Abstract
We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A100M101D10 triblock terpolypeptoids self-assemble into core-corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (Tgel), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At T ≳ Tgel, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A101M111D21 and A43M92D9, elongated nonspherical micelles with a crystalline D core were observed at T < Tgel. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A153M127D10, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.
Original language | English |
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Pages (from-to) | 6449-6464 |
Number of pages | 16 |
Journal | Macromolecules |
Volume | 57 |
Issue number | 14 |
DOIs | |
State | Published - Jul 23 2024 |
Funding
The authors thank Dr. Jibao He (TU) and Dr. Ying Xiao (LSU) for the cryo-TEM measurements, Dr. Steven J. Weigand (APS), Dr. Shirish Chodankar (NSLS-II), Dr. Lin Yang (NSLS-II) for the synchrotron X-ray scattering measurements. We also gratefully acknowledge the cooperation of the beamline scientists at the BSRF-1W1A and SSRF-BL19U2 beamlines. The work was supported by the National Science Foundation (CHE 1609447 and 2003458) and the National Natural Science Foundation of China (52073025). The N-decyl- d -amine was synthesized and characterized using resources at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The neutron scattering work was supported by the U.S. Department of Energy (DOE) under EPSCoR grant no. DE-SC0012432 with additional support from the Louisiana Board of Regents. Access to NGB 30m-SANS and NG3 vSANS instrument was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology (NIST) and the National Science Foundation under Agreement no. DMR-1508249. The identification of any commercial products does not imply endorsement nor recommendation by NIST. The neutron scattering work also used resources at the High Flux Isotope Reactor, a U.S. DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The Bio-SANS of the Center for Structural Molecular Biology at the High Flux Isotope Reactor is supported by the Office of Biological and Environmental Research of the U.S. DOE. The X-ray scattering work was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357. This research also used resources of the Life Science X-ray Scattering (LiX/16-ID) beamline operated by the National Synchrotron Light Source II at Brookhaven National Laboratory, which is supported by the U.S. DOE, Office of Science, Office of Basic Energy Sciences, under Contract no. DE-SC0012704. The LiX beamline is also part of the Life Science Biomedical Technology Research resource, primarily supported by the National Institute of Health, National Institute of General Medical Sciences under Grant P41 GM111244, and by the DOE Office of Biological and Environmental Research under Grant KP1605010, with additional support from NIH Grant S10 OD012331. A portion of this work is based on the data obtained at Beijing Synchrotron Radiation Facility, 1W1A Diffuse X-ray Scattering Station (BSRF-1W1A). This work was also conducted with the support of the BL19U2 beamline of National Center for Protein Sciences Shanghai (NCPSS) at Shanghai Synchrotron Radiation Facility (SSRF). This work also benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView contains code developed with funding from the European Union\u2019s Horizon 2020 research and innovation program under the SINE2020 project, grant agreement no. 654000. We would like to thank the Coordinated Instrumentation Facility (CIF) Microscopy Lab, Tulane University and the Center for Biological Imaging (CBI), Institute of Biophysics, Chinese Academy of Science for the Cryo-TEM measurements. 21