The Synthesis And Characterization Of Poly(ethylene Glycol Methyl Ether)-b-poly(ethylenimine) And Its Derivatives.

Abstract

The synthesis and characterization of poly(ethylene glycol methyl ether)-b-poly(imino-1,2-ethanediyl)('+), its precursors and derivatives are described. Poly(ethylene glycol methyl ether) was tosylated and the tosylate was used to initiate the polymerization of 2-methyl-2-oxazoline. The resulting block copolymer, poly(ethylene glycol methyl ether)-b-poly (acetylimino)-1,2-ethanediyl *, was separated by fractional precipitation and characterized by gel permeation chromatography and thin layer chromatography. Thus, the (acetylimino)-1,2-ethane- diyl block copolymer was free from the contamination of the poly- meric initiator residue. Poly(ethylene glycol methyl ether)-b-poly (acetyl-imino)1,2-ethanediyl was hydrolyzed to give poly(ethylene glycol methyl ether)-b-poly(imino-1,2-ethanediyl hydrochloride). This hydrochloride salt was characterized by both potentiometric titration and dilute solution viscosity measurements. Interaction of the charged sites were understood in this linear polyelectrolyte. The imino-1,2-ethanediyl backbone polynucleotide analog was prepared by grafting 2-(thymin-1-yl)propionic acid onto the imino-1,2-ethanediyl copolymer. This polynucleotide model compound was soluble in water up to about 0.01 g/10 ml. Hypochromicity as deter- mined by UV absorption indicated that local ordered conformations were present in this model compound. Interactions between the imino-1,2-ethylanediyl backbone polynucleotide analog and poly-A in aqueous solutions were also studied by UV spectroscopic method. Interactions were only observed in neutral water. (l) N-Cbz-Alanine, (L) N-Cbz-phenylalanine, (L) N-Cbz-O-t-Bu-serine and (L) N-FMOC-proline were grafted onto poly(ethylene glycol methyl ether)-b-poly(imino-1,2-ethanediyl) by coupling the protected amino acids and the polyamine with either N,N-dicyclo- hexylcarbodiimide (DCC) or diethylcyanophosphate (DEPC). The DCC route was able to give some optically active products whereas the DEPC route failed to give any optically active grafted polymer. The removal of the FMOC group was easier than the removal of the Cbz group. ('+)Also named as poly(ethylene glycol methyl ether)-b-poly(ethylenimine). *Also named as poly(ethylene glycol methyl ether)-b-poly(N-acetyl ethylenimine).