Evaporation Kinetics in Swollen Porous Polymeric Networks

VELASCO, MANUEL I.; SILLETTA, EMILIA V.; GOMEZ, CESAR G.; STRUMIA, MIRIAM C.; MONTI, GUSTAVO; ACOSTA, RODOLFO H.

Zürich

Congreso; Euromar 2014; 2014

Euromar

Polymer porous matrices are widely used in several areas such as catalysis, enzyme immobilization, HPLC, adsorbents or drugcontrolled 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 a few analyticalmethods provide information about the swollen state, even though most of the applications involve the matrices in this situationand 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 using aCPMG sequence[1].This information allows the characterization of the matrices in terms of porosity, pore distribution, water uptake, and swelling. The results show that the pore architecture differs from the dry to the soaked state. 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, with the DDIF (Decay due to Diffusion in Internal Field) [2] sequence it was possible to determine the pore diameter and the relaxivity parameter, which was determined to be a function of the pore size and of the crosslinker content. Finally, water exchange between different pore sizes, and in particular from the swollen matrix into the structural pores was monitored by means of two-dimensionalT2-T2 experiments [3].This information is of great interest regarding possible and future applications for these types of materials.