Research

Principal Areas

 

The Colby group’s mission is to understand in detail the structure-property relations of all interesting liquids. This is a great challenge and as such, only the best highly motivated students are able to participate in this exciting mission.  

Dr. Ralph Colby

Professor

Introduction

Colby research group studies diverse polymeric materials using rheological, electrical, thermal, and optical methods to probe the dynamics of polymer melts and liquids. Professor Colby’s research group is interested in a molecular-level understanding of dynamics in interesting liquids. Polymer liquids are good examples because they are viscoelastic: While polymer liquids do flow, they have considerable elastic character. Other examples include many “complex fluids” such as liquid crystals and surfactants. The Colby group measures the dynamics of these liquids using mechanical rheology and dielectric spectroscopy and also characterizes the liquid structure using neutron and x-ray scattering and optical methods. This is classical materials science research on structure-property relations but at the same time is highly innovative because it is applied to the liquid state. 

Current research interests include polyelectrolyte solutions and gels, polymerized ionic liquids, hydrolyzed polymers, cellulose and chitosan solutions in ionic liquids, anhydrous proton and lithium conductors, conjugated polymers, and flow-induced crystallization of thermoplastics, engineering thermoplastics, liquid crystalline polymers, and polymer blends. Other past work has also included block copolymers, miscible polymer blends, branched polymers, glassy polymers, surfactants, protein dispersions, biopolymers, Polloids, or colloidal suspensions that self-assemble into polymers, and nanocomposites. 

Technology Impacted By Research

Polymer dynamics, characterized by rheology, plays a vital role in solution and melt processing of polymers. Ion-containing polymers are a poorly understood class of materials that are potentially very important for actuators, sensors, separators between the electrodes of advanced batteries and fuel cell membranes.  

One nice example is the study of ion transport in ionomer membranes. Ionomers are polymers with one type of ion covalently bonded to the chain and are ‘single-ion conductors’ in that only the unattached counterions can move rapidly in response to an applied electric field. Designing ionomers for facile ion transport is challenging and the Colby group is attacking this problem with ab initio calculations of ion interactions that guides our synthesis of new ionomers.  

We use small-angle X-ray scattering, mechanical rheology and dielectric spectroscopy to understand what the ions are doing in these new ionomers. We quantify the temperature dependences of the fraction of ions in ion pairs, conducting triple ions and quadrupoles, for different ionomers with various counterions. There are a great many interesting liquids known in the world today and more are being discovered every day.  

  Motivation: Conventional molecular weight characterization methods do not work well with polyelectrolyte solutions.  

Goal: Using the semidilute unentangled regime to determine the number-average molecular weight of polyelectrolytes 

Materials:  

 Cesium polystyrene sulfonate

 (CsPSS)  

 

Cesium poly(2-acrylamido-2- methylpropanesulfonate)

(CsPAMS) 

Results:  

  • Specific viscosity and the relaxation time are obtained from rheology 

  • Correlation length is measured for each concentration using SAXS
  • Number-average molecular weight characterized by rheology and SAXS 

Current work done by graduate student Bahar Baniasadi in collaboration with Prof. Carlos Lopez

Bahar is working on the rheology of unentangled polyelectrolyte solutions and neutral polymer solutions to determine their molecular weights. She is testing the Rouse scaling theory and measurement methods including solution rheology to measure the specific viscosity, X-ray scattering to measure the correlation length, and NMR diffusometry to measure the diffusion coefficient on a wide array of polyelectrolyte chemistries.

Active undergraduate students: 

 

Graduate student Dr. Aijie Han (Ph.D. 2022)

A. Han and R. H. Colby, Rheology of Entangled Polyelectrolyte Solutions, Macromolecules 54, 1375 (2021).

A. Han, V. V. S. Uppala, D. Parisi, C. George, B. J. Dixon, C. D. Ayala, X. Li, L. A. Madsen and R. H. Colby, Determining the Molecular Weight of Polyelectrolytes Using the Rouse Scaling Theory for Salt-free Semidilute Unentangled Solutions, Macromolecules 55, 7148 (2022).

