【作者】 刘晓亚；

【导师】 江明；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2010， 博士

【摘要】 高分子科学家们在双亲性嵌段共聚物自组装方面开展了许多有意义的工作,取得了骄人的成绩。本课题组则以非嵌段共聚物为“组装基元”通过非共价键作用构建非共价键胶束NCCM,开辟了颇具特色的自组装研究新天地。大分子自组装发展至今,研究热点逐渐向功能性组装基元设计,自组装体的功能化及其应用研究领域转移,但大多研究的构建单元还是以嵌段共聚物为主。但由于其合成相对困难,故规模化应用受到限制。无规共聚物简单易得、来源丰富,较之于嵌段共聚物而言更有潜在的应用价值,已有科学家包括我们小组开始关注无规共聚物自组装研究并有论文发表,但无规共聚物胶束是否也能通过分子设计、引入功能基团以构建响应性功能化胶束并最终将其推向实际应用?这是本论文关注的一个问题。根据无规共聚物链结构特点,其组装体的亲疏水微区分布比较无序,不存在类似于嵌段共聚物胶束的核壳结构,但胶束外层亲水微区比较富集,内部疏水微区比较富集,这就使得胶束表面具有双亲性。100年前Pickering等最先发现固态胶体颗粒有表面活性,可以稳定乳状液。但直到上世纪90年代随着纳米科技的发展,颗粒乳化剂才逐渐成为众多化学家关注的热点,在以无机和无机/有机杂化颗粒乳化剂研究方面取得了丰硕成果。这些颗粒乳化剂表面同时有亲水和疏水微区存在,其接触角一般在60°-120°范围内,可以稳定的存在于油水界面上。表面具有双亲性的组装胶束是否也可以作为颗粒乳化剂?因此我们提出是否可以利用无规共聚物胶束具有表面活性的特点构建聚合物软颗粒乳化剂,并系统研究其乳化及应用。这是本论文要研究的另一个问题。围绕上面提出的两个主要问题,本论文研究工作以“非嵌段共聚物”--无规-交替共聚物为主要研究对象,根据聚合物颗粒乳化剂的表面活性特性要求,从链结构与组装体微结构间的关系着手、设计并合成一系列简单易得的非嵌段双亲性无规-交替共聚物,并在聚合物链上引入响应性基元赋予其环境响应性。以该无规-交替共聚物为组装构筑基元通过自组装途径制备结构稳定且具有表面活性的大分子胶体粒子,对其作为颗粒乳化剂的功能进行研究,由此开辟了聚合物软颗粒乳化剂制备和应用的新途径。本论文研究的主线是：首先以结构确定且具有最短亲／疏水“链段”的功能化交替双亲共聚物经自组装得到稳定的表面活性胶体粒子,确认其具有良好的乳化性能,是一种新型的软颗粒乳化剂；其次,制备了链结构部分无序且引入光交联功能的无规-交替链结构双亲共聚物,通过自组装、光交联得到的胶体粒子同样具有表面活性。进一步拓展思路,合成了链结构完全无序且具有多重响应性基元的无规双亲共聚物,在选择性溶剂中自组装得到了具有多重响应性的表面活性胶体粒子,乳化性能良好。最后,结合生物大分子,我们研究了链结构也呈无规分布的大豆分离蛋白(简称SPI,一种天然的胶体粒子)及其接枝改性物的乳化性能,证实了表面接枝改性可以提高大豆分离蛋白的乳化性。研究结果表明,具有短亲/疏水“链段”的非嵌段双亲性共聚物胶体粒子没有亲水壳疏水核式的核壳结构,但其表面仍有疏水微区存在,且亲水微区富集,因此而具有双亲性即表面活性。上述研究表明双亲性无规-交替共聚物自组装制备表面活性胶体粒子的方法具有一定的普适性,可以适用于制备多种表面活性胶体粒子。具体研究工作包括以下几部分：1、双亲性交替共聚物P(St-alt-MAn)的合成、改性及自组装研究以甲苯为溶剂,通过自由基共聚合法合成了交替共聚物聚(苯乙烯-alt-马来酸酐)P(St-alt-MAn),并用多巴胺氨解得到双亲性共聚物P(St-alt-MA-Dopa)。在选择性溶剂(DMF/水)中,对P(St-alt-MAn)及P(St-alt-MA-Dopa)进行溶液自组装,可以得到稳定的球形纳米胶体粒子,P(St-alt-MA-Dopa)胶体粒子具有pH响应性、离子响应性和表面活性,是一种新型的聚合物软颗粒乳化剂,以P(St-alt-MA-Dopa)胶体溶液为水相,甲苯为油相,均质乳化后可以得到稳定的水包油型Pickering状乳液。胶体粒子表面zeta电位绝对值随着胶束溶液pH值的增大而增大,随盐浓度的增大而减小；胶体粒子的粒径随pH值增大而增大。用荧光光谱法表征了P(St-alt-MA-Dopa)胶体粒子的亲疏水性,结果表明胶体粒子的亲水性随pH值的增大而增强,而离子强度的增大对胶体粒子的亲疏水性基本没有影响。P(St-alt-MA-Dopa)胶体粒子在较宽的pH范围内、很低浓度(如0.5 mg/mL)下就表现出良好的乳化性能,酸、碱及盐浓度对P(St-alt-MA-Dopa)胶体粒子的乳化性能有一定影响。以上研究结果初步证实前面提出的问题,即无规-交替共聚物自组装也可以得到具有功能性和响应性的胶体粒子；具有最短亲/疏水“链段”的功能化交替双亲共聚物自组装胶体粒子具有表面活性和乳化性能,是一种新型的软颗粒乳化剂。2、双亲性无规-交替共聚物PSMVM的合成及自组装以苯乙烯衍生物富电子光敏单体7-(4-乙烯基苄氧基)-4-甲基香豆素(VMn)与苯乙烯(St)、马来酸酐(MAn)为共聚单体,通过自由基共聚得到双亲性无规-交替共聚物聚(苯乙烯-alt-马来酸酐-co-(4-乙烯基苄氯氧基)-4-甲基香豆素-alt-马来酸酐)P(St-alt-MAn)-co-P(VM-alt-MAn) (PSMVM)。在选择性溶剂中该共聚物自组装得到了稳定的具有光、pH、离子响应性的双亲性PSMVM球形胶体粒子,其粒径在50-100 nm间。TEM结果显示粒子具有弥散的微相分离结构,这可能与PSMVM链的无规-交替结构有关。借助于香豆素基团的光交联反应,使粒子固化。胶体粒子在光交联过程中有塌缩变形的趋势,粒径减小,过度光照会引起粒子间聚并发生。紫外光交联后的交联胶体粒子CL-PSMVM较未交联胶体粒子UCL-PSMVM有更好的耐溶剂性。XPS结果分析证实在聚集体表层有相对富集的氧原子,可能是羧基等亲水基团在粒子表面相对富集的结果,起到了稳定胶体粒子的作用。PSMVM胶体粒子因含羧基而具有pH响应性,其zeta电位随pH值的增大而变得更负,但粒径则随pH的增加而增大；增加离子强度可以屏蔽PSMVM胶体粒子的表面电荷致使zeta电位绝对值减小,表面疏水性增加,粒子间聚集使粒径有所增大。本章所得的PSMVM胶体粒子通过光交联实现固定化,对确保聚合物软颗粒乳化剂的制备和应用有实际意义。3、双亲性无规-交替共聚物PSMVM胶体粒子乳化行为研究本章重点研究对象是无规-交替共聚物PSMVM自组装软颗粒乳化剂。研究了环境对胶体粒子乳化性能的影响,探索了胶体粒子对油性物质的乳化包埋及其在油水界面的吸附行为。实验结果表明,PSMVM胶体粒子作为软颗粒乳化剂,在很低浓度下即可单独稳定甲苯等油相,制得稳定的水包油Pickering乳液。PSMVM胶体粒子在较宽的pH范围内具有良好的乳化性,所形成的乳液滴粒径随pH的增大而减小,pH值大于10时,乳液的稳定性下降,最终导致破乳。光交联对PSMVM胶体粒子的乳化性能有较大影响,交联胶体粒子在pH值2-11范围内乳化性能均优于未交联胶体粒子,且无破乳。加盐有利于提高胶体粒子的乳化性能。用简便的乳化-油相聚合固化的方法,证明PSMVM颗粒乳化剂在油水界面形成粒子膜以保护油滴的稳定,验证了颗粒乳化机理。PSMVM胶体粒子乳状液具有长期稳定性。此外,我们用PSMVM胶体粒子成功地实施了对油性染料的乳化包埋,得到稳定的油性染料乳状液。分子量对PSMVM胶体粒子乳化性能有影响,小分子量PSMVM2胶体粒子制备的乳液在pH值为10左右就发生破乳。