Patricia McGuiggan - Academia.edu (original) (raw)

Papers by Patricia McGuiggan

Research paper thumbnail of Effect of Roughness and Elasticity on Interactions between Charged Colloidal Spheres

Langmuir, 2019

The eects of realistic roughness and elasticity on the interactions between charged silica sphere... more The eects of realistic roughness and elasticity on the interactions between charged silica spheres are studied as a function of surface potential, screening length, interfacial energy and roughness. The repulsive force F rep that must be overcome to bring charged spheres into contact is relatively insensitive to elasticity unless spheres are hundreds of times softer than silica. F rep is also insensitive to roughness and interfacial energy. In contrast, roughness has a large eect on the binding energy of spheres and the force F sep to separate them. Both are lowered by 1 to 2 orders of magnitude by the measured surface roughness of less than 1 nm on 1 µm silica spheres. The reason is that interactions between rigid spheres are dominated by the highest surface peaks rather than the entire spherical surface. Elasticity can increase the pull-o force of rough spheres by a factor of two or more because additional surface area can be brought into contact. The implications of these results for shear-thickening transitions are discussed. 1

Research paper thumbnail of High Throughput Measurement of Peel of a Pressure Sensitive Adhesive | NIST

The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied l... more The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied linearly in temperature. As the tape is peeled from the surface, the adhesive is peeled from a surface at a different temperature. The temperature can be correlated with peel distance, giving the temperature dependence of the peel force with one peel test. In addition, the temperature of the transition from cohesive to interfacial failure could be easily identified, not only by the relative peak in the peel force, but also by the clearly visible adhesive layer which remained on the stainless steel plate. Introduction The performance of a PSA can be characterized by adhesion, shear, and tack tests. Testing of the PSA is necessary since theoretical models have not been able to quantitatively predict the performance of the PSA based solely on rheological or surface properties. Adhesion tests include the T-peel test, the 180° peel test, and the 90° peel test. Standard peel tests are carried o...

Research paper thumbnail of Photoinduced Contact Angle Hysteresis on a Single Microsphere

APS, Nov 1, 2011

ABSTRACT An atomic force microscope (AFM) is used to measure the meniscus force on individual mic... more ABSTRACT An atomic force microscope (AFM) is used to measure the meniscus force on individual microspheres as they contact and are retracted from an air/liquid interface. The glass microspheres, whose radii ranged from 20 to 50 micrometers, had organic or inorganic coatings on their surfaces. By exposing the microspheres to light, the contact angle and thus the meniscus force could be dramatically altered. The measured force-distance curves are fitted to macroscopic wetting theory. From these measurements, the contact angle, contact angle hysteresis, position of the contact line pinning, and surface tension were simultaneously determined.

Research paper thumbnail of Effect of Roughness and Elasticity on Interactions between Charged Colloidal Spheres

Langmuir, Oct 1, 2019

The eects of realistic roughness and elasticity on the interactions between charged silica sphere... more The eects of realistic roughness and elasticity on the interactions between charged silica spheres are studied as a function of surface potential, screening length, interfacial energy and roughness. The repulsive force F rep that must be overcome to bring charged spheres into contact is relatively insensitive to elasticity unless spheres are hundreds of times softer than silica. F rep is also insensitive to roughness and interfacial energy. In contrast, roughness has a large eect on the binding energy of spheres and the force F sep to separate them. Both are lowered by 1 to 2 orders of magnitude by the measured surface roughness of less than 1 nm on 1 µm silica spheres. The reason is that interactions between rigid spheres are dominated by the highest surface peaks rather than the entire spherical surface. Elasticity can increase the pull-o force of rough spheres by a factor of two or more because additional surface area can be brought into contact. The implications of these results for shear-thickening transitions are discussed. 1

Research paper thumbnail of Contact Angle Hysteresis of Photo-Responsive Materials

Bulletin of the American Physical Society, Mar 20, 2013

Research paper thumbnail of Dynamics of a Disturbed Sessile Drop Measured by Atomic Force Microscopy (AFM)

Langmuir, Sep 2, 2011

A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demo... more A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (<100 nm) oscillations are readily measured with AFM. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

Research paper thumbnail of Nondestructive characterization of aged paper using spectral and directional reflection measurements

Proper care of aging books in libraries requires nondestructive diagnostic techniques for measuri... more Proper care of aging books in libraries requires nondestructive diagnostic techniques for measuring the condition of the paper. Optical techniques offer nondestructive capability. For this reason, both spectral reflection and visible bidirectional reflectance distribution function measurements (BRDF) are examined. Both new and aged Whatman paper are measured. Spectral measurements are sensitive to changes in the location and width of spectral features in the paper. This can be indicative of paper degradation. BRDF measurements show changes in the paper fiber structure such as broken fibers. Fiber scatter cross sections are modeled using an improved anomalous diffraction approximation and Kubelka- Munk equations.