R. H. Colby and A. Han, Specific Viscosity of Polymer Solutions with Large Thermal Blobs, Rheol. Acta 62 (2023).

 

Graduate student Dr. Shichen Dou (Ph.D. 2007)

S. Dou and R. H. Colby, Charge Density Effects in Polyelectrolyte Solution Rheology, J. Polym. Sci., Polym. Phys. 44, 2001 (2006).

S. Dou, S. Zhang, R. J. Klein, J. Runt and R. H. Colby, Synthesis and Characterization of Poly(ethylene glycol)-based Single-Ion Conductors, Chem. Mat. 18, 4288 (2006).

S. Dou and R. H. Colby, Solution Rheology of a Strongly Charged Polyelectrolyte in Good Solvent, Macromolecules 41, 6505 (2008).

Graduate student Dr. Liang Guo (Ph.D. 2003)

L. Guo, R. H. Colby, M. Y. Lin and G. P. Dado, Micellar Structure Changes in Aqueous Mixtures of Nonionic Surfactants, J. Rheol., 45, 1223 (2001).

L. Guo, R. H. Colby, C. P. Lusignan and T. H. Whitesides, Kinetics of Triple Helix Formation in Semidilute Gelatin Solutions, Macromolecules 36, 9999 (2003).

L. Guo, R. H. Colby, C. P. Lusignan and A. M. Howe, Physical Gelation of Gelatin Studied with Rheo-Optics, Macromolecules 36, 10009 (2003).

 

With collaborators Dr. Federico Bordi and Dr. Cesare Cametti

F. Bordi, C. Cametti, J. S. Tan, D. C. Boris, W. E. Krause, N. Plucktaveesak and R. H. Colby, Determination of Polyelectrolyte Charge and Interaction with Water Using Dielectric Spectroscopy, Macromolecules 35, 7031 (2002).

F. Bordi, C. Cametti, T. Gili and R. H. Colby, Dielectric Relaxations in Aqueous Polyelectrolyte Solutions: A Scaling Approach and the Role of the Solvent Quality Parameter, Langmuir 18, 6404 (2002).

F. Bordi, R. H. Colby, C. Cametti, L. De Lorenzo and T. Gili, Electrical Conductivity of Polyelectrolyte Solutions in the Semidilute and Concentrated Regime: The Role of Counterion Condensation, J. Phys. Chem. B 106, 6887 (2002).

F. Bordi, C. Cametti, T. Gili, S. Sennato, S. Zuzzi, S. Dou and R. H. Colby, Conductometric Properties of Linear Polyelectrolytes in Poor-Solvent Condition: The Necklace Model, J. Chem. Phys. 122, 234906 (2005).

F. Bordi, C. Cametti, T. Gili, S. Sennato, S. Zuzzi, S. Dou and R. H. Colby, Solvent Quality Influence on the Dielectric Properties of Polyelectrolyte Solutions: A Scaling Approach, Phys. Rev. E 72, 031806 (2005).

F. Bordi, C. Cametti, S. Sennato, S. Zuzzi, S. Dou and R. H. Colby, Dielectric Scaling in Polyelectrolyte Solutions with Different Solvent Quality in the Dilute Concentration Regime, Phys. Chem. Chem. Phys. 8, 3653 (2006).

 

Graduate students Dr. Wendy Krause (Ph.D. 2000) and Katherine Oates (M.S. 2002)

W. E. Krause, J. S. Tan and R. H. Colby, Semidilute Solution Rheology of Polyelectrolytes with No Added Salt, J. Polym. Sci., Polym. Phys. Ed, 37, 3429 (1999).

W. E. Krause, E. G. Bellomo and R. H. Colby, Rheology of Sodium Hyaluronate Under Physiological Conditions, Biomacromolecules, 2, 65 (2001).

K. M. N. Oates, W. E. Krause and R. H. Colby, Using Rheology to Probe the Mechanism of Joint Lubrication: Polyelectrolyte/Protein Interactions in Synovial Fluid, Mat. Res. Soc. Symp. Proc. 711, 53 (2002).

K. M. N. Oates, W. E. Krause, R. L. Jones and R. H. Colby, Rheopexy of Synovial Fluid and Protein Aggregation, J. Royal Soc. Interface 3, 167 (2006).

