Sum Frequency Generation Vibrational Spectroscopy Investigation of BuriedPolymer and Organic Interfaces.

[摘要] It is difficult to elucidate buried interfaces because of the lack of appropriate analytical techniques.In this thesis, it was shown that sum frequency generation vibrational spectroscopy (SFG) can be used to probe molecular structures of buried interfaces, leading to important understanding of polymer adhesion, two dimensional crystal structure, and pharmaceutical polymorphs on polymer surfaces. SFG was used to investigate the interface between the amine and aldehyde functionalized poly-p-xylyene surfaces to understand the mechanism for the Solventless Adhesive Bonding technique.It was found that the adhesion is due to the chemical reaction between the amine and aldehyde groups. STM image of a monolayer of 17 metadiester phthalates on graphite under a phenyloctane solution does not provide orientation information of these molecules.SFG results indicate that the C=O groups were tilting ~30º away from the surface.This is due to the two different interactions: monolayer-phenyloctane solvent interaction and monolayer-graphite surface interaction.This new finding needs to be incorporated in future modeling of these systems. C=O groups are important surface interaction sites in polymers.SFG was used to study surface C=O groups of several poly-n-methacrylates in air and in water.In water, interfacial hydrogen bonds formed between polymer C=O groups and water molecules.The orientations of the C=O groups on various polymers were determined and discussed. The mechanism of polymer-induced heteronucleation of acetaminophen was also examined using SFG.Poly-methyl-methacrylate and poly-n-butyl-methacrylate were found to heteronucleate different polymorphs of acetaminophen from saturated solutions.Evidence of hydrogen bonding between the NH of the acetaminophen and the C=O of the polymers was observed for both PMMA and PBMA.The difference in orientation of the C=O groups of polymers when hydrogen bonded to the acetaminophen molecule is thought to be responsible for the polymorph selection.In addition, SFG was applied to study polymer/acetaminophen crystal interfaces to further understand polymer-acetaminophen interactions.Different crystal growth methods, solution and sublimation, were compared. The design and implementation of a SFG imaging system was also discussed.A preliminary result of microcontact printed PMMA surface with resolution better than 5µm is shown.

[发布机构] University of Michigan

[效力级别] Vibrational Spectroscopy

[关键词] Sum Frequency Generation (SFG);Vibrational Spectroscopy;Surface Science;Polymer Induced Heteronucleation;Polymer Surface Chemistry;Chemistry;Physics;Science (General);Science;Applied Physics