Synthesis And Characterization Of Nanocapsules Derived From Different Topological Polyethylenimines

Modified hyperbranched and linear polyethylenimine (PEI) as nano-sized inverted micelles for the encapsulation and release of polar guest molecules was comparatively studied.Two methods were adopted for the modification of PEI with apolar groups. The first one is the partially modification of PEI with palmitic acid (C16) through the convalent amide linkage, yielding the partially C16 modified PEI (PEI-C16). The quaternization of the residual amino groups of PEI-C16 with excess HCl or methyl iodide yielded quaternized PEI-C16 (PEI-C16N+). All the obtained polymers are soluble in apolar solvents, which can be used as nano-sized inverted micelles to encapsulate water-soluble dyes, such as Methyl Orange, Eosin Y, Sodium Fluorescein. The dye-encapsulation capacity of C16 modified linear PEI (LPEI-C16) is very low,while that of C16 modified hyperbranched PEI (HPEI-C16) is high. Quatenization of the residual amino groups can effectively enhance nearly one times of the dye-encapsulation capacity of HPEI-C16. The effect of quaternization for LPEI-C16 was much significant. The dye-encapsulation capacity increased almost 7 times. The dye-encapsulation capacity of quaternized LPEI-C16 is comparable to that of HPEI-C16, but less than that of quaternized HPEI-C16. Moreover, the dyes encapsulated by quaternized PEI-C16 can be released under basic condition.The other method for the modification of PEI is the complexation between PEI and different aliphatic carboxylic acid through non-covalent bonding. The obtained supramolecular complex can be used as nano-sized inverted micelles to encapsulate water-soluble dyes. PEI was complexed with lauric acid, palmitic acid and stearic acid, espectively, in different ratio. With the increase of aliphatic chain, the dye-encapsulation capacity of the formed supramolecular complexes increased. The supramolecular complexes based on both HPEI and LPEI can efficiently encapsulate the water-soluble dyes by controlling the ratio of pEI with aliphatic acid.