苯乙烯与甲基丙烯酸及丙烯酸无皂乳液共聚过程研究

研究了油溶性单体苯乙烯分别与水溶性功能单体 (甲基丙烯酸 ,丙烯酸 )的共聚过程。通过透射电镜以及红外测试等对聚合过程进行了跟踪研究。结果表明 。

(膨润土/淀粉)分别接枝丙烯酰胺制备吸水树脂的研究

采用膨润土、淀粉分别接枝丙烯酰胺制备吸水树脂 ,本文研究了当吸水倍率相近时两种接枝共聚物在吸液性能、共聚过程。

线性低密度聚乙烯

LLDPE通常在更低温度和压力下， 由乙烯和高级的a烯烃如丁烯、己烯或辛烯共聚合而生，共聚过程生成的LLDE聚合物具有比一般LDPE更窄的分子量分布，同时具有线性结构使其有着不同的流变特性。

Study on Optimal Strategy of Grade Transition in Industrial Fluidized Bed Gas-Phase Polyethylene Production Process

A model of grade transition is presented for a commercialized fluidized bed gas-phase polyethylene production process. The quantity of off-specification product and the time of grade transition can be minimized by the optimization of operating variables, such as polymerization temperature, the ratio of hydrogen to ethylene, the ratio of co-monomer to ethylene, feed rate of catalyst, and bed level. A new performance index, the ratio of melt flow (MFR), is included in the objective function, for restraining the sharp adjustment of operation variables and narrowing the distribution of molecular weight of the resin. It is recommended that catalyst feed rate and bed level are decreased in order to reduce the grade transition time and the quantity of off-specification product. This optimization problem is solved by an algorithm of sequential quadratic programming (SQP) in MATLAB. There is considerable difference between the forward transition and reverse transition of grade with regard to the operating variables due to the non-linearity of the system. The grade transition model is extended to a high space time yield (STY) process with the so-called condensed model operation. In the end, an optimization strategy for multi-product transition is proposed with two-level optimization of the objective function J(x,u) on the basis of the optimal grade transition model. A sequential transition of six commercial polyethylene grades is illustrated for an optimal multi-product operation.

Diffusion of an Antifogging Agent in Polyethylene Film

The diffusion of an antifogging agent, EO/PO (epoxyethane/epoxypropane) copolymer, through apolyethylene PE film was studied using a simple experimental system. It was found that the temperature, concentration of antifogging agent, crystallinity of PE film and film thickness affect the diffusion process.

Observation on Double Fertilization and Early Embryonic Development in Autotetraploid Polyembryonic Rice

The process of double fertilization and the characters of embryo and endosperm development in an autotetraploid polyembryonic mutant rice IR36-Shuang were studied with a laser scanning confocal microscopy. Some abnormalities including degenerated ovary, abortive embryo sac, single fertilization, double-ovule and double-embryo and so on. were found dudng double fertilization and embryo development in IR36-Shuang. The rate of the abnormalities was 46.67% in IR36-Shuang, significantly higher than that in the control, an autotetraploid rice line IR36-4X （33.00%）. Cytological and embryonic evidences were provided for seed setting decline and the initiation of additional embryo in IR36-Shuang.

In vivo detection of mucosal healing-involved histiocytes by confocal laser endomicroscopy

Histiocytes have a pivotal role in wound repair and intestinal epithelial recovery-the most important goal to sustain gut functionality.Yet,an in vivo description of colonic histiocytes by confocal laser endomicroscopy(CLE) is missing.Here,we report the case of a 45-yearsold male patient who was referred to our clinic with weight loss and a history of two consecutive Clostridium difficile colitis episodes,the latter cured 3 wk before present admission.Stool microbiology was negative.Conventional colonoscopy showed atrophy and a light mucosal oedema in the distal colon.During on-going endoscopy,we performed a fluorescein-aided CLE which revealed large polygonal(histiocytes-like) cells with copious cytoplasm and large nuclei in the lamina propria of the sigmoid colon as well as regenerative epithelial changes.Histopathological assessment of biopsies from the same areas confirmed the endomicroscopical findings:Periodic acid-Schiff-and CD68-positive foamy histiocytes in the colonic lamina propria and an advanced epithelial recovery.Since stool microbiology was repeatedly negative and polymerase chain reaction-analysis from colonic biopsies could not detect any mRNA for Thropheryma whippleii and common pathogens,we interpreted this particular setting as a mucosal healing process after consecutive Clostridium difficile infections.In conclusion,by describing these colonic histiocytes,we highlight the clinical usefulness of CLE in describing the entity of histiocytes in vivo and in real-time during the process of post-infectious mucosal healing in the colon.

Preparation of pH-responsive membranes with amphiphilic copolymers by surface segregation method

Novel pH-responsive membranes were prepared by blending pH-responsive amphiphilic copolymers with polyethersulfone(PES) via a nonsolvent-induced phase separation(NIPS) technique. The amphiphilic copolymers bearing Pluronic F127 and poly(methacrylic acid)(PMAA) segments, abbreviated as PMAA n–F127–PMAA n,were synthesized by free radical polymerization. The physical and chemical properties of the blend membranes were evaluated by scanning electron microscopy(SEM), Fourier transform infrared(FTIR) spectrum, water contact angle, Zeta potential and X-ray photoelectron spectroscopy(XPS). The enrichment of hydrophilic PMAA segments on the membrane surfaces was attributed to surface segregation during the membrane preparation process. The blend membranes had signi ficant p H-responsive properties due to the conformational changes of surface-segregated PMAA segments under different pH values of feed solutions. Fluxes of the blend membranes were larger at low p H values of feed solutions than that at high pH values. The pH-responsive ability of the membranes was enhanced with the increase of the degree of PMAA near-surface coverage.

Surface-imprinted polymers in microfluidic devices

Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices.