Nanostructured polymers with embedded self-assembled networks: reversibly tunable phase behaviors and physical properties

• Published in: Soft matter Vol. 15; no. 31; pp. 6427 - 6435
• Main Authors: Lai, Wei-Chi, Hsueh, Chi-Yuan, Chang, Chun-Wai
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 21.08.2019
• Subjects: Collapse; Crystal structure; Crystallization; Fibrils; Gels; High temperature; Light microscopy; Liquid polymers; Melting point; Melting points; Microscopy; Morphology; Networks; Optical microscopy; Organic solvents; Physical properties; Polyethylene glycol; Polymers; Self-assembly; Small angle X ray scattering; Solidification; Sorbitol; Transmission electron microscopy; X-ray scattering
• ISSN: 1744-683X; 1744-6848; 1744-6848
• DOI: 10.1039/c9sm00997c

1,3:2,4-Dibenzylidene sorbitol (DBS) can self-assemble into nanofibrillar networks to form organogels in a variety of organic solvents and liquid polymers. In this study, we induced the formation of organogels in solid poly(ethylene glycol) (PEG) polymers. The DBS gels appeared at temperatures above the melting point of PEG. When the DBS/PEG systems were heated at higher temperatures, they exhibited transparent, clear solution states due to the collapse of the DBS networks. Upon cooling to room temperature, the DBS self-assembled nanostructures appeared again, followed by the solidification (crystallization) of PEG. These DBS/PEG systems possess three different phases (solid, gel and liquid) and can be tuned by changes in the composition and temperature. Using polarized optical microscopy, all the gel systems were found to exhibit spherulite-like morphologies. Small-angle X-ray scattering results revealed lamellar packing in these spherulite-like morphologies. Transmission electron microscopy verified that these features were formed due to the presence of DBS nanofibrillar networks consisting of fibrils that were approximately 10-20 nm in diameter. In addition, the crystallization of PEG was strongly templated by the existing DBS nanofibrils. Moreover, there were no significant distortions in the PEG crystal structures due to the confinement of PEG between the DBS nanofibrils. Above the melting point of PEG, gel states were obtained due to the formation of DBS nanofibrillar networks in the PEG matrix, followed by liquid states upon further heating.