含铵根离子等规聚丙烯离聚体的合成及性能研究

合成了一系列高分子量、窄分子量分布且高等规度,含有不同―NR_3~+X~-离子基团含量的聚丙烯离聚体(iPP-NR_3~+X~-).以PP/IUD共聚物作为反应中间体,与三乙胺或N-甲基咪唑氨化得到聚丙烯离聚体.通过离子交换反应制备不同反离子的N-甲基咪唑聚丙烯离聚体,包括双三氟甲基磺酰亚胺根离子(Tf_2N~-)、四氟硼酸根离子(BF_4~-)和六氟磷酸根离子(PF_6~-).热重分析结果发现N-甲基咪唑聚丙烯离聚体的热稳定性明显优于三乙胺聚丙烯离聚体,表明不含β-H的N-甲基咪唑聚丙烯离聚体具有较高的热稳定性.同时,聚丙烯离聚体的表面亲水性得到明显改善.并且,聚丙烯离聚体的断裂伸长率也得到显著提高,最高达到900%.比较不同反离子聚丙烯离聚体的屈服强度和断裂强度发现I~-聚丙烯离聚体具有最优的力学性能.

Synthesis and Properties of Isotactic Polypropylene Ionomers Containing Ammonium Ions

A series of well-defined isotactic polypropylene ionomers containing up to 6.47 mol％ of-NR3+X-ionic groups were synthesized using dimethyl (pyridylamino) hafnium catalyst,and proved to possess high molecular weight,narrow molecular weight distribution and high isotacticity.The propylene/l 1-iodo-l-undecene copolymers were taken as intermediates and the iodine groups underwent nucleophilic substitution reaction with triethylamine or N-methylimidazole to give isotactic polypropylene ionomers.N-methylimidazole polypropylene ionomers with different counter ions were prepared by ion exchange reaction,including bis (trifluoromenthylsulfonyl) imide ion (Tf2N-),tetrafluoroborate ion (BF4-) and hexafluorophosphate ion (PF6-).For the synthesized ionomers,their thermal stability,hydrophilic and mechanical properties were studied in depth.First of all,the thermogravimetric analysis results showed that the thermal stability of the N-methylimidazole polypropylene ionomer was significantly higher than that of the triethylamine polypropylene ionomer.It was demonstrated that the N-methylimidazole polypropylene ionomers without β-H could improve the thermal stability of the copolymer.With increasing ion content,the average length of the polypropylene segments decreases,leading to the decreases of crystallization temperature and melting point for the polypropylene ionomers.Secondly,the surface hydrophilicity of the polypropylene ionomers was improved compared with PP.The critical ion contents for behaving as hydrophilic material (with water contact angle ＜ 90°) are 5.42 mol％ and 2.97 mol％ for triethylamine polypropylene ionomer and N-methylimidazole polypropylene ionomer,respectively.Thirdly,compared with polypropylene,the strain at break of polypropylene ionomers is remarkably increased,which even reaches 900％.For N-methylimidazole polypropylene ionomers,an ion content as low as 0.91 mol％ can effectively improve the break strain to 815％.Among these various ionomers,the triethylamine polypropylene ionomers with 2.02 mol％ and 2.97 mol％ incorporation have good yield stress and break strain simultaneously.Furthermore,the type of the counter ion also has an impact on the yield strength and fracture strength of polypropylene ionomers,of which for the 6.47 mol％ ion content,the N-methylimidazole polypropylene ionomer possessing I-anions has the highest yield and fracture strength among those with other counter ions (Tf2N-,BF4-and PF6-).