The effect of end groups (2NH(2)) Of poly (ethylene glycol) (PEG) on the miscibility and crystallization behaviors of binary crystalline blends of PEG/poly(L-lactic acid) (PLLA) were investigated. The results of conductivity meter and dielectric analyzer (DEA) implied the existence of ions, which could be, explained by the amine groups of PEG gaining the protons from the carboxylic acid groups of PLLA. The miscibility of PEG(2NH(2))/PLLA blends was the best because of the ionic interaction as compared with PEG(2OH, 1OH-1CH(3), and 2CH(3))/PLLA blends. Since the ionic interaction formed only at the chain ends of PEG(2NH(2)) and PLLA, unlike hydrogen bonds forming at various sites along the chains in the other PEG/PLLA blend systems, the folding of PLLA blended with PEG(2NH(2)) was affected in a different manner. Thus the fold surface free energy played an important role on the crystallization rate of PLLA for the PEG(2NH(2))/PLLA blend system. PLLA had the least fold surface free energy and the fast crystallization rate in the PEG(2NH(2))/PLLA blend system, among all the PEG/PLLA systems studied. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3616-3623, 2008