PREFERABLE STRUCTURE OF POLY(ETHYLENE GLYCOL) FOR GRAFTING ONTO A CELLULOSIC MEMBRANE TO INCREASE HEMOCOMPATIBILITY WITHOUT REDUCTION IN SOLUTE PERMEABILITY OF THE MEMBRANE

Swelling layers formed by poly(ethylene glycol) (PEG) chains grafted onto surfaces of a cellulosic membrane are known to improve hemocompatibility of the membrane. Three types of hemodialysis membranes were derived from the same regenerated-cellulose hollow-fiber membrane by grafting PEG with different formulas onto the surfaces to clarify the influence of the grafted PEG chains on solute permeability of the membranes. Determination of volume fractions of nonfreezing water contained in the membranes by differential scanning calorimetry revealed that most of the PEG chains were grafted onto the external surfaces and less into the pores in the membranes. Permeability of vitamin B-12 for the PEG-grafted membranes except for the one with the shortest PEG chains was reduced as compared with the original membrane, while that of tritium-labeled water for all the PEG-grafted membranes was the same as that of the original membrane. Structural parameters only of the PEG-grafted membrane with the largest alkyl groups at the terminal of the PEG chains were different from those of the other PEG grafted and original membranes. The shorter PEG chains with the larger terminal alkyl groups are suitable for grafting onto a cellulosic membrane to increase hemocompatibility of the membrane without significant reduction in the solute permeability of the membrane. (C) 1995 John Wiley & Sons, Inc.