We investigated the conformation of PMMA in thin films at the air-water interface by sum frequency generation (SFG) spectroscopy and discuss the effect of stereoregularity on the interfacial structure of PMMA. At the air interface, isotactic PMMA takes a helical conformation where the hydrophilic carbonyl groups are oriented towards the interfacial region of the film. Thus, even though the polymer chains come in contact with water, the chain conformation at the interface changes very little. The structure of syndiotactic PMMA at the air and water interfaces is significantly different. Poly(methyl 2-propenyl ether) (PMPE), synthesized via living cationic polymerization, is structurally similar to PMMA, but it lacks the carbonyl group. We discuss the effect of the carbonyl group on the water structure at the interface by comparing the results of our measurements to the previously reported PMMA-water system. This knowledge is crucial for the design and construction of highly-functionalized polymer interfaces for biological applications.
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