Chiral liquid crystals based on pillararene and supramolecular self-assembly-induced chirality amplification

Macrocyclic liquid crystals combine the unique property of liquid crystals and excellent supramolecular assembly ability of macrocyclic compounds.It is a significant challenge to make rational use of the advantages of macrocyclic compounds to prepare new macrocyclic mesogens.Pillararenes,a type of macrocycles with rigid pillar-shaped frameworks and easy-tofunctionalize property,are excellent building blocks to fabricate liquid crystal materials.However,the site-selective modification property of pillararene has been rarely exploited to tailor liquid crystal behaviors.Previously reported pillararene-based liquid crystal systems are almost prepared by per-functionalized pillararenes.Herein,we report the regulation of chiral liquid crystal behaviors by different derivatization of pillararene.Lyotropic and thermotropic liquid crystals with different chirality were obtained by self-assembly of pillararene with different numbers of cholesterol groups.The bridge between thermotropic liquid crystal and lyotropic liquid crystal based on pillararene is built.In addition,the chirality of the mesogens can be amplified through supramolecular self-assembly driven by noncovalent interactions.Based on the different liquid crystal behaviors,the optical signal of the pillararene-based chiral liquid crystals was used to fabricate an information encryption system.This work provides a simple strategy to regulate liquid crystal behaviors via pillararene-based mesogens and realizes information encryption through the combination of different types of liquid crystals.

Improving Thermal-oxidative Aging Resistance of Styrene-butadiene Rubber by Antioxidant Loaded Silica Aerogel

The antioxidant N-isopropyl-N'-phenyl-p-phenylenediamine(4010NA)was dissolved in ethanol and impregnated into silica aerogel(SAG)via vacuum-pressure cycles,yielding composite particles(A-N)with enhanced sustained-release and reinforcing capabilities.The effect of A-N on the mechanical properties and thermal-oxidative aging resistance of styrene-butadiene rubber(SBR)vulcanizates was investigated.TGA and BET assessments indicated that the loading efficiency of 4010NA in SAG reached 14.26%within ethanol's solu bility limit.Incorporating A-N into SBR vulcanizates significantly elevated tensile strength by 17.5%and elongation at break by 41.9%over those with fumed silica and free4010NA.Furthermore,A-N notably enhanced the thermal-oxidative aging resistance of SBR.After aging for 96 h at 100℃,the tensile strength and elongation at break of SBR with A-N sustained 70.09%and 58.61%of their initial values,respectively,with the retention rate of elongation at break being 62.8%higher than that of SBR with fumed silica and free antioxidant.The study revealed that A-N composite particles significantly inhibited the crosslinking in SBR's molecular chains,reducing hardening and embrittlement during later thermal-oxidative aging stages.

A Fluorescent Supramolecular Crosslinked Polymer Gel Formed by Crown Ether Based Host-Guest Interactions and Aggregation Induced Emission

Based on the combination of B21C7/dialkylammonium salt host-guest interactions and tetraphenylethylene （TPE）-based aggregation-induced emission （AIE） effect, a fluorescent supramolecular crosslinked polymer gel was successfully prepared. Compared with the solution of TPE-containing small molecules, this gel exhibited remarkable fluorescence enhancement due to the AIE effect of TPE units. The ＂gelation induced fluorescence emission＂ phenomenon can be explained by the hindered intramolecular rotation of phenyl rings of TPE. Because of the reversibility and stimuli-responsiveness of the B21C7/dialkylammonium salt host-guest interactions, the transition between the fluorescent supramolecular crosslinked polymer gel and the disassembled sol with very weak fluorescence can be realized by adding pH and thermal stimuli. This novel material contributes to the development of supramolecular chemistry, polymer science and fluorescent materials and offers a new method to construct functional supramolecular materials.