Interactions between naproxen and maltoheptaose,the non-cyclic analog ofβ-cyclodextrin

The crystallinity of naproxen in solid combinations with amorphous maltoheptaose, the non-cyclic analog of -cyclodextrin, was assessed using differential scanning calorimetry supported by X-ray powder diffractometry. Cogrinding induced a decrease in drug crystalinity to an extent which depended on the grinding time, and was most pronounced for the combination of equimolecular composition. Thermal analysis showed that the mechanism behind the conversion of crystalline naproxen into the amorphous state by cogrinding with maltoheptaose differed from that with randomly substituted, amorphous -cyclodextrins. Interactions of naproxen with maltoheptaose in aqueous solution were studied by means of fluorescence spectroscopy, phase-solubility analysis, and computeraided molecular modelling. Maltoheptaose can wrap up naproxen, taking on a cyclic conformation and forming a pseudo inclusion complex (apparent binding constant K_{1: 1} = 1.0 × 10³ (–20%) L mol^–1 at 25 °C) which is about as stable as the true inclusion complex with -cyclodextrin in the lowest temperature range (0-100 K). A better complexing ability for naproxen in terms of binding constant values, however, was displayed by both native and derivatized -cyclodextrins, the hosts with covalently-bound cyclic structures.     

Morphology and crystallization of blends of linear low density polyethylene with a semiflexible liquid crystalline polymer

The morphology and the crystallization behavior of blends of linear low density polyethylene (LLDPE) with an experimental sample of a semiflexible liquid crystalline polymer (SBH 112 by Eniricerche, Italy) have been studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and scanning electron microscopy (SEM). The blends possess a two-phase morphology, due to immiscibility of the two components. SEM observations show that dispersion of the minor SBH phase is favored at low (相似文献   

弱碱性和强碱性阴离子交换树脂的离子交换平衡的比较SO_4~(2-)-Cl~--NO_3~-体系

本文详细地比较了在弱碱性和强碱性阴离子交换树脂上,SO_4~(2-)-Cl~-、NO_3~--Cl~-及NO_3~--SO_4~(2-)二元交换的等温线和修正选择系数。实验测定及理论计算了上述三种二元交换反应的标准自由能的改变量。测得了在弱碱性树脂上的SO_4~(2-)-Cl~--NO_3~-三元交换的等温线。适用于强酸性和强碱性树脂的从二元交换平衡数据推算三元交换平衡数据的方法推广应用于弱碱性树脂。     

Poly(ethylene oxide) blends with crosslinking polyester resin

The miscibility of polyethylene oxide (PEO) with oligoester and polyester resin, the morphology of the blends and the kinetics of PEO crystallization in the blends were studied by optical microscopy and differential scanning calorimetry. The blends were found to be miscible with uncured resin at 60°C. After isothermal crystallization of PEO from liquid oligoester or UV cured polyester about 20% of the PEO material is still dissolved in the resin and it is incorporated between lamellae or in the interspherulitic regions. It was observed that the growth rate of PEO spherulites and the degree of crystallinity of PEO in the blends decreases very fast together with a decrease of the PEO content and the progress of the resin crosslinking.     

Micro construction of poly(epsilon-caprolactone)/poly(L-lactic acid) blend film by solution casting under microwave irradiation

The micro construction of poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) blend films fabricated by solution casting under microwave irradiation was investigated by selective enzymatic degradation and scanning electron microscopy (SEM). The results were totally different from the blends obtained by conventional methods. The blend was more homogeneous and the PCL continuous phase more compact as no spherulites and tiny zone separation were observed from the film surface and no PCL network was observed inside the film, and the degradation of a PCL plank by Pseudomonas lipase was significantly retarded. The distributed PLLA micro spheres were enlarged and amorphous. The thermal behavior of the blend by microwave heating revealed that PCL and PLLA underwent a melting process, which induced the variations of the PCL phase and PLLA spheres. The weight loss caused by degradation of the PCL/PLLA blend obtained by conventional methods (B50c) is greater than that of the blend obtained by microwave methods (B50m), which reflects the change in morphology from a loose PCL network (B50c) to a dense PCL plank (B50m).     

Radiation grafting from binary monomer mixtures. I. Vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol

Gamma-radiation grafting of vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol (VEEG) on polyethylene films has been studied from binary monomer mixtures. The effect of co-monomer composition and total exposure radiation dose on the grafting process is investigated. A combination of potentiometric and gravimetric techniques is applied to determine the grafting degree of each monomer in the final graft copolymer. The presence of more active monomer VEEG in the mixture was found to enhance the grafting of both monomers because the increasing of copolymerization rate which in turn increases the total grafting degree. The modification of the hydrophilic properties of the graft copolymer is studied by examining the grafted films for water- and copper (II) ions uptake.     

Miscible blends through hydrogen bonding: effects on polymer properties

Miscible blends through hydrogen bonding have been intensively studied. The effects of a variety of miscible hydrogen bonded polymer blends on properties such as thermal and thermal oxidative stability, moisture sensitivity, modulus and glass transition temperature are discussed. In addition, the preparation of semi-interpenetrating polymer networks (IPNs) and studies of the effect of crosslinking on the miscibility in hydrogen bonded polymer blends are reviewed.     

聚环氧乙烷／脂肪族聚碳酸酯共混研究

本文用差热分析(DSC)和红外光谱仪(FTIR)研究了聚环氧乙烷(PEO)和新型聚合物——脂肪族聚碳酸脂(PPC)共混热行为和大分子间的相互作用。由熔点下降方法给出PEO/PPC混合体系在320K下相互作用参数为-0.46;FTIR谱表明PPC大分子链和PEO大分子链存在较强的相互作用;PEO/PPC共混形态随PPC含量增加发生了较大变化。     

Phase morphology of iPP/aPS/SEP blends

Supermolecular structure and phase morphology of the ternary isotactic polypropylene/atactic polystyrene/poly(styrene-b-ethylene-co-propylene) (iPP/aPS/SEP) compression molded blends with 100/0, 90/10, 70/30, and 50/50 iPP/aPS weight ratios and with different amounts of added SEP compatibilizer were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). SEP significantly reduced the size of dispersed aPS particles that enabled better spherulitization in the iPP matrix. Furthermore, iPP spherulites in ternary blends with 90/10 iPP/aPS weight ratio became larger in comparison with the pure iPP. TEM revealed that the SEP formed continuous interface layer around the dispersed aPS particles even when only 2.5 wt.% of SEP was added. Particle size distribution was distinctly bimodal. When the SEP content was increased to 10 wt.%, joining together smaller and bigger aPS and SEP particles formed dispersed aggregates. Additionally, both amorphous components (aPS and SEP) influenced crystallization process of iPP matrix and so modified, to some extent, its final supermolecular structure. SEP compatibilizer did not significantly affect crystallite orientation. The increase of crystallite sizes, which was more affected by the addition of aPS than by the addition of SEP, seemed to be influenced by the solidification effect rather than by the phase morphology of the blends.     

Thermoanalytical study of nucleating effects in polypropylene composites

Nucleating and transcrystallization behaviour of additives in engineering PP composites and the effect of modified interfacial structure is the subject of this series of papers. The first part concentrates on polypropylene/liquid crystalline polyester blends. Increased crystallisation temperature and degree of crystallinity of polypropylene is characteristic to the blends containing different amount of LCP additive. Transcrystallization process governs the formation of crystalline structure in these systems in course of isothermal crystallisation at 132C. The nucleating effect of LCP gives rise to more uniform crystalline structure in the polypropylene phase.The financial support of the OTKA 014194 is acknowledged with gratitude.