Lopes Sónia I C, da Silva Amélia M P S Gonçalves, Brogueira Pedro, Piçarra Susana, Martinho J M G
Centro de Química Estrutural, Complexo I, and ICEMS, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisboa, Portugal.
Langmuir. 2007 Aug 28;23(18):9310-9. doi: 10.1021/la700988s. Epub 2007 Jul 26.
The interfacial behavior of poly(isoprene-b-methyl methacrylate) diblock copolymers (PI-b-PMMA), with similar PMMA blocks but differing in the percentage of PI segments, SP19 (5% PI) and SP38 (52% PI), was studied at the air-water interface. The surface pressure-area (pi-A) isotherms, compression-expansion cycles, and relaxation curves were compared with those of the PMMA homopolymer. The short hydrophobic PI block of SP19 does not contribute to the mean molecular area at low surface pressures and yet has a negative contribution (condensing effect) when the surface pressure increases. On the contrary, the long PI block of SP38 contributes considerably to the surface area from low to high surface pressures. The A-t relaxation curves compare well with those of PMMA at low surface pressures (pi = 2 mN.m-1), but not at intermediate and high pressures (pi = 10, 30 mN.m-1), where a clear dependence on the length of the PI block was observed. The quantitative analysis of the relaxation curves at high pressures shows both a fast and slow component, attributed mostly to the local and middle-to-long-range reorganization of PMMA chains, respectively. PI-b-PMMA diblocks and PMMA were further blended with PS. The PS and PMMA are immiscible at the air-water interface. The addition of PS does not change the pi-A isotherm of PMMA, but the copolymers blended with PS form films that are more condensed at low pressures. The Langmuir-Blodgett (LB) films transferred onto mica substrates were analyzed by atomic force microscopy (AFM). The LB films of single diblocks are uniform, while those of PI-b-PMMA and PMMA blended with PS show aggregates with variable patterns.
研究了聚（异戊二烯 - b - 甲基丙烯酸甲酯）二嵌段共聚物（PI - b - PMMA）在空气 - 水界面的界面行为，其中PMMA嵌段相似，但PI链段百分比不同，分别为SP19（5% PI）和SP38（52% PI）。将表面压力 - 面积（π - A）等温线、压缩 - 膨胀循环和松弛曲线与PMMA均聚物的进行了比较。SP19中短的疏水PI链段在低表面压力下对平均分子面积没有贡献，但在表面压力增加时具有负贡献（凝聚效应）。相反，SP38中长的PI链段在从低到高的表面压力下对表面积有很大贡献。在低表面压力（π = 2 mN·m⁻¹）下，A - t松弛曲线与PMMA的比较良好，但在中高表面压力（π = 10、30 mN·m⁻¹）下则不然，在这些压力下观察到对PI链段长度有明显依赖性。高压下松弛曲线的定量分析显示出快速和慢速成分，分别主要归因于PMMA链的局部和中长程重排。PI - b - PMMA二嵌段共聚物和PMMA进一步与PS共混。PS和PMMA在空气 - 水界面不相容。添加PS不会改变PMMA的π - A等温线，但与PS共混的共聚物形成的薄膜在低压力下更致密。通过原子力显微镜（AFM）分析了转移到云母基板上的朗缪尔 - 布洛杰特（LB）膜。单二嵌段共聚物的LB膜是均匀的，而PI - b - PMMA和与PS共混的PMMA的LB膜则显示出具有可变图案的聚集体。
