Kiyoshi Suzuki

Kinetics of microemulsion polymerization of styrene

Abstract The effect of pH on polymerization rate is studied. The rate of polymerization was found to be unaffected by pH. A kinetic model for the polymerization of styrene in O/W microemulsion, which has previously been proposed by the present authors, was extended to predict the particle size distribution (PSD) of the polymer particles produced. The proposed kinetic model is also extended so as to be applicable to a system containing chain transfer agent. The predicted PSD was found to agree fairly well with the measured value, which demonstrates the importance of radical desorption from polymer particles in determination of particle size.

Circulating Levels of Tartrate-Resistant Acid Phosphatase in Rat Models of Non-Insulin-Dependent Diabetes Mellitus

In order to investigate the pathogenic role of bone resorption by osteoclasts in altered bone metabolism in non-insulin-dependent diabetes mellitus (NIDDM), the circulating levels of tartrate resistant acid phosphatase (TRACP) were simultaneously determined with osteocalcin, in rat models of NIDDM, i.e., genetic Wistar fatty rats and neonatally streptozotocin-induced diabetic rats (NSZ rats). In Wistar fatty rats exhibiting hyperglycemia and hyperinsulinemia, plasma TRACP was 40.0+/-0.4 U/l (mean+/-SE), significantly higher than that of 32.8+/-1.3 U/l in their lean littermates (p < 0.01). Bone length, bone strength, and weight of powdered bone in Wistar fatty rats were significantly decreased compared to control rats (p < 0.02-0.001). On the other hand, plasma TRACP in NSZ rats was 13.6+/-1.0 U/l, significantly lower than that of 31.4+/-1.2 U/l in their controls (p < 0.01). In addition, there were positive correlations between circulating TRACP and insulin levels in both NIDDM rat models (p < 0.05-0.01). Furthermore, plasma osteocalcin levels in these NIDDM models were significantly decreased than those of their corresponding controls (p < 0.001). Consequently, in Wistar fatty rats with hyperinsulinemia, it is suggested that the bone formation by osteoblasts was decreased, while the bone resorption by osteoclasts was increased. In contrast, in NSZ rats with hypoinsulinemia, both of bone formation and resorption were speculated to be decreased, indicating the decreased bone turnover. These results suggest that, although the deterioration in the osteoblastic function can be commonly observed in NIDDM animal models, the osteoclastic function is heterogeneous under NIDDM conditions.

An experimental study on the kinetics and mechanisms of styrene polymerization in oil‐in‐water microemulsion initiated by oil‐soluble initiators

In order to clarify the kinetic role of oil-soluble initiators in microemulsion polymerization, the oil-in-water (O/W) microemulsion polymerizations of styrene are carried out using four kinds of azo-type oil-soluble initiators with widely different water-solubility. The results are compared with those observed when a water-soluble initiator, potassium persulfate (KPS) is used. For all the oil-soluble initiators used, the molecular weight of polymers and the average size of polymer particles do not change with the monomer conversion and the initial initiator concentration. The monomer conversion is expressed as a function of ri0.5t, where ri is the rate of radical generation in the whole reaction system and t is the reaction time. These characteristics are quite the same as those observed when KPS is used as an initiator. When the polymerizations are carried out with the rate of radical generation in the whole reaction system fixed at the same value, the rates of polymerization are almost the same for all the oil-soluble initiators employed, irrespective of their water-solubility, but are significantly lower (ca. 1/3) than that with KPS. Then, the following conclusions are given: (1) The radicals generated not only in the aqueous phase, but also in the micelle and polymer particle phase are almost equally effective for the polymerization. However, (2) only a small portion (ca. 1/9) of the radicals generated in both phases participate in the polymerization. (3) Bimolecular termination of a growing radical in the polymer particle with an entering radical and with a pair of radicals generated in the polymer particles is negligible, and hence, the molecular weight of polymers is determined only by chain transfer to monomer.

The Urinary Concentration of Sialic Acid is Increased in Non-insulin-dependent Diabetic Patients with Microangiopathy: a Possible Useful Marker for Diabetic Microangiopathy

In order to investigate the relationship between urinary excretion of sialic acid and the severity of diabetic microangiopathy, urinary levels of sialic acid were determined in patients with non‐insulin‐dependent diabetes mellitus. The urinary molar ratio of sialic acid to creatinine in the diabetic patients was significantly higher than in the healthy controls (p < 0.01). Moreover, the urinary ratio was found to be gradually increased with the degree of diabetic microangiopathy. Urine molar ratio of sialic acid to creatinine in patients with proliferative diabetic retinopathy was significantly higher than in patients without retinopathy (p < 0.01). Urinary excretion in patients with macroproteinuria was also significantly higher than in patients without nephropathy (p < 0.01). Since urinary levels of sialic acid are proportionally increased with the severity of diabetic microangiopathy, the measurement of urinary sialic acid could become a useful biochemical means to monitor the degree of diabetic microangiopathy.