Research paper thumbnail of Capillary forces on nanowires

Bulletin of the American Physical Society, Mar 16, 2009

Research paper thumbnail of A Dichlorinated Dithienylethene-Diketopyrrolopyrrole-Based Copolymer with Pronounced P–N Crossover: Evidence for Anionic Seebeck Contribution

ACS materials letters, May 16, 2022

Research paper thumbnail of Dynamics of a Disturbed Sessile Drop measured by AFM

Bulletin of the American Physical Society, Nov 20, 2011

the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic mi... more the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r =20 micrometers) is brought into contact with a small sessile drop resting on a hydrophobic surface. When the microsphere touches the liquid surface, the meniscus rises onto the microsphere due to capillary forces. Although the microsphere volume is six orders of magnitude smaller than the drop, it excites the lowest normal resonance modes of the liquid interface. The sphere is pinned at the interface whose small (less than 100 nm) oscillations are readily measured with the AFM. Resonance oscillation frequencies were measured for drop volumes between 5 microL and 200 microL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for resonance of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension and viscosity of small drops.

Research paper thumbnail of Dynamics of a Disturbed Sessile Drop Measured by Atomic Force Microscopy

Bulletin of the American Physical Society, Mar 20, 2013

microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 µm) attached to an... more microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 µm) attached to an AFM cantilever is brought into contact with a sessile water drop. Immediately after the initial rise of the meniscus, the microsphere oscillates about a fixed average position while partially immersed in the liquid. The small (< 100 nm) oscillations of the interface are readily measured with AFM. The oscillations correspond to the resonance oscillation of the entire droplet. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 µL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

Research paper thumbnail of Blended Conjugated Host and Unconjugated Dopant Polymers Towards N‐type All‐Polymer Conductors and High‐ZT Thermoelectrics

Angewandte Chemie, Apr 26, 2023

N‐Type thermoelectrics typically consist of small molecule dopant+polymer host. Only a few polyme... more N‐Type thermoelectrics typically consist of small molecule dopant+polymer host. Only a few polymer dopant+polymer host systems have been reported, and these have lower thermoelectric parameters. N‐type polymers with high crystallinity and order are generally used for high‐conductivity ( ) organic conductors. Few n‐type polymers with only short‐range lamellar stacking for high‐conductivity materials have been reported. Here, we describe an n‐type short‐range lamellar‐stacked all‐polymer thermoelectric system with highest of 78 S−1, power factor (PF) of 163 μW m−1 K−2, and maximum Figure of merit (ZT) of 0.53 at room temperature with a dopant/host ratio of 75 wt%. The minor effect of polymer dopant on the molecular arrangement of conjugated polymer PDPIN at high ratios, high doping capability, high Seebeck coefficient (S) absolute values relative to , and atypical decreased thermal conductivity ( ) with increased doping ratio contribute to the promising performance.

Research paper thumbnail of High Throughput Measurement of Peel of a Pressure Sensitive Adhesive | NIST

The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied l... more The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied linearly in temperature. As the tape is peeled from the surface, the adhesive is peeled from a surface at a different temperature. The temperature can be correlated with peel distance, giving the temperature dependence of the peel force with one peel test. In addition, the temperature of the transition from cohesive to interfacial failure could be easily identified, not only by the relative peak in the peel force, but also by the clearly visible adhesive layer which remained on the stainless steel plate. Adhesion tests include the T-peel test, the 180° peel test, and the 90° peel test. Standard peel tests are carried out at constant peel rate and temperature. However, to completely characterize the performance of the PSA, multiple peel tests are made at a variety of peel rates or temperatures and a peel force master curve is produced, as shown in Figure 1.

