KiRyong Ha

Highly Sensitive Photoaligning Materials on a Base of Cellulose-Cinnamates

We report on development and characterization of new photoaligning polymers based on cellulose main chain and side fragments based on cinnamic acid containing alkenyl groups. The materials possess excellent photosensitivity, rather strong anchoring energy, low sticking parameter and can be considered as a promising candidate for LCD application, especially for plastic LCDs.

Monolayer studies of perfluorostearic acid at air/water interface

Abstract We report the formation of a monolayer of perfluorostearic acid (PFS, CF 3 (CF 2 ) 16 COOH) using a mixed solvent of pentafluorobenzene (PFB) and methanol (weight ratio of methanol/PFB=∼1:86) as a PFS spreading solvent. PFS formed very stable monolayer at air/water interface, which has 0.32 nm 2 of molecular area and 63.4 mN/m of collapse pressure on DI water. The presence of all the metal cations such as Na + , Ca 2+ , Co 2+ , Cu 2+ , and La 3+ results in the expansion of the monolayer, the surface pressure ( π )–area ( A ) curves of PFS on Ca 2+ or La 3+ subphase showing the most expanded isotherms. Polyion complex formation between PFS and water-soluble polymers was observed. Especially, polyethyleneimine (PEI) formed a strong polyion complex with PFS. Changing the pH of the subphase controlled the degree of the complex formation between PFS and the PEI. The mixed monolayers of PFS and stearic acid (SA) showed positive molecular area change on mixing due to repulsion between PFS domains and the SA domains on the subphase.

FTIR study of E7 liquid crystal orientations confined to cylindrical cavities of Anodisc membranes

The orientation of E7 liquid crystal (LC) confined within 200 nm diameter cylindrical cavities of Anodisc membranes was investigated by FTIR dichroism techniques. The cavity walls of the confining pores were chemically modified with different length aliphatic acids (C n H2n+1COOH, n=5, 6, 7, 9) at 2 and 4% concentrations. From the FTIR spectra of the aliphatic acid-treated alumina Anodsic membranes, we found salt formation between the -COOH group of the aliphatic acids and the Anodisc membranes. From the FTIR spectra of LC-filled Anodisc membranes, we found an abrupt alignment direction change, from parallel to perpendicular, of the LC molecules along the long axis of the cavities between n=6 and n=7 for the 2% concentration of aliphatic acid. However for the 4% concentration of aliphatic acid the parallel to perpendicular alignment direction of LC molecules changed between n=5 and n=6. The same trend was previously observed for 2H NMR measurements by other researchers.

Temperature-Induced Phase Separation of Side-Chain LCP/LMWLC Blends

A blend of side-chain liquid crystal polymer (SCLCP) and low molecular weight liquid crystal (LMWLC) was used to investigate a phase separation behavior induced by temperature. Phase separation at room temperature was observed only for the compositions higher than 60 wt% LMWLC because of good miscibility between two components. An interesting phenomenon was observed when the film transmittance for a phase-separated sample as a function of temperature was measured under cross-polarizer. That is, transmittance below TNI of LMWLC was observed lower than that below TSI of SCLCP, which was not expected initially. The fact was considered as a micro-phase separation induced by an interfacial effect between SCLCP and LMWLC phase.

Characterization of orientation of perfluorostearic acid Langmuir–Blodgett multilayers by infrared spectroscopic methods

Abstract The molecular orientation of perfluorostearic acid [CF3(CF2)16COOH] deposited by Langmuir–Blodgett technique has been investigated by grazing incidence reflection absorption and transmission infrared spectroscopy. In the former, the electric field vector is normal to the film surface whereas in the latter, it is parallel to the surface. The intensities of the infrared bands that tend to exhibit perpendicular polarization, e.g. symmetric stretching of COO−, are much higher in reflection absorption than in transmission for deposited perfluorostearic acid. Therefore, these Fourier transform infrared results strongly support that the perfluorostearic acid molecules are preferentially oriented with their chain axes perpendicular to the substrate surface.

