Jarno Kansikas

Factors affecting crystallization and crystallization kinetics in amorphous corn starch

Abstract The levelling-off extent of crystallization and crystallization behaviour in corn starch were studied using an X-ray diffraction technique, taking into account the glass transition temperature range of amorphous corn starch. Amorphous corn starch samples at 60, 70, or 80% solids were stored at various temperatures giving various temperature differences between storage temperature and glass transition temperature ( T − T g ). Corn starch was observed to crystallize into the same crystal form, independent of water content and storage temperature and, therefore, of the T − T g . The Avrami equation was found to be useful in modelling of crystallization kinetics in starch. The data obtained can be used in prediction of stability during storage of starch-containing products with various water contents.

Crystallization and X-ray Diffraction of Crystals Formed in Water-Plasticized Amorphous Lactose

Effects of storage time and relative humidity on crystallization and crystal forms produced from amorphous lactose were investigated. Crystallization was observed from time‐dependent loss of sorbed water and increasing intensities of peaks in X‐ray diffraction patterns. The rate of crystallization increased with increasing storage relative humidity. Lactose crystallized mainly as α‐lactose monohydrate and anhydrous crystals with α‐ and β‐lactose in a molar ratio of 5:3. The results suggested that the crystal form was defined by the early nucleation process. The crystallization data are important in modeling of crystallization phenomena and prediction of stability of lactose‐containing food and pharmaceutical materials.

Investigations on the Humidity-Induced Transformations of Salbutamol Sulphate Particles Coated with l-Leucine

PurposeThe crystallization and structural integrity of micron-sized inhalable salbutamol sulphate particles coated with l-leucine by different methods are investigated at different humidities. The influence of the l-leucine coating on the crystallization of salbutamol sulphate beneath the coating layer is explored.MethodsThe coated particles are prepared by an aerosol flow reactor method, the formation of the l-leucine coating being controlled by the saturation conditions of the l-leucine. The coating is formed by solute diffusion within a droplet and/or by vapour deposition of l-leucine. The powders are humidified at 0%, 44%, 65% and 75% of relative humidity and the changes in physical properties of the powders are investigated with dynamic vapour sorption analysis (DVS), a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM).ResultsVisual observation show that all the coated particles preserve their structural integrity whereas uncoated salbutamol sulphate particles are unstable at 65% of relative humidity. The coating layer formed by diffusion performs best in terms of its physical stability against moisture and moisture-induced crystallization. The degree of crystallization of salbutamol in the as-prepared powders is within the range 24–35%. The maximum degree of crystallization after drying ranges from 55 to 73% when the salbutamol crystallizes with the aid of moisture. In addition to providing protection against moisture, the l-leucine coating also stabilizes the particle structure against heat at temperatures up to 250°C.ConclusionIn order to preserve good flowability together with good physical stability, the best coating would contain two l-leucine layers, the inner layer being formed by diffusion (physical stability) and the outer layer by vapour deposition (flowability).

Synthesis and characterisation of cyclopentadienyl complexes of barium: precursors for atomic layer deposition of BaTiO3.

Cyclopentadienyl complexes Ba(C5Me5)2(THF)2 (1), Ba(C5Me5)2(A) (A = THF, dien, trien, diglyme, triglyme) (2-5), Ba(Pr(i)3C5H2)2(THF)2 (6), Ba(Bu(t)3C5H2)2(THF) (7), Ba(Me2NC2H4C5Me4)2 (8) and Ba(EtOC2H4C5Me4)2 (9) were prepared and characterised with TGA/SDTA, NMR and MS. Crystal structures of 2, 4, 5, 7, 8 and 9 are presented. All complexes prepared sublime under reduced pressure and complexes 1, 6 and 7 showed volatility also under atmospheric pressure. Complexes 1, 6 and 7 lose the coordinated THF when evaporated while complexes 2-5 are sublimable as complete molecules under reduced pressure. Complexes with bulky cyclopentadienyl ligands (6 and 7) are the most thermally stable and volatile among the prepared barocenes. X-ray structure determinations reveal that all the complexes studied are monomeric. Complexes 1, 7 and 8 were successfully tested in BaTiO3 thin film depositions by atomic layer deposition (ALD).

