Faculty


Thomas

Samuel W. Thomas

Department of Chemistry
Pearson Chemistry Laboratory
62 Talbot Avenue
Tufts University 
Medford, MA 02155 

Office: P-305C

Tel: 617-627-3771   Fax: 617-627-3443

E-mail: sam.thomas@tufts.edu

Research Homepage


Current Appointment

 

Professor of Chemistry, Department of Chemistry

Graduate Program Director

 

Education

 

B.S., 2000, University of Rochester, NY
Ph.D., 2006, Massachusetts Institute of Technology, Cambridge, MA
American Cancer Society Postdoctoral Fellow, Harvard University, 2006-2009

 

Research Interests


Organic Materials Chemistry 

Our group applies the philosophy of physical organic chemistry to organic materials, in the forms of polymers, crystals and surfaces. Specifically, we investigate new materials that show macroscopic changes in properties upon exposure to external stimuli. Our main focus has been new materials that respond to light, which has a unique combination of characteristics: i) easy control over where light goes and when it goes there (spatiotemporal control), ii) easy control over intensity and energy, and iii) the ability to pass through many solid materials that traditional chemical reagents cannot. Our research has focused in three separate areas. 
1. Photochemical control of charge. As interactions between charges dictate much of molecular behavior, controlling charge can yield control over matter. We have developed a series of materials in which light switches the charge-based interactions between polymer chains from attractive. By combining this top-down fabrication approach of with the bottom-up fabrication method of layer-by-layer assembly, we have developed thin films in which photochemical lability is confined to individual nanoscale compartments, yielding photo-delaminated free-standing films and multi-height photolithography.
2. Using functional side chains to control conjugated materials. Conjugated materials hold great promise for applications including solar cells and displays. We have focused on expanding the role of the side-chains of these materials, which occupy up to half of their mass but are typically reserved only for solubility. Early work in our group focused on integrating photolabile side chains for negative conjugated photoresists.  This has evolved to using the non-covalent interactions of aromatic side-chains for controlling interactions between molecules, and therefore their material properties, including the use of mechanical force to control luminescence—mechanofluorochromism.
3. Singlet-oxygen responsive materials. Singlet oxygen (1O2) is a critical reactive oxygen species in photodynamic therapy for cancer as well as in damage to plants upon overexposure to light.  Its photochemical production is also chemically amplified through a photochemical reaction, which is the lynchpin of several commercial bioanalytical technologies.  Through a combination of fundamental physical organic chemistry and materials chemistry, we have luminescent conjugated polymer nanoparticles as probes for 1O2 in water that shows improved limit of detection over the commercially available luminescent probe for 1O2.

 

Selected Recent Publications

 

“Reversible Mechanofluorochromism of Aniline-Terminated Phenylene Ethynylenes” Sharber, S. A.; Shih, K.-C.; Mann, A.; Frausto, F.; Haas, T. E.; Nieh, M.-P.; Thomas, S. W., III Chem. Sci. 2018, 9, 5415-5426.


“Tuning Key Properties of Singlet Oxygen Responsive Acene-Doped Conjugated Polymer Nanoparticles” Frausto, F.; Thomas, S. W., III (Invited Article for Special Issue on Singlet Oxygen) ChemPhotoChem, 2018, 2, 632-639.


“Forcing Ladderenes into Plastic Semiconductors with Mechanochemistry” Thomas, S. W., III  Angew. Chem. Int. Ed. 2017, 56, 15196-15198. (Invited Highlight)


“Directly Photopatternable Polythiophene as Dual-Tone Photoresist” Hu, X.; Lawrence, J. A., III; Mullahoo, J.; Smith, Z. C.; Wilson, D. J.; Mace, C. R.; Thomas, S. W., III  Macromolecules, 2017, 50, 7258-7267.


“UV and NIR-Responsive Layer-by-Layer Films Containing 6-Bromo-7-hydroxycoumarin Photolabile Groups” Feeney, M. J.; Hu, X.; Srinivasan, R.; Van, Nhi M.; Hunter, M.; Georgakoudi, I.; Thomas, S. W., III Langmuir, 2017, 33, 10877-10885.


“Correlated Rotational Switching in 2D Self-Assembled Molecular Rotor Arrays” Wasio, N. A.; Slough, D. P.; Smith, Z. C.; Ivimey, C. J. Thomas, S. W., III; Lin, Y. S.; Sykes, E. C. H. Nat. Commun. 2017, 8, 16057.


“Ratiometric Singlet Oxygen Detection in Water Using Acene-Doped Conjugated Polymer Nanoparticles” Frausto, F.; Thomas, S. W. III ACS Appl. Mater. Interf. 2017, 9, 15768-15775.

 

“Substituent Effects That Control Conjugated Oligomer Conformation Through Non-Covalent Interactions” Sharber, S.; Baral, R.; Frausto, F.; Haas, T.; Müller, P.; Thomas, S. W. III  J. Am. Chem. Soc. 2017, 139, 5164-5174.

