woon Jung

A new copolymerization process leading to poly(propylene carbonate) with a highly enhanced yield from carbon dioxide and propylene oxide

Using excessively loaded propylene oxide (PO) as a solvent, the copolymerization of carbon dioxide (CO2) and PO was carried out with zinc glutarate catalyst, consequently producing poly(propylene carbonate) of high molecular weight in a high yield (64–70 g polymer per gram of catalyst) never achieved before. Both the PO used as solvent and the excessively loaded CO2 were fully recoverable, respectively, and reusable for their copolymerization, indicating that this is a clean, green polymerization process to convert CO2 to its polycarbonate. The polymer yield was further improved by scaling up the copolymerization process. Among zinc glutarate catalysts prepared through several synthetic routes, one from zinc oxide delivered the highest yield in the copolymerization.

Copolymerization of carbon dioxide and propylene oxide using an aluminum porphyrin system and its components

The catalytic activities of tetraphenylporphinatoaluminum chloride (TP-PAlCl) and its propylene oxide adduct (TPPAl(PO) 2 Cl) were investigated in detail together with a quarternary salt Et 4 NBr for the copolymerization of carbon dioxide and propylene oxide. In addition, for the components and starting raw materials of the catalyst systems, catalytic activities were examined for the copolymerization. The TPPAlCl catalyst delivered oligomers containing ether linkages to a large extent, regardless of its PO adduction. And cyclic propylene carbonate, as byproduct, was formed in a very small portion. Using the TPPAlCl coupled with Et 4 NBr as a catalyst system, the formation of ether linkages was reduced significantly in the copolymerization; however, the obtained oligomer still contained ether linkages of 25.0 mol % in the backbone. On the other hand, the formation of cyclic carbonate was increased to 22.4 mol % relative to the oligomer product. The results indicate that the salt, which was coupled with the TPPAlCl catalyst, plays a key role in reducing the formation of ether linkage in the oligomer and, however, in enhancing the formation of cyclic carbonate. Similar results were obtained for the copolymerization catalyzed by the TPPAl(PO) 2 Cl/ Et 4 NBr system. That is, the formation of ether linkages was not restricted further by the PO adduction of the TPPAlCl component in the catalyst system. Only oligomers with a relatively high molecular weight were produced. This indicates that the PO adduction of the TPPAlCl component contributes highly to the initiation and propagation step in the oligomerization, consequently leading to a relatively high molecular weight oligomer. In contrast, the Et 4 NBr, as well as the Et 2 AlCl, produced only cyclic carbonate in a very low yield. Furthermore, tetraphenylporphine exhibited no catalytic activity, regardless of using together with Et 4 NBr, On the other hand, the Et 2 AlCl coupled with Et 4 NBr provided a low molecular weight oligomer having ether linkages of 92.3 mol % in addition to the cyclic carbonate.

The biocompatability of mesoporous inorganic-organic hybrid resin films with ionic and hydrophilic characteristics.

New mesoporous silicate-titania resin systems hybridized with 4,5-dihydroxy-m-benzenedisulfonic acid and poly(ethylene glycol)-dimethacrylate component were developed. These inorganic-organic hybrid resins were found to reveal highly controlled ionic and hydrophilic surface with excellent durability and adhesion onto various substrates. The resin films revealed high resistance to nonspecific adsorption of fibrinogen and to adherence by several bacterial pathogens such as Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis. Furthermore, excellent biocompatibility of the developed resins was proved by both HEp-2 cell adhesion in vitro and subcutaneous implantation in mice. The inorganic-organic hybrid resins are strongly promising for biomedical applications including biomedical devices and biosensors.

Well-defined DNA-mimic brush polymers bearing adenine moieties: synthesis, layer-by-layer self-assembly, and biocompatibility.

Two new DNA-mimicking brush polymers were synthesized: poly[oxy(11-(3-(9-adeninyl)propionato)-undecanyl-1-thiomethyl)ethylene] (PECH-AP) and poly[oxy(11-(5-(9-adenylethyloxy)-4-oxopentanoato)undecanyl-1-thiomethyl)ethylene] (PECH-AS). These polymers were found to be thermally stable up to 220 °C and could be applied easily by conventional coating processes to produce good quality films. Interestingly, both brush polymers formed molecular multibilayer structures to provide an adenine-rich surface. Despite the structural similarities, PECH-AS surprisingly exhibited higher hydrophilicity and better water sorption properties than PECH-AP. These differences were attributed to the chemical structures in the bristles of the polymers. The adenine-rich surfaces of the polymer films demonstrated selective protein adsorption, suppressed bacterial adherence, facilitated HEp-2 cell adhesion, and exhibited good biocompatibility in mice. However, the high hydrophilicity and good water sorption characteristics of the PECH-AS film suggest that this brush polymer is better suited to applications requiring good biocompatibility and reduced chance of bacterial infection compared with the PECH-AP film.

ISAR Imaging of Multiple Targets Using Edge Detection and Hough Transform

This paper describes a fast method to derive ISAR images of multiple targets with different motion parameters. We use image processing techniques, edge detection and the Hough transform to find the slope of the range profile history of each target and to separate each range profile history. Simulation results of two closely spaced targets with different motion parameters confirm the effectiveness of this method.

