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Objective: This study investigates the effect of selected excipients on microcapsules properties of seeds extracts of Garcinia kola (GK) and Hunteria umbellata (HU). Method: Extracts from macerated dried powdered seeds were microencapsulated with chitosan-alginate including either talc, HPMCAS, Eudragit®RLPO or Eudragit®L100 up to 25% in the core. Microcapsules were characterized using differential scanning calorimertry (DSC), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and In vitro release. Results: DSC, XRD and FTIR showed no change in crystalline properties and functional groups of microcapsules and excipients in the formulations. In vitro extract release showed retardation of extract release in acid medium after 2 h and between 80 to 100% at pH 6.8. Generally, the microcapsules fitted more closely to first order model than the other models. Conclusion: Inclusion of these excipients did not impart negatively in interaction and release profile on microcapsules containing GK and HU aqueous extracts and can therefore be added to facilitate microcapsule production and enhance dosage form performance.

We investigate the structure, the morphology and mechanical properties of crystalline-crystalline and crystalline-amorphous di-block copolymers synthesized by using living, stereoselective polymerization catalysts. Cystalline-crystalline block copolymers (BCP) are formed by polyethylene (PE) block linked to isotactic polypropylene (iPP) or syndiotactic polypropylene (sPP) blocks while crystalline-amorphous samples are formed by PE or sPP block linked to an amorphous rubbery ethylene-co-propylene (EP) segment. A detailed structural characterization has been performed for samples crystallized in the bulk, thin films and stretched fibers and stress-induced phase transformations have been also analyzed. Thin films of BCPs have been epitaxially crystallized onto crystals of organic substrates to achieve a control over the crystallization of both blocks and to obtain ordered nanostructures where the two blocks are organized in separated alternating lamellar domains guided by the orientation of the crystalline lamellae.

The concept of “catalyst ligand design” for olefin polymerization has been deeply modified by the use of high throughput screening techniques in the last ten years. A special case is the new class of Hf(IV)-pyridylamido-based olefin polymerization catalysts discovered by a Dow/Symyx collaboration. These systems have attracted a lot of attention because of several unique features: a) they are industrially relevant producing highly isotactic polypropylenes with a solution process technology at temperature > 100 °C; b) in combination with a second catalyst they undergo reversible trans-alkylation, performing novel olefin block copolymers via ‘chain shuttling’. The stereoselectivity mechanism of propene polymerization promoted by such systems is still unknown . In this communication by means of computational methods we investigated the enantioselectivity of propene insertion for systems I-III reported in Chart 1. Surprisingly, the generally accepted model of "chiral growing chain orientation" was ineffective for this class of catalysts and a new model for the propene enantioselectivity has been sorted out.

The transformations related to phase changes of the crystals, and at lamellar length scales by effect of tensile deformation are studied in the case of some isotactic polypropylene samples having high molecular mass, polydispersity index ≈2, and stereodefects at different concentrations and with a uniform distribution, The stress induced transformations are followed in real time during stretching through wide and small angle X-ray scattering measurements. The data analysis evidences that during the transformations of the spherulitic into the fibrillar morphology, stress-induced phase transitions occurring during plastic deformation are regulated by the same factors that govern the textural and morphological changes, that is the ability of the entangled amorphous chains to transmit the stress and the intrinsic stability of the lamellar crystals. Since the relative stability of the different polymorphic forms involved in the structural transformations and the intrinsic flexibility of the chains depend on the stereoregularity, precise correlations between the stereoregularity of the chains, and the deformation behavior are outlined, paving the way for understanding the material properties at molecular level

This study investigates the properties of microparticles prepared from Andrographis paniculata (AP) and Annona muricata (AM) aqueous extracts for controlled release. Extracts obtained by maceration of the dried powdered plant leaves were microencapsulated by counterion coacervation method. Microcapsules were characterized using Fourier-transform infrared-spectroscopy (FTIR), x-ray difractometry (XRD) and differential scanning calorimetry (DSC).In vitro release studies were carried out at pH 1.2 for 2 h and 6.8 for a further 10 h. Release was monitored at274 and 230 nm for AM and AP, respectively. Encapsulation efficacy was less than 52% for AP and 70% for AM. In vitro drug release at pH 1.2 showed less than 40% release from the microcapsules after 2h while over 90% of extract was released after 6h at pH 6.8. Conventional capsules released the content within 1 h in simulated gastric fluid. FTIR, XRD and DSC results indicate the stable character of the extract within the microcapsules. Microencapsulation with chitosan- alginate controlled the release of Andrographis paniculata (AP) and Annona muricata (AM) aqueous extracts.

Palladium (Pd) and palladium oxide (PdO) nanoparticles (NPs) synthesis has gained considerable interest in the last few decades due to their numerous potential utilizations [1-3]. Systems based on Pd show high activity and selectivity in numerous catalytic processes [2, 3], like the catalytic formation of C-C bonds, one of the most useful transformations in organic synthesis [2]. Because sustainable development involves the utilization of reusable catalysts, the search for new catalytic systems to replace existing homogeneous ones is one important issue [4]. In this context, the immobilization of NPs on a solid support is an interesting alternative since the catalyst can be recycled by simple filtration and the atom/ion leaching from the particles can be minimized. Also, many electronic devices, such as resistors, use compositions containing palladium. All these applications may be more suitable with NPs in a patterned form and, since the majority of unique NPs properties are highly microstructure-dependent, to form Pd and PdO arrays on solid supports with a precise control of nanoparticles dimensions and spacing is a an important issue. Here, we report a simple method to fabricate arrays of palladium (Pd) nanoclusters and palladium oxide (PdO) nanoparticles with tunable dimensions and lateral spacing by using polystyrene-block-poly(ethylene oxide) copolymers (PS-b-PEO) as both stabilizers for Pd NPs and templates controlling the distribution of them. The cylindrical self-assembled nanostructure formed from PS-b-PEO has been used as host for selectively sequestering a nanoparticles precursor (palladium(II) acetate) in cylindrical domains of PEO. Then, Pd NPs have been obtained by reduction of the precursor in presence of the BCPs. In this way, nanocomposite thin films of well-defined morphology based on PS-b-PEO matrices and Pd NPs have been obtained. Furthermore, PdO NPs of improved stability against aggregation have been obtained on a solid and conductive support (silicon wafer) by treating the Pd containing films in air at elevated temperatures. We were able to modulate the dimensions of Pd nanoclusters and PdO NPs and their inter-distance by using as template two different PS-b-PEO copolymers having different molecular weights of both PS and PEO blocks.

