jerry land | University of Texas at Arlington (original) (raw)

Papers by jerry land

Research paper thumbnail of Photocontrolled micellar aggregation of amphiphilic DNA-azobenzene conjugates

Colloids and surfaces. B, Biointerfaces, Jan 15, 2015

We demonstrate the reversible micellar aggregation of a DNA-azobenzene conjugate in aqueous condi... more We demonstrate the reversible micellar aggregation of a DNA-azobenzene conjugate in aqueous conditions, in which the photoisomerization of the initially apolar trans-azobenzene moiety to the polar cis isomer causes disassembly of the aggregates. The molecular basis for this phenomena is a change in the hydrophobic/hydrophilic balance of the conjugate as the more polar cis azobenzene isomer is formed upon exposure to 365nm irradiation. The conjugates were prepared by copper-free Click chemistry between an azide-modified, 53-base ssDNA and a cyclooctyne derivative of azobenzene. The photocontrolled aggregation of the conjugate was studied by dynamic light scattering and atomic force microscopy. The reversible micellar aggregation for a DNA-azobenzene conjugate has not been previously reported and holds promise for photocontrolled drug delivery applications.

Research paper thumbnail of Improving the physical properties of PEA/PMMA blends by the uniform dispersion of clay platelets

Polymer, 2006

Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined wi... more Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined with unmodified montmorillionite (MMT) to improve the physical properties via nanocomposite formation. We prepared a cationic PEA/PMMA latex and used a heterocoagulation process to create a homogeneous dispersion of the clay platelets in the matrix. The cationic PEA/PMMA emulsion blends were prepared using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous slurry of MMT. The PEA/PMMA-MMT nanocomposites could be processed at low temperatures. Low temperature processing prevented the commonly observed discoloration associated with many thermoplastic nanocomposites. DSC, SAXS, TEM and AFM were used to study the dispersion of MMT and morphology of PEA/PMMA-MMT nanocomposites. Tensile stress, elongation at break and Young's modulus demonstrated a significant reinforcing effect of clay. q

Research paper thumbnail of Synthesis, Characterization, and Properties of ABA Type Triblock Copolymer Brushes of Styrene and Methyl Acrylate Prepared by Atom Transfer Radical Polymerization

Research paper thumbnail of Selective ordering of surfactant modified gold nanoparticles in a diblock copolymer

Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-pol... more Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-poly(methyl methacrylate) has been observed. The morphology of the diblock copolymer/Au-nanocomposite was dependent on the composition of the thiol modifier. For the thiol modifier that does not preferentially interact with one of the blocks, a perpendicular (relative to the substrate) lamellar morphology is maintained. However, for a thiol with a surfactant structure similar to one of the blocks, we observed a parallel lamellar morphology and speculate that the nanoparticles have localized at the microdomain interface. These conclusions are based on transmission electron microscopy, angle-dependent X-ray photoelectron microscopy and tensiometry. These results are consistent with theoretical predictions on the hybrid systems composed of block copolymers and nanoparticles.

Research paper thumbnail of Synthesis, Characterization, and Properties of Polyelectrolyte Block Copolymer Brushes Prepared by Atom Transfer Radical Polymerization and Their Use in the Synthesis of Metal Nanoparticles

Research paper thumbnail of Surface initiated polymerizations from silica nanoparticles

Soft Matter, 2006

Surface initiated polymerizations yield covalently bonded polymer on the substrate. The propertie... more Surface initiated polymerizations yield covalently bonded polymer on the substrate. The properties of such nanoparticles are unique finding a wide range of applications. This article reviews the different techniques of synthesis of these hybrid nanoparticles and their ...