Construction of Training Database Based on High Frequency RCS Prediction Methods For ATR

Due to the difficulty of creating training databases using all real enemy targets, it is necessary to derive them using computer simulations. In this paper, we apply three high frequency radar cross section (RCS) methods to create a training database for automatic target recognition (ATR) using 1-D range profiles. These methods are: physical optics (PO), physical theory of diffraction (PTD) and shooting and bouncing ray (SBR). Experimental results derived from the performance of combinational feature space trajectory with a new distance metric (FSTND) classifier show that PO+PTD is the most efficient method for ATR because of the additional information by diffraction terms. SBR shows poor performance due to the cavity structure.

Molecular layer-by-layer self-assembly and mercury sensing characteristics of novel brush polymers bearing thymine moieties.

Two new brush polyoxyethylenes bearing thymine moieties at the bristle ends have been synthesized as model polymers in which the chemical loading of the thymine functional group into the polymer is maximized: poly(oxy(11-thyminoacetyloxyundecylthiomethyl)ethylene) (PECH(S)-T) and poly(oxy(11-thyminoacetyloxyundecylsulfonylmethyl)ethylene) (PECH(SO(2))-T). These brush polymers are thermally stable up to around 225 °C, and their glass transitions occur in the range 23-27 °C, but they have significantly different properties despite the similarity of their chemical structures. In particular, PECH(SO(2))-T films exhibit better performance in sensing mercury ions than PECH(S)-T films. These differences were found to originate in the differences between their morphological structures. The PECH(SO(2))-T film has a multi-bilayer structure without interdigitation, in which the layers stack along the out-of-plane of the film and provide a thymine-rich surface. In contrast, the PECH(S)-T film is amorphous with a relatively low population of thymine moieties at the surface. This study demonstrated that a thymine-rich surface is required for recyclable thymine-based polymers to provide highly improved sensitivity and selectivity as well as full reversibility in the sensing of mercury ions. A thymine-rich surface can be achieved with a brush polymer bearing thymine moieties that can self-assemble into a multi-bilayer structure. Because of the thymine-rich surface, the PECH(SO(2))-T thin films even in only 6 nm thickness demonstrate the detection of mercury ions in aqueous solutions with a detection limit of 10(-6) M.

Bacterial adherence on self-assembled films of brush polymers bearing zwitterionic sulfobetaine moieties

In this study we synthesized a series of well-defined brush polymers, poly(oxy(11-(3-sulfonylpropyltrimethylglycinyl)undecylesterthiomethyl)ethylene-co-oxy(n-dodecylthiomethyl)-ethylene)s (PECH-DMAPSm, where m is the mol% of DMAPS (sulfobetaine) end group). The thermal properties and phase transitions of these polymers were investigated. The polymers were thermally stable up to 185 °C. The polymers were found to form favorably into multi-bilayer structures, always providing hydrophilic, zwitterionic sulfobetaine end groups at the film surface. For the films, water sorption behavior was examined. In addition, surface energy components were determined for the polymer films and the bacterial cells deposited on cellulose acetate membranes. The brush polymer films were found to suppress bacterial adherence significantly. An understanding of the suppression of bacterial adherence was attempted in terms of surface energies and thermodynamics. The results collectively indicate that the sulfobetaine-containing brush polymers are suitable for use in biomedical applications that require the reduced possibility of post-operative infection.

Biocompatible characteristics of sulfobetaine-containing brush polymers

AbstractA series of well-defined brush polymers, poly(oxy(11-(3-sulfonylpropyltrimethyl-glycinyl)undecylesterthiomethyl) ethylene-co-oxy(n-dodecylthio-methyl)ethylene)s (PECH-DMAPSm, where m is the mol% of the DMAPS [sulfobetaine] end group) were synthesized. The thermal properties and phase transitions of these polymers were investigated. The polymers were thermally stable up to 185 °C and were found to form favorably into multibilayer structures, always providing hydrophilic, zwitterionic sulfobetaine end groups at the film surface. Because of the presence of these sulfobetaine groups at the surface, the polymer films promoted HEp-2 cell adhesion and revealed biocompatibility in mice but significantly suppressed protein adsorption. These results collectively indicate that the sulfobetaine-containing brush polymers are suitable for use in biomedical applications, including medical devices and biosensors that require biocompatibility.

Comparisons of Four Feature Extraction Approaches Based on Fisher's Linear Discriminant Criterion in Radar Target Recognition

In this paper, the goal is to produce a highly separable and small-dimensional feature set for improving the target recognition strategy called Invariant Feature-based Method (IFM), which uses the conventional principal component analysis to reduce redundant information and feature space dimension. To meet this end, the principal component analysis is replaced with Fishers linear discriminant criterion, originally developed for discriminating various patterns. Among the various versions of Fishers criterion, four computationally efficient techniques including classical linear discriminant vectors (CLDV), classical linear discriminant vectors with whitening process (CLDVW), and weighted pairwise Fisher criteria vectors (WPFCV), weighted pairwise Fisher criteria vectors with whitening process (WPFCVW) are considered. It is shown that among the four techniques, CLDVW and WPFCVW outperform CLDV, WPFCV, and the conventional principal component analysis. In addition, an optimum number of feature dimension for Fishers criterion combined with IFM is experimentally derived, and associated theoretical background is discussed.