Synthesis and characterization of biodegradable amphiphilic PEG-grafted poly(DTC-co-CL)

<正>A novel biodegradable copolymer,poly(5,5-dibromomethyltrimethylene carbonate-co-ε-caprolactone)(poly(DBTC-co-CL)) with pendant bromine groups,was synthesized via ring-opening polymerization(ROP) ofε-caprolactone(CL) and 5,5- dibromomethyltrimethylene carbonate(DBTC) using stannous octoate(Sn(Oct)_2) as catalyst.Then the pendant bromine groups were completely converted into azide form,which permitted"click"reaction with alkyne-terminated polyethylene(A-PEG) by Huisgen 1,3-dipolar cycloadditions preparing biodegradable amphiphilic poly(DTC-co-CL)-g-PEG graft copolymer.The graft copolymer was characterized by nuclear magnetic resonance(NMR) and size-exclusion chromatography(SEC).     

Investigation of craze development using small-angle X-ray scattering of synchrotron radiation

The development of crazes in polycarbonate was investigated with the method of ultra-small-angle X-ray scattering (USAXS) of synchrotron radiation. Measurements at different temperatures and with different draw rates were carried out. The two-dimensional scattering patterns were analyzed by means of a fibrillar model of the craze. The geometrical parameters of the craze as a function of the macroscopic draw ratio were determined by using a curve-fitting procedure. From the measured values of the diameter and the mean distance of the fibrils, it is possible to calculate the volume fraction v_f of the fibrils directly. Additional scattering caused by submicrocracks is discussed.     

STUDIES ON MISCIBILITY OF POLY (ε-CAPROLACTONE) AND ALIPHATIC POLYCARBONATE BLENDS AND DETERMINATION OF THEIR INTERACTION PARAMETER*

In this paper the miscibility of poly (ε-caprolactone) (PCL) and aliphatic polycarbonate (APC) is studied by using DSC. The results show that PCL and APC are miscible in all ranges of composition. The interaction parameter between the polymers is calculated from the melting point depression data. Using optical microscope, the shapes of the PCL spherulites in the blends are observed.     

Evaluation of physico-chemical properties of electron beam-irradiated polycarbonate film

In this work, polycarbonate (PC) film samples were irradiated with 10 MeV electrons at different doses ranging from 25 to 250 kGy. Characterization techniques viz. thermogravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction analysis (XRD) and electron paramagnetic resonance (EPR) were exploited to understand the induced changes in the physico-chemical properties of the polymer. An increase in the decomposition temperature with increasing dose was observed, while the crystallinity remained unchanged as a result of the formation of cross-link bond. EPR technique characterized the stability of the free radicals in the irradiated PC. The result showed that cross-linking process occurs at low absorbed doses, whereas polymer degradation happens at higher doses.     

Evaluation of polycarbonate substrate hologram recording medium regarding implication of birefringence and thermal expansion

In this paper, we evaluate photopolymer media using a polycarbonate (PC) substrate. In holographic data storage medium, substrates that sandwich the photopolymer material are needed to protect the photopolymer material against exogenous shock and open air. An optical glass such as BK-7 is normally used as a substrate, but a PC substrate has a cost advantage and is easy to fabricate compared with optical glass. For holographic recording and reading, however, the high birefringence and high thermal expansion of a PC substrate are significant problems. First, we analyze the degree of degradation of output power by the polarization change and estimate the threshold value of birefringence to record hologram normally. Next, we estimate the temperature tolerance of hologram readout with polycarbonate substrate hologram medium. These analyses results indicate the possible usage of the PC substrate as holographic recording media.     

Organic nanoparticles suspensions preparation by underwater excimer laser ablation of polycarbonate

Ablation with excimer laser pulses on polycarbonate (PC) film has been performed in ultrapure water. It is demonstrated that it is a new efficient method for organic nanoparticles (ONP) suspensions synthesis. Proof of the formation of ONP is given by analysis of the water phase with AFM and UV-vis spectroscopy. The obtained transmission measurements are approached with the aid of Mie theory to estimate composition of suspensions. Results indicate that the polycarbonate film is partly ablated into nanometric particles with size ranging from 8 up to 180 nm. This is also supported by force atomic microscopy. Confocal Raman microspectroscopy was done directly on water suspensions. Thanks to the optical trapping phenomenon of the nanoparticles, their vibrational Raman spectrum was more easily obtained. Original polycarbonate is lost although some polymeric structures are detected along with graphitic carbon.     

PC/尼龙6共混合金的结晶结构与性能

聚碳酸酯(PC)由于具有突出的冲击韧性、良好的透明性、尺寸稳定性和电气绝缘性而广泛应用于电子电气、仪器仪表、汽车、机械、医疗、照明和建筑等领域,是一种综合性能优良的工程塑料.但也存在着加工流动性差和耐药性差、易应力开裂及对缺口敏感等缺陷,且价格昂贵,因而限制了它的应用范围.对PC进行合金化,提高PC的性能,降低成本是PC改性的重要研究方向,开发成功的PC合金有PC/ABS,PC/PET,PC/PBT[1]和PC/PE[2]等.制备高性能PC/尼龙6(PA6)合金是目前国内外PC改性的热点.PA6的加入可以改善PC的耐药性、耐应力开裂性及加工性能,降…     

Fluorescence behavior of individual charge-transfer complexes revealed by single-molecule fluorescence spectroscopy: Influence of the host polymer matrix

Extremely pure polymer matrices were used for elucidating the fluorescence properties of singly isolated charge-transfer (CT) complexes formed between the donor N-ethylcarbazole and the acceptor 1,2,4,5-tetracyanobenzene. Simultaneous measurements (time traces of CT fluorescence intensities and lifetimes) using single-molecule fluorescence spectroscopy showed three patterns: (1) fluctuations in the fluorescence intensities and lifetimes seldom occurred, (2) the fluorescence intensities frequently fluctuated together with the lifetimes, or (3) in addition to the above fluctuations with time, blinking and/or off-states longer than 1 s were observed. For methacrylate polymers, both the degree of fluctuations in the CT fluorescence lifetimes and the percentage of the CT complexes showing off-states increased with the free volume of the host polymers. These results suggest that the degree of fluctuations in the relative geometrical arrangements of the donor and acceptor molecules is related to the availability of space in the host polymer, and that the free volume provides the necessary space for formation of non-fluorescent donor-acceptor geometries of the CT complexes and/or temporal dissociation of the CT complexes. Survival times of the CT fluorescence were also closely related with the free volume of the host polymers.     

Study on the etching conditions of polycarbonate detectors for particle analysis of safeguards environmental samples

The fission track technique was applied to the particle analysis for safeguards environmental samples to obtain information about the isotope ratio of nuclear materials in individual particles. To detect the particles containing nuclear material with high detection efficiency and less particle loss, the influence of uranium enrichments on etching conditions of a fission track detector made of polycarbonate was investigated. It was shown that the increase in uranium enrichment shortened the suitable etching time both for particle detection and for less particle loss. From the results obtained, it was suggested that the screening of the uranium particles according to the enrichment is possible by controlling the etching time of the detector.