Polymer Protons Research Articles

Imidazole and pyrazole-based proton conducting polymers and liquids

The properties of imidazole (pyrazole) as a solvent for acidic protons in polymers and liquids are reported. The creation of protonic defects and the mobility of protons in these environments are found to be similar to the situation in corresponding water containing systems. The temperature stability is, however, increased and imidazole (pyrazole) is a stronger Bronstedt base compared to water, which may be useful for the application of such materials as electrochemical cells such as fuel cells and secondary batteries.

Effect of High Molecular Mobility of Poly(vinyl alcohol) on Protein Stability of Lyophilized γ-Globulin Formulations

□ The protein stability of lyophilized serum γ-globulin (BGG) formulations containing poly(vinyl alcohol) (PVA) and dextran was studied in relation to the molecular mobility as determined by proton NMR. The critical temperature, Tmc, at which the Lorentzian relaxation process due to liquid polymer protons appears in these lyophilized formulations was lower than the glass transition temperature, Tg. Above Tmc, protein aggregation in the formulations was related to the Tmc according to the Williams–Landel–Ferry equation by replacing Tg with Tmc. Protein aggregation appears to occur substantially in a “rubbery-like” state even below Tg, if the formulations become microscopically liquidized above Tmc. Lyophilized BGG formulations containing PVA with a lower water content were less stable than those containing dextran with a higher water content. The difference in stability can be explained by the difference in the Tmc of these formulations. Tmc that is determined by NMR relaxation measurement appears to be a useful parameter for the characterization of protein formulations, for which the Tg cannot generally be determined by standard calorimetric techniques. Furthermore, Tmc appears to be more closely related to protein stability than does Tg.

A NOESY NMR Study of the Interaction between Sodium Dodecyl Sulfate and Poly(Ethylene Oxide)

The system poly(ethylene oxide) (PEO) and sodium dodecyl sulfate (SDS) will in aqueous solution form SDS micelle-like aggregates on the polymer when a critical surfactant concentration (c.a.c.) is reached. The two-dimensional nuclear Overhauser enhancement NMR (NOESY) experiment capable of revealing spatial relationships among proximal protons has been applied to the PEO/SDS system to study structural details of their interaction. NOESY cross-peaks at sample temperatures of 283.1 and 298.1 K indicate proximity (<5 Å) of the polymer protons and the main part of the surfactant hydrocarbon chain. The results indicate that the polymer (PEO) penetrates into the interior of the SDS micelles.

Comparative 1H-NMR studies on the physical state of water in soft contact lens and mouse lens

The physical state of water in mouse lenses (2-, 4- or 8-wk-ohl) and soft contact lenses (SCLs, water content from 18.4 to 79.2%) were studied by measuring spin-lattice relaxation times ( T 1) and apparent intermolecular cross-relaxation times ( T 1S) from irradiated protein or polymer protons to water protons, using 360 MHz 1H-NMR spectrometer at 25°C. (1) 1 T 1 values of SCLs increased gradually with increasingly dry weight ( W(%)). 1 T is values of SCLs were approximately zero at W of 20.8 and 26.8%, increased gradually from 26.8% and then steeply above ∼ 50%. (2) A plot of 1 T 1 vs. W(%) of mouse lenses was almost equal to that of SCLs. However, a plot of 1 T is vs. W(%) was an approximately straight line with the intercept at W of 23% and with the slope which is almost equal to that of SCLs above W of ∼ 50%. The plot of 1 T is vs. W(%) of mouse lenses might indicate the significant change in the physical state of water and/or protein-water interactions above W of 23%.

Noninvasive measurement of temperature distributions with high spatial resolution using quantitative imaging of NMR relaxation times

The steady-state temperature distribution within a block of cis-polybutadiene has been mapped using quantitative magnetic resonance imaging. The experiment described makes use of the temperature dependence of the nuclear magnetic longitudinal relaxation time (T1) of the polymer protons. Hot and cold water flowed through two axially mounted pipes in a cylindrical sample, creating a dipolar temperature distribution. A fast inversion recovery imaging sequence was used to map T1 values in the sample with a spatial resolution of 0.3 mm and random error of ±5% for individual pixels in the 128×128 image. The T1 values thus obtained were converted into temperatures using an empirical calibration curve, leading to a temperature resolution of ±2 K for each pixel. Using a median filter (which reduces the image resolution by a variable factor of up to 3), the data are rendered smooth enough to obtain a clear contour plot. This is compared with a finite element solution of Laplace’s equation over the same domain, demonstrating that the MRI technique is reliable. A number of experimental problems limiting both the exact comparison between theory and experiment and the long-term utility of the technique are discussed.

