Dispersion of Nano TiO2 in Ethylene Glycol and Poly(ethylene terephthalate)

Nano TiO₂ was dispersed in ethylene glycol (EG) by the replacement of dispersion medium from water sol. EG/TiO₂ suspension was well stabilized by the electrostatic repulsive force when pH value of suspension was less than 4.3. In situ polymerization starting from bis(2-hydroxyethyl) terephthalate (BHET) and EG/TiO₂ suspension was carried out to prepare a series of poly(ethylene terephthalate) (PET)/TiO₂ nanocomposites. Under highly acidic conditions, 97% particles dispersed in PET matrix had the size less than 100 nm. With the increase of pH value, aggregation occurred and larger size particles appeared. A tensile test showed that Young's modulus of PET was increased by the addition of nano TiO₂     

Preparation of Silica/Poly(divinylbenzene) Composite Particles by Dispersion Polymerization in Supercritical Carbon Dioxide

Silica/poly(divinylbenzene) (PDVB) composite particles were synthesized by the dispersion polymerization of divinylbenzene (DVB) with ultrafine silica particles in supercritical carbon dioxide (scCO₂). Silica particles of average diameter 130 nm were pretreated with 3-(trimethoxysilyl) propyl methacrylate in order to be well dispersed in CO₂ and participated in the polymerization. Random copolymeric dispersant, poly(diisopropylaminoethyl methacrylate-co-heptafluorobutyl methacrylate) was used as a stabilizer to provide sufficient stabilization to latexes in scCO₂ and the silica/PDVB composite powder was obtained in high yield from the polymerization. SEM analysis revealed that the composite particles prepared at 5% silica loading ratio and 6% stabilizer concentration with respect to monomer have the average diameter of 1.60 μm with uniform and spherical morphology. The composites were also characterized by FTIR spectroscopy and TGA.     

Polymer-Nanoparticle Composites Composed of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Coated Silver Nanoparticles

The effects of addition of synthesized organic-suspension silver nanoparticles on the crystallization and thermal stability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD), UV-Vis absorption spectroscopy, polarized optical microscopy (POM), and thermal gravimetric analysis (TGA). The TEM images showed the average primary size of the as-synthesized silver nanoparticles, coated with a monolayer of the surfactants consisting of oleic acid and an alkylamine, was about 5 nm with narrow distribution, and that they were uniformly dispersed in n-heptane. PHBV/silver nanocomposites were prepared by melt mixing in an internal mixer and then injection molded into rectangle-shaped specimens by a labscale injection molding device. The coated silver nanoparticles showed a homogenuous dispersion in the PHBV matrix when the content of coated silver nanoparticles was about 1%. Both the DSC and POM data showed the efficient heterogeneous nucleation by the coated silver nanoparticles for facilitating PHBV crystallization. The thermal stability of the PHBV/silver nanocomposites improved with the increase in the content of the coated silver nanoparticles.     

无规聚甲基丙烯酸甲酯立构复合的红外光谱研究

用红外光谱研究了无规聚甲基丙烯酸甲酯的丙酮、苯、氯仿溶液成膜样品的立构复合状况。结果表明无规聚甲基丙烯酸甲酯在丙酮和苯中确能形成立构复合结构,结构的形成主要是依靠分子链中间规和等规链段的相互作用。对丙酮样品的退火实验表明,在退火过程中能够发生间规链段的自聚集现象。     

Hydrophobic Modification of Poly(Ethylene Terephthalate) with Epoxy-Modified Polysiloxane by Reactive Extrusion

Hydrophobic poly(ethylene terephthalate) (PET) was prepared by reactive blending of PET with double epoxy groups modified polysiloxane (diepsi) or multiepoxy groups modified polysiloxane (multiepsi). The structure of the modified PET was characterized by ¹H NMR and intrinsic viscosity. The grafted ratio of diepsi and multiepsi was 1.3 and 0.03 wt%, respectively. With the introduction of diepsi and multiepsi to PET, the water contact angle of modified PET increased from 73° to a maximum of 106°, showing the good hydrophobicity of the modified PET. The samples of modified PET were washed with different solvents and their water contact angles did not significantly decrease, indicating good durability of the hydrophobicity. Moreover, the films of modified PET prepared by solution casting (phenol and 1, 1, 2, 2-tetrachloroethane mixed solution) showed excellent hydrophobicity with the contact angle 151°. Scanning electron microscopy images showed the surface of the modified PET films to be rougher than those of unmodified PET because the introduction of polysiloxane to PET resulted in phase separation during the solvent evaporation process.     

