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Full-Text Articles in Physical Sciences and Mathematics
Dynamics Of Pipa-D₇ On Silica Surface, Piyawan Krisanangkura, Frank D. Blum
Dynamics Of Pipa-D₇ On Silica Surface, Piyawan Krisanangkura, Frank D. Blum
Chemistry Faculty Research & Creative Works
Molecular motion of polymer chains is an important determinant in understanding the physical properties of polymeric materials. Glass transition temperature (Tg) is a physical property of polymers, which is of primary interest. The study of the dynamics of polymer segments assists in understanding the dependence of Tg on polymer structure.1 For decades, studies have addressed the molecular motion in various polymers. Some of them have probed the dynamics of polymer backbones.2,3 the properties of a polymer at an interface may change because of the type of polymer, the substrate, or other variables. The side chain of a polymer can also …
Molecular Mass And Dynamics Of Poly(Methyl Acrylate) In The Glass Transition Region, Burak Metin, Frank D. Blum
Molecular Mass And Dynamics Of Poly(Methyl Acrylate) In The Glass Transition Region, Burak Metin, Frank D. Blum
Chemistry Faculty Research & Creative Works
The segmental dynamics of bulk poly(methyl acrylate) (PMA) were studied as a function of molecular mass in the glass-transition region using 2H NMR and modulated differential scanning calorimetry (MDSC). Quadrupole-echo 2H NMR spectra were obtained for four samples of methyl-deuterated PMA-d3 with different molecular masses. The resulting spectra were fit using superpositions of simulated spectra generated from the MXQET simulation program, based on a model incorporating nearest-neighbor jumps from positions on the vertices of a truncated icosahedron (soccer-ball shape). The lower molecular-mass samples, influenced by the presence of more chain ends, showed more heterogeneity (broader distribution) and lower glass transitions …
Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum
Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum
Chemistry Faculty Research & Creative Works
For a polymer film deposited on a surface, the strength of the surfacesegment interaction affects the mobility of polymer-chain segments. The selfconsistent field lattice model of Scheutjens and Fleer,1 based on mean-field lattice models of polymer at interfaces,2 has been used to describe the distribution of conformations of polymers on surfaces. Adsorbed-polymer segments may be classified as belonging to loops, trains or tails. There are different techniques used to study the molecular motion of the polymer including modulated differential scanning calorimetry (MDSC)3 and nuclear magnetic resonance (NMR).4,5 in this work, solid-state deuterium (2H) NMR was used to characterize the polymer …
Deuterium Nmr Studies Of Segmental Dynamics Of Anopore-Adsorbed Poly(Methyl Acrylate), Macduff O. Okuom, Frank D. Blum
Deuterium Nmr Studies Of Segmental Dynamics Of Anopore-Adsorbed Poly(Methyl Acrylate), Macduff O. Okuom, Frank D. Blum
Chemistry Faculty Research & Creative Works
Studies of segmental dynamics of polymers at interfaces provide a basis for understanding the properties of composite materials. Interfacial phenomena in multi-phase systems need to be understood as devices made from multi-phase polymeric systems become smaller. Various techniques have been used to investigate interfacial polymers at the air-polymer-solid interface; for example, ellipsometry,1 X-ray,2 and neutron reflectometry.3 These techniques typically characterize the structure (often the thickness) of the polymer layer and are normally used to determine the glass-transition temperature (Tg) through a break in the thicknesstemperature curve. There have been a few reports where the dynamics of polymers at the surface-air …
Nmr And Modulated Differential Scanning Calorimetry Of Adsorbed Poly(Methyl Acrylate) On Silica, Frank D. Blum, Burak Metin
Nmr And Modulated Differential Scanning Calorimetry Of Adsorbed Poly(Methyl Acrylate) On Silica, Frank D. Blum, Burak Metin
Chemistry Faculty Research & Creative Works
The interaction between polymers and solid substrates can be studied by a variety of techniques. The results from different experiments can be affected by the nature of the polymer, surface, polymer-surface interactions and, also, the experiment. A great deal has been learned about the behavior of polymers at interfaces, but there is also much to be learned about the interactions and how they affect the physical properties of adsorbed polymers. In the present study, we report both deuterium nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry (MDSC) of poly(methyl acrylate) (PMA) adsorbed on Cab-O-Sil silica. The focus of this …
Solid-State Deuterium Nuclear Magnetic Resonance Of The Methyl Dynamics Of Poly(Alpha-Methylstyrene) And Polymethylphenylsilane, Robert D. O'Connor, Eric J. Ginsburg, Frank D. Blum
Solid-State Deuterium Nuclear Magnetic Resonance Of The Methyl Dynamics Of Poly(Alpha-Methylstyrene) And Polymethylphenylsilane, Robert D. O'Connor, Eric J. Ginsburg, Frank D. Blum
Chemistry Faculty Research & Creative Works
The methyl-d3 dynamics of two relatively similar polymers, poly(alpha-methylstyrene) (PAMS-d3) and polymethylphenylsilane (PMPS-d3), are investigated via deuterium NMR relaxation experiments. Our analysis of the relaxation data uses the entire solid-echo spectra to maximize the precision of the experiments with regard to the information available on the methyl dynamics. The analysis is novel in that it does not use M[infinity] or M0 to fit the relaxation data. Additionally, the three-site symmetric jump model is shown to not have an observable azimuthal angular dependence for T1 relaxation. The methyl dynamics are quantified with taum, sigma, and f which are the log-average correlation …
Deuterium Nmr Of Adsorbed Poly(Methyl Acrylate)-D₃, Frank D. Blum, Wuu-Yung Lin
Deuterium Nmr Of Adsorbed Poly(Methyl Acrylate)-D₃, Frank D. Blum, Wuu-Yung Lin
Chemistry Faculty Research & Creative Works
The dynamics of polymers at interfaces are important in a variety of applications, especially where those applications depend on the mechanical or surface properties. Unfortunately, the surface properties of interfacial species like polymers used in composites are not easily measured macroscopically. Microscopic techniques, especially spectroscopic ones, have been successful. In our laboratory we have been successful in applying NMPR to determine the behavior of absorbed polymers. NMR has several advantages for this kind of study, the principal ones being that it can be used on opaque materials, different nuclei can be used as probes, and interfacial material can sometimes be …