4、双亲无规共聚物P(DM-co-AA-co-CA)的自组装及其性能研究本章主要以链结构完全无规的聚(甲基丙烯酸二甲胺乙酯-co-丙烯酸-co-香豆素丙烯酸酯化物)P(DM-co-AA-co-CA)为组装基元,在选择性溶剂中自组装可以得到稳定的,具有多重响应性及乳化功能的P(DM-co-AA-co-CA)胶体粒子。实验结果表明,改变外界刺激诸如光、pH、离子强度、温度可以调控胶束的粒径、荷电性、LCST、光响应性、以及乳化性能。P(DM-co-AA-co-CA)胶体粒子同时含有PDM和PAA链段,具有两性聚电解质特点。酸性条件下,该胶体粒子荷正电,而碱性条件下,则显负电；在等电点(pH=8)粒子的静电荷为零,粒径最小,无表面活性故而也没有乳化能力；但在等电点之外的强酸及强碱条件下,P(DM-co-AA-co-CA)胶体粒子都具有良好的乳化性。PDM链段赋予该胶束温敏性,加碱则使其LCST降低,加盐使其LCST提高。离子强度对其乳化性有较复杂的影响；在pH为8.54时胶束溶液的紫外吸收和荧光强度达到最大值；光交联可以提高胶体粒子本身的稳定性及乳化性能。5、大豆分离蛋白-g-PAMPAS接枝物的合成及溶液性质研究首先以巯基乙胺为链转移剂,过硫酸铵为引发剂,进行单体2-丙烯酰胺基-2-甲基丙磺酸(AMPS)的溶液聚合得到氨基封端聚2-丙烯酰胺基-2-甲基丙磺酸(H2N-PAMPS)；再以1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐(EDC)和N-羟基琥珀酰亚胺(NHS)催化大豆分离蛋白上的羧基与H2N-PAMPS长链上的端氨基进行缩合反应,得到接枝物SPI-g-NH-PAMPS。实验结果表明,大豆分离蛋白SPI表面接枝含亲水磺酸基团聚AMPS后,由于改变了SPI表面荷电性,从而改善其亲水性。SPI为球蛋白,其粒径约在180 nm左右,而SPI-g-NH-PAMPS聚集体形态则呈核壳结构,在SPI外围可见有一层淡晕状PAMPS接枝壳层,且粒径较SPI增大至200多纳米。接枝物SPI-g-NH-PAMPS等电点消失,在原SPI等电点(pH=4.5)附近的亲水性和乳化性能等均有所提高。我们通过对四个具有不同链结构的大分子双亲体系,即交替共聚物、无规-交替共聚物、无规共聚物以及大豆蛋白接枝物的合成、自组装及其功能和乳化性能研究,回答了前面提出的两个主要问题：1、证实了利用简单易得的无规-交替类共聚物通过常规的选择性溶剂自组装,可以得到具有环境响应性的表面活性胶体粒子；2、此类胶体粒子具有良好的乳化性能,可以作为聚合物软颗粒乳化剂应用于Pickering乳液的制备,油性物乳化包埋等。因此,本文在以无规-交替共聚物为组装基元构筑自组装胶体粒子--颗粒乳化剂及其应用方面开辟出一条新路径。此外,与通常报道的表面活性胶体粒子的制备方法--乳液聚合、分散聚合相、表面修饰等相比,自组装更容易通过设计和调整聚合物化学组成和链结构、控制自组装环境来得到形态及性质不同的胶体粒子,更容易通过环境因素控制组装和解组装过程,这有益于胶体粒子乳化机理的研究。本研究拓展了聚合物自组装胶束化的研究领域,对最终实现聚合物自组装的商业化或工业化应用有重要意义。更多还原

【Abstract】 Due to the significance of the great range of potential applications, there has been great progress in the past decade in the research of self-assembly of amphiphilic copolymers. During the past few years, our group has focused on the research of non-covalently connected micelles(NCCM) formed by the non-covalent interaction between non-block copolymers, and has had many successes. Up to now, the hot topic of macromolecular self-assembly has shifted into the design and functionalization of functional assembly units as well as their application in drug delivery, encapsulation, and medical imaging.As yet, most self-assemblies are based on amphiphilic block copolymers, owning to their well-defined architectures and narrow polydispersities. However, the synthesis of block copolymers is relatively inconvenient, which limits their large-scale applications. Compared with block copolymer, random copolymers are abundant in sources, easy to obtain and are of more potential value in large-scale applications. Although random copolymers have,relatively ill-defined structures compared to block copolymers, there have been some publications of random copolymer self-assembly into stable and ordered aggregations. One main aspect of this dissertation is whether or not the random copolymer micelle could be endowed with responsiveness via molecular design and functionalization and whether it would be possible to finally turn the random copolymer micelle into a practical application. According to the structure of random copolymers, we speculate that the hydrophilic/hydrophobic micro-domains of the assembly should be of disordered distribution with enriched hydrophilic microdomain at the surface of micelle and should be enriched hydrophobic micro-domain inside the micelle, which makes them amphiphilic.As early as a century ago, Pickering has already discovered that the solid colloid particles possessed surface activity and could stabilize emulsions. However it is not until the