Sorption and Diffusion of Sub/Supercritical Carbon Dioxide in Poly(methyl methacrylate)

Sorption and desorption processes of subcritical and supercritical carbon dioxide in poly(methyl methacrylate) (PMMA) at various temperatures and pressures were investigated systematically. The gravimetric method was used to study the desorption and sorption diffusivities. It was found that there existed a characteristic value of pressure in the sorption isotherm of PMMA, above which saturation was observed to increase more rapidly with pressure. From the measured diffusivities of sorption and desorption under a wide range of operating conditions, the diffusivities of sorption was found to increase with increasing temperature, whereas the diffusivities of desorption showed a contrary trend.     

Tribological Properties of Poly(Para-Phenylene Sulfide) and its Carbon Fiber Composites with Water Lubrication

Tribological properties of poly(para-phenylene sulfide) (PPS) with different molecular mass were studied. PPS properties were compared with the same properties of its carbon fiber-filled plastics. For the interpretation of tribological test results an especial role was assigned to the load capacity of materials. The concept of load capacity permits consideration of different tribological dependencies as phase diagrams. The structure of the samples was characterized by X-ray diffraction and differential scanning calorimetry techniques.     

Surface modification of magnesium aluminum hydroxide nanoparticles with poly(methyl methacrylate) via one-pot in situ polymerization

Hydrophobic magnesium aluminum hydroxide composite particles (PMMA-MAH) were obtained by means of grafting poly(methyl methacrylate) (PMMA) onto the surface of magnesium aluminum hydroxide(MAH) nanoparticles after a novel type of phosphate coupling agent (DN-27) modification. The introduction of functional double bonds was firstly conducted on the surface of nanoparticles by DN-27 modification, followed by one-pot in situ polymerization on the particles surface using methyl methacrylate (MMA) as monomer, azoisobutyronitrile (AIBN) as initiator and sodium dodecyl sulfate (SDS) as stabilizer to graft PMMA on the surface of DN-27-modified MAH particles. The obtained composite particles were characterized by field-emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD). The results show that the organic macromolecule PMMA could be successfully grafted on the surface of DN-27-modified MAH nanoparticles and the thermal stability of the PMMA-MAH composite particles had been improved. Compared with unmodified blank MAH sample, the product obtained with this method possesses better hydrophobic properties such as a higher water contact angle of 108° and a well dispersion.     

Liposomal Templating,Association with Mammalian Cells,and Cytotoxicity of Poly(vinyl alcohol) Physical Hydrogel Nanoparticles

The assembly, cellular internalization, and cytotoxicity of nanoparticles based on physical hydrogels of poly(vinyl alcohol) (PVA) are reported. PVA nanoparticles are assembled using a liposomal templating technique followed by removal of the lipids using isopropanol, a process that requires the presence of a custom‐made block copolymer, poly(vinyl alcohol‐b‐vinyl pyrrolidone), to avoid aggregation of the nanoparticles. Polymer hydrogelation is induced via incubation in aqueous isopropyl alcohol solution, which results in PVA hydrogel nanoparticles (PVA HNP) with excellent colloidal stability and stability towards disintegration over at least 24 h. Pristine PVA HNP are found to be remarkably stealth‐like and exhibit negligible cellular internalization. This feature is likely inherent with the low fouling nature of PVA and makes PVA HNP attractive for targeted drug delivery with a low level of association with non‐targeted cells and tissues. Blending PVA with varied amounts of collagen results in colloidal hydrogel particles with a well pronounced tendency towards association with mammalian cells, specifically hepatocytes and endothelial cells. The association of PVA HNP elicits minimal changes in cellular proliferation, making these novel hydrogel particles convenient tools for drug delivery applications and creation of implantable artificial organelles and sensors.     