Graduate students Andrew Konop (M.S. 1998) and Dr. Noparrat Plucktaveesak (Ph.D. 2003)

A. J. Konop and R. H. Colby, Role of Condensed Counterions in the Thermodynamics of Surfactant Micelle Formation with and without Oppositely-Charged Polyelectrolytes, Langmuir 15, 58 (1999).

A. J. Konop and R. H. Colby, Polyelectrolyte Charge Effects on Solution Viscosity of Poly(acrylic acid), Macromolecules 32, 2803 (1999).

R. H. Colby, N. Plucktaveesak and L. Bromberg, Critical Incorporation Concentration of Surfactants added to Micellar Solutions of Hydrophobically Modified Polyelectrolytes of the same Charge, Langmuir 17, 2937 (2001).

N. Plucktaveesak, A. J. Konop and R. H. Colby, Viscosity of Polyelectrolyte Solutions with Oppositely Charged Surfactant, J. Phys. Chem. B 107, 8166 (2003).

E. Sauvage, D. A. Amos, B. Antalek, K. M. Schroeder, J. S. Tan, N. Plucktaveesak and R. H. Colby, Amphiphilic Maleic Acid-Containing Alternating Copolymers 1. Dissociation Behavior and Compositions, J. Polym. Sci., Polym. Phys. 42, 3571 (2004).

E. Sauvage, N. Plucktaveesak, R. H. Colby, D. A. Amos, B. Antalek, K. M. Schroeder and J. S. Tan, Amphiphilic Maleic Acid-Containing Alternating Copolymers 2. Dilute Solution Characterization by Light Scattering, Intrinsic Viscosity and PGSE NMR Spectroscopy, J. Polym. Sci., Polym. Phys. 42, 3584 (2004).

E. Di Cola, N. Plucktaveesak, T. A. Waigh, R. H. Colby, J. S. Tan, W. Pyckhout-Hintzen, R. K. Heenan, Structure and Dynamics in Aqueous Solutions of Amphiphilic Sodium Maleate-Containing Alternating Copolymers, Macromolecules 37, 8457 (2004).

 

Graduate student Dr. David Boris (Ph.D. 1996)

R. H. Colby, D. C. Boris, W. E. Krause and J. S. Tan, Polyelectrolyte Conductivity, J. Polym. Sci., Polym. Phys. Ed. 35, 2951 (1997).

D. C. Boris and R. H. Colby, Rheology of Sulfonated Polystyrene Solutions, Macromolecules 31, 5746 (1998).

R. H. Colby, D. C. Boris, W. E. Krause and S. Dou, Shear Thinning of Unentangled Flexible Polymer Liquids, Rheol. Acta 46, 569 (2007).

 

With collaborators Dr. Andrey Dobrynin and Dr. Michael Rubinstein

M. Rubinstein, R.H. Colby and A.V. Dobrynin, Dynamics of Semidilute Polyelectrolyte Solutions, Phys. Rev. Lett. 73, 2776 (1994).

A.V. Dobrynin, R.H. Colby and M. Rubinstein, Scaling Theory of Polyelectrolyte Solutions, Macromolecules 28, 1859 (1995).

M. Rubinstein, R.H.Colby, A.V. Dobrynin and J.-F. Joanny, Elastic Modulus and Equilibrium Swelling of Polyelectrolyte Gels, Macromolecules 29, 398 (1996).

A. V. Dobrynin, R. H. Colby and M. Rubinstein, Polyampholytes, J. Polym. Sci., Polym. Phys. 42, 3513 (2004).

 

sMotivation:

  • Lithium ion conducting membranes play a significant role in advancement in lithium-ion batteries.
  • Anhydrous proton makes the fuel cell application at high temperature applicable and decrease the cost of fuel cell assembly.

Goal:

  • Developing ionic polymers with high lithium and proton conductivity.
  • Implementing Dielectric Relaxation Spectrum (DRS) and NMR to explore the ion conduction mechanism in these systems.