development of nanotechnology in the 1990s,had the particle emulsifiers become the focus of attention and scored great usage in the field of inorganic and organic/inorganic hybrid particle emulsifiers. With both hydrophilic and hydrophobic micro-domains on its surface, particle emulsifiers have contacted angles normally in the range of 60°120°and can lie stably at the oil/water interface. We would like to consider and focus on whether the amphiphilic assembly micelle could also be used as a particle emulsifier. In this case, we proposed that we could obtain polymeric soft emulsifier by taking advantage of the surface activity of random copolymer micelle and systematically studied its emulsification as well as the application, which is the another point of research focus of this thesis.Based on those two areas of research foci mentioned above, we have designed and synthesized a series of simple and readily available amphiphilic non-block random alternating copolymers, in which responsive units have been incorporated to acquire stimuli-responsive property. Macromolecular colloid particles with structural stability and surface activity were obtained from the self-assembly of these randomly alternating copolymers as assembly units, and their function as particle emulsifiers was also studied and therefore we developed a new strategy to prepare polymeric soft particle emulsifier for application.The main framework and feature of this thesis are:(1) stable surface-active colloid particles were prepared from the self-assembly of functional alternating copolymers with determined structure and shortest hydrophilic/hydrophobic chain segments to confirm that they possess good emulsification property and form a novel kind of soft particle emulsifier; (2) surface-active colloid particles were prepared from the self-assembly and photo-crosslinking of randomly alternating amphiphilic photo-crosslinkable copolymers with partly disordered chain structure; (3) multi-sensitive surface active colloid particles with good emulsification properties were prepared from the self-assembly of completely disordered random amphiphilic copolymers with multi-sensitive units in selective solvents; (4) finally combining with biological macromolecules, the emulsification property of soy protein isolate(SPI) and its graft copolymers with random structures were examined, which confirmed the improvement of emulsification property after the graft modification of SPI. The results showed that the colloid particles of non-block amphiphilic copolymer with short hydrophilic/hydrophobic chain segments did not demonstrate the typical core-shell structure, whereas hydrophobic micro-domains still existed on the surface of the colloid particles, imparting surface activity to them. Therefore these results showed that the present methodology of preparing surface active colloid particles from the self-assembly of amphiphilic random-alternating copolymer is general and has a wide range of applications. The main contents of this thesis are as follows:1. Synthesis, modification and self-assembly of the amphiphilic alternating copolymer P(St-alt-MAn)Using toluene as solvent, an alternating copolymer P(St-alt-MAn) was prepared by free radical polymerzation which then underwent ammonolysis with