Yu-Jun Li

Preparation of ultrafine particle multilayers using the Langmuir-Blodgett technique

X-Type Langmuir–Blodgett multilayers of magnetic ultrafine particles such as 100 A magnetite (Fe3O4), 1000 Aγ;-diiron trioxide (γ-Fe2O3), 70 A titanium dioxide (TiO2), 500 A barium ferrite (BaFe12O19), and ultraconducting fine-particle Y–Ba–Cu have been prepared. They were dispersed in oleic acid or stearic acid in a ballmill. The dispersed products were assembled into LB multilayers deposited onto a fresh poly(ethylene terephthalate) or MgO film plate. The morphology of the LB multilayers of the ultrafine particles was investigated by high-resolution transmission electron microscopy and scanning electron microscopy and it was found that they have fine lamellar structures. In addition, the obtained multilayers have magnetic anisotropy behaviour observed by magnetic property measurements.

Synthesis and Hemocompatibilities of Cellulose‐Containing Segmented Polyurethanes

Novel segmented polyurethanes (SPUs) have been synthesized using hydrolyzed cellulose triacetate (HCTA) and 1,4-butanediol (BD) as diol component. By altering the molar ratio of HCTA to diphenylmethane diisocyanate (MDI), a series of polymers having poly(butadiene) (PBD) diol soft segments and varying content of HCTA was prepared. Then the polymers were further deacetylated with NaOCH 3 /CH 3 OH. Viscosity measurements showed the polymers had the viscosity behavior of common polyelectrolytes. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and water contact angle measurements revealed that the cellulose is oriented on the surface of these materials. The hemocompatibility in vitro was evaluated with platelet-rich plasma (PRP) contact tests and viewed by scanning electron microscopy (SEM) using commercial BioSpan® and cellulose-free SPU as control samples. Platelet adhesion to cellulose-containing SPUs was inhibited by 30-75% compared with cellulose-free polyurethanes. Cell spreading was observed on the control SPUs but not on any of other surfaces. The incorporation of cellulose into the SPUs backbone effectively reduced platelet adhesion and thus potentially could result in better hemocompatibility.

Synthesis and properties of phospholipid polyurethanes with poly(isoprene) soft segment

Polyrethanes, based on 2-[bis(2-hydroxyethyl)methylammoni]ethylstearylphosphate, alone or together with 1,4-butanediol as the chain extender, poly(isoprene) diol and 4,4′-methylenediphenyl diisocyanate, were prepared. These segmented phospholipid polyurethanes were characterized by IR, elemental analyses, and gel permeation chromatography. The polyurethane, with both phospholipid diol and 1,4-butanediol as the chain extender, was further investigated by differential scanning calorimetry, x-ray diffraction, scanning electron microscopy, plasma contact and clotting time. An x-ray diffraction measurement for the polymer shows a intense scattering at 79.3 A corresponding to the length of soft segments, which is hydrophobic poly(isoprene), and a weak diffuse scattering at 5.1 A corresponding to the distance between the hydrophobic poly (isoprene) layers. The hemocompatibilities of the polymer were evaluated by platelet rich plasma contacting studies and by scanning electron microscopy using medical grade poly(vinyl chloride) as control. The hot-pressed films of the polymer exhibit a favorable surface in terms of platelet adhesion, and the morphology of adhered platelets undergoes to a relatively lower degree of variation compared to poly(vinyl chloride). Moreover, the clotting time of the polymer in contact with human platelet rich plasma was 220, 100, and 86 s for the phospholipid-based polyurethane, poly(vinyl chloride), and glass, respectively.

Synthesis and Properties of Polyurethanes Containing Phosphatidylcholine Analogues in the Side Chains

Abstract Several polyurethanes containing phosphatidylcholine analogues in the side chains were synthesized by reaction of oleyl-2-[N-(methyldiethanolammonium) ethyl phosphate (3a) or (p-onylphenyl)-2-[N-(methyldiethanolammonium) ethyl phosphate (3b) with diisocyanates such as 2,4-tolylene diisocyanate (TDI), 4,4′-methylene diphenyl diisocyanate (MDI), and m-xylylene diisocyanate (XDI), respectively. The new diols 3a and 3b were characterized by their IR and 1H-NMR spectral data and elemental analyses. Polyurethanes were characterized by their IR spectral data. Polyurethanes with properties similar to the usual polyelectrolytes are described.

