NMR of guest‐host systems: 8CB in chiral nematic porous glasses

Manning, Alan P.; Giese, Michael; Terpstra, Andrea S.; MacLachlan, Mark J.; Hamad, Wadood Y.; Dong, Ronald Y.; Michal, Carl A.

doi:10.1002/mrc.4101

Cited by 14 publications

(7 citation statements)

References 45 publications

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“…When a decrease of the index of refraction of the material occurs, the pitch of the nematic chiral phases increases due to the presence of an isotropic liquid between the layers. The effect of temperature was also observed in chiral nematic glasses impregnated with 8CB and the initial iridescence of the films was lost when the liquid crystal attains the isotropic phase. The different behavior observed for CNC/5CB composites is mainly ruled by the anchoring of the liquid‐crystal/cellulose system …”

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confidence: 84%

Mind the Microgap in Iridescent Cellulose Nanocrystal Films

et al. 2016

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A new photonic structure is produced from cellulose nanocrystal iridescent films reflecting both right and left circularly polarized light. Micrometer‐scale planar gaps perpendicular to the films' cross‐section between two different left‐handed films' cholesteric domains are impregnated with a nematic liquid crystal. This photonic feature is reversibly tuned by the application of an electric field or a temperature variation.

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confidence: 84%

Mind the Microgap in Iridescent Cellulose Nanocrystal Films

et al. 2016

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“…27 In another study we demonstrated reversible switching of the photonic properties of CNMO by loading its pores with a calamitic liquid crystal, 8CB (4 0 -n-octyl-4-cyano-biphenyl). 28,29 Detailed solid-state NMR spectroscopic investigations proved that the 8CB is aligned with the pores when it is in a mesophase.…”

Section: Introductionmentioning

confidence: 99%

“…They are readily modied by switching donor/acceptor motifs. Although a number of mesoporous silica composites with LCs are known, 17,29 SMLCs have not been previously investigated in mesoporous hosts. With the goal of developing temperature-sensitive photonic materials, we therefore set out to investigate SMLCs in chiral nematic mesoporous hosts.…”

Section: Introductionmentioning

confidence: 99%

Tuning the photonic properties of chiral nematic mesoporous organosilica with hydrogen-bonded liquid-crystalline assemblies

et al. 2015

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“…[67][68][69] For mesoporous SBA-15 silica, the dimensionless C constant is typically between 100 and 150, indicating the high energy, polar surfaces of surface silanol groups. [70] Using pulsed-field gradient NMR diffusion measurements, the effective diffusion coefficient of absorbed water can be measured in both the longitudinal direction (D ) The films containing mixed systems of the longer alkylene-bridged and ethylenebridged precursors (Prop/Et-CNMO to the Hex/Et-CNMO) displayed lower C constants, with values ranging from ≈65 to 80.…”

Section: Surface Properties and Pore Structure Within The Organosilicmentioning

confidence: 99%

Iridescent Chiral Nematic Mesoporous Organosilicas with Alkylene Spacers

Terpstra

Arnett

Manning

et al. 2018

Advanced Optical Materials

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surfactants and inorganic precursors, it has been possible to create mesoporous materials with different symmetries and pore sizes, and diverse compositions. [5,8] For example, using chiral surfactants as a liquid crystal template has created chiral mesoporous materials with twisted helical structures. [13] In 1999, three research groups independently reported on the incorporation of organic groups into mesoporous silica by using (R′O) 3 SiRSi(OR′) 3 precursors in the place of Si(OR) 4 precursors for the sol-gel condensation. [7,9,14] It proved possible to construct periodic mesoporous silica with organic groups directly integrated into the walls of the mesoporous structure. [11,[15][16][17][18][19][20][21][22][23] Sol-gel processing of silicate materials is highly versatile-it can incorporate various types of precursors and can be carried out under a variety of reaction conditions (e.g., variable pH, temperature, concentration, and solvent mixtures). [24] Therefore, mesoporous organosilica materials have attracted increasing interest for applications including catalysis, [1,25] metal scavenging, [26] chromatography, [27] and biomedical applications. [2] Cellulose nanocrystals (CNCs) obtained from sulfuric-acidcatalyzed hydrolysis of biomass are remarkable materials. [28,29] In 1951, Rånby isolated the crystalline regions within plant cellulose microfibers to form colloidal CNCs with nanoscale dimensions. [28] CNCs have impressive mechanical properties that arise from their high crystallinity and large aspect ratios. [30] Remarkably, CNCs also form a chiral nematic liquid crystal in water. [31] This order can be retained upon drying the aqueous suspension to give a colored, iridescent film. [32] The CNCs arrange into a Bouligand structure, where the crystallites themselves are aligned in layers, but twist with a characteristic helical pitch, P. It is the repeating helicoidal structure that leads to diffraction of circularly polarized light from the CNC films. [33] Many researchers are making new materials that take advantage of the unique properties of CNCs. [30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] In 2010, we discovered that films of mesoporous silica with chiral nematic structure could be prepared using CNCs as a template. [20] When Si(OR) 4 is condensed with CNCs in water, the resulting composite film contains silica and a chiral nematic assembly of CNCs. CNCs can be removed from the composite materials using pyrolysis, leaving behind thin films of iridescent mesoporous silica with a chiral nematic arrangement of pores inside the glass. These materials are of interest Mesoporous organosilica films with chiral nematic structures are prepared with a bridging urea group and with alkylene bridges, where the length of the alkylene bridge varies from C 1 -C 6 . To synthesize these materials, cellulose nanocrystals (CNCs) are used as liquid crystal templates, which coassemble with the organosilica precursor to give composite materials with a chiral nematic structure of CNCs embedded within. Remova...

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NMR of guest‐host systems: 8CB in chiral nematic porous glasses

Cited by 14 publications

References 45 publications

Mind the Microgap in Iridescent Cellulose Nanocrystal Films

Mind the Microgap in Iridescent Cellulose Nanocrystal Films

Tuning the photonic properties of chiral nematic mesoporous organosilica with hydrogen-bonded liquid-crystalline assemblies

Iridescent Chiral Nematic Mesoporous Organosilicas with Alkylene Spacers

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