dopamine to obtain an amphiphilic alternating copolymer P(St-alt-MA-Dopa). In selective solvent, both P(St-alt-MAn) and P(St-alt-MA-Dopa) assembled into stable spherical colloid particles. The P(St-alt-MA-Dopa) colloid particles showed the pH-sensitivity and ion responsitivity as well as surface activity. In addition, the P(St-alt-MA-Dopa) colloid particle was a novel polymeric soft particle emulsifier:with P(St-alt-MA-Dopa) solution as water phase and toluene as oil phase, stable Pickering oil-in-water emulsions were produced. The absolute zeta potential value of the colloid particle increased with the increase of pH and decreased with the increase of salt concentrations; the size of the colloid particles increased with the increase of pH. The hydrophobility of the P(St-alt-MAn-Dopa) colloid particle was determined by fluorescence technique and the result showed that the increasing pH led to the increase of hydrophilicity, whereas the ionic strength had little effect on its hydrophobility. The P(St-alt-MA-Dopa) colloid particle exhibited good emulsifying property within a wide range of pH and very low concentration (0.5 mg/mL) and the pH and salt concentration had some influence on its emulsification property. The above results preliminarily attest our proposed conjectures:functional and responsive colloid particles can also be prepared from the assembly of random-alternating copolymers; functional alternating amphiphilic copolymer with the shortest hydrophilic/hydrophobic chain segments can self-assemble into a surface active colloid particle with emulsification property, which makes it a novel soft particle emulsifier.2. The synthesis and self-assembly of amphiphilic random alternating PSMVM copolymersA new amphiphilic random alternating-like copolymer PSMVM P(St-alt-MAn)-co-(VM-alt-MAn) was prepared through free radical copolymerization with St, coumarin-containing styrene monomer (VM) and MAn as monomers. The copolymer self-assembled into a stable amphiphilic spherical colloid particle (50-100 nm diameter) in selective solvent, which has photo, pH and ionic strength sensitivity. The transmission electron microscopy (TEM) showed that the PSMVM colloid particle exhibited dispersion microphase separation structure which was possibly related to the structure of PSMVM. The UV irradiation led to the cross-linking of coumarin group inside PSMVM particle and the TEM showed that the colloid particle had a tendency of collapse deformation and smaller size with the increasing irradiation time and the over-irradiation led to aggregation of the colloid particles. Compared with the uncrosslinked colloid particles (UCL-PSMVM), the crosslinked colloid particles (CL-PSMVM) showed better solvent resistance. The XPS results confirmed that there were relatively enriched oxygen at the surface of the aggregate and it may be caused by the accumulation of hydrophilic carboxyl acid group on the surface of particles which stabilized the colloid particles. The carboxyl group of PSMVM imparted pH sensitivity to PSMVM colloid particle:the zeta potential became more negative and the size increased with increasing pH value. The addition of NaCl could shield the surface charge of the PSMVM colloid particle and thus led to a decrease in absolute zeta potential value