STUDIES ON POLYMERIZATION KINETICS OF METHYL METHACRYLATE AT HIGH CONVERSION

The bulk polymerization of methyl methacrylate which was carried out in a metallic dilatometer and in a differential scanning calorimeter has been studied over the complete course of the reaction. An attempt was made to quantitatively express the relation on the onset of gel effect and the final conversion with polymerization conditions such as temperature, kinds and concentration of initiators. It was demonstrated further that the final conversion of polymerization in homogeneous ideal systems is only dependent upon the reaction temperature.     

橡胶接枝苯乙烯本体共聚合全程动力学研究(Ⅰ)--接枝行为

橡胶接枝苯乙烯本体聚合的研究目前主要集中于预聚阶段接枝动力学和聚合条件对相转变的影响[1]. 对于后聚阶段, 即相转变后的接枝行为, 尤其是接枝率与橡胶相内包容物的关系、接枝率与高转化率聚合动力学的关系, 接枝率与橡胶相结构的关系等则研究很少. 这些因素对最终聚合物的性能起着至关重要的作用, 因此, 研究橡胶接枝苯乙烯本体聚合相转变以后接枝率的变化, 并找出橡胶相形态演绎过程的规律很有意义.     

Effect of Hydrophobic Chain of Dye Molecule and Surface of Active Crystal on the Organized Assemblies Formation of Dyes

Four derivatives of 5,5',6,6'-tetrachlorobenzimidazolocarbocyanine iodide with different long alkyl chain substituents in N-position of polymethine chromophore have been used for investigating the influence of hydrophobicity of dyes on the aggregation.It has been found that all dyes formed monomeric species in methyl alcohol. However, after addition of water to CH_3OH to change the polarity of the solvent, difference between dyes appeared.Addition of inorganic salt facilitated the J-aggregation of easy soluble dye, but it seems useless for the sparely soluble dye.Platelets cut from AgBr polycrystal or pressed AgBr powder have been used as substrate for adsorbing dyes. After addition of hexanoic acid, eventually the J-aggregate on AgBr surface could be destroyed.Voltammetry is a useful tool to investigate the interaction between dyes and AgBr. Experimental results showed that the longer the carbon chain substituents is, the stronger the interaction between AgBr and dyes would be.     

CONCENTRATION EFFECT OF SENSITIZING DYE ON SPECTRAL SENSITIZATION OF SILVER HALIDE

The effect of concentration of four dyes has been investigated, which are of similar mo-lecular structures, same spectroscopic absorption spectra, and very close values in redox po-tential upon the spectral sensitization of photographic emulsion. The results have shownthat dyes which are liable to form J-aggregate diminish the effect of dye-induced desensiti-zation, while dyes which are not easy to form J-aggregate exhibit a very strong effect ofdye-induced desensitization. According to phosphorescence and electrochemistry experimentalresults, we could assume that the aggregate state acts in a way to regenerate the oxidizeddye, thus being favorable to the spectral sensitization. In this paper, the factor of inhibi-tion of development by dye adsorption has also been proposed to be a factor which cannotbe neglected in dye-induced desensitization.     

超高分子量聚苯乙烯的流变性能

以毛细管流变仪和Hakke转矩流变仪对稀土催化合成的超高分子量聚苯乙烯 (UHMWPS)的流变与加工性能进行了研究 .结果表明 ,UHMWPS最显著的流变特征为超高的熔体粘度和低剪切速率下出现不稳定流动 .不稳定流动与超高分子量聚合物长的松弛时间有关 ,并提出了临界剪切速率与分子量和温度的定量关系式 .较低的分子量和较高的温度有利于提高临界剪切速率 ,改善挤出物外观质量和降低熔体粘度 .分子链极度缠结不仅导致超高的熔体粘度 ,也使UHMWPS链解缠加快 ,导致更高的剪切速率敏感性 .UHMWPS塑化时熔体粘度高 ,转矩大 ,加工性能劣于通用聚苯乙烯 (GPPS)     

户外用耐候性粉末涂料的研究进展

概述了适用于户外的五大类耐侯性粉末涂料：聚酯、聚丙烯酸酯类、聚氨酯类、氟及改性有机硅类。阐述各种树脂的应用现状,并从分析了结构角度剖析提高树脂耐候性的可能性及拟采用的各种方法,指出以脂肪族环氧乙烷代替三缩水甘油基异氰脲酸酯杂化的聚酯树脂体系将成为今后户外用粉末涂料的重要发展方向。     

GHD室温自交联乳液的聚合及贮存稳定性

采用半连续种子乳液聚合技术合成了含甲基丙烯酸缩水甘油酯（GMA）、甲基丙烯酸羟乙酯（HEMA）和甲基丙烯酸二甲氨基乙酯（DMAEMA）的室温自交联乳液（GHD）。实验结果表明,在甲基丙烯酸甲酯（MMA）－丙烯酸丁酯（BA）－GMA种子乳液存在下,聚合温度升高,聚合过程稳定性下降,但乳液的贮存稳定性提高;乳化单体滴加速度加快,种子聚合物的玻璃化温度升高,可减少聚合过程的交联凝聚作用,提高聚合过程的稳定性;而HEMA和DMAEMA用量增加对聚合过程的稳定性没有明显影响,但使乳液的贮存稳定性下降,官能团间的交联凝聚作用可能是影响室温自交联乳液聚合及贮存过程稳定性的关键因素。     

激光诱导菌紫质LB膜快速光电动力学研究

在ITO导电玻璃上拉制了10层定向菌紫质LB膜,组成了ITO电极/菌紫质LB膜/KCl溶液/铜电极结构的湿光电池。用调Q倍频Nd:YAG激光器输出的10Hz,8ns巨脉冲序列作用于菌紫质LB膜,在300MHz数字示波器上直接得到了薄膜的快速光电动力学曲线。理论上建立了菌紫质光电动力学方程。通过对不同时基下采集到的实验曲线的非线性最小二乘拟合,综合出了理论模型的实验公式,并计算出了菌紫质光循环过程中各步的电位移参数和衰减时间常数。     

增感染料浓度对卤化银乳剂光谱增感的影响

本文使用四种结构相似,吸收光谱及氧化还原电位相近的噻碳菁染料研究了染料浓度对光谱增感的影响,实验证明,易形成J-聚集态者,其浓度减感效应缓慢,不易形成J-聚集态者,其浓度减感效应明显。本文并根据磷光及电化学的实验,认为聚集态有助于还原被氧化的染料分子,从而有利于光谱增感;并认为在考虑减感作用的机理时应当考虑染料抑制卤化银还原的因素。