Effect of nucleation and plasticization on the stereocomplex formation between enantiomeric poly(lactic acid)s

The effect of nucleation and plasticization on the stereocomplex formation between poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was investigated in blends where PDLA is added as a minor phase in a major phase of PLLA. The use of small amounts of PDLA is aimed at creating a high melting point stereocomplex phase that in turn can serve as nucleating agent for the major phase of PLLA. Blends containing 5% PDLA with talc or organic phosphonate as nucleants and polyethylene glycol as plasticizer were prepared via melt-blending. Their crystallization behavior was investigated through Differential Scanning Calorimetry (DSC) using various thermal histories. Two peculiar stereocomplex melting endotherms were found. The peak temperature and enthalpy of these two endotherms were correlated to prior isothermal crystallization temperature. The different endotherms were also associated with two different crystalline morphologies observed by optical microscopy and referred to as Network and Spherulitic morphologies. The influence of plasticization and of heterogeneous nucleation on these morphologies was investigated through optical microscopy and calorimetric observations.     

Spontaneous formation of polylactide stereocomplex microspheres containing metal ions

Linear poly(l ‐lactides) (PLLAs ) and poly(d ‐lactides) (PDLAs ) with M _n in the range 2000 ? 4300 containing a different number and placement of carboxyl groups were obtained via cationic ring‐opening polymerization and post‐polymerization functionalization. PLA stereoisomers (PLLA ‐(COOH )_x and PDLA ‐(COOH )_x , where x = 1 ? 3) were used for the investigation of stereocomplexation in solution performed in the presence of metal cations such as Ca²⁺, Mg²⁺, Zn²⁺, Fe³⁺. Spherical microparticles with a diameter in the range 0.7 ? 3.0 µm were obtained in all cases which was confirmed on the basis of scanning electron microscopy (SEM ) analysis. The microsphere size and homogeneity were analyzed depending on the stereocomplexation conditions and the molecular weight as well as the number of carboxyl end groups in the PLLA and PDLA used for stereocomplexation. The PLA microspheres obtained were analyzed by Fourier transform IR spectroscopy, wide angle X‐ray spectroscopy and energy‐dispersive X‐ray spectroscopy methods which confirmed the presence of metal cations inside. The application of regular microspheres with metal ions as drug delivery systems is considered. © 2016 Society of Chemical Industry     

Rapid stereocomplex formation of polylactide using supercritical fluid technology

It is generally believed that stereocomplex polylactide is a prospect for rigorous application in the future due to enhancement of the physical properties of its homopolymers. There have been many studies about the formation and characterization of this stereocomplex. However, we are the first to report that supercritical fluid technology can yield a high‐degree stereocomplex polylactide (ca 98%) in a relatively short time (1 min). “This method generated a dry product and feasible for polylactide with weight‐average molecular weight (Mw) up to 70 000–160 000 g mol^?1 or higher by modifying the material feed of the homopolymer.” The “feasible” term is used to explained that our system is suitable for stereocomplexation of the polylactide material with molecular weight 70 000–160 000 or above. We also discovered that modification of the material feed did not affect the properties of the stereocomplex polylactide generated. The process and outcome of this research indicate that supercritical fluid technology is suitable for a continuous stereocomplex polylactide formation process. Copyright © 2012 Society of Chemical Industry     

Porous bead polyaromatic copolymers containing ester groups. II. The influence of the preparation conditions on surface properties of copolymers

Porous bead copolymers of styrene with 4,4′-di(methacryloyloxymethyl)diphenylmethane (DMD) have been prepared. Preparation conditions (composition of the monomer mixture with an inert component) were discussed with respect to the porous properties of copolymers (the specific surface area, pore size distribution and mean pore radius).     

The activity and properties of a hepatic acid cholesteryl ester hydrolase obtained from rats of different age groups

The activity of lysosomal acid cholesteryl ester hydrolase (acid CEH, EC 3.1.1.13) in rat liver was determined at 3, 5, 7, 10 and 20 wk following birth. The levels of acid CEH activity showed a marked decrease as rats grew older, whereas those of other lysosomal marker enzymes, such as acid phosphatase, β-glucuronidase and cathepsin B and D, showed only a slight decrease. On the other hand, acid CEH activity was detected in all subcellular fractions obtained from rat liver, but the enzyme activity in these fractions did not show the age-related decrease observed in the lysosomal fraction. The results presented here suggest that the marked alteration of lysosomal acid CEH activity that accompanies aging may be related to its possible involvement in the regulation of cholesterol concentration in rat liver.     

