SOLUTIONS OF FLEXIBLE POLYMERS - NEUTRON EXPERIMENTS AND INTERPRETATION
SOLUTIONS OF FLEXIBLE POLYMERS - NEUTRON EXPERIMENTS AND INTERPRETATION
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DOI：
10.1021/ma60048a024
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发表时间：
1975-01-01
期刊：
影响因子：
5.5
通讯作者：
GENNES, PGD
中科院分区：
文献类型：
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作者：
DAOUD, M;COTTON, JP;GENNES, PGD
我们提供了良好溶剂（二硫化碳）中聚苯乙烯（正常或氘化）的小角中子散射数据。所有的数据都是在半稀释制度，其中链重叠强烈，但溶剂分数仍然很大。（a）氘代链在浓度为c的正常链溶液中的回转半径Rg（c）。我们发现Rg ~ 2（c）与分子量成正比，Rg ~ 2随浓度c~ x（x= 0.25±0.02）而减小。(b)筛选长度ε（c）（引入，但Edwards计算得不太正确）给出了（c（r）c（r '））相关性的范围。我们发现ε ~ c~ z，其中z= 0.72±0.06。(c)渗透压缩系数x（c）（通过小角度极限下相同链的散射强度）。从早期的光散射实验中，我们发现~ c~ y，y= 1.25±0.04。这些结果与平均场（Flory-Huggins-Edwards）理论的预言作了比较，后者在半稀释范围内Rg与c无关，~ c-1，ε ~ c-1/2。在本文中，我们表明，测量的指数都可以解释在一个简单的物理图片。其基本依据是Des Cloizeaux最近发现的外场作用下半稀释系统与铁磁体之间的类比。然而，在本文中，我们主要强调聚合物方面。在短距离（r<ε）处，相关性由排除的体积效应确定。在大的距离（ε < r< Rg），链是高斯的，同一链的亚基之间的有效相互作用很弱。
We present small angle neutron scattering data on polystyrene (normal or deuterated) in a good solvent (carbon disulfide). All data are taken in the semidilute regime where the chains overlap strongly, but the sol-vent fraction is still large. We have measured the following,(a) The radiusof gyration Rg (c) for one deuterated chain in a solution of normal chains with concentration c. We find that Rg2 (c) is proportional to the molecular weight and that Rg2 decreases with concentration like c~ x where x= 0.25±0.02.(b) The screening length£(c)(introduced, but not quite correctly calculated by Edwards) giving the range of the (c (r) c (r')) correlations. We find£~ c~ z, with z= 0.72±0.06.(c) The osmotic compressibility x (c)(through the scattering intensity of identical chains in the small angle limit). From an earlier light-scattering experiment, we find~ c~ y with y= 1.25±0.04. These results are to be compared with the predictions of the mean field (Flory-Huggins-Edwards) theory which are: Rg independent of c,~ c-1, and£~ c-1/2 in the semidilute range. We show in the present paper that the measured exponents can all be interpreted in terms of a simple physical picture. The underlying basis is the analo-gy, recently found by Des Cloizeaux, between the semidilute system and a ferromagnet under an external field. However, in this paper, we emphasize mainly the polymer aspects. At short distances (r<£) the correlations are determined by excluded volume effects. At large distances (£< r< Rg) the chains are gaussian and the effective interaction between subunits of the same chain are weak.