Preparation and Properties of Polyurethane Hydrogels Based on Hexamethylene Diisocyanate/Polycaprolactone-Polyethylene Glycol

Hydrogels are considered an optimum material for controlled release drug systems and tissue engineering scaffolds since they are tri-dimensional networks. In this work hexamethylene diisocyanate (HMDI), polycaprolactone (PCL) and polyethylene glycol (PEG) were used to prepare polyurethane prepolymers using diethylene glycol (DEG) as a chain-extender. Then the prepolymer was used to fabricate the HMDI/PCL-PEG/DEG polyurethane hydrogels by free radical polymerization using benzoyl peroxide (BPO) as a cross-linking agent. The influences of the ratio of polyol on the contact angle, swelling ratio, morphology and cytotoxicity in-vitro of the HMDI/PCL-PEG/DEG polyurethane hydrogel were investigated. The biological behavior of the polyurethane hydrogels was analyzed by studying the cell behavior using the standard biological MTT (3–4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) test. The Fourier transform infrared (FTIR) spectra results showed that the polyurethane hydrogels were successfully synthesized. The change of the molar the ratio of the polyhydric alcohols (PEG and PCL) played important roles in the swelling degree, the contact angle and the pore size. The HMDI/PCL-PEG/DEG polyurethane hydrogel (PCL/PEG = 1:3) was hydrophilic with many more large pores while the polyurethane hydrogel with PCL/PEG = 3:1 had a dense structure. The fibroblastic cell proliferation improved with decreasing relative PEG content; however, there were insignificant differences (P > 0.05) on all days of observation of the samples with various PEG contents compared with the negative control group. The MTT assays revealed that the cells were able to grow and proliferate quite quickly in the extracts of the HMDI/PCL-PEG/DEG polyurethane hydrogels as well as the extract of the negative control.     

Solvent and support effects in enantioselective hydrogenation of isophorone with (s)-α,α - diphenyl-2-pyrrolidinemethanol modified palladium

Asymmetric heterogeneous catalytic hydrogenation of isophorone has been investigated over (S)-α,α-diphenyl-2-pyrrolidinemethanol modified Pd. The influence of solvent and support effects is discussed. The impact of water, acidic and basic additives on enantioselectivity is described. This revised version was published online in June 2006 with corrections to the Cover Date.     

耐高温,耐腐蚀乙烯基酯树脂的研究

本文就乙烯基酯树脂进行了一些探讨,旨在提高其耐热、耐腐蚀性能,并着重研究了用异氰酸酯改性的乙烯基酯树脂。通过玻璃化转变温度、红外分析、静态试验样浸泡、透光率、介电损耗的变化,以及对其力学性能进行了考察。试验结果表明用甲苯二异氰酸酯对乙烯基酯树脂进行改性是有效的。     

二醋酸纤维素与聚乙二醇接枝共聚物的制备与表征

二醋酸纤维素与聚乙二醇接枝共聚物的制备与表征;二醋酸纤维素-聚乙二醇;接枝共聚物;己二异氰酸酯;制备;表征     

Preparation and Properties of Polyurethane Hydrogels Based on Methylene Diphenyl Diisocyanate/Polycaprolactone-Polyethylene Glycol

Polyurethane (PU) hydrogel is an important biomedical material for drug controlled release systems, wound dressings and medical bandages. Three series of polyurethane prepolymers based on methylene diphenyl diisocyanate (MDI), polycaprolactone (PCL) and polyethylene glycol (PEG), using diethylene glycol (DEG), N-methyldiethanolamine (MDEA) or dimethylolpropionic acid (DMPA), as the chain-extender, were prepared. Then the polyurethane hydrogels were obtained from the prepolymers, using benzoyl peroxide (BPO) as a cross-linking agent, by free radical polymerization. The influences of the types of chain-extenders and polyols on the contact angle, swelling ratio and morphology of the polyurethane hydrogels were investigated. The effect of the variety of the chain-extenders in the PU hydrogel on the drug release behavior was also studied. The FT-IR results showed that the PU hydrogels were successfully synthesized. The introduction of PEG improved the hydrophilicity of the PU hydrogels. The MDI/PCL-PEG/DEG hydrogel was hydrophobic, and there were small micropores on its surface; while the MDI/PCL-PEG/DMPA and MDI/PCL-PEG/MDEA hydrogels had high hydrophilicity and a micropouous structure on their surface due to the existence of carboxyl and tertiary amino functional groups. The change of chain-extenders had no significant effect on the cumulative drug release of chloramphenicol from the PU hydrogels. However, the introduction of PEG increased the drug release rate. The chloramphenicol release kinetics from the MDI/PCL-PEG hydrogels indicated non-Fickian diffusion.     