涂料用丙烯酸酯乳液聚合影响因素研究

本文对涂料用丙烯酸酯乳液聚合反应的影响因素进行研究,证明当十二烷基苯硫酸钠(SDS)与OP-10的比例为1∶3时,乳液的稳定性好;当乳化剂用量为4%时乳液机械稳定性和稀释稳定性都能达到要求;适当提高预乳化体系的温度(大于45℃),可以在相对短的预乳化时间内得到稳定的预乳化液。加料时间大于45m in可以得到稳定的预乳化液。搅拌速度过快或过慢都对预乳化液稳定性不利。聚合反应中随着活性交联单体丙烯酰胺加入量的增加,涂膜吸水率先下降然后又增加,丙烯酰胺含量为2%时,涂膜吸水率最低。     

The formation of cysteine-S-sulphonate groups in wool and the effect on shrink-resistance

The different stages of wool oxidation during the Dylan XCP permonosulphuric acid based shrinkproofing process have been followed using second-order derivative Fourier transform infrared analysis. After oxidising wool with Caro's salt, some of the cystine residues present were oxidised to cysteic acid, but cystine-S-monoxide and cystine-S-dioxide concentrations remained the same. After treating the oxidised wool with bisulphite, cysteine-S-sulphonate groups were formed and the fibre acquired significant shrink-resistance to washing. The effect on shrink-resistance of reducing the concentration of cysteine-S-sulphonate groups was determined. It was found that when these residues were reconverted to disulphide bonds the shrink-resist effect was lost.     

The influence of amino acids on the formation of nanocrystalline hydroxyapatite

The influence of amino acids on the formation of particles of synthetic analogs of hydroxyapatites of renal calculi with different degrees of nonstoichiometry is investigated. It is demonstrated that the electrokinetic properties (the charge and the potential) and the dispersion composition of the synthesized hydroxyapatite sols depend on the Ca/P atomic ratio. The results obtained allow the assumption that, under the normal physiological conditions, free amino acids are natural inhibitors for the formation of renal calculi in the human organism.     

The influence of air-gap conditions on the structure formation of lyocell fibers

The influence of an air gap on the formation of a filament spun from a solution of cellulose in N-methylmorpholine N-oxide was studied. A number of parameters were investigated, principally, air-gap length, temperature, and humidity and the water content in the polymer solution. Their effect on the draw-down profile and orientation of the filament in the air gap was determined and compared to the structure and properties of the resulting fibers. It is shown that all these parameters have a strong influence on the structure formation process. Depending on the combination of parameters used, the phenomenon of draw resonance may or may not be observed. The results indicate that the cooling of the filament is driven by two simultaneous processes. Modifying the parameters studied also causes significant changes to the resulting fiber properties, but the fiber structures, measured by birefringence and wide-angle X-ray diffraction, appear almost identical. © 1996 John Wiley & Sons, Inc.     

The influence of fuel additives on the formation of carbon during combustion

We show that the fuel additive ferrocene leads to the formation of condensation nuclei in the combustion zone prior to the formation of carbonaceous particles. The condensation nuclei most likely are iron oxides. The carbonaceous matter preferentially condenses at the surface of the iron oxide nuclei where it is burnt in the last stage of the combustion. Similar results are obtained if palladium aerosol instead of ferrocene vapor is added to the fuel. Under the ideal conditions of a laminar acetylene flame diluted with argon and seeded with ferrocene almost complete burnout of the carbonaceous matter is achieved. In turbo-charged heavy duty diesel construction engines, the same basic phenomena are observed, yet the burnout is far from complete.     

The influence of different irradiation sources on the treatment of nitrobenzene

This work describes the influence of light on the treatment of nitrobenzene (NB) in aqueous solutions. Three different experimental devices were used to perform a detailed study: a photoreactor with four low-pressure mercury lamps (λ=253.7 nm), a tubular photoreactor with a polychromatic Xe lamp (290<λ<1200 nm), and finally a solar reactor (sunlight). TOC analyses were performed in order to monitor and compare the extent of these processes, each of them being performed with one of the three different sources of light. The influence of Fe(II), Fe(III), H₂O₂, and light on the mineralization of NB in aqueous solutions was also studied. The successful use of sunlight as a source of energy and its effectiveness regarding Fenton processes as well as direct photolysis in the treatment of NB are presented.     

Statistics of the formation of ester on syndiotactic methacrylic anhydride-methacrylic acid copolymers

Summary The mode of ring opening during methanolysis of syndiotactic methacrylic anhydride-methacrylic acid copolymers has been studied by statistical calculation, Monte Carlo Simulation,and H-NMR. Significant deviations from random ring opening are found, indicating that the nature of the monomer unit adjacent to the anhydride ring may exert an influence.     

