Yimeng Zhang,Pengyao Xing,Minmin Yang,Yajie Wang,Bo Wang,Aiyou Hao,Mingfang Ma
Anthracen-9-ylmethyl octadecylcarbamate (A-9-YMOC) contains an anthracen headgroup, an imide group, and a long alkyl chain, which could show π–π stacking, hydrogen-bonding, and van der Waals interactions, respectively. The capability of A-9-YMOC to form well-ordered micro/nanostructures in different solvents was explored. And the influence of solvents with various polarities that can modulate the self-assembly behavior, including H-bond-forming solvents, π-stacking-forming solvents or van der Waals-type solvents was studied. In addition, different supramolecular architectures, including nanofibers and nanoflowers were observed during the solvent-polarity-tuned process, which were found to have different molecular arrangements. This work may provide a facile method to manipulate the morphology and properties of self-assembled low-molecular-weight organic building blocks.
Yiyang Gu,Chunyu Ru,Zhen Zhao,Danming Chao,Xincai Liu
Shape memory polymers have attracted much attention due to their promising applications in biomedicine, textiles, aerospace et al. Here, novel poly(aryl ether ketone)s bearing flexible alkyl segments and pendant anthracene groups were synthesized via nucleophilic copolycondensation coupled with post-polymerization functionalization. Their chemical structure, thermostability and mechanical properties were characterized through Fourier Transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermal gravimetric analysis and dynamic mechanical analysis. The soft-rigid alternative segment structure endows these poly(aryl ether ketone)s with promising shape memory properties. After the photodimerization of pendant anthracene units, the resultant polymers exhibit enhanced shape memory performance in terms of satisfying shape fixity ratio and high shape recovery ratio, attributed to their photocrosslinked polymeric network architecture. This shape memory polymer with reversible photodimerization holds great promise for a deep understanding of the mechanism and future applications.
The shape memory thermoplastic polyurethane (TPU) generally exhibits a phase-separated structure, in which the hard segments form the hard domains via hydrogen bonds, and plays an important role in shape recovery. However, the physical interaction in the hard domains is always weak, resulting in a permanent deformation and thus decreasing the shape-recovery ability of TPU significantly. In this research, a new type of diol chain extender containing anthracene groups was synthesized, and the photoresponsive anthracene groups were incorporated into the hard segment of TPU. The stability in hard domains and recoverability could be tailored by different UV irradiation times via the photodimerization of anthracene groups, and the shape-recovery ratio and the shape-fixing ratio were still both above 93%, even when the strain reached 270%. More importantly, the shape-free reconfiguration is achieved through the dimerization of anthracene groups under UV irradiation, which achieved free construction of three-dimensional (3D) shapes without templates. Thus, the spontaneous shape change from two-dimensional (2D) to 3D was realized, in combination with melting transition, and the dedimerization of anthracene ensured the recyclability of polyurethane at T = 150 °C. This simple and facile strategy could be used to fabricate the recyclable and photoplasticity shape memory TPU with a high shape-fixing/recovery ratio at large deformation, and it would have a wider range of potential application in stents.
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