沉淀聚合制备聚脲微球的机理探讨
发布时间：2018-08-27 19:24
【摘要】：沉淀聚合制备聚合物单分散微球时无需表面活性剂或稳定剂等助剂,所得微球因表面洁净而备受关注。迄今报道的沉淀聚合大都基于自由基聚合机理,存在着单体用量和微球产率低、聚合时间长等问题,制约了聚合物单分散微球的应用及发展。本文以异佛尔酮二异氰酸酯(IPDI)为单体,以水和N,N-二甲基甲酰胺(DMF)等为溶剂,通过逐步沉淀聚合制备了单分散聚脲微球,探讨了使用水和DMF为溶剂时制备单分散微球的实验最佳条件,并研究了微球的形成和增长机理。以IPDI为单体,以水和DMF的混合溶剂作为反应介质在静置条件下通过沉淀聚合制备单分散了聚脲微球。探讨了反应时间、IPDI用量、反应温度以及混合溶剂水/DMF的质量比对聚脲微球粒径和单分散性的影响。结果表明,随着单体含量的增加,微球粒径和微球产率逐渐增加。随着混合溶剂中DMF用量的增加,制备单分散微球的最大单体用量也显著提高。反应温度为30oC,当混合溶剂中水/DMF质量比为25/75时(即混合溶剂中DMF用量75 wt%),可制备单分散微球的单体用量最高为3.0 wt%,将混合溶剂中DMF用量提高至85 wt%时,制备单分散微球的单体最大用量达到了6.0 wt%。将聚合温度由30oC提高至50oC并未有效提高获得单分散微球的单体用量。此外,DMF对聚合反应具有明显催化加速作用,在30oC聚合15 min微球粒径和产率即达到最高值,与在纯水中或者水与丙酮或乙腈的混合溶剂中相比,聚合时间明显缩短。本研究中的IPDI沉淀聚合属于逐步聚合,单体及聚合物随时间的变化与自由基聚合截然不同,两者在微球形成及增长过程也必然存在差异。为此我们对IPDI沉淀聚合中微球的形成及增长机理进行了研究。在质量比为30/70的水/丙酮混合溶剂中,在IPDI沉淀聚合制备单分散聚脲微球过程中设计了三种方法对聚合过程中的微球进行分离以达到对不同聚合阶段聚合物进行表征的目的。其中快速抽滤法是最为有效的方法。该方法是使用孔径为0.22μm的滤膜对聚合体系中的聚合物微球与混合溶剂进行有效分离。该方法分离速率快(约5 s),结果的重复性好。采用快速抽滤法对聚合63 min时分离出的微球粒径约为3.226μm,微球产率为2.5%,在随后的25 min内微球大小及产率随时间急速增加,反应至90 min时微球粒径和产率分别达到了8.814μm和65%。这表明聚合时间63 min至90 min是本体系聚合反应的加速期。在该时间段聚合体系中的粒子数目基本保持恒定(7.6×10~7个/mL),微球大小均一而且也不发生聚并。微球的增长是通过吸附低聚物或微球表面功能基团与低聚物反应而实现的。反应时间超过90 min时体系中形成的微球开始沉淀,反应器底部聚合物微球增多,这使得反应体系中聚合物微球的均匀分散发生了变化,反应介质中新形成或未被吸附的低聚物因此形成了新的聚合物粒子,反应体系中微球数目有所增加(8.9×10~7个/m L),微球单分散性变差。
[Abstract]:In the preparation of monodisperse polymer microspheres by precipitation polymerization, no surfactants or stabilizers are needed, and the resulting microspheres have attracted much attention due to their surface cleanness. Most of the precipitation polymerization reported up to now is based on the mechanism of free radical polymerization. There are some problems such as low monomer dosage, low yield of microspheres and long polymerization time, which restrict the application and development of polymer monodisperse microspheres. In this paper, monodisperse polyurea microspheres were prepared by precipitation polymerization with isophorone diisocyanate (IPDI) as monomer, water and N-dimethylformamide (DMF) as solvent. The optimum conditions for the preparation of monodisperse microspheres using water and DMF as solvent were discussed, and the formation and growth mechanism of the microspheres were studied. Monodisperse polyurea microspheres were prepared by precipitation polymerization with IPDI as monomer and mixed solvent of water and DMF as reaction medium under static conditions. The effects of reaction time, reaction temperature and mass ratio of mixed solvent water / DMF on the particle size and monodispersity of polyurea microspheres were investigated. The results showed that the particle size and the yield of microspheres increased with the increase of monomer content. With the increase of the amount of DMF in the mixed solvent, the maximum amount of monomer used in the preparation of monodisperse microspheres also increased significantly. The reaction temperature is 30oC, when the mass ratio of water / DMF in the mixed solvent is 25 / 75 (that is, the amount of DMF in the mixed solvent is 75 wt%), the monomer content of the monodisperse microspheres is up to 3.0 wt%, and the amount of DMF in the mixed solvent is increased to 85 wt%. The maximum amount of monomers prepared by monodisperse microspheres was 6.0 wt%.. The increase of polymerization temperature from 30oC to 50oC did not increase the amount of monomers of monodisperse microspheres. In addition, DMF can accelerate the polymerization obviously, and the particle size and yield of 30oC polymerization reached the highest value at 15 min, which is shorter than that in pure water or in the mixed solvent of acetone or acetonitrile, and the polymerization time is obviously shorter than that in pure water or in the mixed solvent of acetone or acetonitrile. The precipitation polymerization of IPDI in this study belongs to gradual polymerization. The change of monomer and polymer with time is very different from that of free radical polymerization, and there must be differences between them in the process of microsphere formation and growth. Therefore, the formation and growth mechanism of microspheres in IPDI precipitation polymerization were studied. In water / acetone mixed solvent with a mass ratio of 30 / 70, three methods were designed for the separation of monodisperse polyurea microspheres during the preparation of mono-dispersed polyurea microspheres by IPDI precipitation polymerization in order to characterize the polymers in different polymerization stages. The fast filtration method is the most effective method. In this method, the polymer microspheres in the polymerization system are effectively separated from the mixed solvents by using a filter membrane with a pore size of 0.22 渭 m. The separation rate of this method is fast (about 5 s), results have good reproducibility. The particle size and yield were 3.226 渭 m and 2.5, respectively. The size and yield of the microspheres increased rapidly with time in the following 25 min. The size and yield of the microspheres reached 8.814 渭 m and 65 渭 m respectively at the reaction time of 90 min. This indicates that the polymerization time from 63 min to 90 min is the accelerated period of the polymerization reaction. The number of particles in the polymerization system was almost constant (7.6 脳 10 ~ 7 / mL), and the size of the microspheres was uniform and there was no coalescence. The growth of microspheres is achieved by adsorption of functional groups on the surface of oligomers or microspheres. When the reaction time exceeded 90 min, the microspheres formed in the reaction system began to precipitate, and the number of polymer microspheres at the bottom of the reactor increased, which resulted in a change in the uniform dispersion of the polymer microspheres in the reaction system. As a result, new polymer particles were formed from newly formed or unadsorbed oligomers in the reaction medium, and the number of microspheres in the reaction system was increased (8.9 脳 10 ~ 7 / m L), microspheres) with poor monodispersity.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.5
