Aramid fibers products have been widely used in both civil and military fields. However, improper disposal of waste aramid fibers products will result in potential environmental problems and waste of...

Vertical alignment of liquid crystal (LC) was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA) monomers initiated by polyimide based on 3,3 ,4,4 -benzophenonetetracarboxylic dianhydride and 3,3 -dimethyl-4,4 -diaminodiphenyl methane (BTDA-DMMDA PI). The alignment behavior and alignment stabilities were characterized by a polarizing optical microscope (POM), which showed a stable vertical alignment after 12 h of thermal treatment. The chemical structures, morphology, and water contact angles of alignment films peeled from LC cells with and without DA monomers were analyzed by means of a Fourier transform infrared spectrometer (FTIR), a scanning electron microscope (SEM), and a contact angle tester, separately. The results confirmed that the DA monomers underwent self-polymerization and grafting polymerization initiated by the BTDA-DMMDA PI under ultraviolet irradiation, which aggregated on the surfaces of PI films. The water contact angles of the alignment films were about 15 • higher, indicating a relative lower surface energy. In conclusion, the vertical alignment of LC was introduced by the low surface free energy of PI films grafted with DA polymer and intermolecular interactions between LC and DA polymers.

For various existing thermoresponsive (co)­polymers, one of the most significant drawbacks is them being inherently nondegradable, which results in a latent risk of environmental pollution and a restriction in some application fields. In addition, it is extremely significant for both fundamental research and practical application to enrich the thermoresponsive species with multifunctionality and unconventional thermoresponsive building blocks. Herein, we present a degradable amphiphilic diblock copolymer without conventional thermoresponsive building blocks as a first example which simultaneously possesses fluorescence and UCST < LCST dual thermoresponsiveness in water. By a coupling reaction between hydrophilic biocompatible poly­(ethylene glycol) monomethyl ether (MPEG) and hydrophobic degradable pyrene end-capping poly­(p-dioxanone) (Py-PPDO), the various copolymers with controlled and well-defined structure were readily synthesized. Under standard conditions, the UCST and LCST can be regulated over a wide temperature range by systematically changing the chain length of the Py-PPDO and MPEG blocks. In addition, the fluorescence of copolymer was strongly in connection with the UCST and LCST, and the differences of fluorescence intensities between excimer and monomer emission (I E – I M) were linearly dependent on the temperature in the range 10–80 °C, indicating a potential application of the copolymer as a fluorescent thermometer in the biologically significant temperature range. Significantly, a mechanism of dual thermoresponsiveness and temperature-dependent fluorescence, namely the synergy of crystallization and supramolecular interactions, was revealed by variable temperature (VT) 1H NMR and NANO DSC.

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