两亲性线形嵌段共聚物的合成及溶液自组装研究

【作者】 阿孜古丽·木尔赛力木；

【导师】 陈永明；

【作者基本信息】 西北大学 ， 高分子化学与物理， 2014， 博士

【摘要】 近年来,嵌段共聚物自组装方面的研究成果十分丰富,对于嵌段共聚物溶液中的胶束化行为的研究也较为深入。然而,找出三嵌段共聚物自组装行为中的普遍性规律则是目前该领域中尚未得到完全解决的颇具挑战性的问题之一。对于线形三嵌段共聚物的溶液自组装行为的研究更是已有研究中涉及不深的一个方向。本文采用ATRP法和RAFT法合成一系列两嵌段及三嵌段共聚物。通过对其中的几组线形ABC三嵌段共聚物进行溶液分级自组装行为研究,得到了一系列结构新颖且可控的自组装聚集体。同时,在由这些共聚物自组装形成的有序结构制备功能性模板以及利用相应模板构筑导电聚合物纳米结构方面做了初步尝试。具体研究内容包括以下几点：1)通过ATRP法合成了两组两亲性两嵌段共聚物PEO45-b-PtBAx(x=28,35,53)及PEO113-b-PSx(x=72,82,100).成功制得了转化率较高,分子量分布窄的PEO45-b-PtBAx(x=28,35,53)(Mw/Mn≤1.07)。在tBA相对于PEO-Br的投料比较小时实现了对嵌段共聚物结构及分子量的精确调控。发现tBA投入量的增大会因引发体系粘度增大而导致分子量分布的变宽。相比之下,所得PEO113-b-PSx(x=72,82,100)的分子量分布略宽(Mw/Mn≤1.17)且通过改变反应时间对产物结构进行调控的效果不是十分理想。2)通过RAFT法合成了两组两亲性两嵌段共聚物PtBA145-b-PSx(x=270,200)及PnBA28-b-PSx(x=21,37,51,75),得到了分子量分布较窄(Mw/Mn≤1.22)的目标产物。扩第二单体St以制得两嵌段共聚物阶段,大分子链转移剂(带有RAFT端基的PtBA或PnBA)与第二单体投入质量越小,St投料比越大,反应时间越长,越有利于PS嵌段聚合度的增大。3)通过ATRP法合成了一组ABC三嵌段共聚物PEO45-b-PtBA53-b-PSx(x=42、84、102、165)。仅通过改变成核段(PS段)长度,在溶液分级自组装过程中成功实现了共聚物自组装形貌从颗粒状渐变为柱状,最终缠结成树莓状。分级组装过程中,胶束直径较为均匀,除PEO45-b-PtBA53-b-PS165,各样品粒径分布较窄；将各样品1mg/mL THF溶液透析到水中的一步透析过程中,得到了预期的囊泡结构,囊泡壁清晰可辨,壁厚基本均匀,团聚现象不是十分明显。PEO45-b-PS270-b-P2VPx出现了一层套一层的形貌。4)通过RAFT法成功合成了一组线形ABC三嵌段共聚物PtBA145-b-PS270-b-P2VPx(x=215,70)。采用两步分级组装方法对嵌段共聚物进行了自组装行为研究。PtBA145-b-PS270-b-P2VP215的一级组装过程中采用不同方法直接导致溶剂状况的差异,使嵌段共聚物聚集形态也相应地出现了明显差异。随体系中甲醇含量的增大分别得到了分散性较强的球形核分段胶束,分布较为密集的球形核分段胶束以及带有“小补丁”的复合胶束。在对应的二级组装过程中分别得到了复合胶束相互粘连而形成的密集度各异的胶束串和相互缠连的柱状复合胶束。PtBA145-b-PS270-b-P2VP70的分级组装结果证实成壳段长度的减小不仅使一级组装过程中复合胶束分布的更加密集,而且在某些区域内使复合胶束间发生了轻度粘连。在二级组装过程中所得到的柱状胶束长度与PtBA145-b-PS270-b-P2VP215的二级组装样品相比有所增长。5)通过RAFT法成功合成了PnBA28-b-PS37-b-P2VP73,采用两步分级组装方法对所得样品溶液自组装行为进行了研究。通过一级组装过程中选用PnBA和PS两个嵌段的不良溶剂,在分级组装第一步就得到了以这两段为复合胶束核,P2VP段为壳的补丁胶束。在分级组装第二步所实施的透析操作中,在对应于不同的一级组装浓度下,得到了一级组装过程中形成的补丁胶束进一步聚集而成的MCMs。当一级组装液浓度为2mg/mL时,因透析液中PnBA28-b-PS37-b-P2VP73的浓度高出了其cmc值,借助于相近或相连的补丁胶束及MCMs所引起的胶束核段的“有效碰撞”,得到了具有清晰分相结构的多分段柱状胶束。通过聚合物、选择性溶剂和浓度的选择,简单实现了多相多组分聚合物柱状胶束的形成。6)①对PEO45-b-PtBA35和PEO45-b-PtBA53-b-PS165进行水解制得了嵌段共聚物模板。选用其中PEO45-b-PtBA35的水解产物PEO45-b-PAA35为功能性模板合成了微／纳米结构导电聚合物材料一聚苯胺(PAni)。考察了模板剂含量恒定时单体加入量对嵌段共聚物模板中制得的PAni颗粒形貌及尺寸的影响。证实了以PEO45-b-PAA35为模板制备PAni的过程中,单体Ani的加入量不宜过低或过高；②尝试以V205片层为模板的常规硬模板法制备了PBZ微米棒／纤维。随V205掺杂量的增大PBZ/V2O5复合材料的形貌由较短的微米棒,变为较长的微米级纤维状结构。V205的掺入有利于聚联苯胺的结晶性、热稳定性及电化学活性的提高。更多还原

