Abstract
An important group of water soluble polymers are associative ones in which hydrophobic
parts of the polymer molecules interact, self-assemble and enhance the viscosity of
aqueous solutions even at low polymer concentrations. For many applications it would be
beneficial to be able to combine the associative behaviour with stimuli-responsiveness.
Suitable stimuli include for example temperature, pH, ionic strength or variation of
polymer or additive concentration. Developments in the controlled radical polymerization
methods has enabled versatile modification of polymer structures, which in tum enables
design of novel associating polymers. Two different stimuli-responsive hydrogel systems
will be discussed.
Poly(N-isopropylacrylamide) (PNIPAM) has attracted attention due to its sharp and
reversible transition behavior and well-defined demixing temperature in aqueous
medium. This however only applies to atactic PNIPAM that is water-soluble at room
temperature, as isotactic PNIPAM is insoluble in water and syndiotactic PNIPAM only
barely soluble. By utilising reversible addition-fragmentation transfer polymerization
(RAFT) ABA stereoblock copolymers of PNIPAM with atactic and isotactic blocks have
been synthesized. l The properties of aqueous solutions and hydrogels of these
stereoblock copolymers were studied with respect to the molecular characteristics, ego
order ofthe blocks, block lengths and molecular weight.2
Atom transfer radical polymerization (ATRP) was used in the synthesis of 4-armed star
block copolymers having arms of poly(acrylic acid) (PAA) as the inner block and
polystyrene (PS) as the outer block. By making the PS block sufficiently short compared
with the water soluble polyelectrolyte, PAA, block, water-soluble polymers with
associative PS groups were realized. The resulting hydrogels were studied with respect to
the polymer concentration, temperature and ionic strength.3
REFERENCES
1. Nuopponen M.; Kalliomaki K.; Laukkanen A.; Hietala S.; Tenhu H. 1. Polym. Sci.
Polym. Chern. 2008, 46, 38-46.
2. Hietala S.; Nuopponen M.; Kalliomaki K.; Tenhu H. Macromolecules, in press.
3. S. Hietala, P. Mononen, S. Strandman, P. Jarvi, M. Torkkeli, K. Jankova, S. Hvilsted,
H. Tenhu Polymer, 48 (2007) 4087-4096.
Original language | English |
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Title of host publication | NPD Nordic Polymer Days 2008 |
Number of pages | 78 |
Publication date | 2008 |
Publication status | Published - 2008 |
Event | Nordic Polymer Days 2008 - Stockholm, Sweden Duration: 11 Jun 2008 → 13 Jun 2008 |
Conference
Conference | Nordic Polymer Days 2008 |
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Country/Territory | Sweden |
City | Stockholm |
Period | 11/06/2008 → 13/06/2008 |