Research paper thumbnail of Effect of clay type on morphology and thermal stability of PMMA–clay nanocomposites prepared by heterocoagulation method

Polymer, 2004

Poly(methyl methacrylate) (PMMA) -clay nanocomposites were prepared by a heterocoagulation method... more Poly(methyl methacrylate) (PMMA) -clay nanocomposites were prepared by a heterocoagulation method. A cationic PMMA emulsion was prepared by emulsion polymerization using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous clay slurry. Clays used in present research included montmorillonite (MMT), synthetic hectorites and fluorohectorites (with two different sizes). WAXD results and TEM images indicate that the morphologies of these nanocomposites depend on clay colloid stability as well as clay loadings. WAXD and TEM results also indicate the good morphology preservation of the nanocomposites during solution and melt processing. Thermal stability of these nanocomposites was studied by TG -DTG analyses; the mechanism of thermal stability improvement is discussed based on experimental results. q

Research paper thumbnail of Study of Protein Adsorption onto Well-Defined Surfaces of Self-Assembled Monolayers

Using self-assembled monolayers (SAMs), very well-defined, chemically homogenous, and reproducibl... more Using self-assembled monolayers (SAMs), very well-defined, chemically homogenous, and reproducible surfaces can be easily created. By varying the packing density of the alkyl chains of the SAMs and the chain end functionality, the properties of the surfaces can be changed. Human Serum Albumin (HSA) and Human Immunoglobulin G (HGG) were adsorbed to surfaces with various functionalities and packing densities. The

Research paper thumbnail of Bottom-up synthesis of PS–CNF nanocomposites

Polymer, 2005

Polystyrene–carbon nanofiber (CNF) nanocomposites have been synthesized by a 'bottom-up&... more Polystyrene–carbon nanofiber (CNF) nanocomposites have been synthesized by a 'bottom-up' method through electrostatic assembly. First, a cationic polystyrene (PS) latex was synthesized by conventional emulsion polymerization. The latex was mixed with an ...

Research paper thumbnail of Use of Precipitons for Copper Removal in Atom Transfer Radical Polymerization

Macromolecules, 2002

Atom transfer radical polymerization (ATRP) methods have been improved in recent years and provid... more Atom transfer radical polymerization (ATRP) methods have been improved in recent years and provide a promising set of tools for the controlled synthesis of polymers. 1 One drawback of ATRP, arising when standard homogeneous catalysts are used, is contamination of the polymer by the ligand/metal complex. The colored catalyst complex is typically removed by passing through a column of alumina, followed by precipitation of the polymer. Post-polymerization processing to remove catalyst increases the cost of polymer production. Methods that generate a clean polymer solution after reaction and allow for catalyst recycling are desirable.

Research paper thumbnail of In-situ Neutron Reflectivity Measurements of Human Serum Albumin Adsorption onto Functionalized Monolayers

Neutron reflectivity (NR) was used for the first time to study, in situ, adsorption of a human bl... more Neutron reflectivity (NR) was used for the first time to study, in situ, adsorption of a human blood protein onto well-characterized functionalized surfaces. CH_3- and NH_2-terminated self-assembled monolayers (SAM) deposited on silicon wafers were used as substrates. Electron density profiles of SAMs before adsorption were determined using X-ray reflectivity (XR). Changes of neutron scattering density profiles upon adsorption of human

Research paper thumbnail of Structure and properties of naphthalene containing polyesters, 1. High resolution solid state13C NMR study of poly(ethylene naphthalene-2,6-dicarboxylate)

Macromolecular Chemistry and Physics, 1998

Research paper thumbnail of Preparation of polyacrylate-clay nanocomposites by in-situ polymerization and heterocoagulation

Journal of Applied Polymer Science, 2006

Polyacrylate-clay nanocomposites were prepared by an in situ polymerization method followed by he... more Polyacrylate-clay nanocomposites were prepared by an in situ polymerization method followed by heterocoagulation. In the heterocoagulation method, a cationic polyacrylate emulsion was prepared by emulsion polymerization using a cationic initiator in the presence/absence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous clay slurry. WAXD results and TEM images suggest that morphologies of these nanocomposites depend on preparation method, mixing method, and the amount of free surfactant. TG-DTG analyses demonstrate the improvement in thermal stability of these nanocomposites, while DSC results indicate no significant changes in glass transition temperature of these nanocomposites.