Research paper thumbnail of 3,4,5‐Trimethoxy Substitution on an N‐DMBI Dopant with New N‐Type Polymers: Polymer‐Dopant Matching for Improved Conductivity‐Seebeck Coefficient Relationship

Angewandte Chemie, Nov 17, 2021

Achieving high electrical conductivity and thermoelectric power factor simultaneously for n‐type ... more Achieving high electrical conductivity and thermoelectric power factor simultaneously for n‐type organic thermoelectrics is still challenging. By constructing two new acceptor‐acceptor n‐type conjugated polymers with different backbones and introducing the 3,4,5‐trimethoxyphenyl group to form the new n‐type dopant 1,3‐dimethyl‐2‐(3,4,5‐trimethoxyphenyl)‐2,3‐dihydro‐1H‐benzo[d]imidazole (TP‐DMBI), high electrical conductivity of 11 S cm−1and power factor of 32 μW m−1 K−2are achieved. Calculations using Density Functional Theory show that TP‐DMBI presents a higher singly occupied molecular orbital (SOMO) energy level of −1.94 eV than that of the common dopant 4‐(1, 3‐dimethyl‐2, 3‐dihydro‐1H‐benzoimidazol‐2‐yl) phenyl) dimethylamine (N‐DMBI) (−2.36 eV), which can result in a larger offset between the SOMO of dopant and lowest unoccupied molecular orbital (LUMO) of n‐type polymers, though that effect may not be dominant in the present work. The doped polymer films exhibit higher Seebeck coefficient and power factor than films using N‐DMBI at the same doping levels or similar electrical conductivity levels. Moreover, TP‐DMBI doped polymer films offer much higher electron mobility of up to 0.53 cm2 V−1 s−1than films with N‐DMBI doping, demonstrating the potential of TP‐DMBI, and 3,4,5‐trialkoxy DMBIs more broadly, for high performance n‐type organic thermoelectrics.

Research paper thumbnail of A New Polystyrene–Poly(vinylpyridinium) Ionic Copolymer Dopant for n‐Type All‐Polymer Thermoelectrics with High and Stable Conductivity Relative to the Seebeck Coefficient giving High Power Factor

Advanced Materials

A novel n‐type copolymer dopant polystyrene–poly(4‐vinyl‐N‐hexylpyridinium fluoride) (PSpF) with ... more A novel n‐type copolymer dopant polystyrene–poly(4‐vinyl‐N‐hexylpyridinium fluoride) (PSpF) with fluoride anions is designed and synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. This is thought to be the first polymeric fluoride dopant. Electrical conductivity of 4.2 S cm–1 and high power factor of 67 µW m–1 K–2 are achieved for PSpF‐doped polymer films, with a corresponding decrease in thermal conductivity as the PSpF concentration is increased, giving the highest ZT of 0.1. An especially high electrical conductivity of 58 S cm–1 at 88 °C and outstanding thermal stability are recorded. Further, organic transistors of PSpF‐doped thin films exhibit high electron mobility and Hall mobility of 0.86 and 1.70 cm2 V–1 s–1, respectively. The results suggest that polystyrene–poly(vinylpyridinium) salt copolymers with fluoride anions are promising for high‐performance n‐type all‐polymer thermoelectrics. This work provides a new way to realize organic the...

Research paper thumbnail of The Permeability of PET by Formic and Acetic Acid Vapors

Studies in Conservation, 2022

Research paper thumbnail of Comparing the Bending Stiffness Measurements of Brittle Paper

Bulletin of the American Physical Society, 2016

has been estimated that one third of the paper materials in libraries are too brittle to handle. ... more has been estimated that one third of the paper materials in libraries are too brittle to handle. A typical paper sheet is comprised of semi-rigid cellulose fibers that are more than ten times longer than the sheet thickness and can be considered a two dimensional random fiber network. The main pathways of degradation, acid-catalyzed hydrolysis and oxidation, cause depolymerization of the cellulose chains and breaking of the intrafiber bonds. Conventional mechanical measurements of aged paper are destructive and often too severe to understand the true extent of deterioration. By comparing the roll test, folding endurance tests, tensile tests and stiffness tests of naturally aged papers with varying amounts of brittleness, we intend to show the limits of each test and relate the state of the paper degradation to the mechanical test results.

