Aggregation, Adsorption, and Surface Properties of Multiply End-Functionalized Polystyrenes

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• 作者：Imtiyaz A. Ansari ; Nigel Clarke ; Lian R. Hutchings ; Amilcar Pillay-Narrainen ; Ann E. Terry ; Richard L. Thompson ; John R. P. Webster
• 刊名：Langmuir
• 出版年：2007
• 出版时间：April 10, 2007
• 年：2007
• 卷：23
• 期：8
• 页码：4405 - 4413
• 全文大小：384K
• 年卷期：v.23,no.8(April 10, 2007)
• ISSN：1520-5827

文摘

The properties of polystyrene blends containing deuteriopolystyrene, multiply end-functionalized with C₈F₁₇fluorocarbon groups, are strikingly analogous to those of surfactants in solution. These materials, denoted F_xdPSy,where x is the number of fluorocarbon groups and y is the molecular weight of the dPS chain in kg/mol, were blendedwith unfunctionalized polystyrene, hPS. Nuclear reaction analysis experiments show that F_xdPSy polymers adsorbspontaneously to solution and blend surfaces, resulting in a reduction in surface energy inferred from contact angleanalysis. Aggregation of functionalized polymers in the bulk was found to be sensitive to F_xdPSy structure and closelyrelated to surface properties. At low concentrations, the functionalized polymers are freely dispersed in the hPS matrix,and in this range, the surface excess concentration grows sharply with increasing bulk concentration. At higherconcentrations, surface excess concentrations and contact angles reach a plateau, small-angle neutron scattering dataindicate small micellar aggregates of six to seven F₂dPS10 polymer chains and much larger aggregates of F₄dPS10.Whereas F₂dPS10 aggregates are miscible with the hPS matrix, F₄dPS10 forms a separate phase of multilamellarvesicles. Using neutron reflectometry (NR), we found that the extent of the adsorbed layer was approximately halfthe lamellar spacing of the multilamellar vesicles. NR data were fitted using an error function profile to describe theconcentration profile of the adsorbed layer, and reasonable agreement was found with concentration profiles predictedby the SCFT model. The thermodynamic sticking energy of the fluorocarbon-functionalized polymer chains to theblend surface increases from 5.3k_BT for x = 2 to 6.6k_BT for x = 4 but appears to be somewhat dependent upon theblend concentration.