Polymeric Drug Nanoparticles Prepared by an Aerosol Flow Reactor Method

AbstractPurpose. Our purpose was to study the possibility of using a novel method, namely, aerosol flow reactor method, for the preparation of drug-containing nanoparticles with varying amounts of drug and polymer. The physical properties of the prepared nanoparticles were analyzed. Methods. The nanoparticle size distributions were measured using differential mobility analyzer. The structure of the prepared nanoparticles was assessed by x-ray diffraction, differential scanning calorimetry, and electron microscopy. Drug release from the nanoparticles was analyzed. Results. The spherical particles produced showed a unimodal and lognormal size distribution, and the geometric number mean size of the nanoparticles could be varied between 90 and 200 nm. When the amount of drug in the polymeric matrix was small, the nanoparticles had a homogeneous, amorphous structure. Drug crystals were formed when the amount of drug was increased over the solubility limit of the drug into the polymer. The amounts of drug and polymer controlled the drug release from the nanoparticles. Conclusions. The aerosol flow reactor method was found to be able to produce homogeneous amorphous matrix-type nanoparticles that can directly be collected as dry powder.

Comparison of microencapsulation properties of spruce galactoglucomannans and arabic gum using a model hydrophobic core compound.

In the present study, microencapsulation and the physical properties of spruce ( Picea abies ) Omicron-acetyl-galactoglucomannans (GGM) were investigated and compared to those of arabic gum (AG). Microcapsules were obtained by freeze-drying oil-in-water emulsions containing 10 wt % capsule materials (AG, GGM, or a 1:1 mixture of GGM-AG) and 2 wt % alpha-tocopherol (a model hydrophobic core compound that oxidizes easily). Microcapsules were stored at relative humidity (RH) of 0, 33, and 66% at 25 degrees C for different time periods, and their alpha-tocopherol content was determined by HPLC. X-ray microtomography analyses showed that the freeze-dried emulsions of GGM had the highest and those of AG the lowest degree of porosity. According to X-ray diffraction patterns, both freeze-dried AG and GGM showed an amorphous nature. The storage test showed that anhydrous AG microcapsules had higher alpha-tocopherol content than GGM-containing capsules, whereas under 33 and 66% RH conditions GGM was superior in relation to the retention of alpha-tocopherol. The good protection ability of GGM was related to its ability to form thicker walls to microcapsules and better physical stability compared to AG. The glass transition temperature of AG was close to the storage temperature (25 degrees C) at RH of 66%, which explains the remarkable losses of alpha-tocopherol in the microcapsules under those conditions.

Diastereoselectivity in Reactions of Lithiated 2-Phenylthiomethylthiotetrahydropyrans

Diastereoselectivities of up to 95:5 in alkylations of lithiated O,S,S-acetals are rationalized by the locked conformation of the five-membered ring caused by lithium-to-oxygen coordination. The relative configurations of the two diastereomers obtained in benzylation of lithiated 2-(phenylthiomethylthio)tetrahydropyran were confirmed by comparison with reference compounds of known stereochemistry obtained by benzylic reduction of crystalline hydroxyalkylated derivatives.

(1S,2R,2′S)- and (1S,2S,2′S)-1-phenyl-2-phenyl­thio-2-(tetra­hydro­pyran-2′-yl­thio)­ethanol diastereoisomers at 193 K

In the synthesis of 1-phenyl-2-phenylthio-2-(tetrahydropyran-2-ylthio)ethanol, C(19)H(22)O(2)S(2), four diastereoisomers are formed. Two non-centrosymmetric enantiomeric forms which crystallize in space groups P2(1)2(1)2(1) and Pna2(1) are presented. The former has an intramolecular hydrogen bond between the hydroxyl group and the O atom of the tetrahydropyran ring. In the latter isomer, the hydroxyl group forms an intermolecular hydrogen bond to the O atom of the tetrahydropyranyl group of a neighbouring molecule, joining the molecules into chains in the c-axis direction; the O.O distances are 2.962 (4) and 2.764 (3) A, respectively. The tetrahydropyran rings are in chair conformations in both isomers and the S side chain has an equatorial orientation in the former, but an axial orientation in the latter molecule.

Di-9-anthryl disulfide at 193 K

The title compound, C28H18S2, crystallizes in the monoclinic space group P21/n and the structure shows pseudosymmetry close to the space group C2/c. At 193 K the compound has a long S—S bond of 2.1089 (12) A and the S atom to anthracene bond distances are 1.776 (3) and 1.770 (2) A. The C—S—S—C torsion angle is 76.06 (13)°.

Two 9-alkylthiophenanthrenes at 193 K (alkyl = dodecyl and tetradecyl)

Two isostructural 9-thiophenanthrene derivatives, 9-dodecylthiophenanthrene, C 26 H 34 S, (I), and 9-tetradecylthiophenanthrene, C 28 H 38 S, (II), are reported. They crystallize in the monoclinic space group P2 1 /c with four molecules in a unit cell. The S-C phenanthrene bonds are 1.767 (2) and 1.772 (4) A and S-C alkyl bonds are 1.809 (2) and 1.804 (4) A for (I) and (II), respectively. The bond angles at S are 104.04 (11) and 104.0 (2)° for (I) and (II), respectively.