Blends of crystalline and amorphous poly(lactide). III. Hydrolysis of solution-cast blend films

Hydrolysis of blend films prepared from amorphous poly(DL-lactide) (a-PLA) and isotactic crystalline poly(D- or L-lactide) (c-PLA) having different c-PLA contents [X = c-PLA/(a-PLA + c-PLA)] was performed in phosphate buffered solution of pH 7.4 at 37°C. The blend films before and after hydrolysis were studied using gel permeation chromatography, tensile testing, differential scanning calorimetry (DSC), and optical rotation. The mass of the blend films remaining after hydrolysis of longer than 20 months was larger with the increasing initial X. The tensile strength of the blend films remained unchanged in the early stage of hydrolysis, followed by a rapid decrease with time, the duration of period for the tensile strength remaining unchanged was longer for the blend films of smaller X. The change in crystallinity, molecular weight, and specific optical rotation during hydrolysis of the blend films revealed that degradation took place preferentially in the amorphous region than in the crystalline region of the blend films. A double melting peak was observed in the DSC spectra of blend films with X = 0.75 and 0.5 after hydrolysis for 20 months. The time difference in the induction of reduction between the tensile strength and the mass due to hydrolysis of the blend films increased with an increase in X. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 855–863, 1997     

Facilitated transport of ethyl docosahexaenoate through solution-cast perfluorosulfonated ionomer membranes

The facilitated transport of ethyl docosahexaenoate (DHA-Et) through the thin solution-cast perfluorosulfonated ionomer membranes has been studied. The carrier of DHA-Et was silver ion and was immobilized in the support ionomer membrane by electrostatic forces. In this system, the feed phase, membrane phase, and receiving phase had the same solvent. This system was already proved to be highly stable in our previous work. When ethanol/water (85/15) was used as the solvent, the DHA-Et permeance in the cast membrane was about four times higher than that in the commercial Nafion® 117 membrane, due to the smaller membrane thickness. In the case of acetone solvent, a high selectivity of DHA-Et to ethyl oleate of 42 and a high facilitation factor of 153 were obtained. These membrane performances were superior to those of the Nafion® 117 membrane. The effects of membrane preparation conditions, such as annealing temperature and kinds of polar solvents added to the ionomer solution before annealing, on the membrane performance was investigated in detail. Furthermore, small-angle X-ray scattering (SAXS) measurement was carried out to study the membrane structure. The experimental result suggests higher crystallinity in the cast membrane annealed at higher temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 961–968, 1999     

Membrane formation via phase separation induced by penetration of nonsolvent from vapor phase. I. Phase diagram and mass transfer process

The isothermal phase diagram for poly(vinylidene fluoride)/dimethyl formamide/water system was derived. The binodal and spinodal were calculated based on the Flory–Huggins theory and the calculated binodal was approximately in agreement with the experimental data of the cloud points. The isothermal crystallization line was also obtained according to the theory of melting point depression. Mass transfer of the three components during membrane formation by the precipitation from the vapor phase has been analyzed. During this process, phase separation of the polymer solution is induced by the penetration of water vapor in the solution. The calculated result on the changes of the cast film weights indicated the good agreement with the experimental data. The time‐course of the polymer concentration profile in the film was calculated for various cases of different humidity of the vapor phase and different initial polymer concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 159–170, 1999     

Poly(L‐lactide): v. effects of storage in swelling solvents on physical properties and structure of poly(L‐lactide)

