Hydrogen bonded polymers are of great interest owing to their reversible and dynamic nature of interactions, from which many unique and fascinating functions are achieved. Most of the interesting properties in polymers with secondary amide group, like nylons and proteins originate from the formation of hydrogen bonds. The studies on these materials usually are focused on the impact introduced by hydrogen bonding interactions, whereas the effect of chain flexibility is often neglected. We studied the design and development of polyesters containing one ester-propyl group (P(1EP)), one amide-propyl group (P(1AP)) and two amide-propyl groups (P(2AP)) in the side chain. The results showed that P(1EP) and P(2AP) had the lowest and highest Tg, respectively. P(2AP) displayed the highest Young’s modulus and shortest elongation at break among the three materials at room temperature. The hydrogen bonds functioned as physical crosslinks, which strengthened the material and limited chain mobility. Interestingly, we observed that at higher temperature (Tg + 50 °C ), the rheological study showed that P(2AP) had the shortest chain relaxation time, as well as the lowest zero shear viscosity and moduli. The results indicate that there is a competition between side-chain flexibility and hydrogen bonding interaction. The addition of the second amide-propyl group in the side chain improves processability at higher temperature due to the low viscosity, yet gives better mechanical properties at room temperature. We will discuss the structure property relationships for this class of materials and how to achieve desirable material properties by modulating environmental conditions like temperature, humidity, and selecting the number of amide groups in the side chain.

Side-chain flexibility competes with hydrogen bonding on properties of supramolecularly crosslinked polyesters

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.