Control of temperature-sensitive properties of poly(amidoamine) dendrimers using peripheral modification with various alkylamide groups

Isobutyramide (IBAM) group, a common structural unit with thermosensitive poly(N-vinylisobutyramide) was introduced to every chain end of dendrimers for the preparation of thermosensitive dendrimers. The IBAM-terminated poly(amidoamine) or poly(propylenimine) dendrimer exhibited lower critical solution temperature. The resultant dendrimers with temperature sensitive properties retain their globular structure and uniformity at the molecular level. The molecular shape of the PNIPAM modified dendrimer might more closely resemble that of star polymers rather than globular dendrimers. The number of terminal alkylamide groups agree well with the numbers of chain ends of the corresponding dendrimers for all alkylamide-modified dendrimers. NMR relaxation time for the terminal alkylamide groups attached to the dendrimers to obtain information on their mobility was examined. Dendrimers that exhibits LCST are thermosensitive polymers with three dimensional structures.