Recent progress of phospholipid polymers

Since in 1982 the first phosphatidylcholine analogues-containing vinyl monomer 2-(methacryloyloxy)ethyl-2-(trimethylammonium)ethyl phosphate (MTP) was reported, more and more attention has focused on its polymers, as phospholipid polymers have been found to show excellent biocompatibility. We reviewed the progress of phospholipid polymers in 1997 which covered literature from 1974 to 1997; and mainly focused on phosphatidylcholine analogues-containing vinyl polymers. This review reflects mainly recent research (i.e., mostly later than 1997) and important development progress on polymeric polyphospholipid analogues. A variety of approaches for design, synthesis, characterization, property investigation and potential applications for phospholipid-analoguecontaining polyurethanes and 2-methacryloyloxyethylphosphorylcholine-containing polymers have been extensively discussed. The polymeric phospholipid analogues include polymers such as side- and main-chain types of phosphatidylcholine-analogue-containing polyurethanes, side- and main-chain types of phosphatidylcholine-analogue-containing segmented polyurethanes, phosphatidylcholineanalogue-grafted polyurethanes, 2-methacryloyloxyethylphosphorylcholine-containing polymers, 2-methacryloyloxyethylphosphorylcholine-modified acrylamide hydrogel, etc. Design and synthesis of phosphatidylcholine-analogue-containing diols and their polyurethanes with various commercially available diisocyanates and phosphatidylcholine-analogue surface-modified polyurethanes are described. New ring-opening reagents such as 2-dimethylaminoethanol for the main-chain type of phosphatidylcholine-analogue-containing polyurethanes, N-methyldiethanolamine for the side-chain type of phosphatidylcholine-analogue-containing polyurethanes and trimethylamine for grafting phosphatidylcholine-analogue-containing vinyl monomers are discussed. A general reaction route to design and synthesize phosphatidylcholine-analogue-containing diols and polyurethanes is summarized. Various phosphatidylcholine-analogue-containing segmented polyurethanes are also discussed. Various phosphatidylcholine-analogue-containing diols, together with 1,4-butanediol or ethylenediamine as chain extender were used to synthesize phosphatidylcholine-analogue-containing segmented polyurethanes or polyurethaneureas, which are based on diphenylmethane diisocyanate and various types of soft segments such as a polycarbonate, polyether, polyester and hydrocarbon diols. Characterization techniques for phosphatidylcholine-analogue-containing polyurethanes and polymers are also described. These include infra-red spectroscopy, 1H-NMR, viscosity and gel-permeation chromatography measurements for bulk property; X-ray diffraction methods for structure; dynamic viscoelasticity and tensile measurements for mechanical properties. Moreover, attenuated total reflectance-Fourier transform infrared spectroscopy, electron spectroscopy for chemical analysis and contact angle measurements for surface properties are all described. Hemocompatibility evaluation via platelet-rich plasma contact studies and scanning electron microscopy observation and their potential applications are also discussed.

Studies on the synthesis and properties of novel phospholipid analogous polymers

Two kinds of phospholipid analogous compounds, methacrylate monomers (4a-b) and acrylamide monomers (5a-b), were prepared and polymerized with a radical initiator in water at room temperature. The viscosity behavior of these charged polymers were investigated in the presence or absence of inorganic salts, and the found inherent viscosity [η] of amide polymer (poly7a) is higher than those of ester polymers (poly6a1 and poly6b). On the other hand, the radical copolymerization of monomer 5b with acrylamide (AAm) was also carried out in water. Based on the x-ray analyses, it is proposed that some of the obtained polymers show ordered bilayer structures in condensed phase. Furthermore, the thermal properties were studied by DSC anti TG-DTA measurements.

