Biobased polyhydric alcohols (bis-LG, tri-LG, tetra-LG) with different numbers of hydroxy groups (n=4,6,8, respectively) were synthesized using limonene glycol (LG). Cross-linking reaction of polyhydric alcohols and methylenediphenyl 4,4'-diisocyanate (MDI) with [OH]₀/[NCO]₀=1/1(mol/mol) afforded the corresponding polyurethane networks in 40%, 60%, and 92% yields, respectively. Thermal resistance of the network polymers increased with increasing number of hydroxy groups in polyhydric alcohols. Metal-tometal adhesive using bis-LG and tetra-LG was evaluated by lap shear test, resulting in 2.7 MPa and 5.9 MPa, respectively. When polyurethane foam was prepared by PPG (polypropylene glycol) (90%) and bis-LG (10%), the 5% thermal decomposition temperature and tensile strength of the corresponding polyurethane foam was 16 °C higher and 4 times stronger, respectively, compared to that derived from PPG only. (Received March 22, 2023; Accepted April 5, 2023) Key-words : limonene glycol, polyhydric alcohols, polyurethane networks, polyurethane foams Biobased polyhydric alcohols (bis-LG, tri-LG, tetra-LG) with different numbers of hydroxy groups (n=4,6,8, respectively) were synthesized using limonene glycol (LG). Cross-linking reaction of polyhydric alcohols and methylenediphenyl 4,4'-diisocyanate (MDI) with [OH]₀/[NCO]₀=1/1(mol/mol) afforded the corresponding polyurethane networks in 40%, 60%, and 92% yields, respectively. Thermal resistance of the network polymers increased with increasing number of hydroxy groups in polyhydric alcohols. Metal-tometal adhesive using bis-LG and tetra-LG was evaluated by lap shear test, resulting in 2.7 MPa and 5.9 MPa, respectively. When polyurethane foam was prepared by PPG (polypropylene glycol) (90%) and bis-LG (10%), the 5% thermal decomposition temperature and tensile strength of the corresponding polyurethane foam was 16 °C higher and 4 times stronger, respectively, compared to that derived from PPG only. (Received March 22, 2023; Accepted April 5, 2023) Biobased polyhydric alcohols (bis-LG, tri-LG, tetra-LG) with different numbers of hydroxy groups(n=4,6,8, respectively) were synthesized using limonene glycol (LG). Cross-linking reaction of polyhydric alcohols and methylenediphenyl 4,4'-diisocyanate (MDI) with [OH]₀/[NCO]₀=1/1(mol/mol) afforded the corresponding polyurethane networks in 40%, 60%, and 92% yields, respectively. Thermal resistance of the network polymers increased with increasing number of hydroxy groups in polyhydric alcohols. Metal-tometal adhesive using bis-LG and tetra-LG was evaluated by lap shear test, resulting in 2.7 MPa and 5.9 MPa, respectively. When polyurethane foam was prepared by PPG (polypropylene glycol) (90%) and bis-LG (10%), the 5% thermal decomposition temperature and tensile strength of the corresponding polyurethane foam was 16℃ higher and 4 times stronger,respectively,compared to that derived from PPG only.

The report introduces the fabrication method of a homogeneous liquid crystal (LC) alignment by exposure of a polarized ultraviolet (UV) above the nematic-isotropic transition temperature of the LC material (T_NI) to the cell including the mixture of the LC material and the monomer carrying an azobenzene moiety. First, the mixture of the LC material and the monomer was injected into the empty cell without forming a conventional alignment layer on substrates. The cellwas then exposed to polarized UV from the normal direction above the T_NI of the LC material. Finally, the homogeneous LC alignment was obtained, which shows the equal level of electro-optical and response properties of the conventional alignment layer on the substrates. The conventional fabrication process needed much amount of solvents and high temperature above 200℃ for forming the alignment layer, thus the proposed fabrication method would be significantly useful because it is expected to be eco-friendly.

A novel crosslinking type polyphenylene ether prepolymers (VS-970) with a low dielectric loss tangent (D_f) value was synthesized and was evaluated for multilayer laminate applications in high-speed communication field. VS-970 single cured product showed low D_f value and high T_g, and its curing mechanism was analyzed. VS-970 exhibits excellent compatibility with hydrogenated styrene-butadiene block copolymer (SEBS), which has an extremely low D_f value and has the capability to formulate a uniform curable resin composition without a compatibilizer causing increase of the D_f value. As a result, the cured product of VS-970/SEBS showed a quite low D_f value (0.0029@10 GHz). A phenomenon was observed in which the D_f value of the cured product varied greatly depending on the structural ratio of the SEBS, and this was found to be due to the difference in the phase separation structure of the cured product formed.

We investigated a simple and highly sensitive analytical method for free bisphenol A (BPA) in latent curing agents for epoxy resins using a high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) system. The mobile phase for high-performance liquid chromatography (HPLC) consisted of a 0.01% acetic acid aqueous solution and acetonitrile, and the column used was an L-column3 C18 (2.1×150 mm, 3 μm). The ionization mode for MS/MS was negative electrospray ionization (ESI), and the multiple reaction monitoring (MRM) transition was set at m/z 227－133. N, N-dimethylformamide (DMF) was used as the sample solvent because it is miscible with both the sample and the mobile phase. Quantification was performed using the internal standard method and the standard addition method, and equivalent quantification values were obtained. This indicates that the measurement was not affected by impurities. The results demonstrate that this method can be used for the simple and highly sensitive quantification of free BPA in latent curing agents.

A new acid-base organocatalyst inspired by enzyme has been developed focusing on the enzymatic active site of lipase-catalyzed ring-opening polymerization. Both solution polymerization and bulk polymerization are possible, and "precise poly (lactic acid)s" with a theoretical molecular weight calculated from the monomer/initiator ratio can be obtained quantitatively up to enough high degree of polymerization for industrial use. In addition, depending on the initiator, it is possible to design various polymers with controlled structures, including the introduction of linear and branched structures, modification of both terminal groups, and block copolymerization. In this paper, at first, the reaction mechanism of acidbase organocatalyst and the relationship between the primary structures and function of poly (lactic acid)s obtained by this precision synthesis method have been shown. Next, application to adhesives of poly (lactic acid)s with long-chain multibranched structures has been explained. Finally, a new try for networked poly (lactic acid)s with controlled distances of cross-linking will be discussed.