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Volume 51 (2024)
- Issue 3 Pages 105-
- Issue 2 Pages 63-
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Kazuhiko Ishikiriyama2024 Volume 51 Issue 3 Pages 105-111
Published: July 25, 2024
Released on J-STAGE: September 09, 2024
JOURNAL RESTRICTED ACCESSThis study investigates quantitative structure-property relationships for polymers using machine learning techniques, leveraging the ATHAS data bank. Developed by Wunderlich et al., this data bank contains specific properties of polymers. These properties encompass essential information, including the glass transition temperature (Tg0) of fully amorphous polymers, the heat capacity difference at Tg0, the equilibrium melting temperature, the heat of melting point at 100 % crystallinity, Θ temperature, the number of skeletal vibrations, and the temperature dependence of heat capacities, etc. Our methodology focuses on establishing correlations between these polymer-specific physical properties and the repeating structural units within the polymers. To achieve this, we employed various regression models, including artificial neural networks with equivalent and damping structures, Lasso, Random Forest, and XGBoost regression. Model validations were conducted using 5-Fold cross-validation. Our results indicate that the artificial neural network model exhibited the lowest error. Furthermore, we showcase the practical application of quantitative structure-property relationships in predicting the properties of two polymers not yet included in the ATHAS data bank.View full abstractDownload PDF (2227K) -
Tetsuo Asaji2024 Volume 51 Issue 3 Pages 112-118
Published: July 25, 2024
Released on J-STAGE: September 09, 2024
JOURNAL RESTRICTED ACCESSMolecular rotors, or amphidynamic crystals, which consist of static groups and dynamic components, have a rich potential to provide functional properties such as ferroelectricity and to control them by molecular motion. A nuclear magnetic resonance (NMR) relaxation study, which is very important to elucidate molecular motion in amphidynamic crystals, is described. In the molecular complexes having 1,4-diazabicyclo[2.2.2]octane (DABCO) as a rotator, DABCO reorientation about its pseudo C3 rotation axis was shown to reach up to the order of 10−1 THz around the phase transition temperature, which frequency is comparable to that of motion in the liquid phase. The correlation time of reorientation is compared with the free rotation time of a hypothetical free rotator.View full abstractDownload PDF (602K) -
Hirokazu Kobayashi, Hidehiko Honda2024 Volume 51 Issue 3 Pages 119-123
Published: July 25, 2024
Released on J-STAGE: September 09, 2024
JOURNAL RESTRICTED ACCESSThis article describes the recent history of calorimetry and thermal analysis in the Faculty of Arts and Sciences at Fujiyoshida, Showa University, at the base of Mt. Fuji. Sample observation TG-DTA of a light curing composite resin comprising bisphenol A glycidyl methacrylate (bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) was conducted to observe thermal shrinkage due to residual stress and color change, generated in the photopolymerization process. TG-DTA results for inclusion compounds (ICs) using 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) as a one-dimensional (1D) host material are also reported. In CLPOT ICs that incorporated free radicals such as 4- substituted-2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (4-X-TEMPO), desorption of guest radicals from CLPOT nanochannels was confirmed using TG-DTA. The combined results of sample observations and TG-DTA indicated a change in the physical/chemical state of these ICs. In CLPOT ICs that incorporated acetaminophen, a popular antipyretic analgesic agent, TG-DTA played a decisive role in the confirmation of the inclusion of acetaminophen in the CLPOT nanochannels. Sample observation combined with TG-DTA is thus a useful approach to obtain fundamental information on various materials of interest, allowing their future applications to be considered.View full abstractDownload PDF (2003K) -
Taro Yamamoto, Hal Suzuki2024 Volume 51 Issue 3 Pages 124-130
Published: July 25, 2024
Released on J-STAGE: September 09, 2024
JOURNAL RESTRICTED ACCESSA differential scanning calorimeter equipped with a shearing system was developed to reveal thermodynamic properties of fluid materials under shear flow. Using the developed calorimeter, liquid crystalline material 4′-n-octyl-4-cyano-biphenyl (8CB) and rod-like micellar system of cationic surfactant cetyltrimethylammonium bromide (CTAB) aqueous solution were investigated. The heat flow caused by the shearing was evaluated from the shear stress data, and successfully subtracted from the measured DSC curve. The shear-rate dependences of the transition peaks were investigated for both systems. For 8CB, onset temperature of the smectic-A to nematic transition was found to be lowered by the shearing, whereas no considerable change was found for the nematic to isotropic liquid transition. For CTAB/water system, the transition from CTAB crystal coexisting with its aqueous solution to the rod-like micellar state was found to shift to lower temperature with increasing shear rate at 0 < 𝛾 < 1 s-1, whereas it shifted to higher temperature at 30 < 𝛾 < 100 s-1. The former change was attributed to the decrease in the grain size of the crystallites, whereas the latter one was ascribed to the orientational ordering of the rod-like micelles due to the shearing.View full abstractDownload PDF (1091K) -
Yoshinobu Hosoi2024 Volume 51 Issue 3 Pages 134-135
Published: July 25, 2024
Released on J-STAGE: September 09, 2024
JOURNAL RESTRICTED ACCESSDownload PDF (655K)
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2024 Volume 51 Issue 3 Pages 131-133
Published: July 25, 2024
Released on J-STAGE: September 09, 2024
JOURNAL RESTRICTED ACCESSDownload PDF (329K)
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