聚对苯二甲酸丁二醇酯/聚(对苯二甲酸丁二醇酯-e-己内酯)二元结晶共混体系的相容性和结晶行为

聚对苯二甲酸丁二醇酯(PBT)/聚(对苯二甲酸丁二醇酯-e-己内酯)(PBT-PCl)是一个新制备的具有分子间排斥相互作用的A/AxB1?x型两元结晶共混体系. 根据两元平均场模型,报道对苯二甲酸丁二醇酯(BT)与"-己内酯(CL)结构单元的相互作用参数为0.305. DSC研究发现,此共混物呈现了与典型的共聚物/均聚物共混物不同的结晶特征. PBT-PCL影响PBT链的活动力和晶片堆积;同时PBT-PCL的结晶受到先期结晶的PBT晶粒的阻滞. 尽管拥有相同的BT单元,共混的两组分在组成变化范围内仍没有形     

Improved Dispersion of Carbon Nanoparticles Modified by Poly(Sodium 4-Styrenesulfonate) and Its Influence on the Properties of Natural Rubber Latex

A novel strategy of radical polymerization of sodium 4-styrenesulfonate on the surface of carbon black (CB) in the solid state was developed to prepare hydrophilic carbon nanoparticles (PNASS-CB). A high performance natural rubber latex (NRL)/PNASS-CB composite was produced by the latex compounding technique. Scanning electron microscope shows considerable improvement in the dispersion of PNASS-CB in rubber matrix. The lower degree of filler–filler networks and the stronger filler–rubber interaction of PNASS-CB in rubber matrix were confirmed by dynamic mechanical thermal analysis. Rheometric properties of NRL/PNASS-CB, like scorch time and optimum cure time, decreased. Tensile strength, tear strength, and elongation at break increased due to stronger interaction between the PNASS-CB and rubber matrix. Dynamic mechanical properties of the modified carbon nanoparticles further corroborated a significant contribution from the better dispersion and efficient load transfer of PNASS-CB on the static and dynamic mechanical properties of composites.     

Phase Structure,Thermal, and Mechanical Properties of Polypropylene/Hollow Glass Microsphere Composites Modified with Maleated Poly(ethylene-octene)

Maleated poly(ethylene-octene) (POE-g-MAH), as a compatilizer and toughener, was incorporated in polypropylene/hollow glass microspheres (PP/HGM) binary composites, and the phase structure and thermal and mechanical properties of these composites were investigated. Scanning electron microscopy analysis indicated that the phase structure of ternary composites could be controlled by POE-g-MAH and the surface treatment of HGM. Fourier transform infrared spectroscopy revealed that there was an amidation reaction between the treated HGM and POE-g-MAH during melt compounding. Differential scanning calorimetry suggested that the crystallization and melting behaviors of ternary composites were influenced by phase structure. Evaluation of mechanical properties showed that the amide linkage between the treated HGM and POE-g-MAH was favorable for improving the properties of ternary composites.     

Membranes of Poly (Vinyl Butyral) (PVB) or Cationic PVB (CPVB) Blended with Poly (Vinylidene Fluoride) (PVDF) Prepared by a Nonsolvent Induced Phase Separation Method: Miscibility and Hydrophilicity

The synthesized hydrophilic polymers [poly (vinyl butyral) (PVB) and cationic PVB (CPVB)] blended with poly (vinylidene fluoride) (PVDF) were used to fabricate hydrophilic ultrafiltration membranes. A visual inspection method and a glass transition temperature method were applied to study the miscibility of PVDF/PVB and PVDF/CPVB blend systems. The results showed that the PVDF/PVB was an immiscible blend and the PVDF/CPVB was a partially miscible blend. Dynamic contact angle experiments showed that the hydrophilicity of the blend membranes was significantly improved with the addition of PVB and CPVB. The pure water permeation (PWP) of blend membranes increased with the content of PVB and CPVB.     

Analysis of 13C-mixed Triacylglycerol in Stool by Bulk (Ea-IRMS) and Compound Specific (GC/MS) Methods

Abstract

This paper was presented in poster form at the 17th International Congress of Nutrition, August 27-31, Vienna. Austria (Annals of Nutrition & Metabolism 2001; 45(Suppl.1):349). Some of the data were also presented in poster form at the British Society of Gastroenterology Meeting, March 18-21, Glasgow, UK (Gut 2001; 48(Suppl.1):A91).

