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Conformational statistics of polymer chain terminally attached to wall (Ⅲ)——NRW model loop chain 总被引:1,自引:0,他引:1
When the two end groups of a linear polymer chain are absorbed on a solid surface,the polymer chain forms the "loop" conformation.Investigation has been made on the conformational statistics of a model loop chain by the normal landom walk (NRW) on a lattice confined in the half-infinite space.Based on the conformational distribution function of the NRW model tail chain,it is easy to deduce an analytical formula expressing the conforma-tional number of the model loop chain.It was found that the ratio of the conformational number of the model loop chain to that of the free chain varies with the power function N-2/3 when the chain length N→∞ The same result was obtained by means of the recursion equation.The ratio of the mean square end-to-end distance h2 for the model loop chain to its mean square bond length I2 is 2N/3 Compared with the free chain with the same length N,the mean square end-to-end distance of the model loop chain contracts to a certain extent.The basic relationships deduced were support 相似文献
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保尔·弗洛里(Paul J. Flory)1910年生于美国伊利诺斯州斯特林,祖辈务农,父母为教员。他1931年毕业于印第安纳州曼彻斯特大学化学系,随后进入俄亥俄州立大学,在约翰斯通(Johnston)教授指导下于1934年完成了光化学和光谱学方面的物理化学博士论文。同年,受聘于杜邦公司,开始了他在高分子科学领域的漫长研究生涯,显示出他巧妙地将化学问题加以精确数学处理的惊人才智。从那时算起近半个世 相似文献
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热塑性聚酯醚液晶弹性体的合成与表征 总被引:6,自引:0,他引:6
液晶聚酯醚嵌段共聚物是一类新型的高分子材料,已有较多研究[1~3].当共聚物中软、硬段比例适当,在一定温度范围内,这类液晶聚合物可能出现高弹性.但系统报道聚酯醚液晶弹性体的工作并不多.Lenz[2]报道得到了类似橡胶的低强度、低模量和高伸长率的液晶弹... 相似文献
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Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amountof hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750.The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility inwater. It was shown by experimental measurement at 30.0±0.1℃ that the surface tension of the aqueous solution of thehighest substituted FPVA decreased to 16.6 mN/In at a higher concentration, e.g about 0.1 g/mL. Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobicperfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed. 相似文献
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本文从理论上研究了聚对羟基苯甲酸酯(简称PHB或PHBA)的分子量分布。理论分析表明,由对羟基苯甲酸酯缩聚制得的PHB的分子量分布与Flory分布稍有不同,可以认为是修正的Flory分布;而由对羟基苯甲酸制得的PHBA仍可用Flory分布表征。由于未发现上述聚合物的溶剂,故不可能对其分子量分布进行实验研究。 相似文献
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静电纺丝法和气流-静电纺丝法制备聚砜纳米纤维 总被引:7,自引:0,他引:7
应用电纺法制备了聚砜纳米纤维.设计了一种新型的气流静电纺丝装置,其特点是在喷丝头上添加了喷气组件.电纺过程中所用聚砜的特性粘数为0.97dLg,溶剂为二甲基乙酰胺,载气为氮气.研究了聚砜纳米纤维的平均直径与过程参数之间的关系.研究表明影响聚砜纳米纤维的平均直径的主要因素为电压、纺丝液的流速、喷丝头与收集器之间的距离、操作温度以及纺丝液的性质(如粘度、表面张力和电导率).纳米纤维的平均直径和直径分布用扫描电镜表征.应用这种气流静电纺丝法制备的纳米纤维的直径范围是50~500nm.所得纳米纤维的直径依赖于电压、喷丝头与收集器之间的距离以及喷丝液的浓度.结果表明,采用气流静电纺丝不仅能制备较细而且均匀的纳米纤维,而且产量更高. 相似文献
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涤纶工业丝等温收缩中的结构变化 总被引:4,自引:0,他引:4
采用广角X 射线衍射、密度梯度、声速和差示扫描量热等实验方法对 145 5dtex/ 110f成品涤纶工业丝等温收缩的结构变化进行了表征 ,外加张力为 0 3N ,测定温度范围 375~ 494K .结果表明 ,涤纶工业丝的热收缩在宏观上表现为速率不同的两个过程 ,对应两种不同机理 .其中快过程对应非晶区的解取向 ,对收缩的贡献是主要的 ;慢过程对应晶区的变化 ,包含了晶粒的增长 ,新的不完善晶粒的形成和晶区的完善 .晶粒的增长在较短的时间内基本完成 ,再结晶则存在于整个收缩过程 .随温度的升高 ,晶区变化速度明显加快 ,对非晶区解取向的抑制效应因此变大 . 相似文献