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궈위엔항,이지은,안석균 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Liquid crystal elastomers (LCEs) are a class of smart materials renowned for their reversible shape transformation under heat, light and solvent. In the thermotropic LCEs, the contraction parallel to the director orientation occurs when heated above nematic-isotropic temperature (Tni). we report the synthesis of a series of surface aligned LCEs prepared by aza-Michael addition between diacrylate functionalized nematic monomers and alkylamine chain extenders followed by photopolymerization. In particular, we used the spacer length of nematic monomers as a handle to manipulate thermal, mechanical and rheological as well as actuation properties of the resulting LCEs. Specifically, both Tni and actuation temperature significantly reduce with decreasing methylene spacer from 11 to 3. Thus, molecular engineering of the LC monomers can bring a significant impact on the actuation behavior of the LCEs, which can advance in the design of programmed shape switching materials.
4D Printing of Water- and Humidity-Responsive Liquid Crystal Elastomer Actuators
김금비,궈위엔항,배재희,최수비,안석균 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Herein, we present a new class of humidity-responsive liquid crystal elastomer incorporating dimethylamino moities that can be prepared by versatile processing, including surface alignment and 3D printing. The humidity-responsive properties are introduced by activating one of the LCE surfaces with an acidic solution, which generates cations on the surface, and provides asymmetric hydrophilicity to the LCE. The resulting humidity-responsive LCE undergoes programmed and reversible hygroscopic actuation, and its shape transformation can be directed by cut angle with respect to a nematic director or by localizing activation regions in the LCE. Furthermore, various humidity-responsive LCE actuators, including a concentric square array and a soft gripper, are successfully fabricated by employing LC inks in DIW 3D printing. Most importantly, by preparing 3-dimensional bilayer actuators that printed in z-direction as well, we suggested the possibility of 4D printing of humidity-responsive LCE.
Impact of Isomeric Amine Chain Extenders on the Properties of Liquid Crystal Elastomers
이유진,안석균,이지은,궈위엔항,손진하 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Among various types of shape changing materials, liquid crystal elastomers (LCEs) received a great attention due to their capability to exhibit reversible shape transformation (i.e., reversible actuation) in a programmed manner. The molecular engineering of LCEs is the key to manipulate the phase transition, mechanical properties as well as actuation performance of the LCEs. In this work, LCEs containing three different types of butylamine (n-butyl, iso-butyl and sec-butyl) were synthesized to investigate the impact of isomeric amine chain extenders on the thermal, mechanical and actuation properties of the resulting LCEs. It was revealed that both glass transition temperature and the rubbery modulus were greatly altered by the choice of butylamine potentially due to change in packing of mesogens. Our results suggest a facile and promising method to control the properties of LCEs, which may advance developing actuators for soft robots, 4D printing and aerospace applications.