玻璃表面的紫外光诱导氧化还原自由基聚合

利用伯胺分子层与二苯甲酮(BP)构成光引发体系在玻璃表面引发丙烯酸、丙烯酰胺、丙烯酸酯等的自由基接枝聚合。衰减全反射红外光谱、接触角与原子力显微镜的结果证明聚合物成功接枝于玻璃表面。以N,N-二甲基丙烯酰胺(DMAAm)为单体,研究了聚合条件的影响。当原料配比m(BP)∶m(DMAAm)∶m(acetone)=5∶100∶1000,反应时间为5min时,样品的接枝率和单位面积接枝量分别达到了0.330%和0.87mg/cm2,表面形貌发生了明显变化。结果表明接枝有PDMAAm的玻璃表面与丙烯酸树脂的粘接性能有显著提升。     

小本体聚丙烯的透明改性研究

以小本体聚丙烯为原料,通过添加成核剂和相对分子质量调节剂,制备了具有良好透明性能和力学性能的小本体聚丙烯.探讨了成核剂的含量、相对分子质量调节剂种类等因素对结晶和透明性的影响.结果显示成核剂和相对分子量调节剂共同作用,不仅能有效地提高小本体PP的透明性,而且能有效地改善小本体PP的综合力学性能;通过XRD谱图分析表明成核剂的加入能有效地提高小本体PP的结晶度,降低体系β晶型的含量.     

超临界聚合法等规聚丙烯的结晶行为

采用差示扫描量热法及带热台在线偏光显微镜直接观察法,研究了超临界聚合与常规淤浆聚合这两种不同聚合工艺所制备等规聚丙烯的等温结晶行为.结果表明,超临界法聚丙烯（sc-iPP）由于其较低的分子量及较窄的分布,使得等温结晶速率比常规淤浆法聚丙烯（c-iPP）快,结晶度高,且sc-iPP的晶体呈负光性,倾向于异相成核.而c-iPP的晶体则呈混光性,倾向于均相成核,但两者均为典型的球晶,均体现热成核机理.     

聚丙烯熔体结晶过程中声发射源的实验研究

用光学显微镜观察了六种聚丙烯试样熔体在非等温结晶过程中形态织构的变化。并且与在同样条件下试样结晶过程中观察到的声发射现象进行对照。证实聚丙烯熔体结晶过程中产生声发射讯号主要是在结晶后期,特別是球晶生长结束并形成边界后,在球晶边界和球晶内部形成微缺陷的过程所导致的。它与球晶形成时体积收缩、内应力的产生和增加直接有关。     

纳米TiO2、钠米ZnO对聚丙烯抗紫外光老化及结晶性能的影响

借助DSC、FT-IR、DMA现代分析表征技术，首次以马来酸酐接枝聚雨烯作为聚丙烯／纳米TiO2或纳米ZnO复合材料的相容剂和相分散剂，系统研究了它们对聚丙烯的耐紫外光老化性能的影响．同时，探讨了纳米TiO2和纳米ZnO对聚丙烯的结晶成核作用。研究结果表明．纳米TiO2、纳米ZnO的加入使PP的β-晶型熔融峰消失．对聚丙烯结晶有明显的成核促进作用；随着紫外光老化时间的延长，PP熔融峰高度下降，峰宽和熔融温度基本不变．1750cm^-1处的峰面积增加幅度减小；纳米TiOz和纳米ZnO可以减缓PP在紫外光照射下的降解速度，提高PP对外界能量的耗散作用；PP纳米复合材料的损耗模量明显增大，阻尼因子（即tanδ）在添加PP—g—MAH后峰值也明显下降。     

纳米TiO2、纳米ZnO对聚丙烯抗紫外光老化及结晶性能的影响

借助DSC、FT-IR、DM A现代分析表征技术,首次以马来酸酐接枝聚丙烯作为聚丙烯/纳米T iO2或纳米ZnO复合材料的相容剂和相分散剂,系统研究了它们对聚丙烯的耐紫外光老化性能的影响,同时,探讨了纳米T iO2和纳米ZnO对聚丙烯的结晶成核作用。研究结果表明,纳米T iO2、纳米ZnO的加入使PP的β-晶型熔融峰消失,对聚丙烯结晶有明显的成核促进作用;随着紫外光老化时间的延长,PP熔融峰高度下降,峰宽和熔融温度基本不变,1750 cm-1处的峰面积增加幅度减小;纳米T iO2和纳米ZnO可以减缓PP在紫外光照射下的降解速度,提高PP对外界能量的耗散作用;PP纳米复合材料的损耗模量明显增大,阻尼因子(即tanδ)在添加PP-g-M AH后峰值也明显下降。     