Measurement of the cross relaxation rate for a polymer dispersed liquid crystal system

Proton cross relaxation between liquid crystal and polymer in a polymer dispersed liquid crystal (PDLC) system has been studied by the use of magic angle spinning and polarization transfer. The cross relaxation rates have been determined as functions of temperature, irradiation power, and off-resonance frequency setting. The data at each temperature are treated by a new set of relaxation equations which are not limited by the assumption of complete saturation of the polymer protons. The cross relaxation rates for the aromatic and aliphatic protons are similar over the temperature range studied, indicating that the liquid crystal molecules anchor parallel to the polymer surface. Before the glass transition, the cross relaxation rates increase with temperature due to a reduction in the contact time. After the glass transition, at about 37 °C, the cross relaxation rates decrease rapidly with temperature due to an increase in the motions of the polymer molecules which cause a reduction in the efficiency of spin energy exchange.

Energy loss of 70 MeV protons in organic polymers.

Using Bragg ionization curves, measurements of the average stopping power of organic polymers relative to that of water have been made for 70 MeV protons losing about 30 MeV in the absorbers. By comparing calculated curves to experimental ones, I-values for the polymers were obtained, relative to the I-value for A1. For repeated measurements with A-150 tissue equivalent plastic, the standard deviation of the ratio of the average stopping powers q was +/- 0.06%. It was found that q depends on the year of production of A-150. For other absorbers, the uncertainty of q is estimated to be +/- 0.2%, with a corresponding uncertainty of the I-values of +/- 1.5%. Most measured I-values exceed values calculated with the additivity rule by about 10%. During the course of the measurements, fluctuations of the proton energy from the cyclotron of up to 0.8% were found.

Proton NMR relaxation in hydrogel contact lenses: correlation with in vivo lens dehydration data

A study of hydrogel contact lenses was undertaken to determine whether NMR relaxation data can be used as a predictor for on-eye lens dehydration. Proton NMR relaxation times (T1 and T2), were determined for a series of contact lenses for which on-eye dehydration data were also available. NMR relaxation times were found to depend upon lens water content, but the dependence was not monotonic. T1 values varied between 100 and 800 msec, and T2 values varied between 6 and 85 msec for the lenses studied. In this study, the NMR signal and corresponding relaxation times are average values, derived both from lens water protons as well as from exchangeable polymer protons. A simple analysis of the data indicates that the mobility of these protons varies by more than a factor of 10 for the lenses studied. A test for linear correlation between NMR relaxation rate, 1/T1 and relative change in lens water mass, % delta mw gave r = -0.830 for all data, and r = 0.904 if one lens was excluded.

Proton spin–lattice relaxation in nematic microdroplets

The frequency and temperature dependences of the proton spin–lattice relaxation rate have been studied in nematic droplets embedded in a solid polymer matrix. The comparison of these data to those for bulk nematic and pure polymer samples shows that cross-relaxation between liquid crystal and polymer protons dominates the liquid crystal relaxation in the MHz frequency region, while at low frequencies the translationally induced molecular rotation becomes important. The cross-relaxation rate is found to be ≈103 s−1 giving an order of magnitude estimate 10−4–10−3 s for the time for which a liquid crystal molecule is bonded to the surface.

CPS K 221 Model of proton longitudinal magnetic relaxation in hydrated crosslinked poly(methacrylic acid)

Proton longitudinal magnetic relaxation time (T1) measurements have been made at 30 MHz over a wide range of temperature for crosslinked poly(methacrylic acid), PMA, hydrated with H2O as well as with D2O. From the point of view of nuclear magnetic relaxation, PMA hydrogel is a multiregion system in which three proton regions (a, b, c) can be distinguished. Region a is regarded as to be formed by the nonexchangeable polymer protons, region b by the protons of -COOH · H2O combinations, and region c by the protons of remaining water molecules. Cross relaxation between polymer and water protons and a log normal distribution of correlation times have been assumed to take place. Temperature dependences of the T1 time for the particular regions have been determined, from which the distribution width parameter, the second moment and the intramolecular proton-proton distance for sorbed water have been calculated.

NMR study of the demixing process in concentrated polyisobutylene solutions

AbstractA study of the magnetic resonance linewidths of the polymer protons of the polyisobutylene toluene system is presented as a function of concentration c and temperature T. Two distinct regions are observed in the linewidth versus concentration or temperature curves. A phase diagram is constructed, one region of which exhibits characteristic NMR properties supposed to reflect microphase separation of polymer and solvent. The demixing curve derived from NMR measurements is expressed by c = 11.3(267–T). The θ temperature of this system is 260 K.

Mathematical separation procedure of broadline proton NMR spectra of crystalline polymers into components

The molecular motions and their structural relations of solid crystalline polymers are preferably studied by use of the lineshape of the NMR spectra. For that purpose the spectra are separated into components, corresponding to the different kinds of motion of the polymer protons. Since no component lineshapes have been calculated as yet for polymers, in this work a number of lineshapes which seem suitable for polymer broadline spectroscopy is presented. The distortion of the lineshapes resulting from the use of large modulation amplitudes as compared to the linewidths, which is necessary to observe broad and narrow components simultaneously, is considered. Thus, it becomes possible to analyze the spectra and to study the molecular motions of the polymers in a very broad temperature range up close to the melting point.