Research paper thumbnail of Interpreting Sand Formation on Titan: Insight from Interparticle Forces and Mechanical Properties of Titan Organic Analogs

AAS/Division for Planetary Sciences Meeting Abstracts #50, Oct 1, 2018

Research paper thumbnail of The Surface Energy of "Tholin" and Its Implication on Haze-Liquid Interactions on Titan

![Research paper thumbnail of Direct Measurement of Interparticle Adhesion of Titan Aerosol Analogs (`Tholin') Using Atomic Force Microscopy](https://a.academia-assets.com/images/blank-paper.jpg)

LPI Contributions, May 1, 2017

Research paper thumbnail of Effect of Roughness and Elasticity on Interactions between Charged Colloidal Spheres

Langmuir, 2019

The eects of realistic roughness and elasticity on the interactions between charged silica sphere... more The eects of realistic roughness and elasticity on the interactions between charged silica spheres are studied as a function of surface potential, screening length, interfacial energy and roughness. The repulsive force F rep that must be overcome to bring charged spheres into contact is relatively insensitive to elasticity unless spheres are hundreds of times softer than silica. F rep is also insensitive to roughness and interfacial energy. In contrast, roughness has a large eect on the binding energy of spheres and the force F sep to separate them. Both are lowered by 1 to 2 orders of magnitude by the measured surface roughness of less than 1 nm on 1 µm silica spheres. The reason is that interactions between rigid spheres are dominated by the highest surface peaks rather than the entire spherical surface. Elasticity can increase the pull-o force of rough spheres by a factor of two or more because additional surface area can be brought into contact. The implications of these results for shear-thickening transitions are discussed. 1

Research paper thumbnail of High Throughput Measurement of Peel of a Pressure Sensitive Adhesive | NIST

The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied l... more The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied linearly in temperature. As the tape is peeled from the surface, the adhesive is peeled from a surface at a different temperature. The temperature can be correlated with peel distance, giving the temperature dependence of the peel force with one peel test. In addition, the temperature of the transition from cohesive to interfacial failure could be easily identified, not only by the relative peak in the peel force, but also by the clearly visible adhesive layer which remained on the stainless steel plate. Introduction The performance of a PSA can be characterized by adhesion, shear, and tack tests. Testing of the PSA is necessary since theoretical models have not been able to quantitatively predict the performance of the PSA based solely on rheological or surface properties. Adhesion tests include the T-peel test, the 180° peel test, and the 90° peel test. Standard peel tests are carried o...

Research paper thumbnail of Photoinduced Contact Angle Hysteresis on a Single Microsphere

APS, Nov 1, 2011

ABSTRACT An atomic force microscope (AFM) is used to measure the meniscus force on individual mic... more ABSTRACT An atomic force microscope (AFM) is used to measure the meniscus force on individual microspheres as they contact and are retracted from an air/liquid interface. The glass microspheres, whose radii ranged from 20 to 50 micrometers, had organic or inorganic coatings on their surfaces. By exposing the microspheres to light, the contact angle and thus the meniscus force could be dramatically altered. The measured force-distance curves are fitted to macroscopic wetting theory. From these measurements, the contact angle, contact angle hysteresis, position of the contact line pinning, and surface tension were simultaneously determined.

Research paper thumbnail of Effect of Roughness and Elasticity on Interactions between Charged Colloidal Spheres

Langmuir, Oct 1, 2019

The eects of realistic roughness and elasticity on the interactions between charged silica sphere... more The eects of realistic roughness and elasticity on the interactions between charged silica spheres are studied as a function of surface potential, screening length, interfacial energy and roughness. The repulsive force F rep that must be overcome to bring charged spheres into contact is relatively insensitive to elasticity unless spheres are hundreds of times softer than silica. F rep is also insensitive to roughness and interfacial energy. In contrast, roughness has a large eect on the binding energy of spheres and the force F sep to separate them. Both are lowered by 1 to 2 orders of magnitude by the measured surface roughness of less than 1 nm on 1 µm silica spheres. The reason is that interactions between rigid spheres are dominated by the highest surface peaks rather than the entire spherical surface. Elasticity can increase the pull-o force of rough spheres by a factor of two or more because additional surface area can be brought into contact. The implications of these results for shear-thickening transitions are discussed. 1

Research paper thumbnail of Contact Angle Hysteresis of Photo-Responsive Materials

Bulletin of the American Physical Society, Mar 20, 2013

Research paper thumbnail of Dynamics of a Disturbed Sessile Drop Measured by Atomic Force Microscopy (AFM)

Langmuir, Sep 2, 2011

A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demo... more A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;100 nm) oscillations are readily measured with AFM. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

Research paper thumbnail of Nondestructive characterization of aged paper using spectral and directional reflection measurements

Proper care of aging books in libraries requires nondestructive diagnostic techniques for measuri... more Proper care of aging books in libraries requires nondestructive diagnostic techniques for measuring the condition of the paper. Optical techniques offer nondestructive capability. For this reason, both spectral reflection and visible bidirectional reflectance distribution function measurements (BRDF) are examined. Both new and aged Whatman paper are measured. Spectral measurements are sensitive to changes in the location and width of spectral features in the paper. This can be indicative of paper degradation. BRDF measurements show changes in the paper fiber structure such as broken fibers. Fiber scatter cross sections are modeled using an improved anomalous diffraction approximation and Kubelka- Munk equations.

