去氢枞酸类成核剂改性聚丙烯的非等温结晶动力学研究

对以去氢枞酸盐为成核剂的聚丙烯非等温结晶动力学进行了研究，用修正Avrami方程的Jexiorny法和莫志深法进行处理。结果表明：修正Avrami方程的Jeziorny方法和莫志深法都适用于去氢枞酸类成核剂改性的聚丙烯的非等温结晶动力学。在同样的降温速率下纯聚丙烯的t1/2比成核聚丙烯的t1／2要长，当降温速率为20K/min时，纯聚丙烯和成核聚丙烯的t1/2分别为0．78min和0．51min。同时从莫志深法得到的F(T)结果可以看出，达到相同的结晶度时纯聚丙烯所需的降温速率要大于成核聚丙烯所需的降温速率，说明成核剂的加入提高了聚丙烯的结晶速率。从Jeziorny法求出的纯聚丙烯和成核聚丙烯的Avrami指数分别为4．46和2．77，表明成核剂改变了聚丙烯的结晶成核和生长方式。     

丙烯酸及其接枝物对纳米CaCO3/PP结晶与熔融行为的影响

制备了丙烯酸(AA)及其接枝聚丙烯(PP—g-AA)改性的纳米CaC03／PP复合材料。用DSC研究了纳米CaCO3对PP、PP-g-A和AA对纳米CaCO3／PP中PP结晶与熔融行为的影响。结果表明：随纳米CaCO3用量增加，PP结晶与熔融温度提高，PP—g—AA加入使PP结晶温度进一步提高，PP的结晶温度也随从用量增加而提高；在过氧化二异丙苯(DCP)存在下，少量AA能明显提高PP的结晶温度，但增加从用量对结晶温度的影响较小；WAXD证实纳米CaCO3／PP复合材料中存在β晶。     

尼龙11在高压下的结晶研究

用ＤＳＣ、ＷＡＸＤ、ＩＲ等对在０．１ＭＰａ－０．６５ＧＰａ压力下尼龙１１（ＰＡ１１）的结晶样品进行了研究。分析了压力对ＰＡ１１结晶的影响。研究了加入１％液晶聚合物对ＰＡ１１的结晶的诱导作用。结果表明：压力有助于ＰＡ１１晶形的完善，液晶聚合物对ＰＡ１１的结晶有明显的诱导作用，使ＰＡ１１在较低的压力（０．１ＧＰａ）和较短的时间（１５ｍｉｎ）内即可得到较为完整的结晶。     

Predictions of Onset of Crystallization from Experimental Relaxation Times I-Correlation of Molecular Mobility from Temperatures Above the Glass Transition to Temperatures Below the Glass Transition

Purpose Predicting onsets of crystallization at temperatures below T _g, from data above T _g, would require that the correlation between crystallization onset and mobility is same above and below T _g, and the techniques being used to measure mobility above and below T _g are measuring essentially the same kind of mobility. The aim of this work is to determine if the relaxation times obtained using different techniques (DSC, TAM) below T _g correlate with relaxation time obtained above T _g using dielectric spectroscopy.Methods Model compounds for this work were chosen based on their varied ΔH _f, ΔC _p(T _g) and H-bonding in crystalline state vs. amorphous state. Relaxation times above T _g were determined by the simultaneous fit of real and imaginary permittivity to the Cole-Davidson model. Tau and beta below T _g were determined using isothermal microcalorimetry (TAM) or MDSC. MDSC was used to calculate Kauzmann temperature and strength of the glass using established relationships.Results Indomethacin, nifedipine and flopropione showed Arrhenius temperature dependence throughout the entire temperature range and extrapolation of τ ^β measured above T _g by dielectric relaxation agreed with τ ^β measured below T _g by TAM/MDSC. Ketoconazole, however, showed the expected VTF behavior. For at least two compounds compared (indomethacin and ketoconazole), relaxation times measured by TAM and MDSC did not agree, with TAM giving significantly lower values of τ ^β , but TAM and MDSC relaxation times appeared to extrapolate to a common value at T _g.Conclusions It was found that, for all cases studied, relaxation time constants determined above and below T _g did appear to extrapolate to the same value around T _g indicating that molecular mobility measured above and below T _g using different techniques is highly correlated.     