Multiwalled carbon nanotubes and fluoroelastomer antistatic nanocomposite for automotive fuel system components

Fluoroelastomer (FKM) composites, reinforced with multiwalled carbon nanotubes (MWNTs), were prepared by conventional method to determine the possibility of using MWNTs to develop an antistatic composite in automotive fuel systems. The results obtained from the composite containing 0-9 phr of MWNTs were compared. A 5 points increase in hardness was achieved with the addition of only 1 phr of MWNTs and 9 phr added FKM composite was increased 6.4MPa in tensile strength compared to the MWNTs unfilled FKM composite. In addition, electrical conductivity increased from 0 to 1.039 Scm−1 with increase in the MWNTs concentration, and the dynamic damping property was increased in the rubbery state region accordingly. These phenomena can be explained by the MWNTs networks formed in FKM matrix. This research will therefore be useful in the development of an antistatic rubber composite for fuel system components, which are deformed or vibrated while in operation.

Synthesis and characterization of cross-linked poly(acrylic acid)-poly(styrene-alt-maleic anhydride) core-shell microcapsule absorbents for cement mortar

We synthesized core-shell microcapsule absorbents with cPAA (cross-linked poly(acrylic acid)) as the core and PSMA (poly(styrene-alt-maleic anhydride)) as the shell by precipitation polymerization, where the shell served to delay the absorption of excess water in cement mortars. To control shell thickness, the cPAA-PSMA capsules were synthesized with core monomer mass to shell monomer mass ratios of 1/0.5, 1/1, and 1/1.5. We observed the hydrolysis of the PSMA polymer in a cement-saturated aqueous solution by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, core-shell structures were observed for 1/1 (cPAA-PSMA #3) and 1/1.5 (cPAA-PSMA #4) core/shell monomer mass ratios, whereas no core-shell structures were observed for the 1/0.5 (cPAA-PSMA #2) microcapsules by transmission electron microscopy (TEM).

Spectroscopic analysis of methacrylate groups introduced on silica particle surfaces by the aza-Michael addition reaction

We modified silica nanoparticles with a N′-(3-trimethoxysilylpropyl)diethylenetriamine (TPDT) silane coupling agent, which has one primary and two secondary amino groups in each molecule, to introduce amino groups on silica surfaces. After surface modification of silica, we used an acrylate group containing 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) to introduce free radical polymerizable methacrylate groups by the aza-Michael addition reaction. Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), liquid state 1H and 13C nuclear magnetic resonance spectroscopy (NMR) and solid state cross polarization magic angle spinning (CP/MAS) 29Si NMR were used to investigate the effects of various reaction conditions on the degree of reaction between the N-H groups of the TPDT-modified silica surface and the acrylate groups of AHM. We found that approximately 48% of the N-H groups of the TPDT-modified silica surface reacted with the acrylate groups of AHM, compared with approximately 83% of the N-H groups of pure TPDT reacting with the acrylate groups of AHM at the same reaction conditions. This lower degree of the aza-Michael addition reaction between the N-H groups of the TPDT grafted on the solid silica particle versus the N-H groups of pure TPDT, both with acrylate groups of liquid AHM, may be caused by the lower mobility of the N-H groups of the grafted TPDT on the solid silica particle and the higher steric hindrance caused by the solid silica particle.

Application of cross-linked poly(acrylic acid)-poly(styrene-alt-maleic anhydride) core-shell microcapsule absorbents in cement mortars

We synthesized core-shell microcapsule absorbents with crosslinked poly(acrylic acid) (PAA) as the core and poly(styrene-alt-maleic anhydride) (cPAA-PSMA) as the shell by the precipitation polymerization method for delayed absorption of excess water in cement mortar. To control the shell thickness, cPAA-PSMA capsules were synthesized with the core-to-shell monomer mass ratios of 1: 0 (cPAA #1), 1: 0.5 (cPAA-PSMA #2), 1: 1 (cPAA-PSMA #3), and 1: 1.5 (cPAA-PSMA #4). The viscosity of the cement paste with cPAA-PSMA #4 absorbent increased slowly until 90minutes after absorbent addition, beyond which it increased rapidly. This suggests that mortars with cPAA-PSMA #4 absorbents can secure up to 90 minutes of working time. Incorporation of 1.0 wt% cPAA-PSMA #4 into cement mortar increased the compressive and flexural strengths by approximately 35% and 22%, respectively, compared to those of cement mortars without absorbents.

P-129: Rejuvenated Photoalignment of Liquid Crystal on Cinnamoil-Containing Polymers

We report on easy orientation axis alternation in new photoaligning polymers (PG materials) based on cellulose backbone containing photosensitive cinnamoil groups. Materials have strong application potential due to high aligning quality and photosensitivity, strong anchoring energy, small sticking effect. Rejuvenation of polymer after UV-irradiation makes PG attractive for various applications.