PPO was fractionated by solution/precipitation method. Chloroform was served as a good solvent and methanol served as a precipitant. The molecular weight distribution of these fractionated PPO was determined by GPC, and showed narrow distribution. The dependence of $T_m$ and $T_g$ of PPO on the number average molocular weight ($\bar{M}_n$) was determined by DSC. Nylon 6 was dissolved in formic acid/LiCl mixture and fractionated by THF as a precipitant. $\bar{M}_n$ of fractionated Nylon 6 were calculated from intrinsic viscosity data.
One of the most important factor to affect physical property of polymer blend is a characteristic value, $M_c$, which is related to the average molecular weight spacing between entanglement point, $M_e$. Rheological measurement was conducted to determine the $M_e$ of PPO. The $M_e$ of PPO was calculated from the crossover modulus($G_c$) of loss modulus and storage modulus and the average molecular weight spacing between entanglement, $M_e$ was found to be 8,680.
A poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) macroinitiator having carbonylcaprolactam groups was prepared through metalation of methyl group of PPO and subsequent modificationto introduce carboxyl group, acid chloride group, and finally carbocaprolactam group. Anionic ring opening copolymerization of $\varepsilon$-caprolactam took place onto the macroinitiator to give a graft copolymer of PPO and Nylon 6. The structure of intermediate materials and the graft copolymer were confirmed by $^1H$-NMR, $^{13}C$ NMR, UV and IR spectroscopy. Glass transition temperatures and melting temperatures of these materials are also reported.
From the observation with TEM(Transmission Electron microscopy), it was found that the graft copolymer exhibited micro-phase separated morphology and close examination of the structure revealed cylindrical or spherical morphology depending upon the composition of PPO/Nylon. To evaluate the effect of graft copolymer as a compatibilizing agent, domain size of graft copolymer was determined for several different molecular weight of graft copolymer and homopolymer. The dominant factor to affect the domain size of graft copolymer was found to be molecular weight of PPO whereas the effect of molecular weight of Nylon on domain size was relatively small. Meanwhile, the molecular weight of about 10,000 for PPO was observed to be a critical value to affect the domain size. The critical molecular weight of 10,000 is close to the magnitude of the average molecular weight spacing between entanglement point, $M_e$ and compatibilizing effect was drastically increased for graft copolymer having molecular weight of PPO more than 10,000.
Finally, following facts were observed from the thermal characterization of graft copolymers prepared. The DSC thermograms of second heating scan revealed that $T_g$ of PPO and $T_m$ of Nylon 6 were observed even for the copolymer, P30G4N25 having its segmental molecular weight smaller than 3,000. This indicates that phase separation of graft copolymer prepared in this study is easily detectable by DSC. Moreover, the $T_g$ of PPO and $T_m$ of Nylon 6 were not resolved for copolymer with increasing molecular weight of PPO. The melting peak temperature and melting region for Nylon 6 were varied depending upon the molecular weight of Nylon 6.
Crystallization behavior of Nylon 6 in copolymer were studied in the cooling scan after thermal equilibrium at 260℃. The crystallization peak temperature of Nylon 6 in copolymer were lowered about 10 to 20℃ compared with that of pure Nylon 6. For copolymer prepared from low molecular weight of PPO, nylon was crystallized in the vicinity of glass transition temperature for PPO. On the contrary, for copolymer with high $T_g$ due to high molecular weight of PPO, the crystallization temperature of Nylon 6 was shifted to pure homopolymer of Nylon 6.