Solute Crystallization in Frozen Systems–Use of Synchrotron Radiation to Improve Sensitivity

Purpose

To demonstrate the sensitivity of low temperature synchrotron X-ray diffractometry (SXRD) for detecting solute crystallization in frozen sodium phosphate buffer solutions. To determine the effect of annealing on solute crystallization in frozen solutions.

Materials and Methods

Sodium phosphate buffer solutions, at initial buffer concentrations ranging from 1 to 100 mM (pH 7.4) were cooled to ?50°C. The crystallization of disodium hydrogen phosphate dodecahydrate (Na₂HPO₄ ?12H₂O) was monitored using a laboratory as well as a synchrotron source. At selected concentrations, the effect of annealing (at ?20°C) was investigated.

Results

With the laboratory source, solute crystallization, based on the appearance of one diagnostic peak with a d-spacing of 5.4 Å, was evident only when the initial buffer concentration was at least 50 mM. In contrast, using SXRD, crystallization was detected at initial buffer concentrations down to 1 mM. In addition, the use of a high-resolution 2D detector enabled the visualization of numerous diffraction rings of the crystalline solute. At both 10 and 100 mM buffer concentration, there was no increase in solute crystallization due to annealing.

Conclusion

By using synchrotron radiation, solute crystallization was detected with substantially increased sensitivity, making the technique useful for freeze-drying cycles of practical and commercial importance. Since numerous peaks of the crystalline solute appeared, the technique has potential utility in complex, multi-component systems.     

Cocrystal Formation during Cogrinding and Storage is Mediated by Amorphous Phase

Purpose The purpose of this work was to investigate the mechanisms of cocrystal formation during cogrinding and storage of solid reactants, and to establish the effects of water by cogrinding with hydrated form of reactants and varying RH conditions during storage.Methods The hydrogen bonded 1:1 carbamazepine–saccharin cocrystal (CBZ–SAC) was used as a model compound. Cogrinding of solid reactants was studied under ambient and cryogenic conditions. The anhydrous, CBZ (III), and dihydrate forms of CBZ were studied. Coground samples were stored at room temperature at 0% and 75% RH. Samples were analyzed by XRPD, FTIR and DSC.Results Cocrystals prepared by cogrinding and during storage were similar to those prepared by solvent methods. The rate of cocrystallization was increased by cogrinding the hydrated form of CBZ and by increasing RH during storage. Cryogenic cogrinding led to higher levels of amorphization than room temperature cogrinding. The amorphous phase exhibited a T _g around 41°C and transformed to cocrystal during storage.Conclusions Amorphous phases generated by pharmaceutical processes lead to cocrystal formation under conditions where there is increased molecular mobility and complementarity. Water, a potent plasticizer, enhances the rate of cocrystallization. This has powerful implications to control process induced transformations.     

Phase Behavior of Amorphous Molecular Dispersions II: Role of Hydrogen Bonding in Solid Solubility and Phase Separation Kinetics

No HeadingPurpose. To determine the factors influencing solid solubility and phase separation kinetics of drugs from amorphous solid dispersions.Methods. Solid dispersions of griseofulvin-poly(vinyl pyrrolidone) (PVP) and indoprofen-PVP were prepared using solvent evaporation technique. Dispersions demonstrating single T_g were exposed to 40°C/69% RH for 90 days. Drug solid solubility in the polymer and phase separation rates were determined from changes in T_g of solid dispersions. FTIR spectroscopy and XRD were used to characterize drug-polymer interactions and drug crystallinity, respectively.Results. Freshly prepared solid dispersion of up to 30% w/w griseofulvin and indoprofen were molecularly miscible with PVP. Hydrogen bonding was evident in indoprofen-PVP, but not in griseofulvin-PVP dispersions. When exposed to 40°C/69% RH, griseofulvin phase separated completely, whereas the solid solubility of indoprofen was determined as 13% w/w. The first-order rate constants of phase separation for 10%. 20%, and 30% w/w griseofulvin dispersions were estimated as 4.66, 5.19, and 12.50 (×10²) [day^–1], and those of 20% and 30% w/w indoprofen were 0.62 and 1.25 (×10²) [day^–1], respectively.Conclusions. Solid solubility of griseofulvin and indoprofen in PVP is 0% w/w and 13% w/w, respectively. Drug-polymer hydrogen bonding in indoprofen-PVP dispersions favors solid solubility. Phase separation rate of drug from the solid dispersions depends on the initial drug content and the nature of drug-polymer interactions.     