Research paper thumbnail of Capillary forces on nanowires

Bulletin of the American Physical Society, Mar 16, 2009

Research paper thumbnail of A Dichlorinated Dithienylethene-Diketopyrrolopyrrole-Based Copolymer with Pronounced P–N Crossover: Evidence for Anionic Seebeck Contribution

ACS materials letters, May 16, 2022

Research paper thumbnail of Dynamics of a Disturbed Sessile Drop measured by AFM

Bulletin of the American Physical Society, Nov 20, 2011

the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic mi... more the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r =20 micrometers) is brought into contact with a small sessile drop resting on a hydrophobic surface. When the microsphere touches the liquid surface, the meniscus rises onto the microsphere due to capillary forces. Although the microsphere volume is six orders of magnitude smaller than the drop, it excites the lowest normal resonance modes of the liquid interface. The sphere is pinned at the interface whose small (less than 100 nm) oscillations are readily measured with the AFM. Resonance oscillation frequencies were measured for drop volumes between 5 microL and 200 microL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for resonance of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension and viscosity of small drops.

Research paper thumbnail of Dynamics of a Disturbed Sessile Drop Measured by Atomic Force Microscopy

Bulletin of the American Physical Society, Mar 20, 2013

microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 µm) attached to an... more microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 µm) attached to an AFM cantilever is brought into contact with a sessile water drop. Immediately after the initial rise of the meniscus, the microsphere oscillates about a fixed average position while partially immersed in the liquid. The small (< 100 nm) oscillations of the interface are readily measured with AFM. The oscillations correspond to the resonance oscillation of the entire droplet. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 µL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

Research paper thumbnail of Blended Conjugated Host and Unconjugated Dopant Polymers Towards N‐type All‐Polymer Conductors and High‐ZT Thermoelectrics

Angewandte Chemie, Apr 26, 2023

N‐Type thermoelectrics typically consist of small molecule dopant+polymer host. Only a few polyme... more N‐Type thermoelectrics typically consist of small molecule dopant+polymer host. Only a few polymer dopant+polymer host systems have been reported, and these have lower thermoelectric parameters. N‐type polymers with high crystallinity and order are generally used for high‐conductivity ( ) organic conductors. Few n‐type polymers with only short‐range lamellar stacking for high‐conductivity materials have been reported. Here, we describe an n‐type short‐range lamellar‐stacked all‐polymer thermoelectric system with highest of 78 S−1, power factor (PF) of 163 μW m−1 K−2, and maximum Figure of merit (ZT) of 0.53 at room temperature with a dopant/host ratio of 75 wt%. The minor effect of polymer dopant on the molecular arrangement of conjugated polymer PDPIN at high ratios, high doping capability, high Seebeck coefficient (S) absolute values relative to , and atypical decreased thermal conductivity ( ) with increased doping ratio contribute to the promising performance.

Research paper thumbnail of High Throughput Measurement of Peel of a Pressure Sensitive Adhesive | NIST

The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied l... more The peel force of a pressure sensitive adhesive (PSA) tape is measured on a surface that varied linearly in temperature. As the tape is peeled from the surface, the adhesive is peeled from a surface at a different temperature. The temperature can be correlated with peel distance, giving the temperature dependence of the peel force with one peel test. In addition, the temperature of the transition from cohesive to interfacial failure could be easily identified, not only by the relative peak in the peel force, but also by the clearly visible adhesive layer which remained on the stainless steel plate. Adhesion tests include the T-peel test, the 180° peel test, and the 90° peel test. Standard peel tests are carried out at constant peel rate and temperature. However, to completely characterize the performance of the PSA, multiple peel tests are made at a variety of peel rates or temperatures and a peel force master curve is produced, as shown in Figure 1.