Materials:

  • Lithium conducting polymers

 

 

 

 

 

  • Azole and polymer blends as anhydrous proton conductors

 

 

 

 

Current work done by Zitan Huang in collaboration with the FACT EFRC

Zitan’s research is mainly focused on polyelectrolytes with energy applications. The first part of his research is about probing the effect of zwitterionic molecules on the properties of polymeric single-ion conductors as solid polymer electrolytes for batteries. The second part of my research focuses on synthesizing and characterizing ionic polymers with potential applications in fuel cells under both aqueous and nonaqueous
environment.

Equipment used: DRS, NMR, DSC, TGA, SAXS.

Active Undergraduate Student: John Panek

Graduate student Dr. Wenwen Mei (Ph.D. 2022) in collaboration with Dr. Rob Hickey

W. Mei, A. J. Rothenberger, J. E. Bostwick, J. M. Rinehart, R. J. Hickey and R. H. Colby, Zwitterions Raise the Dielectric Constant of Soft Materials, Phys. Rev. Lett. 127, 228001 (2021).

W. Mei, A. Han, R. J. Hickey and R. H. Colby, Effect of Chemical Substituents Attached to the Zwitterion Cation on Dielectric Constant, J. Chem. Phys. 155, 244505 (2021).

W. Mei, R. J. Hickey and R. H. Colby, High Dielectric Constant Zwitterionic Liquids, U.S. Patent (2022) and W.O. Patent (2023).

When a semicrystalline polymer melt is subjected to shear flow before crystallization,

  • the crystallization kinetics are accelerated, and
  • the morphology is changed to anisotropic structures                         

 

SAXS showing the formation of shish-kebab under above sheared sample after preparation for PEEK:

 

 

 

 

Isothermal FIC kinetics modeling of PEEK:

Polarized optical microscopy of PA66 after shear:

Structural Evolution and Orientation of Flow-Induced Lamellae in iPP:

  • Structural evolution and flow-induced lamellar structure is revealed through ex-situ small-angle X-ray scattering (SAXS)
    • Low shear stress leads to an isotropic morphology
    • Moderate shear stress leads to anisotropic morphology
    • High shear stress leads to the formation of a shish-kebab structure

Increase in Hermans’ Orientation Parameter (f) and Crystallinity with larger stress levels,

Isotropic to anisotropic transition occurs beyond a critical stress level.

 

Similarly, we can see the Structural Evolution and Orientation of Flow-Induced Lamellae in HDPE:

Special thanks to Dr. Kirt Page at CHESS (Cornell High Energy Synchrotron Source) for helping collect the SAXS and WAXS data.

Current work done by Arshiya Bhadu and Benson Jacob in collaboration with Dr. Alicyn Rhoades and Dr. Xiaoshi Zhang

Arshiya works on the FIC of HDPE & PEO. Benson works on the FIC of iPP and PHB.

Active Undergraduate Students: Martin Kim, Pavan Kumar Reddy Pothula

Graduate student Benson Jacob in collaboration with Dr. Alicyn Rhoades and Dr. Xiaoshi Zhang

Benson J. Jacob, Xiaoshi Zhang, Jongkyeong Kim, Jason D. Alexander, Manoela E. Cangussú, Alicyn M. Rhoades, and Ralph H. Colby, Particle Concentration Promotes Flow-Induced Crystallization of High-Molecular-Weight Isotactic Polypropylene, Macromolecules 57 (9), 4396-4409

 

Graduate student Jason Alexander (M.S. 2023) in collaboration with Dr. Alicyn Rhoades and Dr. Xiaoshi Zhang

X. Zhang, J. D. Alexander, J. Seo, A. M. Gohn, M. J. Behary, R. P. Schaake, R. H. Colby and A. M. Rhoades, Crystallization Kinetics of Glass Fiber Filled Poly(ether ether ketone) with Nanogram Sample Size: Feasibility Study for Fast Scanning Calorimetry, Thermochimica Acta 7 21, 179442 (2023).

Graduate student Dr. Jiho Seo (Ph.D. 2020) in collaboration with Dr. Alicyn Rhoades and Dr. Daniele Parisi

M. Rhoades, A. M. Gohn, J. Seo, R. Androsch and R. H. Colby, Sensitivity of Polymer Crystallization to Shear at Low and HighSupercooling of the Melt, Macromolecules 51, 2785 (2018).