不同助磨剂对矿渣硅酸盐水泥的性能影响

本文通过调整不同助磨剂[三乙醇胺与柠檬酸中和物（TC）、二乙醇单异丙醇胺（DEIPA）和聚羧酸超塑化剂（PC）]的掺量（0.01%、0.02%和0.03%）,系统研究了其对矿渣硅酸盐水泥的粉磨性能（粒径分布、筛余量和比表面积）、工作性能（凝结时间和需水量）和强度的影响。研究发现,在矿渣硅酸盐水泥中,各助磨剂的粉磨性能大小为DEIPA＞TC＞PC;提高需水量能力大小为DEIPA＞TC＞PC,其中PC能有效降低需水量;DEIPA和TC对3 d和28 d强度均具有较好的提高作用。通过调整三类助磨剂的比例,必定能使助磨剂兼顾粉磨效率高、降低需水量和提高早期后期强度等效果。     

Lyotropic liquid crystalline phase of polyesteramides with different ratio of amide to ester groups in a main chain

Summary Various lyotropic liquid crystalline polyesteramides were prepared from 1,3-bis(4-aminobenzoyloxy)benzene, p-phenylene diamine, and terephthalic acid by changing the ratio of amide to ester groups and were observed by using a cross polarized light microscope. The range of liquid crystalline phase becomes wider with increasing the portion of amide groups in a main chain because the chain rigidity becomes higher and the polymer-solvent interaction stronger. In the case of polyesteramides with flexible spacers, the polymer with one p-phenylene group between two ester groups does not form an anisotropic phase but the polymer with the same group between amide groups shows an anisotropy.     

The influence of formation conditions on the growth and morphology of carbon trees

Carbon trees, quite different from those previously reported, have been produced by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor. The influences of formation conditions such as catalyst mass, toluene flow rate, and reaction time on the tree growth and morphology have been investigated. The yield of carbon trees is greatly affected by catalyst quantity. A lower toluene flow rate (50-100 ml/min) or shorter reaction time (10-30 min) leads to trees with thinner (several microns) and filamentous branches, while a higher toluene flow rate (greater than 200 ml/min) or longer reaction time (60-120 min) produces thicker (tens of microns) and spherical branches. Results suggest that the morphology of the carbon trees can be adjusted by varying the reaction conditions.     

The influence of different chelators on the solubilization/liquefaction of different pretreated and natural lignites

The question was investigated, whether chelators alone can solubilize different lignites. For that purpose the influence of eight chelators were tested on different pretreated or natural lignites. The effects of the pretreatment and of the concentration of chelators were studied. The results show that different chelators have different influence on different lignites. Oxidative pretreatment enhances the solubilization. At low chelator concentrations only leonardite is solubilized to remarkable degree.

Ammonium oxalate is one of the most effective agents. The results confirm that chelators alone are not able to solubilize lignites with a very low ash or oxygen content.     

The effect of the distance between neighboring vinyl groups on template polymerization

Intra-molecular polymerization of methacrylate type multi-vinyl monomer of Noria (Noria-MVM) was investigated from the viewpoint of the structure of Noria-MVM. Noria-MVM was polymerized by atom transfer radical polymerization (ATRP) with different reaction time, temperature, and monomer concentration. Polymerized sequences were derived from polymerized Noria-MVM by hydrolysis and methylation. The degree of polymerization (DP) of polymerized sequence was determined by matrix-assisted laser desorption/ionization time-of-flight mass (MALDI-TOF mass) analyses. The DP values were odd value in a range of 3-23. The distance from radical to the next vinyl group was influenced by the structure of Noria. When the distance was shorter than 5 Å, the polymerization did not terminate. When the distance was longer than 5 Å, the termination tended to occur.     

聚酯二元醇侧基与酯基含量对水性聚氨酯胶粘剂性能的影响

以甲苯二异氰酸酯(TDI),二羟甲基丙酸(DMPA),一缩二乙二醇(DEG)为主要原料,改变聚酯二元醇的结构,合成了不同酯基和侧基含量的稳定水性聚氨酯胶粘剂;傅里叶红外测试表征了聚氨酯结构,并对聚氨酯胶膜进行了拉伸测试、耐水性测试和T型剥离测试,结果表明在聚氨酯结构中酯基含量增加有利于力学强度的提升,而侧基含量增加降低了胶膜的力学性能;酯基含量相差不大的情况下,侧基含量越多,其耐水性能越好;酯基,侧基含量越高,粘接强度越大。