Interfacial Behavior of Poly(isoprene-b-methyl methacrylate) Diblock Copolymers and their Blends with Polystyrene at the Air-Water Interface
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- 作者：Só ; nia I. C. Lopes ; Amé ; lia M. P. S. Gonç ; alves da Silva ; Pedro Brogueira ; Susana Piç ; arra ; J. M. G. Martinho
- 刊名：Langmuir
- 出版年：2007
- 出版时间：August 28, 2007
- 年：2007
- 卷：23
- 期：18
- 页码：9310 - 9319
- 全文大小：722K
- 年卷期：v.23,no.18(August 28, 2007)
- ISSN：1520-5827
文摘
The interfacial behavior of poly(isoprene-b-methyl methacrylate) diblock copolymers (PI-b-PMMA), with similarPMMA blocks but differing in the percentage of PI segments, SP19 (5% PI) and SP38 (52% PI), was studied at theair-water interface. The surface pressure-area (
pi.gif" BORDER=0 >-A) isotherms, compression-expansion cycles, and relaxationcurves were compared with those of the PMMA homopolymer. The short hydrophobic PI block of SP19 does notcontribute 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 surfacearea from low to high surface pressures. The A-t relaxation curves compare well with those of PMMA at low surfacepressures (pi.gif" BORDER=0 > = 2 mN.m-1), but not at intermediate and high pressures (pi.gif" BORDER=0 > = 10, 30 mN.m-1), where a clear dependenceon the length of the PI block was observed. The quantitative analysis of the relaxation curves at high pressures showsboth a fast and slow component, attributed mostly to the local and middle-to-long-range reorganization of PMMAchains, respectively. PI-b-PMMA diblocks and PMMA were further blended with PS. The PS and PMMA are immiscibleat the air-water interface. The addition of PS does not change the pi.gif" BORDER=0 >-A isotherm of PMMA, but the copolymersblended with PS form films that are more condensed at low pressures. The Langmuir-Blodgett (LB) films transferredonto 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.
pi.gif" BORDER=0 >-A) isotherms, compression-expansion cycles, and relaxationcurves were compared with those of the PMMA homopolymer. The short hydrophobic PI block of SP19 does notcontribute 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 surfacearea from low to high surface pressures. The A-t relaxation curves compare well with those of PMMA at low surfacepressures (pi.gif" BORDER=0 > = 2 mN.m-1), but not at intermediate and high pressures (pi.gif" BORDER=0 > = 10, 30 mN.m-1), where a clear dependenceon the length of the PI block was observed. The quantitative analysis of the relaxation curves at high pressures showsboth a fast and slow component, attributed mostly to the local and middle-to-long-range reorganization of PMMAchains, respectively. PI-b-PMMA diblocks and PMMA were further blended with PS. The PS and PMMA are immiscibleat the air-water interface. The addition of PS does not change the pi.gif" BORDER=0 >-A isotherm of PMMA, but the copolymersblended with PS form films that are more condensed at low pressures. The Langmuir-Blodgett (LB) films transferredonto 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.