Core-Shell Poly(Styrene/Sulfonated N-hydroxy Ethyl Aniline) Latex Particles Prepared by Chemical Oxidative Polymerization in Emulsion Polymerization

The kinetic behavior of emulsion polymerizations of styrene in the presence of sulfonated N-hydroxy ethyl aniline (SHEA) was investigated with two initiators: 2,2′-azobisisobutyronitrile (AIBN) and potassium persulfate (KPS). SHEA was synthesized using a stepwise polyurethane reaction method from 3-hydroxy-1-propane sulfonic acid sodium salt, isophorone diisocyanate (IPDI), andN-(2-hydroxyethyl) aniline. Stable core-shell poly(styrene/sulfonated N-hydroxy ethyl aniline, St/SHEA) latex particles were successfully prepared by using an appropriate amount of AIBN, in which SHEA plays the role of ‘surfmer’, i.e., acting as both a surfactant in the emulsion polymerization and a monomer in the chemical oxidative polymerization. The kinetic behavior was dissimilar to that of typical emulsion polymerization systems. A long inhibition period and low rate of polymerization were observed due to radical loss by the oxidative polymerization of SHEA. It was concluded, due to the low water-solubility of AIBN and retardation reaction by SHEA, that the initial loci of polymerization were monomer droplets. However, growing polymer particles as polymerization loci became predominant as polymerization proceeded. It was suggested that AIBN was more effective than KPS in the preparation of the core-shell type poly(St/SHEA) latex particles. With KPS, no substantial polymerization was observed in any of the samples.

Kinetics and mechanisms of o/w microemulsion polymerization of styrene

To clarify the kinetics and mechanisms of o/w microemulsion polymerization, the o/w microemulsion polymerizations of styrene were carried out with different kinds and types of initiators and surfactants. The number of polymer particles and the molecular weight of polymer formed were not affected by the kinds and types of initiators and surfactants. The rate of polymerization with different kinds of azo-type oil-soluble initiators with widely different water-solubility was almost the same, but was much lower than that with KPS. A kinetic model proposed by us could mostly explain the kinetic behavior except for the difference in the polymerization rate with KPS and that with oil-soluble initiators.

The association between impaired proinsulin processing and type 2 diabetes mellitus in non-obese Japanese individuals

We aimed to examine the association between impaired proinsulin processing in pancreatic beta cells and type 2 diabetes mellitus in non-obese Japanese patients. Participants were divided into groups for normal glucose tolerance, prediabetes, and type 2 diabetes based on the oral glucose tolerance test (OGTT). Activities of prohormone convertase (PC) 1/3 and PC2 in fasting states were estimated. Multiple regression analysis was undertaken to ascertain if alteration of the activities of these enzymes contributes to the development of impaired glucose tolerance by comparison with HOMA-β and the oral disposition index (DI(O)). Overall, 452 subjects were included. PC1/3 activity tended to decrease in type 2 diabetes compared with normal glucose tolerance. PC2 activity showed no difference among the three groups. Decreased estimated PC1/3 activity was significantly associated with type 2 diabetes after adjustment for sex, age, creatinine, triglycerides, HOMA-β and DI(O). Odds ratios (95% CI) of PC1/3, HOMA-β, and DI(O) were 2.16 (1.12-4.19), 3.44 (1.82-6.52) and 14.60 (7.87-27.11), respectively. Furthermore, decreased PC1/3(≤1.7) combined with decreased HOMA-β (≤30) had a sensitivity of 73% and specificity of 62%. Decreased PC1/3 activity may be a useful measurement of beta-cell function alongside decreased HOMA-β or DI(O). A combined decrease in estimated fasting PC1/3 activity and HOMA-β measurement led to suspicion of type 2 diabetes in the non-obese Japanese population studied.

Nucleation loci in the ring-opening polymerization of octamethyl- cyclo-tetrasiloxane in Winsor I system with dodecylbenzene sulfonic acid sodium salt and sulfuric acid

Abstract The ring-opening polymerization of octamethylcyclotetrasiloxane (OTS) was carried out in an Winsor I system with dodecylbenzene sulfonic acid, sodium salt (DBSNa) as emulsifier and sulfuric acid as initiator, to clarify the mechanism of the polymerization, especially focusing on the nucleation loci, the rate of generation of nonvolatile molecules and the average diameter of generated polymer droplets. In the system where DBSNa concentration is higher than the critical micellar concentration (CMC), nonvolatile molecules were generated in the aqueous phase and their generation rate became higher with an increase in DBSNa concentration, while nonvolatile molecules were not generated at emulsifier concentrations lower than the CMC. These experimental results support that nucleation did not take place in the true aqueous phase, but originated from the micelles.

Kinetic investigation of styrene emulsion polymerization with surface-active polyelectrolytes as emulsifier, 1 Kinetic study

Abstract A copolymer of methyl methacrylate and methacrylic acid to be used as a polymeric surfactant was synthesized by emulsifier-free semi-batch emulsion copolymerization. Emulsion polymerization of styrene was carried out at 50°C utilizing the ammonium salt of the copolymer as the polymeric emulsifier and potassium persulfate as the initiator, respectively. Both the number of polymer particles produced and the rate of polymerization were proportional to the 0.6 power of the initial emulsifier concentration, to the 0.4 power of the initial initiator concentration, and independent of the initial monomer concentration, respectively. These relationships are almost the same as those observed in the emulsion polymerization of styrene conducted using conventional surfactants like sodium dodecyl sulfate as the emulsifier and potassium persulfate as the initiator.

Kinetics and mechanism of miniemulsion polymerization of a sparingly water-soluble fluoro monomer

Abstract In order to clarify the kinetics and mechanism of miniemulsion polymerization of a sparingly water-soluble monomer, the miniemulsion polymerization of 1,1,2,2-tetrahydroperfluorodecyl acrylate was conducted at 50°C using potassium persulfate as initiator and sodium dodecyl sulfate as emulsifier, respectively. It was found that the rate of polymerization was proportional to the 0.65 power of the initial initiator concentration and to the 0.30 power of the number of miniemulsion droplets (latex particles). It is pointed out that the kinetics of this polymerization system may be subject to the modified case III kinetics of emulsion polymerization with predominant bimolecular termination in the aqueous phase.