Seo, H. Takahashi, B. Nazari, A. M. Rhoades, R. P. Schaake and R. H. Colby, Isothermal Flow-Induced Crystallization of Polyamide 66 Melts, Macromolecules 51, 4269 (2018).

Seo, A. M. Gohn, O. Dubin, H. Takahashi, H. Hasegawa, R. Sato, A. M. Rhoades, R. P. Schaake and R. H. Colby, Isothermal crystallization of poly(ether ether ketone) with different molecular weights over a wide temperature range, Polymer Crystallization 2, e10055 (2019).

Seo, A. M. Gohn, R. P. Schaake, D. Parisi, A. M. Rhoades, and R. H. Colby, Shear Flow-Induced Crystallization of Poly(ether ether ketone), Macromolecules 53, 3472 (2020).

M. Gohn, J. Seo, R. H. Colby, R. P. Schaake, R. Androsch and A.M. Rhoades, Crystal Nucleation in Poly(ether ether ketone)/Carbon Nanotube Nanocomposites at High and Low Supercooling of the Melt, Polymer 199, 122548 (2020).

Parisi, J. Seo, B. Nazari, R. P. Schaake, A. M. Rhoades and R. H. Colby, Shear-Induced Isotropic−Nematic Transition in Poly(ether ether ketone) Melts, ACS Macro. Lett. 9, 950 (2020).

Seo, D. Parisi, A. M. Gohn, A. Han, L. Song, Y. Liu, R. P. Schaake, A. M. Rhoades and R. H. Colby, Flow-Induced Crystallization of Poly(ether ether ketone): Universal Aspects of Specific Work Revealed by Corroborative Rheology and X-ray Scattering Studies, Macromolecules 53, 10040 (2020).

Parisi, J. Seo, R. P. Schaake, A. M. Rhoades and R. H. Colby, Shear-Induced Nematic Phase in Entangled Rod-Like PEEK Melts, Prog. Polym. Sci. 112, 101323 (2021).

Parisi, A. Han, J. Seo and R. H. Colby, Rheological Response of Entangled Isotactic Polypropylene Melts in Strong Shear Flows: Edge Fracture, Flow Curves and Normal Stresses, J. Rheol. 65, 605 (2021).

Seo, X. Zhang, R. P. Schaake, A. M. Rhoades and R. H. Colby, Dual Nakamura Model for Primary and Secondary Crystallization Applied to Nonisothermal Crystallization of Poly(ether ether ketone), Polymer Engineering and Science 61, 2416 (2021).

Graduate student Dr. Fawzi Hamad (Ph.D. 2015) in collaboration with Dr. Scott Milner

G. Hamad, R. H. Colby and S. T. Milner, Onset of Flow-Induced Crystallization Kinetics of Highly Isotactic Polypropylene, Macromolecules 48, 3725 (2015).

G. Hamad, R. H. Colby and S. T. Milner, Lifetime of Flow-Induced Precursors in Isotactic Polypropylene, Macromolecules 48, 7286 (2015).

G. Hamad, R. H. Colby and S. T. Milner, Transition in Crystal Morphology for Flow-Induced Crystallization of Isotactic Polypropylene, Macromolecules 49, 5561 (2016).

Motivation: Understanding the molecular and mechanical properties of these polymers are necessary in creating better design tools

Results:

  • SANS data are fit to the flexible cylinder model to measure the Kuhn length lK.

  • Master curve of Octyl Polyarylene from 220 °C to 100 °C with a reference temperature of 100 °C. The plateau modulus is seen as the crossover point of the rubbery plateau.

  • Plateau modulus GNo is determined by properties of the Kuhn monomer (Kuhn length lK and Kuhn monomer volume v0).
  • Conjugated polymers follow Everaers scaling predictions. The more flexible Polyarylene polymers fit best with the flexible scaling argument (lk/p)7/3 while the other 7 polymers fit best with the semiflexible scaling argument of (lk/p)7/5.