The effects of storage at 25°C in swelling solvents having different solubility parameter (δ_s) values of 16.8–26.0 J^0.5 cm^−1.5 on the physical properties and structure of as‐cast poly(L ‐lactide) (PLLA) films was investigated by the degree of swelling (DS), differential scanning calorimetry (DSC), and tensile tests. It was found that PLLA film shows durabity to swelling solvents having δ_s values much lower or higher than the value range of 19–20.5 J^0.5 cm^−1.5 and that the polymer solubility parameter (δ_p) for PLLA is in the value range of 19–20.5 J^0.5 cm^−1.5. The decrease in the glass transition temperature (T_g) and tensile properties and the increase in melting temperature (T_m) and crystallinity (x_c) were larger for PLLA films swollen in solvents having a high DS at 7 days (DS_7days). The slight increase in T_m and x_c for PLLA films after swelling in solvents with high DS_7days values was due to the crystallization of PLLA that occurred during swelling, while the small increase in T_g and elongation at break (ε_B) for PLLA films after immersion in the solvents having low DS_7days values was ascribed to stabilized chain packing in the amorphous region. The T_g, ε_B, and Young's modulus of the PLLA films after swelling in the solvents varied in the ranges of 47–57°C, 4–8%, and 55–77 kg/mm², depending on their DS_7days or δ_s values. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1582–1589, 2001     

Fat Utilization in Healthy Subjects Consuming Diacylglycerol Oil Diet: Dietary and Whole Body Fat Oxidation

Several studies in animals and humans have reported beneficial effects of diacylglycerol (DAG) on lipid and energy metabolism. We assessed the effect of DAG versus triacylglycerol (TAG) treatment on total energy expenditure (TEE), total fat oxidation (Fox) and respiratory quotient (RQ), and measured the oxidation rate of each oil using a respiratory chamber and the 13C-stable isotope. Eleven healthy subjects participated in a double-blind, randomized crossover study. Subjects consumed an energy maintenance diet consisting of 55% of total calories from carbohydrate, 15% from protein and 30% from fat during both the 3-day pre-chamber and 36-h chamber period. Fifty percent of the fat was test oil, containing either DAG oil or TAG oil. The oxidation rate of ingested test oils was determined by monitoring 13CO2 excretion in the breath from 13C-labeled diolein or 13C-labeled triolein. There were no significant differences in TEE, RQ and total Fox between the DAG and TAG treatment in the overall analysis. In the subgroup analysis, DAG treatment decreased RQ significantly in subjects with a high fat ratio (HFR) compared to TAG treatment. In addition, ingested diolein oxidation in DAG treatment was significantly faster than triolein oxidation in TAG treatment in the HFR group. Enhanced fat utilization with DAG treatment and rapid oxidation of ingested DAG may, at least in part, explain the greater loss of body weight and body fat related to DAG consumption found in the weight-loss studies.     

Highly accelerated stereocomplex crystallization by blending star-shaped 4-armed stereo diblock poly(lactide)s with poly(d-lactide) and poly(l-lactide) cores

Star-shaped 4-armed stereo diblock poly(lactide)s with the core/shell types of poly(d-lactide) (PDLA)/poly(l-lactide) (PLLA) and PLLA/PDLA (abbreviated as 4-DL and 4-LD, respectively) and the number-average molecular weights of about 1 × 10⁴ g mol⁻¹ were synthesized and the crystallization behavior of neat 4-DL, 4-LD, and their 50/50 blend (abbreviated as 4-DL/4-LD blend) was investigated. Solely stereocomplex (SC) crystallites as crystalline species were formed in the neat 4-DL, 4-LD, and 4-DL/4-LD blend, irrespective of crystallization temperature (100–160 °C). The overall SC crystallization of 4-DL/4-LD blend was highly accelerated compared with that of neat 4-DL and 4-LD, due to the largely elevated spherulite nuclei number per unit mass in the blend. Such high density of nuclei formation in 4-DL/4-LD blend is attributable to the facile intermolecular interaction and subsequent SC nucleation between the PLLA shell of 4-DL and the PDLA shell of 4-LD. The blending method reported in the present study is applicable for various core/shell types of star-shaped stereo diblock stereocomplexationable polymers to accelerate overall SC crystallization and can counterbalance the lowered crystallization rate caused by the star-shaped architecture. Despite the highly accelerated overall SC crystallization of 4-DL/4-LD blend by blending 4-DL and 4-LD, the spherulite growth rate, induction period for spherulite growth, final crystallinity, crystalline species, growth morphology, and crystallization mechanism were not altered by blending 4-DL and 4-LD.     

