Role of functionalized terminal groups in formation of nanofibrillar morphology of hyperbranched polyesters

A series of amphiphilic hyperbranched polymers with a polyester-polyol core and 64 terminal hydroxyl groups were modified by substituting various terminal groups: alkyl tails, amino, and carboxyl groups. The effect of the pendant groups' chemical composition on the resulting surface morphology within Langmuir-Blodgett monolayers with respect to their ability to form nanofibrillar surface structures was investigated. We demonstrated that the amphiphilicity of the polyester core with 64 hydroxyl groups can be achieved if a fraction of alkyl tails (C15) is higher than 1/4. Nanofibrillar morphology was consistently formed as the highly polar functional groups were added to the polyester cores in combination with a significant (>30%) fraction of alkyl terminal groups. Addition of amino end groups was observed to be much more effective in promoting the nanofibrillar assembly than the addition of carboxyl end groups.