 

“Self-Cleaning Membranes From Comb-Shaped Copolymers With Photoresponsive Side Groups” Kaner, P.; Hu, X.; Thomas, S. W., III; Asatekin, A. ACS Appl. Mater. Interf. 2017, 9, 13619-13631.

 

“Light Controlled Selective Disruption, Multi-Level Patterning, and Sequential Release with Polyelectrolyte Multilayer Films Incorporating Four Photocleavable Chromophores” Hu, X.; Qureishi, Z.; Thomas, S. W., III Chem. Mater. 2017, 29, 2951-2960.

 

“Triggered Release of Encapsulated Cargo from Photoresponsive Polyelecrolyte Nanocomplexes” Hu, X.; Feeney, M. J.; McIntosh, E.; Mullahoo, J.; Jia, F.; Xu, Q.; Thomas, S. W., III  ACS Appl. Mater. Interfaces, 2016, 8, 23517–23522.

 

“Water-Soluble Fluorescent Polymers that Respond to Singlet Oxygen” Altinok, E.; Thomas, S. W., III J. Polym. Sci. A Polym. Chem. 2016, 54, 2526–2535.

 

“Stimuli-Responsive Side Chains for New Function from Conjugated Materials” Thomas, S. W. III; Pawle, R. H.; Smith, Z. C. (Invited Feature Article) J. Photochem. Photobiol. A: Chemistry 2016, 322-323, 119–128.

 

“Triple-responsive Layer-by-layer Films” Hu, X.; McIntosh, E.; Simon, M. G.; Staii, C.; Thomas, S. W. III Adv. Mater. 2016, 28, 715–721.

 

“Cycloadditions of Singlet Oxygen for Responsive Fluorescent Polymers” Thomas, S. W. III, Altinok, E.; Zhang, J. (Invited Account) Synlett 2016, 27, 355–368.

 

“Chemical Assembly of an Electrically Driven Altitudinal Molecular Rotor via Ullman Coupling” Murphy, C. J.; Smith, Z. C.; Pronschinski, A.; Lewis, E. A.; Liriano, M. L.; Wong, C.; Ivimey, C. J.; Duffy, M.; Musial, W.; Therrien, A.; Thomas, S. W. III; Sykes, E. C. H. Phys. Chem. Chem. Phys. 2015, 17, 31931–31937.

 

“Steric and Electronic Substituent Effects Influencing Regioselectivity of Tetracene Endoperoxidation” Baral, R.; Thomas, S. W. III J. Org. Chem. 2015, 80, 11086–11091.

 

“Two-Dimensional, Acene-Containing Conjugated Polymers That Show Ratiometric Fluorescent Response To Singlet Oxygen” Altinok, E.; Smith, Z. C.; Thomas, S. W. III Macromolecules 2015, 48, 6825–6831.

 

“Photolabile ROMP Gels Using ortho-Nitrobenzyl Functionalized Crosslinkers” Hu, X.; Shi, J. Thomas, S. W. III Polym. Chem. 2015, 6, 4966–4971.


“Two-Dimensional Bricklayer Arrangements of Tolans Using Halogen Bonding Interactions” Frausto, F.; Smith, Z. C.; Haas, T. E.; Thomas, S. W. III Chem. Commun. 2015, 51, 8825–8828.

 

“Thiophene-Based Conjugated Polymers with Photolabile Solubilizing Side Chains” Smith, Z. C.; Meyer, D. M.; Simon, M. G.; Staii, C.; Shukla, D.; Thomas, S. W. III Macromolecules 2015, 48, 959–966.

 

“Electronic Effects of Ring Fusion and Alkyne Substitution on Acene Properties and Reactivity” Zhang, J.; Smith, Z. C.; Thomas, S. W. III J. Org. Chem. 2014, 79, 10081–10093.


“Twisting and Piezochromism of Phenylene-Ethynylenes With Aromatic Interactions Between Side Chains and Main Chains” Pawle, R. H.; Haas, T. E.; Müller, P.; Thomas, S. W., III  Chem. Sci. 20145, 4184–4188.

 

“Reversible Photochemical Tuning of Net Charge Separation from Contact Electrification” Gumbley, P; Thomas, S. W., III ACS Appl. Mater. Interfaces 2014, 6, 8754–8761.

 

“Bandgap Engineering of Conjugated Materials With Non-Conjugated Side Chains” Pawle, R. H.; Agarwal, A.; Malveira, S.; Smith, Z. C. Thomas, S. W., III Macromolecules 2014, 47, 2250–2256.

“Combining Electronic and Steric Effects For Highly Stable Unsymmetric Pentacenes” Zhang, J.; Pawle, R. H.; Haas, T. E.; Thomas, S. W., III Chem. Eur. J. 2014, 20, 5880–5884.

 

“Wavelength-Selective Disruption and Triggered Release with Polyelectrolyte Multilayers” Gumbley, P.; Koylu, D.; Pawle, R. H.; Spedden, E.; Staii, C; Thomas, S. W., III Chem. Mater. 2014, 26, 1450–1456.





Complete listing of publications can be found HERE.