沉淀聚合制備聚脲微球的機(jī)理探討
發(fā)布時(shí)間：2018-08-27 19:24
【摘要】：沉淀聚合制備聚合物單分散微球時(shí)無(wú)需表面活性劑或穩(wěn)定劑等助劑,所得微球因表面潔凈而備受關(guān)注。迄今報(bào)道的沉淀聚合大都基于自由基聚合機(jī)理,存在著單體用量和微球產(chǎn)率低、聚合時(shí)間長(zhǎng)等問(wèn)題,制約了聚合物單分散微球的應(yīng)用及發(fā)展。本文以異佛爾酮二異氰酸酯(IPDI)為單體,以水和N,N-二甲基甲酰胺(DMF)等為溶劑,通過(guò)逐步沉淀聚合制備了單分散聚脲微球,探討了使用水和DMF為溶劑時(shí)制備單分散微球的實(shí)驗(yàn)最佳條件,并研究了微球的形成和增長(zhǎng)機(jī)理。以IPDI為單體,以水和DMF的混合溶劑作為反應(yīng)介質(zhì)在靜置條件下通過(guò)沉淀聚合制備單分散了聚脲微球。探討了反應(yīng)時(shí)間、IPDI用量、反應(yīng)溫度以及混合溶劑水/DMF的質(zhì)量比對(duì)聚脲微球粒徑和單分散性的影響。結(jié)果表明,隨著單體含量的增加,微球粒徑和微球產(chǎn)率逐漸增加。隨著混合溶劑中DMF用量的增加,制備單分散微球的最大單體用量也顯著提高。反應(yīng)溫度為30oC,當(dāng)混合溶劑中水/DMF質(zhì)量比為25/75時(shí)(即混合溶劑中DMF用量75 wt%),可制備單分散微球的單體用量最高為3.0 wt%,將混合溶劑中DMF用量提高至85 wt%時(shí),制備單分散微球的單體最大用量達(dá)到了6.0 wt%。將聚合溫度由30oC提高至50oC并未有效提高獲得單分散微球的單體用量。此外,DMF對(duì)聚合反應(yīng)具有明顯催化加速作用,在30oC聚合15 min微球粒徑和產(chǎn)率即達(dá)到最高值,與在純水中或者水與丙酮或乙腈的混合溶劑中相比,聚合時(shí)間明顯縮短。本研究中的IPDI沉淀聚合屬于逐步聚合,單體及聚合物隨時(shí)間的變化與自由基聚合截然不同,兩者在微球形成及增長(zhǎng)過(guò)程也必然存在差異。為此我們對(duì)IPDI沉淀聚合中微球的形成及增長(zhǎng)機(jī)理進(jìn)行了研究。在質(zhì)量比為30/70的水/丙酮混合溶劑中,在IPDI沉淀聚合制備單分散聚脲微球過(guò)程中設(shè)計(jì)了三種方法對(duì)聚合過(guò)程中的微球進(jìn)行分離以達(dá)到對(duì)不同聚合階段聚合物進(jìn)行表征的目的。其中快速抽濾法是最為有效的方法。該方法是使用孔徑為0.22μm的濾膜對(duì)聚合體系中的聚合物微球與混合溶劑進(jìn)行有效分離。該方法分離速率快(約5 s),結(jié)果的重復(fù)性好。采用快速抽濾法對(duì)聚合63 min時(shí)分離出的微球粒徑約為3.226μm,微球產(chǎn)率為2.5%,在隨后的25 min內(nèi)微球大小及產(chǎn)率隨時(shí)間急速增加,反應(yīng)至90 min時(shí)微球粒徑和產(chǎn)率分別達(dá)到了8.814μm和65%。這表明聚合時(shí)間63 min至90 min是本體系聚合反應(yīng)的加速期。在該時(shí)間段聚合體系中的粒子數(shù)目基本保持恒定(7.6×10~7個(gè)/mL),微球大小均一而且也不發(fā)生聚并。微球的增長(zhǎng)是通過(guò)吸附低聚物或微球表面功能基團(tuán)與低聚物反應(yīng)而實(shí)現(xiàn)的。反應(yīng)時(shí)間超過(guò)90 min時(shí)體系中形成的微球開(kāi)始沉淀,反應(yīng)器底部聚合物微球增多,這使得反應(yīng)體系中聚合物微球的均勻分散發(fā)生了變化,反應(yīng)介質(zhì)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,反應(yīng)體系中微球數(shù)目有所增加(8.9×10~7個(gè)/m L),微球單分散性變差。
[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.
【學(xué)位授予單位】：濟(jì)南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：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.
【學(xué)位授予單位】：濟(jì)南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O631.5
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