The ¹³C-mixed triacylglycerol (MTG) breath test is used to measure intraluminal fat digestion. In normal digestion. 20–40% of the ingested ¹³C label is recovered in breath CO₂. We aimed to identify the proportions of ingested label excreted in stool, as well as breath following ingestion of ¹³C-MTG by children with impaired exocrine pancreatic function and healthy controls. ¹³C enrichment of breath samples was measured by continuous flow isotope ratio mass spectrometry (IRMS) and cumulative percent dose recovered (cPDR) in 10 h was calculated. Total ¹³C of a faecal fat extract from each stool was measured by elemental analyser-IRMS, and ¹³C enrichment and concentration of the TBDMS derivative of octanoic acid was measured by GC/MS after hydrolysis of the fat extract. Stool 5-day cPDR was calculated. Mean breath cPDR was 35%. Mean cPDR in stool by combustion-IRMS and GC/ MS, respectively, was 0.8% and 1.0%. Therefore, the remaining 64% of the ¹³C label must remain in the body and variability in breath cPDR is due to postabsorptive rather than predigestive factors.     

Study by 1H NMR of the Influence of the Porosity and Solvent on the Conformations of Macromolecules at an Interface: Poly(Ethylene Oxide) Grafted on Silica

The ¹H NMR technique was used to study the behaviour of poly(ethylene oxide) chains grafted chemically on silica. A noticeable influence of the nature of the surface and solvent on the conformation of the grafted macromolecules was observed. For precipitated silica the chains adopted a disordered conformation whereas for pyrogenic silica they formed a more uniform layer. The grafting ratio and the solvent can both modify the conformations of the chains. The dependence of the relaxation times (T₁ and T₂) on the grafting ratios is discussed qualitatively from a phenomenological point of view. Different models are proposed for the two extreme grafting ratio levels in both the absence and the presence of solvent. Without solvent, for both grafting ratios, the macromolecules lie very flat on the silica and the layer is more organized, especially at high grafting ratio. In the presence of solvent the chains spread out in the solvent, adopt a more extended conformation and the local concentration of monomers at the surface decreases.     

藻蓝蛋白原位还原Ag（Ⅰ）与纳米Ag（O）形成动态过程的谱学研究

在4℃避光条件下，将藻蓝蛋白（简称PC）与AgNO3作用，通过UV，FS，FTIR等谱学方法研究了PC与Ag（Ⅰ）原位还原与纳米Ag（0）粒子形成的动态过程。结果显示：PC在615nm的特征吸收峰强度明显减弱，并随Ag（Ⅰ）浓度增加和时间延长单调降低；PC的荧光发射峰和荧光激发峰也均呈现衰减趋势。同步荧光光谱观察到纳米Ag（0）粒子形成的动态过程。用TEM观察到所形成的Ag（0）分散于PC表面，形成PC为核，纳米银为壳部分包覆的生物缀合物，粒子呈球形，有较窄的分布尺寸，粒径在15～30nm之间。     

Photophysical and lasing properties of pyrromethene 567 dye in solid poly(trifluoromethyl methacrylate) matrices with different degrees of crosslinking

The effect of increasing the rigidity of the host matrix by controlled crosslinking of the polymeric chains on the lasing and photophysical properties of pyrromethene 567 (PM567) was evaluated. To this end, the dye was dissolved in 2,2,2-trifluoromethyl methacrylate (TFMA) together with different amounts of the crosslinking monomer ethylene glycol dimethacrylate (EGDMA). Increasing the concentration of this crosslinker monomer resulted in significant increases in both lasing efficiency and photostability. Good correlation between fluorescence and lasing properties has been observed, indicating the existence of an optimum degree of crosslinking for which lasing efficiency and photostabilty reach their highest values. These new solid materials show lasing efficiencies up to 18% when transversely pumped at 534 nm and good photostabilities, with a decrease in the initial laser output of 45% after 10000 pump pulses. Received: 16 February 2001 / Revised version: 9 April 2001 / Published online: 8 June 2001