and an increase in hydrophobility and size of the colloid particle. In this part, the immobilization of the PSMVM colloid particles was achieved by crosslinking and could be further inferred that it would have practical significance in the preparation and application of polymeric soft particle emulsifier.3.Emulsification behavior of amphiphilic random alternating PSMVM copolymer colloid particleThe focus of this section was soft particle emulsifier from self-assembling random alternating copolymer. The effect of environment on the emulsification behavior of PSMVM colloid particle was studied and the entrapment of oil substance as well as its absorption behavior on the oil/water interface was also explored. The results showed that PSMVM particle could serve as soft particle to stabilize oil phase such as toluene at very low concentration, resulting in stable oil-in-water Pickering emulsion. The colloid particle had good emulsification property in a wide pH range and the size of the emulsion droplet decreased with increasing pH, however the stability of emulsion declined leading to demulsification when pH value exceeded 11. After UV crosslinking, the obtained crosslinked PSMVM colloid particle showed improved emulsification property and demulsification was not observed in the pH range of 2-11. We also observed that the addition of salt improved the emulsification property. Using the simple emulsion and then solidification by the polymerization of oil phase, the PSMVM colloid particles were immobilized on the surface of the solid oil latex, which indicated that PSMVM colloid particles formed a particle film at the oil/water interface to stabilize the oil droplet, confirming the emulsion mechanism. The PSMVM colloid particle emulsion had longterm stability. Furthermore, successful entrapment of oil dye by the PSMVM colloid particle as emulsifier has been achieved and stable emulsions have been obtained. The molecular weight of PSMVM also had effects on its emulsification property and for the colloid particle with low molecular weight, demulsification occurred at pH=10.4.Self-assembly and property of amphiphilic random copolymer P(DM-co-AA-co-CA)A completely random copolymer P(DM-co-AA-co-CA) were synthesized via free radical copolymerization of coumarin-containing acrylic acid monomer (CA), together with dimethylaminoethyl methacrylate(DM) and acrylic acid(AA). In the selective solvent the copolymer P(DM-co-AA-co-CA) self-assembled into multi-sensitive colloid particle with emulsification property. The results showed that the size, charge, LCST and emulsification of the colloid particle could be controlled through the tuning of the external stimuli such as light, pH, ionic strength and temperature. The PDM and PAA segment in P(DM-co-AA-co-CA) endowed it amphoteric polyelectrolyte characteristics and the charge of the colloid particle was positive in acid condition and negative in base condition. At its isoelectric point (pH=8), the P(DM-co-AA-co-CA) colloid particle was neutral and become the smallest, and it almost lost surface activity, as a consequence its emulsification property disappeared. However, the P(DM-co-AA-co-CA) colloid particle had good emulsification in both acid and base environment and a stable oil-in-water emulsion could