Effect of diluent on poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membrane formation via thermally induced phase separation

Poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membranes with a 44 mol % ethylene content were prepared by thermally induced phase separation. A mixture of 1,3‐propanediol and glycerol was used as the diluent. The effects of the ratio of 1,3‐propanediol to glycerol in the diluent mixture on the phase diagram, membrane structure, and membrane performance were investigated. As the ratio increased, the cloud point shifted to lower temperatures, and the membrane structure changed from a cellular structure due to liquid–liquid phase separation to a particulate structure due to polymer crystallization. Better pore connectivity was obtained in the hollow‐fiber membrane when the ratio of 1,3‐propanediol to glycerol was 50:50, and the membrane showed about 100 times higher water permeability than the membrane prepared with pure glycerol. For the prepared hollow‐fiber membrane, the solute 20 nm in diameter was almost rejected. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 219–225, 2005     

Blends of aliphatic polyesters. I. Physical properties and morphologies of solution-cast blends from poly(DL-lactide) and poly(ε-caprolactone)

Effects of the mixing ratio of poly(DL-lactide) (PDLLA) and poly (ε-caprolactone) (PCL) on the thermal and mechanical properties and morphologies of the solution-cast blends were investigated by differential scanning calorimetry (DSC), polarizing microscopy, tensile tests, and dynamic mechanical analysis. The presence of amorphous PDLLA did not disturb crystallization of PCL over the PDLLA content [X_PDLLA = PDLLA/(PCL + PDLLA)] from 0.1 to 0.9 and allowed PCL to form spherulites over X_PDLLA ranging from 0.1 to 0.6. The spherulite radius was larger for the blends than for the nonblended PCL. Phase separation occurred for the blends with X_PDLLA between 0.1 and 0.9 T^m of PCL remained unchanged in the X_PDLLA range up to 0.6 but decreased at X_PDLLA above 0.6, whereas the crystallinity of PCL was constant around 60%, irrespective of X_PDLLA. The tensile strength (σ_B, the yield stress (σ_Y), the Young's modulus(E), and the storage modulus (G′) of the blends increased monotonously with X_PDLLA if σ_B at X_PDLLA = 0 and 0.6 and σ_Y at X_PDLLA = 0.6 were excluded. Elongation-at-break (ε_B) of PDLLA increased dramatically, while ε_B of PCL decreased remarkably when a small amount of the other component was added. Equations and parameters predicting σ_Y, E, and G′ of the PCL-PDLLA blends were proposed as a function of X_PDLLA. © 1996 John Wiley & Sons, Inc.     

Spiral Removal of Exceptional Patients for Mining Chronic Hepatitis Data

In this paper, we propose a method which removes exceptional patients in a spiral manner for obtaining a definition of a disease in the form of a table of conditional probabilities and we describe its application to chronic hepatitis data. The removal is based on a risk-ratio-based criterion and can be supported by our previously developed data mining methods and medical experts. A series of experiments in which two domain experts decided exceptional patients to be removed show that our proposed method is effective and promising from various viewpoints such as obtaining new hypotheses and improving skills of domain experts. Another series of experiments in which exceptional patients were removed automatically led us to a rediscovery of a piece of knowledge, which had been reported in an article of a medical journal as the main result of the article.     

Continuous fine particle classification by water elutriator with applied electro-potential

In order to classify fine particles in slurry continuously, a horizontal type water elutriator with electrical potential is newly developed. The experimental classification performance was compared with the numerical calculation. Test particles used were pure silica particles with the mass median diameters of 3.5 and 2.5 μm.The effects of inlet flow rate, slurry concentration, applied electro-potential and the shape of inlet on the classification performance were also studied. The classification accuracy increased by applying the electro-potential and the cut size decreased with an increase in the electro-potential. The classification performance with a three-layer inlet was higher than that with a two-layer inlet.The experimental data agreed well with the numerical calculation. It is further shown that the 50% cut size was about 1 μm for a relatively short time, and the newly developed water elutriator is, therefore, effective for the classification of fine particles in slurries.