Research paper thumbnail of Synthesis and characterization of a photoactive monolayer

The synthesis and characterization of photoactive monolayers is described. Monolayers containing ... more The synthesis and characterization of photoactive monolayers is described. Monolayers containing azobenzene were prepared either by direct chemisorption of a trichlorosilane or by covalent attachment to a functionalized self-assembled monolayer (SAM). Preliminary photoisomerization studies show a decrease in wettability upon exposure to ultraviolet light. In addition, a new experimental methodology for measuring protein adsorption to SAMs was developed. Neutron reflectometry

Research paper thumbnail of Polycarbonate carbon nanofiber composites

European Polymer Journal, 2005

Carbon nanofiber (CNF) composites have the potential for creating inexpensive, semiconducting pol... more Carbon nanofiber (CNF) composites have the potential for creating inexpensive, semiconducting polymers. These composites require a homogeneous dispersion within the polymer. Many groups have focused on high shear methods such as twin screw extrusion. Although high shear methods produce a homogeneous dispersion, the aspect ratio of the nanofibers is reduced by the mechanical force. In this report, we present results for low shear composite formation via in situ polymerization of cyclic oligomeric carbonates. The composites were characterized by thermal gravimetric analysis, electrical conductivity, scanning electron microscopy and transmission electron microscopy. The composites exhibit minimal aggregation of the carbon nanofibers even at high weight percents. The polycarbonate/CNF composites exhibit an electrical conductivity percolation threshold of 6.3 wt% which is higher compared with similar CNF composites. The composites also show an increase in thermal stability of 40°C as the CNF loading increases from 0 to 9 wt%.

Research paper thumbnail of Synthesis, Characterization, and Properties of Tethered Polystyrene-b-polyacrylate Brushes on Flat Silicate Substrates

Research paper thumbnail of Atom Transfer Radical Polymerization of Methyl Methacrylate with Polyethylene-functionalized Ligands

Research paper thumbnail of Surface modification of a silicate substrate by a “grafting from” methodology utilizing a perester initiator

The perester silane t-butyl peroxy-11-trichlorosilylundecanoate was synthesized by hydrosilylatio... more The perester silane t-butyl peroxy-11-trichlorosilylundecanoate was synthesized by hydrosilylation of t-butyl peroxy-10undecanoate with trichlorosilane. These radical initiators were covalently bound to the surface of silicate substrates by selfassembled monolayer (SAM) techniques. Several hydrophilic and hydrophobic acrylate monomers were successfully grafted onto the silicate substrate by in situ polymerization from the surface bound perester initiators. The polymer brushes were characterized by the ATR-IR, XPS, AFM and water contact angles. The results of the study indicate this ''grafting from'' technique can be used for the preparation of polymer layers with high graft density. While these surface-bound initiators function similarly to surface-bound azo initiators, the preparation of the surface-active perester is a simple, two-step synthesis.

Research paper thumbnail of In-Plane Ordering in Diblock Copolymer Brushes

ABSTRACT Internal and surface structures of polystyrene-b-polyacrylate and polyacrylate-b-polysty... more ABSTRACT Internal and surface structures of polystyrene-b-polyacrylate and polyacrylate-b-polystyrene diblock copolymer brushes have been studied using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM). Each asymmetric, as-deposited diblock brush that contains a poly(methyl acrylate) (PMA) block shows an in-plane structure with a spacing comparable to the PMA layer thickness. The correlation length of the in-plane ordering is about the nearest neighbor distance and grows with annealing at 180^o C. After a brush is treated with a solvent selective for the bottom block, Bragg rods appear in the GISAXS pattern. The lateral spacing corresponding to the Bragg rods is on the order of the brush total thickness. This lateral correlation is also detected by power spectral density analysis of AFM images of the samples' surfaces. The Bragg rods disappear upon heating to 80^o C.

