发布时间 : 星期二 文章河北科技大学高分子材料专业外语翻译更新完毕开始阅读
polymer-polymer intermolecular forces are high because of crosslinking，crystallinity·or strong hydrogen bonding. But if these forces can be overcome by the introduction of strong polymer-solvent interactions, the second stage of solution can take place. Here the gel gradually disintegrates into a true solution. Only this stage can be materially speeded by agitation. Even so, the solution process can be quite slow (days or weeks) for materials of very high molecular weight.
溶解高分子需要一个缓慢的过程，这个过程分两步发生。溶剂分子缓慢地扩散到高分子中产生溶胀凝胶。例如, 如果因交联，结晶和很强的氢键而形成很大的分子间力，(聚合物的溶解过程)有可能就只停留在这一阶段。但是如果这些力被强的高分子-溶剂之间相互作用克服，溶解的第二阶段就会发生。即，凝胶逐渐变成一个真正的溶液。只有这个阶段可以通过搅拌得到明显促进。虽然如此，对高分子量的材料而言，溶解过程是相当缓慢的（几天或几个星期）。
Solubility relations in polymer systems are more complex than those among low molecular-weight compounds, because of the size differences between polymer and solvent molecules, the viscosity of the system, and the effects of the texture and molecular weight of the polymer. In turn，the presence or absence of solubility as conditions(such as the nature of the solvent，or the temperature)are varied can give much information about the polymer.
因为高分子和溶剂分子之间尺寸上的区别，体系的粘度以及聚合物分子量及织态结构的影响等原因，高分子体系的溶解性关系比低分子量化合物要复杂得多。当条件(溶剂的性质或温度)变化的时候，有无溶解性又可提供出许多关于这种聚合物的信息。
As specified in the literature，the arrangements of the polymer chain differing by reason of rotations about single bands are termed
conformations. In solution, a polymer molecule is a randomly coiling mass most of whose conformations occupy many times the volume of its segments alone. The average density of segments within a dissolved polymer molecule is of 10-4~10-5g/cm3. The size of the molecular coil is very much influenced by the polymer-solvent interaction forces. In a thermodynamically “good” solvent, where polymer-solvent contacts are highly favored, the coils are relatively extended. In a “poor” solvent they are relatively contracted. It is the purpose to describe the conformational properties of both ideal and real polymer chains.
正如在文献中所定义的那样，由于围绕着单键的旋转而导致的聚合物链不同的空间排布叫做构象。在溶液中，聚合物分子是无规线团状,而大部分构象占链段分子自身体积的许多倍。溶解聚合物分子里的平均链段密度是10-4~10-5g/cm3.聚合物-溶剂之间的作用力对分子线团尺寸有很大的影响。在热力学上的好溶剂中，聚合物-溶剂作用较强，线团是相对伸展的。而在不良溶剂中，线团则是相对收缩的。使用上述方法的目的是描述理想的和真实的聚合物链构象。
The importance of the random-coil nature of the dissolved, molten, amorphous, and glassy states of high polymers cannot be overemphasized. Many important physical as well as thermodynamic properties of high polymers result from this characteristic structural feature. The random coil(Fig. 7. 1) arises from the relative freedom of rotation associated with the chain bonds of most polymers and the formidably large number of conformations accessible to the molecule.
我们无论怎样强调溶解的，熔融的，无定形的，玻璃态的高分子无规线团性质的重要性都不过分。高分子的许多重要的物理及热力学性质都是这个结构特征引起的。无规线团(图7. 1)一方面是由于聚合物链上的键自由旋转而产生的，另一方面是由于(聚合物)分子(链)可
达到巨大的构象数而产生的。
One of these conformations, the fully extended chain has special interest because its length, the contour length of the chain, can be calculated in a straightforward way. In all other cases the size of the random coil must be expressed in terms of statistical parameters such as the root-mean-square distance between its ends, (r2)1/2, or its radius of gyration, the root-mean-square distance of the elements of the chain from its center of gravity, (s2)1/2. For linear polymers that are not appreciably extended beyond their most probable shape, the mean-square end-to-end distance and the square of the radius of gyration are simply related:r2=6s2. for extended chains r2>6s2. The use of the radius of gyration is sometimes preferred because it can be determined experimentally.
我们对这些构象之一，也是充分伸展的链有特殊的兴趣，因为它的长度，即链的伸直长度可以直接地计算出来。在所有其他的场合，无规线团的尺寸必须用统计参数来表示，如链末端之间距离的均方根，(r2)1/2或回旋半径，从分子重心（质心）到链节距离的均方根(s2)1/2在线型聚合物的形状没有超出的充分伸展的情况下，平均末端距离的平方和回转半径之间可以简单地相关：r2=6s2。对伸展链则有：r2>6s2. 有时回旋半径更为常用，因为它可以用实验来确定。
UNIT 9 Structure and Properties of Polymers
第九单元 聚合物的结构与性能
Most conveniently, polymers are generally subdivided in three categories, viz., plastics, rubbers and fibers. In terms of initial elastic modules, rubbers ranging generally between 106 to 107dynes/cm2, represent the lower end of the scale, while fibers with high initial moduli of 1010 to 1011dynes/cm2 are situated on the upper end of the scale; plastics, having generally an initial elastic modulus of 108 to
109dynes/cm2, lie in-between. As is found in all phases of polymer chemistry, there are many exceptions to this categorization.
聚合物一般细分为三种类型，就是塑料，橡胶和纤维。就初始弹性模量而言，橡胶一般在106到107达因/平方厘米，在尺度的低端，而纤维具有高的初始模量，达到1010到1011达因/平方厘米，在尺度的高端，塑料的弹性模量一般在108到109达因/平方厘米，在尺度的中间。在高分子化学的各个方面，我们发现这种分类方法有许多例外的情况。
An elastomer (or rubber) results from a polymer having relatively weak interchain forces and high molecular weights. When the molecular chains are ‘straightened out’ or stretched by a process of extension, they do not have sufficient attraction for each other to maintain the oriented state and will retract once the force is released.
弹性体是具有相对弱的链之间作用力和高分子量的聚合物。当通过一个拉伸过程将分子链拉直的时候，分子链彼此之间没有足够的相互吸引力来保持其定向状态，作用力一旦解除，将发生收缩。
However, if the interchain forces are very great, a polymer will make a good fiber. Therefore, when the polymer is highly stretched, the oriented chain will come under the influence of the powerful attractive forces and will “crystallize” permanently in a more or less oriented matrix. These crystallization forces will then act virtually as crosslinks, resulting in a material of high tensile strength and high initial modulus, i.e., a fiber. Therefore, a potential fiber polymer will not become a fiber unless subjected to a 'drawing' process, i.e., a process resulting in a high degree of intermolecular orientation.
然而，如果分子链之间的力非常大，聚合物可以用做纤维。因此，当聚合物被高度拉伸的时候，取向分子链将受强引力的影响在有取向