Size exclusion properties of polyelectrolyte complex microcapsules prepared from sodium cellulose sulphate and poly[diallyldimethylammonium chloride]

Diffusion experiments aided by high performance size exclusion chromatograp hy were carried out to describe the size exclusion properties of microcapsu les prepared from cellulose sulphate and poly[diallyldimethylammonium chlor ide] (PDADMAC). The membrane cut-off was characterised by the dependence of the distribution ratio (luminal concentration/external concentration) of d extran molecules on their Stokes' radius (1-9 nm) after diffusion periods o f 72 and 240 h. When capsules were prepared from standard cellulose sulphate and different polydisperse PDADMAC preparations with high mass portions of size fractions > 10 kDa, the cut-off range was narrow with an upper size limit (USL) of p ermeation close to 2 nm and independent of the residence time in the PDADMA C bath or the presence of salt (155 mM NaCl) in the reacting polymer soluti ons, Capsules prepared with PDADMAC rich in size fractions with lower molec ular weight (<3 kDa) showed higher values of the USL. The cut-off was dependent on the residence time and salt concentration when capsules were produced using polydisperse PDADMAC with high mass portions of small molecules (<0.6 kDa). Prolonged residence of such capsules in a re action bath containing 155 mM NaCl resulted in a strong increase of the USL . (C) 1999 Elsevier Science B.V, All rights reserved.