Surface grafted agents with various molecular lengths and photochemically active benzophenone moieties

Abstract

Homologues of benzophenone silane, a covalently graftable, photochemically active surface functionalizing agent, are investigated as surface functionalization agents for both small particles and planar substrates.

Effects of Composition and Polymerization Conditions on the Electro-Optic Performance of Liquid Crystal–Polymer Composites Doped with Ferroelectric Nanoparticles

“…Here, surface-grafting benzophenone silane derivatives (as described in Ref. [ 40 ]) were used for this purpose. The molecules of this novel type of surfactant ( n -BPS) [inset of Figure 1 a] contain two functional groups, a chlorosilane anchor group and a photo-chemically active benzophenone group, which are separated by an alkyl chain with n = m + 2 carbon atoms.…”

“…Comparing Figure 1 b and Figure 1 c, a decrease in the contact angle is observed for the UV-exposed samples. This result reveals that LC molecules were successfully attached to the surface in the polymerization process, which is expected to reduce surface tension [ 40 ]. In addition, the surface-grafting agents were found to yield smaller particles in the ball milling process than oleic acid at reasonable milling times.…”

“…Surface-grafted photo-initiators based on a silane moiety have been synthesized in order to enable the in situ formation of a polymer network that is covalently bound to a LiNbO 3 :Fe surface, aiming to combine the opportunities of the anomalous photovoltaic effect with the enhanced stability or modified electro-optic response of an LC/polymer network composite [ 39 ]. More recently, this work was extended to LC dispersions, where the LC contains LiNbO 3 :Fe nanoparticles rather than being confined by a monocrystalline LiNbO 3 :Fe substrate [ 40 ]. This preceding study revealed that the surface effect of the silane compounds is also beneficial to the milling process, in which LiNbO 3 :Fe nanoparticles are fabricated from larger LiNbO 3 :Fe crystals.…”

“…This preceding study revealed that the surface effect of the silane compounds is also beneficial to the milling process, in which LiNbO 3 :Fe nanoparticles are fabricated from larger LiNbO 3 :Fe crystals. Adding these silanes to the respective grinding mixture yields sufficiently small particles with a limited size distribution [ 40 ]. Here, the effects of either dispersing ferroelectric LiNbO 3 :Fe nanoparticles in a liquid crystal matrix or adding a stabilizing cross-linked polymer to the same liquid crystal matrix are investigated in greater detail.…”

“…In addition to confirming the influence of these different polymerization conditions on the properties of the resulting PNLCs, we extend hitherto knowledge to the thermal and electro-optic behavior of PNLC/ferroelectric NP nanocomposites. For this purpose, we modified a recently developed protocol for fabricating monodisperse, LC-dispersible ferroelectric NPs [ 40 ]. Because of a higher rotational speed during the grinding process and filtration, stable dispersions of particles smaller than 200 nm could be studied.…”