Synthesis And Property Studies Of Gold Nanorod/Liquid Crystalline Elastomer Composites

When a mono-domain oriented liquid crystalline elastomer (LCE) is heated to above its clearing point, the order arranged molecules will turn to be disorder. Consequently, this kind of change causes the macroscopic contraction of the whole elastomer sample. Gold nanorods (GNRs) can absorb certain wavelength light and give off thermal energy because of its unique surface plasmon resonance (SPR) properties. Therefore, combining gold nanorods’ photo-thermal conversion effect and thermal-responsive mono-domain LCE will give a novel composite material. In such a way, traditional thermal-responsive LCE turns to be a photo-responsive shape memory material. This is the key design of this thesis.GNRs were synthesized by seed growth method. The synthesized GNRs were about 55 nm long and 8 nm wide, and dispersed steadily in water. After surface-functionalized by ligand exchange with poly[3-mercaptopropylmethylsiloxane] (PMMS) which contained abundant mercapto groups, these gold nanorods were dispersed steadily in organic solvent THF. Transmission electron microscope (TEM) images and UV-Vis light absorbance spectra both showed that there were no serious aggregation or shape change behaviors.Mesogenic units were partially grafted onto mercapto groups of PMMS chain by thiol-ene click chemistry approach which gave the liquid crystalline polymer (LCP)--PMMSo.7-g-LC. Nuclear magnetic resonance (NMR) spectra showed that mesogenic units were grafted successfully and the grafting ratio was about 70%. The LCP and functionalized GNRs which dispersed steadily in THF were mixed and crosslinked by UV irradiation. The concentration of GNRs in GNR/LCE composite material was detected by inductively coupled plasma optical emission spectrometry (ICP-OES), which was about 0.09 wt%. The detection results of differential scanning calorimetry (DSC) and precise temperature-controlled polarized optical microscopy (POM) showed that the phase transition temperatures of GNR/LCE composite material and blank LCE were almost exactly the same.The key part of this work was a series of near-infrared-responsive experiments of GNR/LCE composite fibers under illumination of an 808 nm laser. In these experiments, all the GNR/LCE composite materials responded well to the laser and contracted successfully, while the blank LCEs as the reference sample didn’t exhibit any responses. Besides, GNR/LCE composite materials with 5 times concentration GNRs (0.47 wt%) were prepared to explore the correlation of GNRs’concentration and the photo-response rate. However the photo-response rate showed no obvious differences in macroscopic view as the concentration of GNRs was just a few percentage. Continuing to increase the concentration of GNRs, couldn’t provide intact composite fibers since GNRs were inorganic particles which might affect the continuity of LCP matrix.The GNR/LCE composite material prepared in this thesis is a kind of good near-infrared-responsive material which can be used in the areas of biomimetic, robotic technology, micro-electro-mechanical system (MEMS) and so on.