Comparison of Classic Sweat Test and Crystallization Test in Diagnosis of Cystic Fibrosis

Objective

Sweat chloride measurement is considered a standard diagnostic tool for cystic fibrosis (CF). This study was performed to compare sweat chloride values obtained by quantitative pilocarpine iontophoresis (classic test) with sweat crystallization detected by direct observation of a drop of perspiration under light microscopy in patients with and without CF.

Methods

The tests using both techniques were performed simultaneously in patients with and without CF. Cutoff values of ≥60 mmol/L of chloride concentration for the classic sweat test was considered for diagnosis of CF. In crystallization method, observation of typical dendritic forms of salt crystals under light microscopy was interpreted positive.

Findings

Sixty patients suspected to CF (31 males and 29 females) with age range of 9 months to 2 years underwent the sweat test using both techniques. Median sweat chloride values was 26.13+10.85 in group with negative and 72.76+12.78 mmol/L in group with positive sweat test, respectively. All the patients who had positive sweat test in classic method showed typical dendritic forms of salt crystal in sweat crystallization test, which provided the test with 100% sensitivity (95%CI: 93.1–100). Only one of the 31 subjects with negative results for classic sweat test had positive result for crystallization sweat test, which provided the test with 96.7% specificity (95%CI: 92.9–100). Time spent to perform the crystallization test was significantly shorter than the classic method whereas its cost was also lower than the second method.

Conclusion

There was a good correspondence between two studied methods of sweat test. These results suggested the sweat crystallization test as an alternative test for detecting CF disease with high sensitivity and specificity.     

Correlation Between Crystallinity and Solar‐Cell Efficiency of the Low‐Bandgap Polymer PDDTP

Polymer/fullerene bulk heterojunction solar cells consisting of PDDTP:PCBM blends have been investigated and optimized. The structural properties of the photoactive layers were studied by GID‐XRD, which revealed a pronounced response of photovoltaic parameters on the polymer crystallinity. In addition to P3HT, another donor polymer was found that develops crystalline domains upon annealing. We found a clear correlation between annealing time, power conversion efficiency, and polymer crystallinity. The PDDTP crystallization ability is a promising property. This is a first step toward the synthesis of low‐bandgap polymers, which likewise show the ability to form crystalline domains and may therefore lead to a substantial increase in efficiency.

     

Normative data on the Bonn Risk Index for calcium oxalate crystallization in healthy children

Bonn Risk Index (BRI) is being used for the assessment of urinary calcium oxalate (CaOx) crystallization. There are no published data regarding BRI during growth. The objective of this study was to establish age- and sex-dependent BRI values in healthy children and adolescents. A total of 1,050 Caucasian subjects aged 3–18 years (525 males, 525 females) without a history of kidney stone disease were enrolled in the cross-sectional study. The study group was divided into 15 ranges according to age, each comprising 70 subjects. Urinary ionized calcium [Ca²⁺] was measured using a selective electrode while the onset of spontaneous crystallization was determined using a photometer and titrating with 40 mmol/L ammonium oxalate (Ox²⁻). The calculation of BRI value was based on the ratio of [Ca²⁺] to the required amount of ammonium oxalate added to 200 ml of urine to induce crystallization. The median BRI was 0.26 1/L and the values of the 5th and 95th percentiles were 0.06 1/L and 1.93 1/L, respectively. BRI correlated positively with body-area-related BRI (1/L × 1.73 m²) (R = 0.18; P < 0.05), whereas a negative correlation was found between BRI and body weight (1/L × kg) (R = −0.85; P < 0.05). Neither sex nor age differences were detected in BRI across studied children and adolescents. The values of Bonn Risk Index were constant during growth and there was a limited influence of age and sex on BRI in children over 3 years of age. The BRI may be valuable in the evaluation of pediatric patients at risk for kidney stones, particularly if the BRI from stone formers is demonstrated to be higher than in normal children.