Research paper thumbnail of Surface Dynamics of Free PS Chains on Chemically Identical Polymer Brushes: An XPCS Study

We found no relaxation of fluctuations of the brush surfaces within the range of time (0.2 -1100 ... more We found no relaxation of fluctuations of the brush surfaces within the range of time (0.2 -1100 s) and length scale (0.6-3 um) studied by X-ray photon correlation spectroscopy(XPCS). This is true for PS brushes of thicknesses of 9 - 101 nm and grafting density of 0.12-0.6 chains/nm^2 at temperatures up to 130C above bulk Tg. Results on the dynamics

Research paper thumbnail of Photocontrolled micellar aggregation of amphiphilic DNA-azobenzene conjugates

Colloids and surfaces. B, Biointerfaces, Jan 15, 2015

We demonstrate the reversible micellar aggregation of a DNA-azobenzene conjugate in aqueous condi... more We demonstrate the reversible micellar aggregation of a DNA-azobenzene conjugate in aqueous conditions, in which the photoisomerization of the initially apolar trans-azobenzene moiety to the polar cis isomer causes disassembly of the aggregates. The molecular basis for this phenomena is a change in the hydrophobic/hydrophilic balance of the conjugate as the more polar cis azobenzene isomer is formed upon exposure to 365nm irradiation. The conjugates were prepared by copper-free Click chemistry between an azide-modified, 53-base ssDNA and a cyclooctyne derivative of azobenzene. The photocontrolled aggregation of the conjugate was studied by dynamic light scattering and atomic force microscopy. The reversible micellar aggregation for a DNA-azobenzene conjugate has not been previously reported and holds promise for photocontrolled drug delivery applications.

Research paper thumbnail of Improving the physical properties of PEA/PMMA blends by the uniform dispersion of clay platelets

Polymer, 2006

Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined wi... more Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined with unmodified montmorillionite (MMT) to improve the physical properties via nanocomposite formation. We prepared a cationic PEA/PMMA latex and used a heterocoagulation process to create a homogeneous dispersion of the clay platelets in the matrix. The cationic PEA/PMMA emulsion blends were prepared using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous slurry of MMT. The PEA/PMMA-MMT nanocomposites could be processed at low temperatures. Low temperature processing prevented the commonly observed discoloration associated with many thermoplastic nanocomposites. DSC, SAXS, TEM and AFM were used to study the dispersion of MMT and morphology of PEA/PMMA-MMT nanocomposites. Tensile stress, elongation at break and Young's modulus demonstrated a significant reinforcing effect of clay. q

Research paper thumbnail of Synthesis, Characterization, and Properties of ABA Type Triblock Copolymer Brushes of Styrene and Methyl Acrylate Prepared by Atom Transfer Radical Polymerization

Research paper thumbnail of Selective ordering of surfactant modified gold nanoparticles in a diblock copolymer

Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-pol... more Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-poly(methyl methacrylate) has been observed. The morphology of the diblock copolymer/Au-nanocomposite was dependent on the composition of the thiol modifier. For the thiol modifier that does not preferentially interact with one of the blocks, a perpendicular (relative to the substrate) lamellar morphology is maintained. However, for a thiol with a surfactant structure similar to one of the blocks, we observed a parallel lamellar morphology and speculate that the nanoparticles have localized at the microdomain interface. These conclusions are based on transmission electron microscopy, angle-dependent X-ray photoelectron microscopy and tensiometry. These results are consistent with theoretical predictions on the hybrid systems composed of block copolymers and nanoparticles.

Research paper thumbnail of Synthesis, Characterization, and Properties of Polyelectrolyte Block Copolymer Brushes Prepared by Atom Transfer Radical Polymerization and Their Use in the Synthesis of Metal Nanoparticles

Research paper thumbnail of Surface initiated polymerizations from silica nanoparticles

Soft Matter, 2006

Surface initiated polymerizations yield covalently bonded polymer on the substrate. The propertie... more Surface initiated polymerizations yield covalently bonded polymer on the substrate. The properties of such nanoparticles are unique finding a wide range of applications. This article reviews the different techniques of synthesis of these hybrid nanoparticles and their ...

