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Thin film property modification via block copolymer adsorption
by Costa, Ana Claudia Aragao de Almeida, Ph.D., University of Pennsylvania, 2003, 171 pages; AAT 3087388

Abstract (Summary)

Using low-energy forward recoil spectrometry and neutron reflectivity, diblock and triblock copolymer adsorption from a polystyrene, PS, matrix to the substrate is investigated. The diblock copolymers are poly(deuterated styrene- block -methyl methacrylate), dPS- b -PMMA, and poly(deuterated styrene- block -dimethyl amino ethyl methacrylate), dPS- b -PDMAEMA. The PMMA and PDMAEMA blocks readily adsorb to silicon oxide, SiO x , whereas the dPS block extends into the PS matrix. For diblock copolymers having dPS degree of polymerization (DOP), N dPS < 200, the distance between grafted chains, D , is greater than R g , radius of gyration of dPS, whereas for N dPS > 200, D is less than R g . Thus, a crossover from a collapsed to a stretched conformation is expected near N dPS [approximate] 200, which corresponds to the entanglement DOP of PS, N e . Moreover, adsorption strongly increases as N dPS increases from values below to values above N e . Using only the adsorbing block-substrate interaction as a fitting parameter, self-consistent mean-field, SCMF, predictions are in good agreement with experimental results. The dPS- b -PMMA adsorption from a PS matrix to an amine-terminated SiO x surface is also investigated. In contrast to the strong adsorption on SiO x , PMMA adsorption to the amine-terminated surface must compete with the PS matrix chains. Thus, the interfacial width between the PS chains and the non-adsorbing dPS block is broader on the amine-terminated surface. In agreement with this result, PS:dPS- b -PMMA films on amine surfaces show hole growth suppression, whereas on SiO x , hole growth is observed for films having N dPS < P, where P represents the DOP of PS matrix. Tack tests of dPS- b -PMMA in contact with a PS melt show that adhesion improves as N dPS increases. This result suggests that entanglements across the interface increase with increasing N dPS . The effects of triblock chain architecture and anchoring block molar fraction, f A , on thin film dewetting and block copolymer adsorption on SiO x are also investigated. Although chain architecture has a minor effect on dewetting, hole grow is detected when the anchoring block is short and f A < 4%. In comparison to the PS:diblock case, PS:triblock films show less adsorption suggesting that triblocks are less effective adhesion promoters.

Indexing (document details)

Advisor:Composto, Russell J.
School:University of Pennsylvania
School Location:United States -- Pennsylvania
Keyword(s):Polystyrene, PMMA, Thin film, Adsorption
Source:DAI-B 64/04, p. 1863, Oct 2003
Source type:Dissertation
Subjects:Materials science
Publication Number: AAT 3087388
Document URL:http://proquest.umi.com/pqdlink?did=765693051&Fmt=7&clientId =79356&RQT=309&VName=PQD
ProQuest document ID:765693051


 

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