be obtained. The PDM chain segment endows the colloid particle thermosensitivity:the addition of salt increased low critical solotion temperature (LCST) whereas the addition of base led to the decrease of the LCST. The ionic strength had a complex influence on its emulsification property. The UV absorption and fluorescence intensity of the micelle solution reached the maximum at pH 8.54. In addition, the photo-crosslinking improved the stability and emulsification property of the colloid particles.5.Synthesis and aqueous solution properties of soy protein isolate graft copolymers SPI-g-NH-PAMPSGraft copolymers based on soy protein isolate with amino-terminated poly(2-acrylanmido-2-methyl propane sulfonic acid) (SPI-g-NH-PAMPS) were prepared by a grafting reaction between the free carboxylic acid groups of soy protein isolate (SPI) and the amino groups of poly(2-acrylanmido-2-methyl propane sulfonic acid) (H2N-PAMPS) using 1-(3-(dimethylamino)propyl)-3-ethyl-carbodiimide hydrochloride/N-Hydroxy-succinimide as the condensing agents in a buffer solution. The results showed that the hydrophilicity of SPI was improved after the graft reaction, which was attributed to that the hydrophilic sulfonic groups of the grafted H2N-PAMPS chains change the surface charge of SPI. SPI belonged to globulin and its size was around 180nm, whereas SPI-g-NH-PAMPS aggregates presented core-shell structure with a light halo PAMPS grafting shell around SPI and the size increased to ca.200 nm. The graft polymer SPI-g-NH-PAMPS showed no isoelectric point and its hydrophilicity and emulsification properties were improved at the isoelectric point of SPI (pH 4.5).In conclusion, we have synthesized four kinds of macromolecular amphiphilic systems with different chain structures, namely alternating copolymer, random alternating copolymer, random copolymer and graft copolymer of SPI and studied their self-assembly and emulsification properties. The above results showed that we have resolved the two research foci we proposed:1) stable and surface active polymer colloid particle could be prepared from the self-assembly of simple and readily available amphiphilic random alternating copolymers in common selective solvent; 2) this colloid particle have good emulsification property and could serve as polymeric soft particle emulsifier to prepare Pickering emulsion and entrap oil substance. Hence, a new methodology in the exploration of preparing particle emulsifier from self-assembling random alternating copolymer for application has been developed in this thesis. In addition, compared to the commonly reported preparation methods of surface active colloid particles—emulsion polymerization, dispersion polymerization and surface modification, self-assembly can more easily produce colloid particles with different shapes and properties by designing and tuning the chemical composition and chain structure as well as self-assembling environment, which allowed us more easily to control the assembly and disassembly process, benefiting the research of the emulsion mechanism of colloid particles.Our work has expanded the horizons of research interests in polymer self-assembly micellization and has great significance to ultimately realize its commercial or industrial applications.更多还原