On the origin of the non-exponential behaviour of the α-relaxation in glass-forming polymers:: incoherent neutron scattering and dielectric relaxation results
On the origin of the non-exponential behaviour of the α-relaxation in glass-forming polymers:: incoherent neutron scattering and dielectric relaxation results
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DOI：
10.1088/0953-8984/11/10a/033
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发表时间：
1999-03-15
影响因子：
2.7
通讯作者：
Richter, D
中科院分区：
文献类型：
--
作者：
Colmenero, J;Arbe, A;Richter, D
通过玻璃形成聚合物的非相干中子散射技术研究了玻璃形成系统中的初级或弛豫本质上是均匀的还是非均匀的问题。对十多种不同聚合物获得的结果表明，非相干中间散射函数可以通过具有恒定形状参数的 Kohlrausch-Williams-Watts 函数很好地描述。此外，该函数的动量传递依赖性近似遵循高斯近似。这些结果与通常被称为阿尔法过程非指数行为起源的异质图所预期的结果不一致。玻璃形成聚合物中α弛豫函数的表观拉伸似乎主要与亚线性扩散有关，而不是单指数过程叠加的结果，至少在中子散射技术覆盖的介观时间尺度上是这样。根据拉伸松弛函数的分布来研究和解释不同聚合物的高斯行为偏差。根据该范围的新介电结果讨论了将这些结果扩展到接近玻璃化转变温度的低温范围（其中中子散射测量不可行）的有效性。
The question of whether the primary or-relaxation in glass-forming systems is homogeneous or heterogeneous in nature is investigated by incoherent neutron scattering techniques for glass-forming polymers. The results obtained for more than ten different polymers show that the incoherent intermediate-scattering function is well described by a Kohlrausch-Williams-Watts function with a constant shape parameter Moreover, the momentum-transfer dependence of this function approximately follows the Gaussian approximation. These results do not agree with those expected from the heterogeneous picture usually invoked as the origin of the nonexponential behaviour of the alpha-process. It seems that the apparent stretching of the alpha-relaxation function in glass-forming polymers relates dominantly to sub-linear diffusion and is not a result of a superposition of single-exponential processes, at least in the mesoscopic timescale covered by neutron scattering techniques. Deviations from the Gaussian behaviour are evaluated for the different polymers investigated and interpreted in terms of distributions of stretched relaxation functions. The validity of the extension of these results to the low-temperature range close to the glass transition temperature, where neutron scattering measurements are not feasible, is discussed in the light of new dielectric results for this range.