Congresos y reuniones científicas
Título:
PORE SIZE, SURFACE INTERACTIONS AND EVAPORATION KINETICS IN SWOLLEN POROUS POLYMER NETWORKS DETERMINED BY NMR RELAXATION.
Autor/es:
SILLETTA, EMILIA V.; VELASCO, MANUEL I.; GOMEZ, CESAR G.; STRUMIA, MIRIAM C.; MONTI, GUSTAVO; ACOSTA, RODOLFO H.
Reunión:
Congreso; V Encuentro Argentino de Materia Blanda; 2014
Institución organizadora:
INIFTA
Resumen:
Polymer porous matrices are widely used in several areas such as catalysis, enzyme
immobilization, HPLC, adsorbents or drug controlled release. These polymers have
pores in its structure both in the dry and swollen state. Although it is well known that
the structures and properties greatly differ between these two states, only few
analytical methods provide information about the swollen state, even though most of
the applications involve the matrices in this situation and in nearly every case its
performance is a sensitive function of the distribution of internal pore size. Nuclear
Magnetic Resonance is a suitable tool for the study of the molecular dynamics of
different liquids spatially confined in macro, meso and nanopores through changes in
relaxation times.
In this work, we describe the study of the pore structure of the macroporous
polymer of ethylene glycol dimethacrylate and 2-hydroxyethyl methacrylate
[poly(EGDMA-co- HEMA)] in the dry and in the swollen state by measuring relaxation
times of liquids contained in the polymer network [1, 2]. This information allows the
characterization of the matrices in terms of pore distribution, water uptake, and
swelling. The behaviour of polar liquids during evaporation and deswelling dynamics is
monitored and described. An internal migration of water from the swollen polymer
mesh into expanding pores takes place. With this procedure, it is possible to obtain
information about the microscopic morphology behaviour of the matrix during
evaporation and deswelling. Additionally, the pore diameter can be determined by
measuring diffusion which is encoded though magnetic field distortions that arise due
to heterogeneities in the magnetic field, which are produced by changes in magnetic
susceptibilities in going from the pore wall to the pore void (DDIF - Decay due to
Diffusion in Internal Field) [3]. Comparison of the relaxation times present in different
pore sizes provides information on surface interaction [4], in particular the influence of
hydrogen bond between water and hydroxyl groups as a function of the amount of
crosslinker is determined.