NAMS 2002 Workshop - ICOM 2008

also improve the resultant membrane’s hemocompatibility. After being treated in
8000 ppm NaOCl solution for 1 day, fibers show larger pore sizes and porosity in
both inner and outer surfaces, and thinner inner and outer layers than their asspun
counterparts. Based on SEM observations and solute rejection
performance, the further heat treated fibers in an aqueous solution is found to be
an effective way to fine tune membranes morphology and molecular weight cutoff
(MWCO) for kidney dialysis application.
Last but not the least, comprehensive comparisons of the linear and
hyperbranched PES, especially their as-spun hollow fiber kidney dialysis
membranes were conducted based on their physical, chemical, thermal and
rheological properties. The most significant differences between the
hyperbranched PES material and its linear analogue were identified by its higher
molecular weight, wider molecular weight distribution and a much more compact
structure. The molecular characteristics of hyperbranched PES led its as-spun
membrane with smaller pores, narrower pore size distribution, and a smaller
MWCO. In addition, hyperbranched PES bound stronger with the additive PVP
and their blend displayed a lower coefficient of thermal expansion (42.16μm/°C)
than that for linear PES (89.08μm/°C). Both factors resulted in a less
effectiveness of PVP leaching by the NaOCl solution and hot water. A higher
water temperature was required to tailor the as-spun hyperbranched PES hollow
fibers with the pore size and pore size distribution suitable for kidney dialysis
application. To our knowledge, this is the first work to reveal the morphologies
and solute separation performances differences between hyperbranched- and
linear- PES made membranes based on the comprehensive explorations and
fundamental understandings of these two polymer analogues properties.