【Abstract】 There are great amount of research achievements about block copolymer self-assembly have been obtained for the past years. However establish a general concept to investigate the self-assembly process of triblock copolymers still remained as a challenging problem. Particularly, the self-assembly of linear triblock copolymer in solution has not been involved in deep. In this work we have synthesized a series of diblock and triblock copolymers by using ATRP and RAFT. Novel and controllable aggregation structure of several group of linear tribolock copolymers were prepared during hierarchical self-assembly process in solution. Meanwhile the preparation of functional templates based on these ordered self-assembly structure and building the nanostructure of conducting polymers in these templates were preliminarily attempted. The concrete research content of this paper lies in the following aspects:1) Two group of amphiphilic diblock copolymers PEO45-b-PtBAx(x=28,35,53) and PEO113-b-PSx(x=72,82,100) were synthesized by ATRP.PEO45-b-PtBAx(x=28,35,53) had a narrow molecular weight distributions (Mw/Mn≤1.07). Influence of feed ratio to the control of the structure, molecular weight and molecular weight distributions were discussed. When the feed ratio of tBA to PEO-Br was low, the structure and the molecular weight of copolymers could be controlled accurately. By contrast, the molecular weight distribution of PEO113-6-PSx(x=72,82,100), by contrast, were slightly wider (Mw/Mn≤1.17). And the results of regulate the structure of products were not satisfactory.2) Two group of amphiphilic diblock copolymers PtBA145-b-PSx(x=270,200) and PnBA28-b-PSx(xc=21,37,51,75) were synthesized by RAFT. Products with relatively narrow molecular weight distributions (Mw/Mn≤1.22) were obtained. The lower molar ratio of macro chain transfer agent to second monomer (PS), the bigger amount of St in feed and the longer reaction time were beneficial to enlarge the polymerization degree of St block.3) A group of ABC triblock terpolymers PEO45-b-PtBA53-b-PSx (x=42,84,102,165) were synthesized by ATRP. In two-step hierarchical self-assembly, control of secondary self-assembly structure of triblock terpolymer PEO45-6-PtBA53-b-PSx was realized easily just by changing the length of core forming PS block. During the process the micelle structure of PEO45-b-PtBA53-b-PSx changed from spherical to cylindrical and finally entangled to raspberry like structure. Micelles with uniform diameter were obtained. Size distributions of samples after self-assembly were narrow, except PEO45-b-PtBA53-b-PS165; in the self-assembly process of one-step dialysis, we obtained vesicular micelles with distinct vesicle walls had uniform thickness.4) A group of ABC triblock terpolymers PtBA145-b-PS270-b-P2VPx(x=215,70) were synthesized by RAFT. The two-step hierarchical self-assembly was carried out to investigate the self-assembly behaviors of block copolymers in solution. For PtBA145-b-PS27o-b-P2VP215, the different methods were used in the first step of self-assembly. This caused the difference of solution condition and give rise to the discrepancy of aggregation morphology of samples. With the increase of methanol in solution the well dispersed spherical micelles, densely dispersed core-compartmentalized spherical micelles and "patchy" MCMs were obtained respectively. In the corresponding second self-assembly process, there appeared the micellar strings or cylindrical micelles formed by the adherence of the micelles mentioned above. The results of the hierarchical self-assembly of PtBA145-b-PS270-b-P2VP70showed that, the shorter length of shell forming block caused the dispersity of micelles increased and slight adherence between the micelles. The length of cylindrical micelles obtained in second self-assembly process of PtBA145-b-PS270-b-P2VP70were increased in comparison with PtBA145-b-PS270-b-P2VP215.5) PnBA28-b-PS37-b-P2VP73was synthesized successfully by RAFT. Its self-assembly behaviors of in solution was investigated by two-step hierarchical self-assembly. By choosing the non solvent of PnBA and PS in the first step, the patchy micelles with the compound core of this two blocks and the shell of P2VP were obtained. In the second step, the MCMs formed by futhur aggregation of these patchy micelles were prepared. When the concentration of fist self-assembly solution was2mg/mL, the segmented cylindrical MCMs with distinguished phase separation structure were obtained by means of "effective collision" between cores of neighboring or linked micelles for the reason that the concentration of PnBA28-b-PS37-b-P2VP73exceeded its cmc value. The multiphased and multicomponent cylindrical polymer micelles were formed by a simple way.6)①Block copolymer templates were prepared by hydrolysis of PEO45-b-PtBA35and PEO45-b-PtBA53-b-PS165. PEO45-b-PAA35, the hydrolyzed PEO45-b-PrBA35, was used to Psynthesize the micro/nano conducting polymer PAni. The influence of the adding amount of monomer at constant template content to the morphology and size of PAni grown in block copolymer templates was observed and verified that the adding amount of monomers should not be so high to obtain fibrous PAni.②Cylindrical and Fibrous PBZ were prepared in the templates of V2O5lamella. The results showed that the composite materials of PBZ/V2O5were synthesized by using emulsion polymerization at different molar ratio of PBZ to V2O5. The morphology of PBZ/V2O5composite materials changed from short micro-rods to long and thin micro fibers. Adding V2O5was useful to increasing the crystalinity, thermal stability and electrochemical activity of PBZ.更多还原