Research paper thumbnail of Effect of clay type on morphology and thermal stability of PMMA–clay nanocomposites prepared by heterocoagulation method

Polymer, 2004

Poly(methyl methacrylate) (PMMA) -clay nanocomposites were prepared by a heterocoagulation method... more Poly(methyl methacrylate) (PMMA) -clay nanocomposites were prepared by a heterocoagulation method. A cationic PMMA emulsion was prepared by emulsion polymerization using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous clay slurry. Clays used in present research included montmorillonite (MMT), synthetic hectorites and fluorohectorites (with two different sizes). WAXD results and TEM images indicate that the morphologies of these nanocomposites depend on clay colloid stability as well as clay loadings. WAXD and TEM results also indicate the good morphology preservation of the nanocomposites during solution and melt processing. Thermal stability of these nanocomposites was studied by TG -DTG analyses; the mechanism of thermal stability improvement is discussed based on experimental results. q

Research paper thumbnail of Study of Protein Adsorption onto Well-Defined Surfaces of Self-Assembled Monolayers

Using self-assembled monolayers (SAMs), very well-defined, chemically homogenous, and reproducibl... more Using self-assembled monolayers (SAMs), very well-defined, chemically homogenous, and reproducible surfaces can be easily created. By varying the packing density of the alkyl chains of the SAMs and the chain end functionality, the properties of the surfaces can be changed. Human Serum Albumin (HSA) and Human Immunoglobulin G (HGG) were adsorbed to surfaces with various functionalities and packing densities. The

Research paper thumbnail of Bottom-up synthesis of PS–CNF nanocomposites

Polymer, 2005

Polystyrene–carbon nanofiber (CNF) nanocomposites have been synthesized by a 'bottom-up&... more Polystyrene–carbon nanofiber (CNF) nanocomposites have been synthesized by a 'bottom-up' method through electrostatic assembly. First, a cationic polystyrene (PS) latex was synthesized by conventional emulsion polymerization. The latex was mixed with an ...

Research paper thumbnail of Use of Precipitons for Copper Removal in Atom Transfer Radical Polymerization

Macromolecules, 2002

Atom transfer radical polymerization (ATRP) methods have been improved in recent years and provid... more Atom transfer radical polymerization (ATRP) methods have been improved in recent years and provide a promising set of tools for the controlled synthesis of polymers. 1 One drawback of ATRP, arising when standard homogeneous catalysts are used, is contamination of the polymer by the ligand/metal complex. The colored catalyst complex is typically removed by passing through a column of alumina, followed by precipitation of the polymer. Post-polymerization processing to remove catalyst increases the cost of polymer production. Methods that generate a clean polymer solution after reaction and allow for catalyst recycling are desirable.

Research paper thumbnail of In-situ Neutron Reflectivity Measurements of Human Serum Albumin Adsorption onto Functionalized Monolayers

Neutron reflectivity (NR) was used for the first time to study, in situ, adsorption of a human bl... more Neutron reflectivity (NR) was used for the first time to study, in situ, adsorption of a human blood protein onto well-characterized functionalized surfaces. CH_3- and NH_2-terminated self-assembled monolayers (SAM) deposited on silicon wafers were used as substrates. Electron density profiles of SAMs before adsorption were determined using X-ray reflectivity (XR). Changes of neutron scattering density profiles upon adsorption of human

Research paper thumbnail of Structure and properties of naphthalene containing polyesters, 1. High resolution solid state13C NMR study of poly(ethylene naphthalene-2,6-dicarboxylate)

Macromolecular Chemistry and Physics, 1998

Research paper thumbnail of Preparation of polyacrylate-clay nanocomposites by in-situ polymerization and heterocoagulation

Journal of Applied Polymer Science, 2006

Polyacrylate-clay nanocomposites were prepared by an in situ polymerization method followed by he... more Polyacrylate-clay nanocomposites were prepared by an in situ polymerization method followed by heterocoagulation. In the heterocoagulation method, a cationic polyacrylate emulsion was prepared by emulsion polymerization using a cationic initiator in the presence/absence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous clay slurry. WAXD results and TEM images suggest that morphologies of these nanocomposites depend on preparation method, mixing method, and the amount of free surfactant. TG-DTG analyses demonstrate the improvement in thermal stability of these nanocomposites, while DSC results indicate no significant changes in glass transition temperature of these nanocomposites.

