Time-resolved in situ ATR-IR observations of the process of sorption of water into a poly(2-methoxyethyl acrylate) film

A process of water sorption into a biocompatible polymer, poly(2-methoxyethyl acrylate) (PMEA), was investigated by time-resolved, in situ, attenuated total reflection infrared spectroscopy. Evidence for three different types of hydrated water in PMEA, that is, nonfreezing water, freezing bound water, and freezing water, were found. Each hydration structure was elucidated at the functional group level. Nonfreezing water, which never crystallizes, even at -100 degrees C, has a C=O...H-O type of hydrogen bonding interaction with the carbonyl group of PMEA. Freezing bound water, which crystallizes in a heating process below 0 degrees C, interacts with the methoxy moiety in the PMEA side chain terminal. Freezing water, which crystallizes approximately 0 degrees C, has bulk-water-like structure with an O-H...O-H hydrogen bonds network. It has been concluded from the present study that the methoxy moiety in the PMEA side chain terminal plays an important role for the excellent biocompatibility of PMEA.     

Infrared Spectroscopy and X-Ray Diffraction Studies of C?H…O Hydrogen Bonding and Thermal Behavior of Biodegradable Poly(hydroxyalkanoate)

Infrared (IR) spectra and wide-angle X-ray diffraction (WAXD) patterns of poly(3-hydroxybutyrate) (PHB) and its copolyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), P(HB-co-HHx) (HHx = 12 mol%) were measured over a temperature range of 20 °C to higher temperatures (PHB, 185 °C, HHx = 12 mol%, 140 °C) to explore their structure change and thermal behavior and molecular interaction. The WAXD measurements revealed that the a lattice parameter increases significantly with temperature, while the b lattice parameter varies a little in the crystalline PHB and P(HB-co-HHx). It seems that the intermolecular interaction between the CO group of one helical structure and the CH₃ group of the other helical structure decreases along the a axis of crystalline PHB and P(HB-co-HHx) with temperature. The temperature-dependent IR spectral variations were analyzed for the CH stretching, CO stretching, CH₃ deformation, and C O C stretching variation regions, and bands characteristic of crystalline and amorphous parts were identified in each region. It was found from the anomalous frequencies of the CH₃ asymmetric stretching and CO stretching bands of PHB and P(HB-co-HHx) and the X-ray crystallographic structure of PHB that there is an intermolecular interaction (C H…OC hydrogen bond) between the CO group and the CH₃ group combining two helical structures in PHB and P(HB-co-HHx). In this review paper we discuss the role of the C H…OC hydrogen bonding and the crystal and lamella structure of PHB and P(HB-co-HHx) (HHx = 12 mol %) in comparison with the structure of Nylon.     

Enzymatic degradations of copolymers of L-lactide with cyclic carbonates

Syntheses and biodegradation of random copolymers of L -lactide (L -LA) with trimethylene carbonate (TMC), 1,1-dimethyltrimethylene carbonate (1,1-DTMC) and 2,2-dimethyltrimethylene carbonate (2,2-DTMC) were investigated at various monomer ratios using SmMe(C₅Me₅)₂THF as an initiator at 80 °C for 24 h in toluene. Enzymatic degradation of these polymers were performed using cholesterol esterase, lipoprotein lipase, and proteinase K. Poly(TMC) was effectively biodegraded by cholesterol esterase and lipoprotein lipase, while poly(2,2-DTMC) and all the copolymers were hardly degraded using these enzymes. Biodegradations of poly(L -LA-co-TMC) (97:3) and poly(L -LA-co-2,2,DTMC) (95:5) show rapid degradations using TES buffer, a compost and proteinase K. The physical properties of these copolymers were also examined.

Enzymatic degradation of L -LA/2,2-DTMC copolymers by proteinase K in Tricine buffer (pH 8.0) at 37 °C: a 98:2, b 82:18, c 100:0, d 66:34, e 34:66, f 0:100.     

Molecular motion and relaxation studies of aliphatic polyureas by thermal windowing thermally stimulated depolarization current technique

Molecular motion and relaxation studies using a thermal windowing thermally stimulated depolarization current (TW‐TSDC) were performed for aliphatic polyureas 7 and 9. Global thermally stimulated depolarization current gave three characteristic major peaks corresponding to the α, β, and γ relaxation modes at 78.5, −44, and −136°C for polyurea 7 and at 80, −50, and −134°C for polyurea 9, respectively. The α relaxation is related to the large‐scale molecular motion due to micro‐Brownian motion of long‐range segments. This relaxation is significantly related to the glass‐transition temperature. The β relaxation is caused by the local thermal motion of long‐chain segments. The γ relaxation is caused by the limited local motion of hydrocarbon sections. Temperature dependence of relaxation times was expressed well using Vogel–Tammann–Fulcher (VTF) expression. 3‐D simulation of dielectric constants of dielectric strength and loss factor were performed in the frequency range from 10⁻⁶ to 10⁴ Hz and temperature range from −150 to 250°C, using the relaxation parameters obtained from the TW‐TSDC method. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 88–94, 2000     