Current work done by Sara Daryoush in collaboration with Dr. Enrique Gomez

Sara works on the polymer P3HT. 

Graduate student Dr. Abigail Fenton (Ph.D. 2022) in collaboration with Dr. Enrique Gomez

M. Fenton, R. Xie, M. P. Aplan, Y. Lee, M. G. Gill, R. Fair, F. Kempe, M. Sommer, C. R. Snyder, E. D. Gomez and R. H. Colby, Predicting the plateau modulus from molecular parameters of conjugated polymers, ACS Central Science 8, 268 (2022).

Graduate student Dr. Renxuan Xie (Ph.D. 2020) in collaboration with Dr. Enrique Gomez

Fair, R. Xie, Y. Lee, R. H. Colby and E. D. Gomez, Molecular Weight Characterization of Conjugated Polymers through Gel Permeation Chromatography and Static Light Scattering, ACS Applied Polymer Materials 3, 4572 (2021).

 Xie, A. R. Weisen, Y. Lee, M. A. Aplan, A. M. Fenton, A. E. Masucci, F. Kempe, M. Sommer, C. W. Pester, R. H. Colby and E. D. Gomez, Glass Transition Temperature from the Chemical Structure of Conjugated Polymers, Nat. Comm. 11, 893 (2020).

Zhang, J. H. Bombile, A. R. Weisen, R. Xie, R. H. Colby, M. J. Janik, S. T. Milner, and E. D. Gomez, Thermal Fluctuations lead to Cumulative Disorder and Enhance Charge Transport in Conjugated Polymers, Macromol. Rapid Commun. 1900134 (2019).

Xie, M. P. Aplan, N. J. Caggiano, A. R. Weisen, T. Su, C. Müller, M. Segad, R. H. Colby and E. D. Gomez, Local Chain Alignment via Nematic Ordering Reduces Chain Entanglement in Conjugated Polymers, Macromolecules 51, 10271 (2018).

Zhan, W. Zhang, I. E. Jacobs, D. M. Nisson, R. Xie, A. R. Weissen, R. H. Colby, A. J. Moulé, S. T. Milner, J. K. Maranas and E. D. Gomez, Side Chain Length Affects Backbone Dynamics in Poly(3-Alkylthiophene)s, J. Polym. Sci., Polym. Phys. 56, 1193 (2018).

Xie, R. H. Colby and E. D. Gomez, Connecting the Mechanical and Conductive Properties of Conjugated Polymers, Advanced Electronic Materials, 1700356 (2017).

R. Xie, Y. Lee, M. P. Aplan, N. J. Caggiano, C. Müller, R. H. Colby and E. D. Gomez, Glass Transition Temperature of Conjugated Polymers by Oscillatory Shear Rheometry, Macromolecules 50, 5146 (2017).

Not including research conducted by graduate students, the Colby rheology group makes sure to give the undergraduate students the opportunity to lead projects if they show interest! Some students even end up attaining first co-author publications from their research conducted while in the Colby group, which is a great opportunity for any aspiring scientist. 

Current ongoing undergraduate projects include,  

  • Solutions of Native Cellulose in Ionic Liquids for Fiber Spinning 
  • Aqueous Solutions of vinyl alcohol / vinyl acetate Random Copolymers with Salts, funded by Proctor & Gamble (P&G) 

Rheology by itself is not proof enough for any phenomenon being observed. For a thorough experimental study, it always needs to be coupled with electrical, thermal, or optical methods. This is primarily the gap collaborations help us fill.  

For example, graduate students are co-advised with Dr. Alicyn Rhoades at Penn State Behrend, where they have a fantastic Plastics Facility. Her expertise is in thermal analysis and the fast-scanning calorimeter (FSC) mentioned under our facilities page is actually stationed under her and Dr. Xiaoshi Zhang’s guidance at Penn State Behrend. Dr. Rhoades focus is on polymer composites and polymer crystallization, hence the students working on the flow-induced crystallization project are usually the ones co-advised by her and this leads to a lot of interesting research and development of the graduate students. 

The Colby group is always looking for future collaborations, if you are interested, please fill out the contact us form on this website or feel free to directly email Dr. Ralph Colby!