Polymer Functionalized Nanoparticles in Blue Phase LC: Effect of Particle Shape

• Published in: Nanomaterials (Basel, Switzerland) Vol. 12; no. 1; p. 91
• Main Authors: Zhang, Manlin, Lindner-D’Addario, Michael, Roohnikan, Mahdi, Toader, Violeta, Lennox, Robert Bruce, Reven, Linda
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 29.12.2021; MDPI
• Subjects: Acids; Asymmetry; Benzoates; Benzoic acid; blue phase liquid crystals; Crystal defects; Crystals; Defects; Energy; Ethylene oxide; Gold; gold nanoparticles; Ligands; Liquid crystals; Molecular weight; Nanoparticles; Nanorods; Nanospheres; Oligomers; Optics; Particle shape; Phase transitions; Polyethylene glycol; Polymers; Shape effects; Temperature; Canada; blue phase liquid crystals; gold nanoparticles; polymers
• DOI: 10.3390/nano12010091
• ISSN: 2079-4991

Ethylene oxide oligomers and polymers, free and tethered to gold nanoparticles, were dispersed in blue phase liquid crystals (BPLC). Gold nanospheres (AuNPs) and nanorods (AuNRs) were functionalized with thiolated ethylene oxide ligands with molecular weights ranging from 200 to 5000 g/mol. The BPLC mixture (ΔTBP ~6 °C) was based on the mesogenic acid heterodimers, n-hexylbenzoic acid (6BA) and n-trans-butylcyclohexylcarboxylic acid (4-BCHA) with the chiral dopant (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate. The lowest molecular weight oligomer lowered and widened the BP range but adding AuNPs functionalized with the same ligand had little effect. Higher concentrations or molecular weights of the ligands, free or tethered to the AuNPs, completely destabilized the BP. Mini-AuNRs functionalized with the same ligands lowered and widened the BP temperature range with longer mini-AuNRs having a larger effect. In contrast to the AuNPs, the mini-AuNRs with the higher molecular weight ligands widened rather than destabilized the BP, though the lowest MW ligand yielded the largest BP range, (ΔTBP > 13 °C). The different effects on the BP may be due to the AuNPs accumulating at singular defect sites whereas the mini-AuNRs, with diameters smaller than that of the disclination lines, can more efficiently fill in the BP defects.