Asymmetric anionic polymerization of maleimides bearing bulky substituents

Asymmetric anionic homopolymerizations of N‐substituted maleimide (RMI) bearing bulky substituents [R = benzyl, diphenylmethyl (DPhMI), 9‐fluorenyl (9‐FlMI), triphenylmethyl, (diphenylmethyloxycarbonyl)methyl, (9‐fluorenyloxycarbonyl)methyl] were carried out with complexes of organometal compounds (alkyllithium, diethylzinc) with six chiral ligands to obtain optically active polymers. The chiroptical properties of the polymers were affected strongly by the substituents on nitrogen in the maleimide ring, the organometal and chiral ligands. Poly(DPhMI) initiated by an n‐butyllithium/(−)‐sparteine (Sp) complex showed a positive specific rotation ([α] +60.3°). Poly(9‐FlMI) prepared with a florenyllithium/Sp complex exhibited the highest specific rotation (+65.7°). The specific rotations of the poly(RMI) obtained were attributed to different contents between the stereogenic centers (S,S) and (R,R) based on threo‐diisotactic structures of the main chain. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 310–320, 2000     

FTIR studies of conformational energies of poly(acrylic acid) in cast films

Fourier transform infrared (FTIR) spectroscopic measurements have been undertaken to estimate the conformational energies of poly(acrylic acid) (PAA) cast films in the temperature range of 40–130°C. The temperature dependence of the IR spectra in the C=O stretching region has been analyzed to yield the side-chain and backbone conformational energies. The estimated energies are close to those previously obtained by polarized Raman spectroscopic measurements for PAA solutions. Combining the FTIR value of conformational energy with the simplified rotational isomeric state (RIS) model proposed in the Raman analysis provides a persistence length in accordance with earlier SAXS experiments. The data also agree with the Gibbs-DiMarzio predictions, further substantiating the validity of the analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 507–515, 1997     

Effects of Lower-limb Muscle Fatigue,Cardiopulmonary Fatigue,and Brain FatigueTasks on One-legged Landing Motion

Objective: Anterior cruciate ligament (ACL) injury is one of the most frequent sportsinjuries, and previous studies have shown that fatigue is a risk factor for sports injuries.This study aimed to inform prevention of ACL injury by investigating how exercise and desk tasks affect trunk and lower limb alignment and ground reaction force (GRF) during one-legged landing movements. Methods: The study subjects were 12 men who performed a one-legged landing movement from a 30-cm platform before and after fatigue tasks, including lower-limb muscle fatigue, cardiopulmonary fatigue, and brain fatigue tasks. For the measurement of joint angles and moments and GRF, a three-dimensional motion analysis device and a floor reaction-force meter were used. Statistics were performed using Wilcoxon''s signed rank sum test as a multiple comparison test with Bonferroni adjustment to compare the difference in effects. Results: The maximum trunk flexion angle during landing on one leg was significantly lower in the brain fatigue group than in the control group. The time to peak vertical GRF (pGRF) was significantly shorter in the leg-muscle fatigue group than in the control group. Conclusion: Brain fatigue may have altered the postural strategy before and after landing, resulting in a decrease in trunk flexion angle. Time to pVGRF was shortened in the leg muscle fatigue group, suggesting that there may be an increased risk of ACL injury. Time to pVGRF during lower extremity muscle fatigue and trunk flexion angle during brain fatigue may be more pronounced during actual sports activities.     

Aggregation-Enhanced Room-Temperature Phosphorescence from Au(I) Complexes Bearing Mesogenic Biphenylethynyl Ligands

Gold(I) complexes, enabling to form linear coordination geometry, are promising materials for manifesting both aggregation-induced emission (AIE) behavior due to strong intermolecular Au–Au (aurophilic) interactions and liquid crystalline (LC) nature depending on molecular geometry. In this study, we synthesized several gold(I) complexes with rod-like molecular skeletons where we employed a mesogenic biphenylethynyl ligand and an isocyanide ligand with flexible alkoxyl or alkyl chains. The AIE behavior and LC nature were investigated experimentally and computationally. All synthesized gold(I) complexes exhibited AIE properties and, in crystal, room-temperature phosphorescence (RTP) with a relatively high quantum yields of greater than 23% even in air. We have demonstrated that such strong RTP are drastically changed depending on the crystal-size and/or crystal growth process that changes quality of crystals as well as the aggregate structure, of e.g., Au–Au distance. Moreover, the complex with longer flexible chains showed LC nature where RTP can be observed. We expect these rod-like gold(I) complexes to have great potential in AIE-active LC phosphorescent applications such as linearly/circularly polarizing phosphorescence materials.