Stereoregularity of poly(2‐vinylpyridine) determined by 1H‐NMR and 13C‐NMR spectroscopy

AbstractIn order to determine the stereoregularity of poly(2‐vinylpyridine), 2‐vinylpyridine‐β,β‐d2 was synthesized. The 1H‐NMR spectra of the deuterated polymer in D2SO4 and o‐dichlorobenzene solutions showed three peaks, which were assigned to triad tacticities. Since the absorptions of heterotactic and syndiotactic triads of methine protons overlap those of methylene protons in nondeuterated polymers, only isotactic triad intensities can be obtained from the 1H‐NMR spectra of nondeuterated poly(2‐vinylpyridine). The 13C‐NMR spectra of poly(2‐vinylpyridine) were obtained in methanol and sulfuric acid solutions. In methanol solution the absorption was split into three groups, which cannot be explained by triads, and in sulfuric acid solution several peaks were observed. These splittings may be due to pentad tacticity. The results show that poly(2‐vinylpyridine) obtained by radical polymerization is an atactic polymer.

Diamagnetic shielding of the protons in vinyl polymers with aromatic side-groups

Diamagnetic shielding of the protons in vinyl polymers with aromatic side-groups

NMR Investigation of Solvent Mobility in Benzene Solutions of Polymethylmethacrylate

AbstractThe spin lattice relaxation of benzene protons in solutions of polymethylmethacrylate (PMMA) has been studied at several concentrations. By selective deuterium substitution the benzene spin lattice relaxation was separated into three contributions resulting from: 1. the intramolecular interaction of benzene protons; 2. the intermolecular interaction of benzene protons; 3. the interaction between benzene and polymer protons. For that purpose perdeuterated PMMA was prepared. The measured relaxation times and self diffusion coefficients yield information on the rotational and translational motion of benzene molecules in PMMA solution.

Nuclear magnetic resonance and optical spectroscopic studies of poly l and poly d alanine

Nuclear magnetic resonance spectroscopy is finding increasing application to studies of conformational changes in biological macromolecules and their synthetic analogues. It has been suggested that the resonance peaks due to backbone protons in helical polymers will be broadened by non-averaging of dipole-dipole interactions and that the areas of these resonance peaks will be a measure of the random coil content of the system. In agreement with others, we do not find this to be the case for poly l and poly d alanine in trifluoracetic acid (TFA)-deuterochloroform (CDCl 3) solvent systems where the optical rotatory dispersion parameters indicate a helix content in excess of 50 per cent while the n.m.r. spectra for these solutions are still fully developed. It is suggested that the peak narrowing process operating in this system is rapid exchange between random coil and helical segments. Others suggest that, although the b 0 values for the TFA-CDCl 3 solvent systems indicate 54 per cent helix content, this o.r.d. parameter is an unreliable guide to helix content and that the polypeptide is helical; furthermore that they are observing for the first time a well developed n.m.r. spectrum for a polypeptide ‘purported to be in a helical conformation’. These conclusions are not supported by the results obtained from studies of poly l and poly d alanine in dichloracetic acid (DCA)-TFA and DCA-CDCl 3 solvent systems. In these systems it is possible to obtain appreciably higher b 0 values (up to 458°) than was observed for the TFA-CDCl 3 solvent system and these increases in b 0 are accompanied by marked broadening and loss of area of the proton resonance peaks. It is suggested therefore that when the helix content is greater than 50 per cent the motions of helical segments become too slow for the peak narrowing process of exchange between helical and random coil forms to be effective. These observations support the earlier suggestions that in fully helical macromolecules the backbone protons resonance peaks will be broadened by non-averaging of dipole-dipole interactions. It is possible to correlate the shifts in the poly l alanine resonance peaks with helix content and it has been suggested that the shifts are due to exchange of the protons between two chemical environments, i.e. the helical and random coil forms. Infra-red studies show, however, that there is a specific interaction between the carboxylic acid molecule and the helical form of poly alanine and we suggest that part of the shifts observed in the resonance peaks may result from magnetic anisotropy effects of the carboxyolic acid molecules complexed with hydrogen bonded amide groups in the helical form. In agreement with others it is suggested that the mode of interaction of the carboxylic acid molecules with poly alanine is a strong hydrogen bonding interaction and not protonation as has been suggested.

Dynamic polarization of protons in irradiated polymers

Protons were polarized in different types of irradiated polymers by means of the “solid effect” method. The polarization was measured in fields of 3150 Oe and 19200 Oe in a range of temperatures from 1·65 to 4·2°K. The highest polarization was reached on protons in polycaprolactam of type II in a field of 19200 Oe (ν e =53·5 GHz) at a temperature of 2·1°K. Further, the dependence of the polarization on the microwave power and nuclear relaxation times were measured. The temperature dependence of the distance between positive and negative polarization maxima was observed.

Dynamical polarization of protons in some polymers using the solid effect method

Experimental results on the dynamical polarization of protons in various polymers irradiated by neutrons are recapitulated. The measurements were performed at liquid nitrogen temperatures. The dependence was investigated of the degree of polarization on the microwave power, on the irradiation dose and on the change in frequency of the nuclear magnetic resonance. The maximum enhancement of polarization was obtained for polyethylene of a density ∼ 0·95 g/cm3 and was equal to 30.