Paper Number
PO58 

Session
Poster Session

Title
Tuning rheological and structural transitions in ABA/BAB poloxamer hydrogels

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

1. White, Joanna M. (University of Minnesota, Chemical Engineering and Materials Science)
2. Calabrese, Michelle A. (University of Minnesota, Chemical Engineering and Materials Science)

Author and Affiliation Lines (in printed abstract book)
Joanna M. White and Michelle A. Calabrese
Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55414

Speaker / Presenter 
White, Joanna M.

Keywords
applied rheology; biological materials; gels

Text of Abstract
Poloxamer P407 is an ABA triblock polymer widely used in the biomedical field due to its biocompatibility and thermoreversible gelation in water. Temperature increase triggers self-assembly of P407 in water into micelles which can enclose hydrophobic small molecules. Further increases in temperature result in rheological transitions corresponding to micelle ordering into complex phases including face-centered cubic (FCC)-packed structures. However to maintain mechanical integrity in drug delivery applications, development of bridged micellar structures is desired. One potential route for achieving micellar bridging is by incorporating BAB triblock reverse poloxamers (RPs) into P407 systems to induce bridging via the hydrophobic endblocks. Here, we show that the addition of RPs to P407-based systems can drastically affect the mechanical properties, structure, micellization and gel transition temperatures. To reduce unfavorable PPO-water interactions, dangling PPO blocks from the RPs associate with each other, resulting in a physically-bridged network across the micelles. Increasing the extent of bridging through RP incorporation reduces the inter-micelle potential, resulting in the FCC-packed micelles transitioning to a BCC-packing and eventually a breakdown in crystalline structure. Utilizing a combination of rheology, differential scanning calorimetry (DSC), and small-angle x-ray scattering (SAXS), we demonstrate how RP length, composition, and concentration effects the thermal transition and structures of these materials. This understanding allows for the development of thermo-responsive materials with optimal mechanical properties for a wide-variety of applications.