We report the morphology, structure and mechanical properties of semicrystalline, polyolefin-based block copolymers (BCPs) with the aim of obtaining ordered nanostructures and innovative thermoplastic elastomers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene) (sPP-b-EP) and syndiotactic polypropylene-block-polyethylene (sPP-b-PE) were synthetized.1 Thin films of BCPs were prepared from solution by dip-casting. The formation of large-sized, well-oriented lamellar nanostructures of BCPs composed of a crystallizable sPP block linked to an amorphous rubbery block EP (sPP-b-EP) was successfully achieved by using epitaxial crystallization2 with p-terphenyl as substrates. TEM bright field images and electron diffraction patterns of gold decorated nanostructures reveals the presence of well oriented crystalline lamellae ordered over large area alternated to amorphous layers. Crystalline-crystalline block copolymers (sPP-b-PE) epitaxially crystallized onto crystals of p-terphenyl show a more complex lamellar morphology. For BCPs with high volume fraction of sPP block only one lamellar orientation can be observed. In this case sPP crystallize first. For sPP-PE BCPs with similar block lengths, TEM images show regions characterized by double orientation of PE lamellae due to the epitaxial relationship of PE with p-terphenyl. In these regions PE crystallize first. They alternate with regions presenting a single lamellar orientation of sPP according to the epitaxial relationship with p-terphenyl. In these regions sPP crystallize first. In other words the block that crystallize first determines the local morphology. An analysis of the mechanical properties and a detailed structural study of BCPs have been performed in order to clarify the effects of the presence of crystalline (PE) or amorphous (EP) block on the crystallization behavior of sPP, and in particular on the stress-induced transformations.

In the last ten years, the more relevant catalysts for stereoselective olefin polymerization have been discovered by high throughput screening techniques (HTS) [1,2]. The catalyst discovery workflow using the HTS infrastructure reached such a level [3] that the “familiar” concept of “catalyst ligand design” by basic principles [4] seems to play a marginal role at the present stage. By using this approach a greater number of pyridyl-amine ligands with enhanced structural diversity were synthesized (see Figure 1). In designing the expanded ligand array, three convenient positions for structural amplification were identified, labeled in the Figure as R1, R2 and the presence of unusual reactivity of metal-aryl bond (see Hf-CAryl and Hf-CAlkyl bonds in system 3 of Figure 1). However, the stereoselectivity mechanism of propene polymerization promoted by such systems is still unknown [1,2]. In this communication, by means of computational methods, we investigated the enantioselectivity of propene insertion for systems 1-3 reported in Figure 1. Surprisingly, the generally accepted model of "chiral growing chain orientation" [5] was ineffective for this class of catalysts and a new model for the propene enantioselectivity has been sorted out. Despite the computational results tuned by DFT methods combined with dispersion and solvent corrections [6], there are two aspects that we would like to stress: a) our model is able to explain the subtle interplay between the steric and electronic effects as well as the reactivity of metal-aryl bond; b) it appears a general model, able after 35 years to reconnect the Ziegler-Natta catalysis to the more general asymmetric catalysis [7]. Let us make a final comment: we are well aware that discoveries of such systems were possible thanks to experimental HTS technologies because of the huge number of variables involved; nevertheless, we are still convinced that a rational catalysts design is not over the game as soon as new models are developed.

A study of the crystallization of the mesomorphic form of isotactic polypropylene (iPP) in samples of different stereoregularity prepared with metallocene catalysts is presented. Contrary to what claimed in the literature, we have found that the mesomorphic form can be obtained by quenching of the melt at 0 °C also in the case of low stereoregular samples, provided that the samples are kept at 0 °C for long time. The key is the formation of mesomorphic bundles with chains in ordered 3/1 helical conformation of size large enough to be stable and inhibit the crystallization of the alpha form at room temperature. For stereoirregular samples the concentration of long ordered helical stretches is low and this requires long residence time at 0 °C for the formation of mesomorphic aggregates of size larger than the critical size. This result provides evidence that the mesomorphic aggregates are not formed as a result of a cooperative process driven by entropy, as in the case of liquid crystals, but rather they form via a nucleation and growth mechanism, as in the normal crystallization processes, according to the idea that the mesophase of iPP is a highly defective crystalline form.

The effects of the presence of hexene and octene on the crystallization behavior of syndiotactic polypropylene (sPP), and in particular on the stress-induced transformations occurring during stretching have been analyzed. For hexene or octene concentrations higher than 4-5 mol% the helical form I transforms by stretching at high deformation into a different mesomorphic form, characterized by chains in the ordered 2/1 helical conformation, and disorder in the lateral packing of the chains.