Hydrogen-Bonded Multilayers of Thermoresponsive Polymers
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Neutral temperature responsive polymers, such as poly(N-vinylcaprolactam) (PVCL) and poly(vinyl methyl ether) (PVME), were included in ultrathin films using layer-by-layer alternating adsorption of these polymers with poly(methacrylic acid) (PMAA) at low pH. The amounts of polymers adsorbed and ionization of carboxylic groups within a film were quantified using in situ FTIR-ATR (Fourier transform infrared spectroscopy by attenuated total reflection). The strength of interlayer adhesion provided through hydrogen-bonding interactions was inferred from the critical pH value (pH CR) and critical ionization (α CR) for multilayer decomposition which were pH CR 6.2, α CR 2% and pH CR 6.95, α CR 30% for PMAA/PVME and PMAA/PVCL films, respectively. When deposited onto porous support membranes, PMAA/PVME and PMAA/PVCL multilayers exhibited temperature-responsive changes in dye permeability. The transition occurred in a wide temperature range from 25 to 35°C, reflecting lower cooperativity of the phase separation of PVME and PVCL chains included within the film. Finally, PMAA/PVME and PMAA/PVCL self-assembly was performed onto particulate substrates, producing capsules which hold promise as temperature-responsive containers for controlled delivery applications. © 2005 American Chemical Society.
author list (cited authors)
Kharlampieva, E., Kozlovskaya, V., Tyutina, J., & Sukhishvili, S. A.