聚甲基丙烯酸甲酯与苯乙烯-丙烯腈共聚物混合体系相分离初期的固体NMR研究

INVESTIGATION OF PHASE SEPARATION BEHAVIOR IN POLY (METHYL METHACRYLATE)/POLY (STYRENECO-ACRYLONITRILE) MIXTURES WITH PULSED NUCLEAR MAGNETIC RESONANCE

本文用氢谱宽线固体NMR技术研究了聚甲基丙烯酸甲酯(PMMA)和苯乙烯-丙烯腈共聚物(SAN)混合体系不稳相分离初期阶段,得到了在分相过程中弛豫谱的变化规律,测定了相分离增长速率。结果指出:随着退火时间的增加,两相体系形成;大分子扩散方式是由浓度低的区域向浓度高的区域扩散,扩散系数为负值;相分离增长速率的数量级与用光散射研究的结果相同;分子相互作用的相关距离为46.5nm。

Thermally induced phase separation in the mixture of poly (methyl methacrylate) (PMMA) with poly (styrene-co-acrylonitrile) (SAN) has been studied with pulsed nuclear magnetic resonance(NMR) . It is shown that the single spin-lattice relaxation time T_1 of the compatible mixture splitted into two T_1 corresponding to those of PMMA-rich and SAN-rich domains. Meanwhile, both T_1 gradually changing with annealing time provides the direct evidence that the phase separation takes place with a spinodal decomposition mechanism. Diffusion coefficient was estimated to be negative, indicating an uphill diffusion characteristics. The basic parameters governing its kinetics were estimated using NMR data which were in good agreement with those evaluated from time-resolved light scattering experiments for a 60/40(PMMA/SAN) mixture annealed at 180.0℃.