Thermo-mechanical properties of macromolecular materials

Modern synthetic chemistry enables the preparation of macromolecules with controlled topology and functionality. In collaboration with partners in synthetic chemistry, we investigate how molecular architecture, composition, and processing influence morphology and the thermo-mechanical behavior of polymeric materials.
Our work aims to establish structure–property relationships that connect molecular design with macroscopic mechanical performance. We employ tensile testing, rheology, and mechanical and dielectric spectroscopy to study systems such as photo-responsive polymers, nanocomposites, and synthetic and biological gels.

For example, recently we prepared CNT–hydrogel composites by in situ polymerization of poly(ethylene glycol) (PEG) around a preformed carbon nanotube (CNT) meshwork [1]. We found that the composites facilitate long-term survival and differentiation of neural stem cells. The formation of the CNT meshwork was studied by monitoring the  frequency (ω) dependence of the real (G′) and imaginary (G″) parts of the complex shear moduli of gel precursors (PEG solutions) with different CNT content. The frequency response of the precursor of pure PEG hydrogels reveald non-Newtonian liquid behavior, characterized by a terminal region with G′(ω) ~ ω², G″(ω) ~ ω¹. Upon incorporating smal fraction of CNTs, a plateau with G′ > G″ was observed at low frequencies, indicating the formation of weak CNTs percolation meshwork. At higher CNT content, G′ > G″ over a wider range of frequency reflecting the response of a strong CNTs meshwork. After PEG crosslinking, this meshwork is preserved in the final composites.