聚丙烯氧化过程的化学发光的研究EI

研究了不同光谱范围的聚丙烯氧化过程的化学发光动力学特性。研究表明,聚丙烯氧化过程的化学发光分属于两个光谱范围,有三个峰值过程。第一和第三个峰值过程在530到725nm光谱范围依次出现;第二个峰值过程仅在330到590nm光谱范围观测到;530到590nm光谱范围则可观测到所涉及的三个峰值过程。其中,第一个峰值过程与试样的氧化程度有关,第二和第三个峰值过程对应于自催化氧化反应。文中还讨论了聚丙烯氧化过程的化学发光机制。     

聚丙烯微孔膜表面接枝聚合丙烯酰胺的改性研究

用化学方法在聚丙烯微孔膜表面接枝丙烯酰胺单体,分别考察了反应温度、单体浓度、反应时间和引发剂浓度等反应因素对接枝率的影响,红外光谱和扫描电镜证实了丙烯酰胺在聚丙烯微孔膜表面的接枝,水接触角测试显示接枝膜具有良好的亲水性,热分析表明接枝膜基本没有改变聚丙烯微孔膜的基体性质.实验发现当反应温度为60℃,单体浓度为10%,反应时间为4h,引发剂浓度为2.0×10-3mol/L时,获得最佳接枝效果.     

Advanced Photoacoustic Imaging Applications of Near‐Infrared Absorbing Organic Nanoparticles

Progress of nanotechnology in recent years has stimulated fast development of nanoparticles in biomedical research. Photoacoustic (PA) imaging as an emerging non‐invasive technique in molecular imaging has improved imaging depth relative to conventional optical imaging, demonstrating great potential in clinical applications. The convergence of nanotechnology and PA imaging has enabled a broad spectrum of new opportunities in fundamental biology and translation medicine. This review focuses on the recent advances of organic nanoparticles in PA imaging applications. Near‐infrared absorbing organic nanoparticles are classified and discussed according to their different imaging applications, which include tumor imaging, gastrointestinal imaging, sentinel lymph node imaging, disease microenvironment imaging and real‐time drug imaging. The chemistry and PA properties of organic nanoparticles are discussed in details to highlight their own merits, and their challenges and perspectives in PA imaging are also discussed.     

Metabolizable Semiconducting Polymer Nanoparticles for Second Near‐Infrared Photoacoustic Imaging

Photoacoustic (PA) imaging in the second near‐infrared (NIR‐II) window (1000–1700 nm) holds great promise for deep‐tissue diagnosis due to the reduced light scattering and minimized tissue absorption; however, exploration of such a noninvasive imaging technique is greatly constrained by the lack of biodegradable NIR‐II absorbing agents. Herein, the first series of metabolizable NIR‐II PA agents are reported based on semiconducting polymer nanoparticles (SPNs). Such completely organic nanoagents consist of π‐conjugated yet oxidizable optical polymer as PA generator and hydrolyzable amphiphilic polymer as particle matrix to provide water solubility. The obtained SPNs are readily degraded by myeloperoxidase and lipase abundant in phagocytes, transforming from nonfluorescent nanoparticles (30 nm) into NIR fluorescent ultrasmall metabolites (≈1 nm). As such, these nanoagents can be effectively cleared out via both hepatobiliary and renal excretions after systematic administration, leaving no toxicity to living mice. Particularly these nanoagents possess high photothermal conversion efficiencies and emit bright PA signals at 1064 nm, enabling sensitive NIR‐II PA imaging of both subcutaneous tumor and deep brain vasculature through intact skull in living animals at a low systematic dosage. This study thus provides a generalized molecular design toward organic metabolizable semiconducting materials for biophotonic applications in NIR‐II window.     

