Advanced Materials Research Vols. 11-12

Abstract: In order to improve the hydrophilicity of poly (D,L-latide) (PDLLA), a novel amphiphilic ABA-type triblock copolymers of poly-N-vinylpyrrolidone (A) and poly (D, L-lactide) (B), were successfully synthesized by atom transfer radical polymerization (ATRP) using N-vinylpyrrolidone (VP) as monomer, bromide-terminated poly (D,L-latide) oligomer (Br-PDLLA-Br) as functional macromolecular initiator which was prepared when hydroxy-terminated poly(D,L-latide) oligomer (HO-PDLLA-OH) reacted with 2-bromopropanoyl bromide, CuBr/2,2’-bipyridine complex as the catalyst system. The resulting copolymers were characterized by various analytical techniques. The results showed that the introduction of poly (N-vinylpyrrolidone) (PVP) segments into polylactide enhanced the surface hydrophilicity of the copolymers remarkably and amphiphilic polymer can self-assemble into core-shell structure (polymer micelle) in water by the balance of the hydrophilic and hydrophobic interaction.

Abstract: Polypropylene (PP) was modified by melt graft copolymerization with ε-caprolactone (ε-CL) in the absence of initiator. Fourier transform infrared (FTIR)
spectroscopy was used for qualitative and quantitative characterization of the reaction product. The graft copolymer was also characterized by 1H NMR, x-ray and thermogravimetric analysis (TG).

Abstract: The triblock ABA copolymers of poly (D,L-lactide)-b-poly (ethylene glycol)-b-poly (D,L-lactide) (PDLLA-PEG-PDLLA) were synthesized by bulk ring-opening polymerization in the presence of N2 under normal pressure, using the D,L-lactide (DLLA) as monomer, hydroxyl endgroups of poly(ethylene glycol) (PEG) as initiator and the stannous octoate as the catalyst. The resulting copolymers were characterized by various analytical techniques. Effects of molar ratios of lactide to PEG and the chain length of PEG on the viscosity-average molecular weight of the copolymers, the biodegradation behaviors and hydrophilicity of the copolymers were investigated in detail. The results showed that the viscosity-average molecular weight and the contact angle of the copolymers increased with the molar ratio of lactide to PEG, but water uptake and degradability decreased.

Abstract: A disodium tetrakis(phthalimide) palladium(II) complex, [Na2Pd(phthal)4] (1), was synthesized by reaction of four phthalimide molecules with Pd(OAc)2 in the presence of Et3N. The above and below axial sites of the Pd coordination plane formed the spaces suitable for capturing Na+ ions, which were coordinated with the four imidato oxygen atoms. The complex 1 was linked through the Na+ ions bridged by the water molecules, building an infinite chain structure along the crystallographic a axis. The four phthalimidato moieties contacted in the four orthogonal directions together through their π-π stacking interaction. Such a self-assembly of molecule 1 constructed nanopores with a pore size of ca. 3 × 4 Å in the crystals.

Abstract: Modification of polypropylene (PP) by the addition of polyolefin elastomer (POE) and attapulgite (AT) has been investigated. The result have shown that the addition of POE and AT gave PP excellent mechanical properties of improved impact strength and comparable stiffness. The bonding between AT and the matrix was enhanced with the addition of dispersant EBS. AT was an effective nucleating agent for PP crystallization, and finer and more homogeneous spherulites of PP was obtained. In this study, the toughening mechanism of the composites was also discussed.

Abstract: Various morphologies of silver films fabricated by the thermal decomposition of silver behenate have been studied. The morphological structures of silver behenate films at different heating temperatures are characterized by using SEM, IR and XRD. It is found that, while heating the silver behenate films, the formed silver particles are stabilized by the other thermal decomposition products in the range of 193°C∼320°C. The influence of silver behenate concentration in organic solvent on the formation and packing density of as-fabricated silver films by thermal treatment on the silver behenate films at 500°C has been studied. The results show that the silver film fabricated by a millimolar solution of silver behenate possesses a silver monolayer; the silver thick film can be formed at high concentration, and interestingly, silver particles with regular triangular or truncated triangular shape in the silver thick film are also obtained.

Abstract: Wetting can be regarded as a kind of effective nanostructure-forming process. To control the structure, a study on the relationship between atomic interactions and the resultant wetting behaviors is required. To model the wetting system, two sets of interatomic potentials for Metal/MgO(100) systems are derived from first principles calculation results for the simple configurations. A molecular dynamics method is applied to simulate the system and shows that Al atoms wet better than Sn atoms on the MgO substrate. The tendency is consistent with the experimental contact angles. The interfacial structures are different between these two systems.

Abstract: The self-adaptive vegetation concrete is a porous concrete which has characteristics of self-adaptation (suitable for acid-alkali degree and humidity that plant grow automatically), self-supply (the necessary nutrition element offers plants to grow within the structure) and necessary mechanics of the project. To meet the vegetable growth in self-adaptive vegetable concrete, the base body of vegebable concrete is produced with many kinds of cementitious material and complex of different aggregate. The experiment shows that the vegetable concrete base body which has a suitable acid-alkali degree environment of seed sprout (PH < 9) and suitable space environment for plant root system growth( porosity rate > 40%) is produced through using self-made soil stabilizer (the proportion of soil stabilizer and the clay is 1:1) and different aggregates (cobble, coral reef and ceramsite).

Abstract: This work demonstrated an in-situ pyrolysis of gelcast alumina under reduction sintering to make alumina and carbon composite in providing semi-electrical conductivity. To increase the carbon content, the monomer was varied in the premix solution with reduction sintering in nitrogen gas. Two-probe method was used to measure electrical resistance of the sintered samples. The results revealed that the increase of monomer addition and sintering treatment were effective in reducing electrical resistance. The lowest value was 3.6×106
-cm, which is a potential candidate for electrostatic shielding application. The reduction-sintered sample was re-sintered in an air in order to gain insight on the conductive path due to carbon network. Further tests such as XRD, TGA/DTA, and scanning electron microscopy
were used to explain the semi-conductive property of the material.

Abstract: Silvered polyimide films have been prepared by alkali hydroxylation of polyimide film surface and incorporation of silver ions through subsequent ion exchange. Thermal curing had not only re-cycloimidized the poly(amic acid) into polyimide, but also reduced silver ions into silver atoms and near-atomic silver clusters, which diffused and aggregated to give reflective and conductive surfaces without addition of reducing agents. By this method, silvered polyimide films can be easily fabricated with double excellent reflective (reflectivity > 97%) and conductive surfaces (surface resistance: 0.02
/sq), outstanding metal-polymer adhesion, high mechanical properties, and controllable thickness of silver layers at modest cost. As the side-to-side near-surface microstructure difference in the laboratory made samples and commercial PI films, the thickness of alkali induced hydrolysis, loading of silver ions and forming of silver layers at the two sides of the polyimide films were also discussed here. Films were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and tapping mode atomic force microscopy (AFM). Results show that continuous silver layers were formed on the polyimide films.