SYNTHESIS AND BLOOD COMPATIBILITIES OF NOVEL SEGMENTED POLYURETHANES CONTAINING PHOSPHATIDYLCHOLINE ANALOGOUS MOIETIES IN THE MAIN CHAINS AND LONG-CHA IN ALKYL GROUPS IN THE SIDE CHAINS

New segmented polyurethanes containing phospholipid moieties in the main chains and long-chain alkyl groups in the side chains were synthesized. The soft segments used in this study were poly(butadiene), poly(isoprene), hydrogenated poly(isoprene), and poly(1,6-hexyl-1,2-ethylcarbonate) diol. The hard segments of these polyurethanes were 4,4′-methylenediphenyl diisocyanate, bis[2-(2-hydroxyethyldimethylammonio)ethyl]2-cetyl- 1,3-propanediphosphate, and 1,4-butanediol. The blood compatibilities of the new polymers were evaluated by platelet-rich plasma contact studies and viewed by scanning electron microscopy using medical grade BioSpan® and nonphospholipid polyurethane as references. These new materials have good surfaces in terms of platelet adhesion, and the morphology of adhered platelets undergoes a relatively low degree of variation.

Studies on syntheses and properties of novel polyamides containing phosphatidylcholine analogous moieties by interfacial polycondensation

Polyamides (4a-b and 5a-b) were synthesized from interfacial polycondensation of novel diamine containing phosphatidylcholine analogous moiety, hexamethylene diamine with adipoyl chloride, or sebacoyl chloride in the interface of water and carbon tetrachloride at room temperature. The characterizations of synthesized diamine and polyamides were carried out with FT-NMR, or IR spectral method, elemental analysis, and melting point measurements, respectively. These polyamides obtained are insoluble in any normal solvents. From the results of X-ray diffraction analysis and POM observation, it was revealed that the polyamide 4b was prepared with high molecular weight, while polyamide 4a obtained seemed to have low molecular weight. For copolymers 5a and 5b, X-ray reflections from only adipoyl or sebacoyl chloride parts were observed as in crystalline state. In addition, thermal properties were also studied by DSC and transmitted light intensity measurements.

Preparation and polymerization of 2-(acryloyloxy)ethyl-2-(trimethylammonium)ethyl phosphate and 4-(acryloyloxy)butyl-2-(trimethylammonium)ethyl phosphate

Abstract 2-(Acryloyloxyl)ethyl-2-(trimethylammonium)ethyl phosphate (4a) and 4-(acryloyloxyl)butyl-2-(trimethylammonium)ethyl phosphate (4b) were prepared and characterized by their IR and 1H NMR spestral data and elemental analyses. 4a was homopolymerized and compolymerized with 2-hydroxyethyl acrylate, stearyl acrylate, and 1,3-dioleylacylglycerol-2-acrylate using 2,2ϵ-azoisobutyronitrile (AIBN) as initiator. Poly (4a) of the resultant polymers exhibited liquid crystalline behaviors from 118 up to 152°C observed by a polarization microscopy. Moreover, the water-soluble polymer, Poly (4a), among the resulting polymers showed a polyelectrolyte behavior from its viscosity measurement.

SYNTHESIS AND PROPERTIES OF AMPHIPHILIC PHOSPHOLIPID ANALOGOUS POLYACRYLAMIDIC GELS

Abstract New phospholipid analogous acrylamide monomers containing alkyl chains as the hydrophobic groups and phosphatidylcholine analogues as the hydrophilic groups were synthesized. The polymerizations of these monomers were carried out in the presence of α,α′-azobisisobutyronitrile as a radical initiator and N , N ′-methylenebisacrylamide as a cross-linking agent. The obtained gels were found to swell in polar solvents, but shrink in nonpolar solvents. The result of X-ray diffraction analysis proposed that these gels are basically constructed from alternately stacked bilayers with hydrophilic and hydrophobic regions of the side chain. Furthermore, liquid crystalline behaviors for these gels were observed at room temperature.