incorporating stimuli-responsive polymers onto filtration membrane surfaces. When fouling occurs, membrane pores can be temporarily and reversibly enlarged by an external stimulus to aid cleaning. In this study, polysaccharides were chemically modified by adding allylic double bonds to their backbone. Furthermore, these highly reactive double bonds were used for crosslinking and grafting poly(N-isopropylacrylamide) (PNIPAM) to integrate a temperature-responsive property. Hydrogel and membrane samples were prepared. 13C NMR, SEM, chromatographic bromine analysis, DSC, elementary analysis and CR-filtration tests were used to characterize prepared samples. Results of this study demonstrated that cellulosic materials were modified into cellulosic derivatives containing moderate amounts of allyl double bonds. These derivatives were capable of crosslinking and could be grafted with PNIPAM with high grafting efficiencies. LCST of PNIPAM altered slightly depending on the matrix material. Commercial membranes and filter materials were modified by applying these cellulosic derivatives. Stable coatings that changed the surface morphologies were formed, but a temperature-response was not observed around the LCST of PNIPAM in permeability measurements.

AB - Membranes are major components of many water-intensive industrial processes. Fouling, one of membrane technology's main challenges, decreases permeability and increases the need for cleaning. Anti-fouling properties of membranes can be enhanced for example by surface treatment by chemical modification. Additionally, smart cleaning behaviour can be achieved by incorporating stimuli-responsive polymers onto filtration membrane surfaces. When fouling occurs, membrane pores can be temporarily and reversibly enlarged by an external stimulus to aid cleaning. In this study, polysaccharides were chemically modified by adding allylic double bonds to their backbone. Furthermore, these highly reactive double bonds were used for crosslinking and grafting poly(N-isopropylacrylamide) (PNIPAM) to integrate a temperature-responsive property. Hydrogel and membrane samples were prepared. 13C NMR, SEM, chromatographic bromine analysis, DSC, elementary analysis and CR-filtration tests were used to characterize prepared samples. Results of this study demonstrated that cellulosic materials were modified into cellulosic derivatives containing moderate amounts of allyl double bonds. These derivatives were capable of crosslinking and could be grafted with PNIPAM with high grafting efficiencies. LCST of PNIPAM altered slightly depending on the matrix material. Commercial membranes and filter materials were modified by applying these cellulosic derivatives. Stable coatings that changed the surface morphologies were formed, but a temperature-response was not observed around the LCST of PNIPAM in permeability measurements.

KW - stimuli-responsive poymers

KW - filtration membranes

KW - cellulose

KW - grafting

KW - surface functionalization

KW - PNIPAM

M3 - Master's thesis

PB - Aalto University

CY - Espoo

ER -