气相色谱法测定溶剂型木器涂料中异佛尔酮含量

建立一种快速测定溶剂型木器涂料中异佛尔酮含量的气相色谱法。样品经乙酸乙酯提取,采用Rtx–1701毛细管色谱柱分离后,以十四烷作内标物,内标法定量。该方法中异佛尔酮质量浓度在10~200 mg/L范围内呈良好的线性关系,相关系数r=0.999 98,方法检出限为10 mg/kg。样品平均加标回收率为92.2%~97.1%,测定结果的相对标准偏差为0.13%~1.25%(n=6)。该方法能有效地对溶剂型木器涂料中异佛尔酮进行定性、定量分析,而且具有简单、快速、准确、检出限低等特点,能满足实验要求。     

Control of hard segment size in polyurethane formation

In general, segmented polyurethane elastomers are prepared by reacting an isocyanate-capped polyol prepolymer with a short-chain diol chain extender, yielding an elastomer with hard segments of uniform size. However, the hard segment size will not be uniform if the polyurethane polymer is prepared by forming the hard segment first, followed by soft segment formation. Because the mechanical properties of polyurethane elastomers depend on the relative ratio of the hard to soft segments as well as the effectiveness of the hard segment as a physical crosslinker, the control of the size distribution of the hard segment is a key factor in designing polyurethane elastomers. It was found that reaction conditions can affect the size distribution of hard segments derived from an aliphatic diisocyanate with differential reactivity between the two isocyanate groups. Lower reaction temperatures and simultaneous mixing of all reactants gave the preferred size distribution of hard segments. © 1995 John Wiley & Sons, Inc.     

Study of elastomeric polyurethane nanocomposites prepared from grafted organic–montmorillonite

4,4′-Diphenylmethane diisocyanate (MDI) was grafted on to organic–montmorillonite (OMMT) by reaction between hydroxyl groups (−OH) on surface of the montmorillonite and the isocyanate groups (−NCO) of MDI, thus forming grafted organic–montmorillonite (MOMMT). Intercalated nanocomposites based on polyurethane (PU) and MOMMT were prepared by solution intercalation technology. The interface interaction of PU/MOMMT nanocomposites was better than that of PU/MMT composites. The tensile strength, elongation at break, and tear strength of the PU/MOMMT nanocomposites increased for MOMMT content up to 5% w/w, and then decreased with further increase in MOMMT content. At the same filler content, the tensile strength and tear strength of PU/MOMMT nanocomposites were higher than those of PU/OMMT nanocomposites, whereas the elongations at break of PU/MOMMT nanocomposites were smaller than those of PU/OMMT nanocomposites. The initial temperatures of weight loss of PU/MOMMT nanocomposites were lower than for PU/MMT composites in the first step of thermal degradation, whereas in the second step initial temperatures of weight loss were higher for PU/MOMMT nanocomposites.     

Isophorone-based Fluorescent Dopant for Red Organic Electroluminescence Device

IntroductionOrganiclight emittingdiodes (OLEDs)haveattractedconsiderableattentionsincetheinitialworksbyTangetal.1andFriendetal.2 duetotheirpotentialapplicationsinfull colorflat paneldisplays .3,4 Torealizefull colorap plications ,highperformanceorganicmaterialsemittingthethreeelementalcolorsofred ,greenandbluearerequired .Aftertwodecadesofintensiveresearch ,anumberofgreenandblueemitterswithhighluminousefficiencies ,reason ablecolorpurityandpracticallifetimehavenowbeenreal izedinbothsmallmole…     

Microwave step‐growth polymerization of 5‐(4‐methyl‐2‐phthalimidylpentanoylamino)isophthalic acid with different diisocyanates

The utilization of microwave energy in polymer synthesis is a fast growing field of research leading to a more rapid and cleaner polymerization process. In order to synthesize novel optically active monomer 5‐(4‐methyl‐2‐phthalimidylpentanoylamino)isophthalic acid ( 6 ), the reaction of phthalic anhydride with l ‐leucine was carried out in an acetic acid solution and 4‐methyl‐2‐phthalimidylpentanoic acid as an imide acid was obtained in good yield. Then, it was converted to 4‐methyl‐2‐phthalimidylpentanoyl chloride by treatment with thionyl chloride. This acid chloride was reacted with 5‐aminoisophthalic acid and the novel bulky aromatic amide‐imide chiral monomer 6 was obtained in high yield and was characterized with spectroscopy techniques as well as specific rotation and elemental analysis. Polycondensation of monomer 6 with different diisocyanates such as 4,4′‐methylenebis(phenyl isocyanate), toluene‐2,4‐diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate was performed by two different methods: microwave irradiation and classical heating polymerization techniques in the presence of various catalysts and without a catalyst. The microwave polymerization technique provides a new way for the production of polymers at high rates. The resulting novel optically active polyamides have inherent viscosities in the range of 0.25–0.63 dl/g. They show good thermal stability and are soluble in amide‐type solvents. The obtained polyamides were characterized by FT‐IR, ¹H‐NMR spectroscopy, elemental analyses, specific rotation, and thermal analyses methods. Copyright © 2008 John Wiley & Sons, Ltd.