Research paper thumbnail of Synthesis and characterization of a photoactive monolayer

The synthesis and characterization of photoactive monolayers is described. Monolayers containing ... more The synthesis and characterization of photoactive monolayers is described. Monolayers containing azobenzene were prepared either by direct chemisorption of a trichlorosilane or by covalent attachment to a functionalized self-assembled monolayer (SAM). Preliminary photoisomerization studies show a decrease in wettability upon exposure to ultraviolet light. In addition, a new experimental methodology for measuring protein adsorption to SAMs was developed. Neutron reflectometry

Research paper thumbnail of Polycarbonate carbon nanofiber composites

European Polymer Journal, 2005

Carbon nanofiber (CNF) composites have the potential for creating inexpensive, semiconducting pol... more Carbon nanofiber (CNF) composites have the potential for creating inexpensive, semiconducting polymers. These composites require a homogeneous dispersion within the polymer. Many groups have focused on high shear methods such as twin screw extrusion. Although high shear methods produce a homogeneous dispersion, the aspect ratio of the nanofibers is reduced by the mechanical force. In this report, we present results for low shear composite formation via in situ polymerization of cyclic oligomeric carbonates. The composites were characterized by thermal gravimetric analysis, electrical conductivity, scanning electron microscopy and transmission electron microscopy. The composites exhibit minimal aggregation of the carbon nanofibers even at high weight percents. The polycarbonate/CNF composites exhibit an electrical conductivity percolation threshold of 6.3 wt% which is higher compared with similar CNF composites. The composites also show an increase in thermal stability of 40°C as the CNF loading increases from 0 to 9 wt%.

Research paper thumbnail of Synthesis, Characterization, and Properties of Tethered Polystyrene-b-polyacrylate Brushes on Flat Silicate Substrates

Research paper thumbnail of Atom Transfer Radical Polymerization of Methyl Methacrylate with Polyethylene-functionalized Ligands

Research paper thumbnail of Surface modification of a silicate substrate by a “grafting from” methodology utilizing a perester initiator

The perester silane t-butyl peroxy-11-trichlorosilylundecanoate was synthesized by hydrosilylatio... more The perester silane t-butyl peroxy-11-trichlorosilylundecanoate was synthesized by hydrosilylation of t-butyl peroxy-10undecanoate with trichlorosilane. These radical initiators were covalently bound to the surface of silicate substrates by selfassembled monolayer (SAM) techniques. Several hydrophilic and hydrophobic acrylate monomers were successfully grafted onto the silicate substrate by in situ polymerization from the surface bound perester initiators. The polymer brushes were characterized by the ATR-IR, XPS, AFM and water contact angles. The results of the study indicate this ''grafting from'' technique can be used for the preparation of polymer layers with high graft density. While these surface-bound initiators function similarly to surface-bound azo initiators, the preparation of the surface-active perester is a simple, two-step synthesis.

Research paper thumbnail of In-Plane Ordering in Diblock Copolymer Brushes

ABSTRACT Internal and surface structures of polystyrene-b-polyacrylate and polyacrylate-b-polysty... more ABSTRACT Internal and surface structures of polystyrene-b-polyacrylate and polyacrylate-b-polystyrene diblock copolymer brushes have been studied using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM). Each asymmetric, as-deposited diblock brush that contains a poly(methyl acrylate) (PMA) block shows an in-plane structure with a spacing comparable to the PMA layer thickness. The correlation length of the in-plane ordering is about the nearest neighbor distance and grows with annealing at 180^o C. After a brush is treated with a solvent selective for the bottom block, Bragg rods appear in the GISAXS pattern. The lateral spacing corresponding to the Bragg rods is on the order of the brush total thickness. This lateral correlation is also detected by power spectral density analysis of AFM images of the samples' surfaces. The Bragg rods disappear upon heating to 80^o C.

Research paper thumbnail of Surface Dynamics of Free PS Chains on Chemically Identical Polymer Brushes: An XPCS Study

We found no relaxation of fluctuations of the brush surfaces within the range of time (0.2 -1100 ... more We found no relaxation of fluctuations of the brush surfaces within the range of time (0.2 -1100 s) and length scale (0.6-3 um) studied by X-ray photon correlation spectroscopy(XPCS). This is true for PS brushes of thicknesses of 9 - 101 nm and grafting density of 0.12-0.6 chains/nm^2 at temperatures up to 130C above bulk Tg. Results on the dynamics