Research paper thumbnail of 3,4,5‐Trimethoxy Substitution on an N‐DMBI Dopant with New N‐Type Polymers: Polymer‐Dopant Matching for Improved Conductivity‐Seebeck Coefficient Relationship

Angewandte Chemie, Nov 17, 2021

Achieving high electrical conductivity and thermoelectric power factor simultaneously for n‐type ... more Achieving high electrical conductivity and thermoelectric power factor simultaneously for n‐type organic thermoelectrics is still challenging. By constructing two new acceptor‐acceptor n‐type conjugated polymers with different backbones and introducing the 3,4,5‐trimethoxyphenyl group to form the new n‐type dopant 1,3‐dimethyl‐2‐(3,4,5‐trimethoxyphenyl)‐2,3‐dihydro‐1H‐benzo[d]imidazole (TP‐DMBI), high electrical conductivity of 11 S cm−1and power factor of 32 μW m−1 K−2are achieved. Calculations using Density Functional Theory show that TP‐DMBI presents a higher singly occupied molecular orbital (SOMO) energy level of −1.94 eV than that of the common dopant 4‐(1, 3‐dimethyl‐2, 3‐dihydro‐1H‐benzoimidazol‐2‐yl) phenyl) dimethylamine (N‐DMBI) (−2.36 eV), which can result in a larger offset between the SOMO of dopant and lowest unoccupied molecular orbital (LUMO) of n‐type polymers, though that effect may not be dominant in the present work. The doped polymer films exhibit higher Seebeck coefficient and power factor than films using N‐DMBI at the same doping levels or similar electrical conductivity levels. Moreover, TP‐DMBI doped polymer films offer much higher electron mobility of up to 0.53 cm2 V−1 s−1than films with N‐DMBI doping, demonstrating the potential of TP‐DMBI, and 3,4,5‐trialkoxy DMBIs more broadly, for high performance n‐type organic thermoelectrics.

Research paper thumbnail of A New Polystyrene–Poly(vinylpyridinium) Ionic Copolymer Dopant for n‐Type All‐Polymer Thermoelectrics with High and Stable Conductivity Relative to the Seebeck Coefficient giving High Power Factor

Advanced Materials

A novel n‐type copolymer dopant polystyrene–poly(4‐vinyl‐N‐hexylpyridinium fluoride) (PSpF) with ... more A novel n‐type copolymer dopant polystyrene–poly(4‐vinyl‐N‐hexylpyridinium fluoride) (PSpF) with fluoride anions is designed and synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. This is thought to be the first polymeric fluoride dopant. Electrical conductivity of 4.2 S cm–1 and high power factor of 67 µW m–1 K–2 are achieved for PSpF‐doped polymer films, with a corresponding decrease in thermal conductivity as the PSpF concentration is increased, giving the highest ZT of 0.1. An especially high electrical conductivity of 58 S cm–1 at 88 °C and outstanding thermal stability are recorded. Further, organic transistors of PSpF‐doped thin films exhibit high electron mobility and Hall mobility of 0.86 and 1.70 cm2 V–1 s–1, respectively. The results suggest that polystyrene–poly(vinylpyridinium) salt copolymers with fluoride anions are promising for high‐performance n‐type all‐polymer thermoelectrics. This work provides a new way to realize organic the...

Research paper thumbnail of The Permeability of PET by Formic and Acetic Acid Vapors

Studies in Conservation, 2022

Research paper thumbnail of Comparing the Bending Stiffness Measurements of Brittle Paper

Bulletin of the American Physical Society, 2016

has been estimated that one third of the paper materials in libraries are too brittle to handle. ... more has been estimated that one third of the paper materials in libraries are too brittle to handle. A typical paper sheet is comprised of semi-rigid cellulose fibers that are more than ten times longer than the sheet thickness and can be considered a two dimensional random fiber network. The main pathways of degradation, acid-catalyzed hydrolysis and oxidation, cause depolymerization of the cellulose chains and breaking of the intrafiber bonds. Conventional mechanical measurements of aged paper are destructive and often too severe to understand the true extent of deterioration. By comparing the roll test, folding endurance tests, tensile tests and stiffness tests of naturally aged papers with varying amounts of brittleness, we intend to show the limits of each test and relate the state of the paper degradation to the mechanical test results.

Research paper thumbnail of Interpreting Sand Formation on Titan: Insight from Interparticle Forces and Mechanical Properties of Titan Organic Analogs

AAS/Division for Planetary Sciences Meeting Abstracts #50, Oct 1, 2018

Research paper thumbnail of The Surface Energy of "Tholin" and Its Implication on Haze-Liquid Interactions on Titan

![Research paper thumbnail of Direct Measurement of Interparticle Adhesion of Titan Aerosol Analogs (`Tholin') Using Atomic Force Microscopy](https://a.academia-assets.com/images/blank-paper.jpg)

LPI Contributions, May 1, 2017