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Dissertation
Bridging color and chemistry: new classes of sulfur-nitrogen polymers as a platform for advanced materials
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2026
DOI: 10.25820/etd.008387
Abstract
Sulfur-nitrogen (S-N) compounds have attracted significant interest due to their diverse structural motifs and unique optical, chemical, and electric properties. In particular, S-N polymers represent a promising class of functional materials with potential applications in chemical sensing, electronics and advanced materials. Despite this promise, the development of structurally well-defined S-N polymers remains limited due to several limitations (synthetic challenges, poor stability, and limited structural tunability) displayed by its predecessor: polythiazyl. This thesis represents a significant leap forward in the design, synthesis, and characterization of new polymers containing exclusively alternating -NSS- and -NS- backbones.
Chapter 1 provides a comprehensive overview of sulfur-rich polymers and S-N chemistry. Particular emphasis is placed on the role of sulfur chlorides (S2Cl2) as efficient sulfurating reagents for introducing sulfur atoms into nitrogen-containing organic chemicals. The historical development of S-N polymers and heterocycles is discussed, highlighting their synthesis, potential applications, and the limitations.
Chapter 2 describes the polymerization of aromatic diamines with sulfur monochloride (S2Cl2) to yield a new class of highly crosslinked, conjugated polymers containing -NSS- functional groups in the backbone. Twenty poly[N,N’-(phenyldiamino)disulfide]s (polyDNDS) polymers were reported by the polymerization of five structurally different diamine monomers with S2Cl2 in four stoichiometric ratios to vary the degree of crosslinking. These materials displayed bright colors ranging from yellow to green to blue, depending on the conjugation through the NSS backbone and aromatic rings of the monomers and the amount of crosslinking present. The polymers were characterized by SEC-MALLS, UV-Vis spectroscopy, elemental analysis, and NMR spectroscopy. The resulting polymers showed high molecular weights from 15-5100 kg mol-1 and chemical responsiveness towards thiols, demonstrating their potential utility as chemical sensors. Additionally, the rapid rate of reaction of the polymerization enabled the fabrication of patterned 2D materials.
Chapter 3 expands this chemistry to carbamate monomers to produce polymers with -NSS- and -NS- linkages. Six polymers were developed (three poly[N,N-(carbamate)sulfide]s : polyMSC and three poly[N,N-(carbamate)disulfide]s: polyDSC) using S2Cl2 and SCl2 via step growth polymerization. These polymers consistently exhibited red coloration arising from the conjugation within the S-N backbone. Subsequent base-mediated deprotection of the carbamate group yielded polymers exclusively containing sulfur, nitrogen and hydrogen with -N(H)S- and -N(H)SS- repeating units. This approach yielded polymers analogous to polythiazyl framework while incorporating hydrogen atoms that enhanced solubility, processability, and characterization. All polymers were analyzed using NMR spectroscopy, SEC-MALLS, UV-Vis spectroscopy, and elemental analysis.
Chapter 4 reports the reactions of alkyl amines with moderate sulfur transfer reagents to form small S-N heterocycles. The study represents a controlled, clean and an efficient method of preparing 5-, 6-,7-, and 8-membered S-N heterocycles using N,N’-thiobisphthalimide and N,N’-dithiobis phthalimide transfer reagents. This work provided insight into the mechanistic pathways that govern whether the reactions of diamines with sulfur transfer reagents could be used to synthesize polymers with heterocyclic rings embedded on the backbone.
Collectively, the work presented in this dissertation establishes new synthetic strategies for constructing S-N polymers and heterocycles using different sulfur transfer reagents. The results expand the structural diversity of S-N polymers, narrow the knowledge gap of S-N materials and contribute to the broader effort to develop functional sulfur-based materials with potential applications in sensing, electronics, and advanced systems.
Details
- Title: Subtitle
- Bridging color and chemistry: new classes of sulfur-nitrogen polymers as a platform for advanced materials
- Creators
- Shanari Marian Rathnayake Wickremasinghage
- Contributors
- Ned B Bowden (Advisor)David F Wiemer (Committee Member)Scott K Shaw (Committee Member)Tori Z Forbes (Committee Member)Gregory K Friestad (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemistry
- Date degree season
- Spring 2026
- DOI
- 10.25820/etd.008387
- Publisher
- University of Iowa
- Number of pages
- xxvii, 184 pages
- Copyright
- Copyright 2026 Shanari Marian Rathnayake Wickremasinghage
- Language
- English
- Date submitted
- 04/27/2026
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 157-184).
- Public Abstract (ETD)
Modern research is in search of chemical building blocks that can provide materials with useful properties such as diverse colors, electrical conductivity, biocompatibility, and chemical sensitivity. One area of growing interest is materials that contain both sulfur and nitrogen atoms. These elements form a special bond that gives materials unique chemical and physical properties. However, many sulfur-nitrogen compounds discovered in the past are difficult to make, unstable, or hard to study. This thesis explores new ways to design and develop sulfur-nitrogen small molecules and macromolecules that can be classified into three different classes.
The first part of this research focuses on synthesizing new materials called polyDNDS. These macromolecules showed bright colors such as yellow, red, green, and blue due to the special type of bond between sulfur and nitrogen atoms. These polymers were stable in air and showed potential in chemical sensing and 2D patterned applications.
The second part expands this knowledge to create two sets of macromolecules, polyMSC and polyDSC, which produce bright red materials. The study further explored the development of materials that are structurally related to polythiazyl: the first polymeric metal. The newly reported materials aim to address some of the limitations of polythiazyl, such as solubility and tunability, while showing electrical conductivity.
Finally, this work explores the possibilities of constructing ring structures containing sulfur and nitrogen atoms. The understanding gained from these studies will guide the development of macromolecules that incorporate sulfur-nitrogen rings within their structures.
Overall, this thesis demonstrates several new strategies for fabricating sulfur-nitrogen materials with interesting properties, expanding its chemistry and providing new directions for advanced materials for future innovation in responsive and electronically active polymer systems.
- Academic Unit
- Chemistry
- Record Identifier
- 9985177272602771
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