[Abstract]:In the preparation of monodisperse polymer microspheres by precipitation polymerization, no surfactants or stabilizers are needed, and the resulting microspheres have attracted much attention due to their surface cleanness. Most of the precipitation polymerization reported up to now is based on the mechanism of free radical polymerization. There are some problems such as low monomer dosage, low yield of microspheres and long polymerization time, which restrict the application and development of polymer monodisperse microspheres. In this paper, monodisperse polyurea microspheres were prepared by precipitation polymerization with isophorone diisocyanate (IPDI) as monomer, water and N-dimethylformamide (DMF) as solvent. The optimum conditions for the preparation of monodisperse microspheres using water and DMF as solvent were discussed, and the formation and growth mechanism of the microspheres were studied. Monodisperse polyurea microspheres were prepared by precipitation polymerization with IPDI as monomer and mixed solvent of water and DMF as reaction medium under static conditions. The effects of reaction time, reaction temperature and mass ratio of mixed solvent water / DMF on the particle size and monodispersity of polyurea microspheres were investigated. The results showed that the particle size and the yield of microspheres increased with the increase of monomer content. With the increase of the amount of DMF in the mixed solvent, the maximum amount of monomer used in the preparation of monodisperse microspheres also increased significantly. The reaction temperature is 30oC, when the mass ratio of water / DMF in the mixed solvent is 25 / 75 (that is, the amount of DMF in the mixed solvent is 75 wt%), the monomer content of the monodisperse microspheres is up to 3.0 wt%, and the amount of DMF in the mixed solvent is increased to 85 wt%. The maximum amount of monomers prepared by monodisperse microspheres was 6.0 wt%.. The increase of polymerization temperature from 30oC to 50oC did not increase the amount of monomers of monodisperse microspheres. In addition, DMF can accelerate the polymerization obviously, and the particle size and yield of 30oC polymerization reached the highest value at 15 min, which is shorter than that in pure water or in the mixed solvent of acetone or acetonitrile, and the polymerization time is obviously shorter than that in pure water or in the mixed solvent of acetone or acetonitrile. The precipitation polymerization of IPDI in this study belongs to gradual polymerization. The change of monomer and polymer with time is very different from that of free radical polymerization, and there must be differences between them in the process of microsphere formation and growth. Therefore, the formation and growth mechanism of microspheres in IPDI precipitation polymerization were studied. In water / acetone mixed solvent with a mass ratio of 30 / 70, three methods were designed for the separation of monodisperse polyurea microspheres during the preparation of mono-dispersed polyurea microspheres by IPDI precipitation polymerization in order to characterize the polymers in different polymerization stages. The fast filtration method is the most effective method. In this method, the polymer microspheres in the polymerization system are effectively separated from the mixed solvents by using a filter membrane with a pore size of 0.22 渭 m. The separation rate of this method is fast (about 5 s), results have good reproducibility. The particle size and yield were 3.226 渭 m and 2.5, respectively. The size and yield of the microspheres increased rapidly with time in the following 25 min. The size and yield of the microspheres reached 8.814 渭 m and 65 渭 m respectively at the reaction time of 90 min. This indicates that the polymerization time from 63 min to 90 min is the accelerated period of the polymerization reaction. The number of particles in the polymerization system was almost constant (7.6 脳 10 ~ 7 / mL), and the size of the microspheres was uniform and there was no coalescence. The growth of microspheres is achieved by adsorption of functional groups on the surface of oligomers or microspheres. When the reaction time exceeded 90 min, the microspheres formed in the reaction system began to precipitate, and the number of polymer microspheres at the bottom of the reactor increased, which resulted in a change in the uniform dispersion of the polymer microspheres in the reaction system. As a result, new polymer particles were formed from newly formed or unadsorbed oligomers in the reaction medium, and the number of microspheres in the reaction system was increased (8.9 脳 10 ~ 7 / m L), microspheres) with poor monodispersity.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.5
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相关期刊论文 前6条
1 严刚;聂光庭;孔祥权;邝淼;容建华;;温敏聚合物/纳米CuS复合微球在肿瘤光热化学联合治疗中的应用[J];高分子学报;2016年02期
2 李桂英;张停;刘建文;戚e，
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