【作者】 谢定海；

【导师】 张广照；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2009， 博士

【摘要】 本论文中,我们利用激光光散射（LLS）、中子反射仪（NR）和Langmuir天平（LB）等技术研究了氢键对高分子链界面行为的影响,包括氢键对温敏性多嵌段聚合物链聚集机理、高分子聚集体结构演化和高分子链在气液界面上的行为的影响。主要结果如下:1.利用激光光散射对温敏性三嵌段聚合物PnPA-b-PNIPAM-b-PEMA的聚集机理进行了研究。结果表明:三嵌段聚合物的胶束化过程取决于PEMA段的相对长度。由于PnPA的塌缩,形成PnPA为核,PNIPAM和PEMA为壳的胶束。进一步升高温度导致了胶束外层的PNIPAM和PEMA链的塌缩。如果PEMA链较短,不能完全屏蔽和保护由于PNIPAM链的塌缩形成的憎水核时,胶束间的PNIPAM会发生缠结,导致胶束间发生聚集,形成胶束团簇（micelle cluster）。相反,如果PEMA链段足够长时,则可以阻止胶束聚集的发生。另外,在降温过程中,由于高分子链间形成的附加氢键的影响,聚集体的解散明显滞后于聚集。2.利用激光光散射研究了PS-b-PAA聚集体的结构演化。当PS链段较短,不能完全屏蔽憎溶剂的PAA核时,PS-b-PAA在甲苯溶液中会形成两种聚集体,即规整的核壳胶束和松散的胶束团簇。加入PS-b-PEO后,PEO与PAA间的氢键作用,导致PS-b-PEO链插入胶束,形成混合胶束团簇,其结构随时间发生演化。结果表明:壳层PS链间的排斥力和核内PAA与PEO间的氢键主导了演化过程。当排斥力足以克服氢键作用时,混合胶束团簇发生分裂,生成具有规整核壳结构的胶束。3.利用激光光散射研究了PS-b-PAA/PMMA-b-PEO混合胶束在甲苯中的结构演化。结果表明:核内PEO/PAA间的氢键和壳层PS/PMMA间的相分离之间的竞争,主导了混合胶束的结构演化。当相分离相对于氢键作用占支配位置时,混合胶束经长时间的演化,逐步形成松散的超支化结构。4.利用Langmuir天平和中子反射技术的结合,研究了PI-b-PEO和PI-b-PAA混合单层膜在具不同pH值的液相中的界面行为。结果表明:PI-b-PEO能与PI-b-PAA形成混合单层膜,其界面行为强烈依赖于pH值。在pH 10.0和5.7时,大部分的羧酸根基团电离,PAA链对PI-b-PEO膜的界面行为没有任何影响。混合单层膜的表面压力曲线Π-σ^-1存在着三个区域,即:（Ⅰ）表面压力较低时的pancake区:（Ⅱ）PEO链逐渐从液面解吸附并浸没液相中的pseudo-plateau区;（Ⅲ）表面压力急剧增加的brush区。在表面压力快速增加的区域Ⅲ,中子反射实验证明界面高分子伸向水相的部分形成了brush-like的结构。而在pH 2.5时,出现一个新颖的行为:表面压力曲线Π-σ^-1仅仅存在着两个区域,区域Ⅱ（pseudo-plateau）消失:而且,表面压力曲线Π-σ^-1中的压缩-扩张循环曲线重叠。这些结果表明由于未电离的羧酸根基团和PEO链形成了氢键,阻碍了压缩过程中PEO链节的解吸附和链节间的缠结。更多还原

【Abstract】 The thesis deals with the effect of hydrogen-bonding complexation on the interfacial behavior of the polymer chains by using laser light scattering（LLS）, neutron reflectivity（NR） and Langmuir balance（LB）,including the aggregation of thermosensitive multi-blcok copolymers,the structural evolution of the polymeric aggregations and the interfacial behavior of the polymer chains at the air-water interface.The main results are as follows:1.The investigations on the aggregation of thermosensitive PnPA-b-PNIPAM -b-PEMA triblock terpolymers lead to the following conclusions.The micellization process depends on the relative length of the PEMA block.The folding of PnPA led to the formation of polymeric micelles with a collapsed hydrophobic PnPA core and a hydrophilic swollen PNIPAM-PEMA shell.Further increase in temperature leads to the collapse of the PNIPAM and PEMA chains on the periphery of the micelles.When the shorter PEMA block cannot shield the hydrophobic PnPA and PNIPAM core completely,PNIPAM chains in different micelles associate,leading to the clustering of the micelles.A longer PEMA block can prevent or delay the clustering of the micelles.In the cooling process,a hysteresis can be observed in the disruption of the aggregations due to the formation of additional hydrogen bonds.2.The studies on the structural evolution of PS-b-PAA aggregations lead to the following conclusions.When PS block is not long enough to shield the solvophobic PAA core completely,PS-b-PAA chains form bimodal aggregates with regular micelles and micellar clusters in toluene.The introduction of PS-b-PEO chains leads to the formation of mixed micellar clusters whose structure evolves with time.The hydrogen-bonding complexation between PAA and PEO in the core and the repulsion between PS chains in the corona manipulate the evolution.When the latter dominates the former,the mixed micellar clusters split up into regular complex micelles.3.The studies on the structural evolution of PS-b-PAA/PMMA-b-PEO mixed micelles give the following conclusions.The competition between the hydrogen-bonding complexation of PAA/PEO in the core and the segregation of PS/PMMA in the corona manipulate the evolution.When the segregation dominates the hydrogen-bonding complexation,the mixed micelle develops into a hyperbranched structure after a long-time standing.4.The interfacial behavior of PI-b-PAA/PI-b-PEO mixed monolayers has been investigated by LB and NR.It shows that the behavior is highly pH-dependent.At pH 10.0 and 5.7,where the carboxyl acid groups are deprotonated,PAA chains do not induce any unusual effect on the behavior of the PI-b-PEO layer.Theп-σ^-1 isotherms of the mixture exhibit three regions,（Ⅰ） a low-pressuer 2-D "pancake" region,（Ⅱ） a pseuoplateau where PEO segments desorb and are immerse in the subphase;and（Ⅲ） a steep pressure rise region commonly considered as the "brush" regime.In regionⅢ, neutron reflectivity measurements confirm the formation of brush-like structures in the tethered layer.At pH 2.5,a novel behavior is observed;theп-σ^-1 isotherm exhibits only two regions,that is,the pseudoplateau disappears;furthermore,the compression-expansion cycles are completely reversible.These results suggest that desorption of PEO segments and their entanglement are hindered due to the formation of hydrogen-bonding complexation between the undissociated carboxylic groups and the PEO chains.更多还原