高聚物在GPC淋洗过程中分子量降解现象的研究

A STUDY ON MOLECULAR WEIGHT DEGRADATION OF POLYMERS IN THE GPC ELUTIVE PROCASS

本文以聚苯乙烯窄分布标样,在宽广的分子量范围(2.3×10~3—1×10~7)及宽广的流动速度范围内;(0.4—2.6ml/min),对Styragel,μ-Styragel,Ultra-Styragel以及Shodex-800等四种不同系列的凝胶柱组,用GPC-小角激光光散射光度计(LALLS)联用装置,系统地研究了聚合物在GPC淋洗过程中的分子量降解现象。结果表明:对于分子量高达1×10~7以上的极高分子量的聚苯乙烯试样,在所研究的四个系列柱组中进行正常GPC淋洗过程时,发生的分子量降解现象都是十分严重的。对四个系列的柱组,不发生降解现象的分子量极限分别为:(1) Shodex-800柱组:5.8×10~5,(2) Styragel柱组:3.8×10~6,(3)μ-Styragel柱组:2.7×10~6,(4) Ultra-Styragel柱组;6.7×10~5。超过此极限,分子量均有严重的降解。在具有降解现象的情况下,流速的影响特别大,分子量将随流速的增大而减小。

In this paper, the molecular weight degradation phenomenon of polymers in GPC elutive process is investigated systematically using a low angle laser light scattering(LALLS)detector coupled to GPC with four different series of columns (Styragel, μ-Styragel, ultra-Styragel and Shodex-800)and using a wide range of molecular weight(2.3×10~3～1×10~7)of narrow MWD polystyrene samples in THF over a wide range of flow rate(0.4～2.6ml/min). Results show that molecular weight degradation phenomenon in GPC elutire process with all the series of columns are serious at any flow rate when the molecular weight of polystyrene sample is equal to or more than 10~7. For the four series of columns, the limit of molecular weight below which the degradation phenomenon will not take place, is respectively: (1)Shodex-800 columns: 5.8×10~6, (2)Styragel columns. 3.8×10~8, (3)μ-Styragel columns: 2.7×10~8, (4)ultra-Styragel columns: 6.7×10~5. Above the limit, the molecular weight degradation phenomenon will occur in varying degree. In such cases, the effect of flow rate is sensitive, molecular weight of polymer will decrease with the increase of flow rate.