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Effect Of Chain End Functional And Chain Architecture On Surface Segregation

Zhang, Zimo
http://rave.ohiolink.edu/etdc/view?acc_num=akron1498513871263316

Abstract Details

2017, Master of Science, University of Akron, Polymer Science.
The objective of the research was to study the effects on surface segregation in binary polymer blends of both chain end functionalization of linear chains, and changes in architecture. An important question for the formation and application of a polymer thin film is the degree to which end group functionalization can influence the segregation of a chain to the air/polymer and polymer/substrate interfaces. For the first part of this study, well-defined polystyrene and hydroxyethylated functionalized polystyrene of exactly the same molecular weight (Mn = 6000 g/mol) were synthesized using anionic polymerization in order to minimize the impact of factors other than end group functionalization in the study of the segregation driven by the functionalization. Thin (90 nm) films of blends of these two chains spun cast on silicon substrates were investigated. Key to the study was use of a new method called Surface Layer Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (SL-MALDI-TOF-MS) which determines the composition at the surface (< 2 nm depth) of entire polymer chains, rather than the segment or chain end composition measured with other techniques. This technique requires no isotopic labeling. The most striking finding is that the surface region is not only depleted in the high energy chain end functionality, but, in fact, depleted in chains containing the functional group. Thus, for the first time, depletion of the entire chain, driven by only a single functionalized end group, was observed directly. The depletion of the surface in functionalized chains varies with composition and is more pronounced for blends of near-symmetric composition. For the study of the effect of architecture on surface segregation, star-branched polymers with two different architectures were synthesized. Well-defined 5.5k 4-arm star was successfully synthesized using a combination of anionic polymerization and silane linking chemistry. The structure of the product was characterized using Size Exclusion Chromatography (SEC) and MALDI TOF MS. The results show controlled molecular weight, a well-defined structure, and very high purity. “H-shaped” polymers have been much less commonly studied than star polymers and are more challenging to synthesize. Well-defined H-shaped polystyrene was synthesized using end linking of living arms to a polymeric linking agent. The a,¿-functionalized polymeric linking agent was made using a combination of anionic polymerization with a difunctional initiator and a silicon chloride functionalization reaction with inverse addition. The final product was characterized using multi-detector SEC with MALDI quantified parameters of the structure. The overall molecular weight matches well those of a series of well-defined branched chains already studied for their blend surface segregation and pure melt surface fluctuations behavior, allowing for insightful comparisons.
Mark Foster (Advisor)
Li Jia (Committee Member)
92 p.
Physics; Polymer Chemistry; Polymers
Anionic polymerization; Chain end functionalization; Surface segregation; MALDI TOF MS, SL-MALDI-TOF MS; Hydronxy terminated polystyrene; 4-arm star polystyrene; H-shaped polystyrene

Recommended Citations

Citations

  • Zhang, Z. (2017). Effect Of Chain End Functional And Chain Architecture On Surface Segregation [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1498513871263316

    APA Style (7th edition)

  • Zhang, Zimo. Effect Of Chain End Functional And Chain Architecture On Surface Segregation. 2017. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1498513871263316.

    MLA Style (8th edition)

  • Zhang, Zimo. "Effect Of Chain End Functional And Chain Architecture On Surface Segregation." Master's thesis, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1498513871263316

    Chicago Manual of Style (17th edition)

akron1498513871263316
319
© 2017, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.