TY - JOUR
T1 - Stimuli-Responsive amphiphilic polyelectrolyte heptablock copolymer physical hydrogels
T2 - An unusual ph-response
AU - Popescu, Maria Teodora
AU - Tsitsilianis, Constantinos
AU - Papadakis, Christine M.
AU - Adelsberger, Joseph
AU - Balog, Sandor
AU - Busch, Peter
AU - Hadjiantoniou, Natalie A.
AU - Patrickios, Costas S.
PY - 2012/4/24
Y1 - 2012/4/24
N2 - An amphiphilic cationic polyelectrolyte based on poly[2-(dimethylamino) ethyl methacrylate] (polyDMA) and poly(n-butyl methacrylate) (polyBuMA) with a BuMA-DMA-BuMA-DMA-BuMA-DMA-BuMA heptablock copolymer architecture was studied in aqueous media. This copolymer was found to form a physical hydrogel via the intermolecular hydrophobic association (physical cross-linking) of the BuMA blocks. The rheological properties of the heptablock hydrogels were investigated as a function of copolymer concentration, and pH. The results showed a peculiar pH-dependence of the rheological properties, remarkably different from those observed with associative telechelic polyelectrolytes. Aqueous solutions of this copolymer were free-flowing sols at low pH (below 2) and high pH (above 8), whereas they turned into gels at intermediate pH values. The rheological properties studied as a function of pH showed two additional stiff-soft-stiff gel transitions at pH 4.5 and 6.5. Small-angle neutron scattering revealed the formation of a 3D transient network of bridged flower-like micelles whose structural characteristics, i.e., micellar radius, hard-sphere radius and hard-sphere volume fraction, were smoothly evolving with the pD.
AB - An amphiphilic cationic polyelectrolyte based on poly[2-(dimethylamino) ethyl methacrylate] (polyDMA) and poly(n-butyl methacrylate) (polyBuMA) with a BuMA-DMA-BuMA-DMA-BuMA-DMA-BuMA heptablock copolymer architecture was studied in aqueous media. This copolymer was found to form a physical hydrogel via the intermolecular hydrophobic association (physical cross-linking) of the BuMA blocks. The rheological properties of the heptablock hydrogels were investigated as a function of copolymer concentration, and pH. The results showed a peculiar pH-dependence of the rheological properties, remarkably different from those observed with associative telechelic polyelectrolytes. Aqueous solutions of this copolymer were free-flowing sols at low pH (below 2) and high pH (above 8), whereas they turned into gels at intermediate pH values. The rheological properties studied as a function of pH showed two additional stiff-soft-stiff gel transitions at pH 4.5 and 6.5. Small-angle neutron scattering revealed the formation of a 3D transient network of bridged flower-like micelles whose structural characteristics, i.e., micellar radius, hard-sphere radius and hard-sphere volume fraction, were smoothly evolving with the pD.
UR - http://www.scopus.com/inward/record.url?scp=84860157388&partnerID=8YFLogxK
U2 - 10.1021/ma300222d
DO - 10.1021/ma300222d
M3 - Article
AN - SCOPUS:84860157388
SN - 0024-9297
VL - 45
SP - 3523
EP - 3530
JO - Macromolecules
JF - Macromolecules
IS - 8
ER -