Photoacoustic Analysis of Blue Corn Pigments in Nixtamalized Flours

Anthocyanins are natural pigments with antioxidant properties, and recently they have received more attention because these pigments are consumed in nutritional diets with therapeutic effects. In addition, anthocyanins are important in the treatment of diseases caused by oxidation of free radicals in live systems, which could be the cause of chronic diseases, like cancer. Anthocyanins, found in flowers and some fruits, are also present in blue Mexican corn (Zea mays L.). In this work, photoacoustic spectroscopic, chemical and spectrophotometric analyses of nixtamalized blue corn flours are presented. Different Ca(OH)₂ concentrations were used in the fractioned nixtamalization process, and the total anthocyanin concentrations of these flours were obtained by chemical extraction of these pigments and compared with relative intensity of optical absorption obtained by photoacoustic spectroscopy.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Analysis of the Photoacoustic Detector Signal for Thermal Diffusivities of Gases

A resonant and a nonresonant photoacoustic detector were used to determine thermal diffusivities of gases. With a nonresonant detector thermal diffusivities can be determined in a wide range between 10^–3 and 10^–7 m²·s^–1, whereas experiments with the resonant detector deliver thermal diffusivities in a range that is about a factor of 100 smaller. As refrigerants—HFCs, HCFCs, and hydrocarbons—are absorbents in the infrared at a wavelength of 3.39 m, their thermal diffusivity can be determined without the addition of a trace gas, particularly at pressures below 0.01 MPa. At pressures above 0.1 MPa, the addition of ammonia as a trace gas is recommended. The absorption wavelength is then 1.531 m. A simulation model for the nonresonant photoacoustic detector is presented for the design of a detector and for an extended error analysis.     

Photoacoustic Analysis of Pigments from Archeological Ceramics

Photoacoustic spectroscopy (PAS) is widely used for diverse applications in different areas. These include studies in material, environmental, and life sciences. In the present work the study of pigments from pottery surfaces and volumes of Mexican (Aztec) and Poblana cultures that were developed in central Mexico from 1325 to 1521 and 1521 to 1800, respectively, is reported. The optical absorption spectra from each archeological sample was obtained using PAS. The superficial spectra were also compared with standard color pigments and archeological registers. Complementary energy dispersive spectroscopy (EDS) analysis of these archeological potteries gave us their elemental composition which agreed with other studies about their composition and technology of the pottery manufacturing.     

改性聚丙烯和聚丙烯包装膜的研究

用双螺杆挤出机研究了马来酸酐(MAH)对聚丙烯(PP)的自由基熔融接枝.采用正交试验优化了熔融接枝条件, 考察了引发剂过氧化二异丙苯DCP、单体MAH用量对马来酸酐接枝率的影响,并对其影响因素作了分析.研究表明改性以后的PP制成的PP膜性能更进一步提高.确定了较佳的原料(质量)配比为PP:MAH:DCP =100:3:0.4.     

Parylene C膜的光氧老化行为

利用紫外-可见吸收光谱(UV-VIS)、X光电子能谱(XPS)及热裂解-气相色谱/质谱联用测试分析技术(PY-GC/MS),对经过氙灯照射的Parylene C膜的紫外吸收、表面元素组成和含量以及热裂解的产物进行了分析研究。实验结果表明,Parylene C膜在光照过程中会被氧化,表面出现了黄化现象,其表面的氧含量随着光照时间的增加而增加,随后趋于稳定,而裂解产物中氧化碎片的量首先出现了一个最大值,而后迅速减小。     

Photoacoustic analysis and imaging techniques: Sound of light

An unusual form of imaging and analysis applications combines optics and acoustics to probe the features and behaviors of materials. The name of photoacoustic like all other techniques of spectroscopy reveals underlying its theoretical basis. Even if the prefix “photo” makes sense for a spectroscopy, acoustic may be initially amazing. Photoacoustic technique is extension of the photothermal effect, which is based on light beam hitting the sample and altering its thermal status. More precisely, photoacoustic effect is a transformation between light, heat, and sound caused by light absorption. After the successful formulation of general theoretical model, photoacoustic technique, which initially was only used for the analysis of gas samples, has been efficiently extended to analysis of condensed matters. Variety of samples, nondestructive analysis and imaging, depth profiling, high specificity and sensitivity, analysis of opaque samples are the most important advantages of photoacoustic technique. As of today, many researchers have performed in vitro and in vivo analysis and imaging application using photoacoustic technique; moreover, increasing number of companies are manufacturing biomedical imaging devices based on this effect. If the obstacles to experimental restrictions are removed, we will begin to hear the sound of light as more powerfully in many applications, particularly physics, materials science, and medicine.