13C NMR Relaxation of iso-Poly(2-vinylpyridinium chloride) in Aqueous Solution. Effects of Electrostatic Interactions on Local Chain Dynamics

2004

Polym J

Self Cite

To study the segmental motion of poly(N "-hydroxyethyl L-glutamine) (PHEG) in aqueous solution, the 13 C spin-lattice relaxation time (T 1) and the nuclear Overhauser enhancement (NOE) were measured at six resonance frequencies (! C =2) ranging from 15 to 150 MHz and at 100 MHz, respectively, at the temperatures from 20 to 90 C. For the backbone C, plots of logðT 1 =! C Þ against logð! C Þ gave the well superposed master curve, showing that the frequency-temperature reduction rule is realized. The shift factor obeyed the Arrhenius type temperature dependence with the activation energy of 29.6 kJ mol À1. Using this activation energy for the temperature dependence of the correlation time, the master curve and NOE were well reproduced by the Dejean-Lauprêtre-Monnerie (DLM) model. One of parameters relating to the segmental motion was 0 = 1 ¼ 5, where 0 and 1 are the correlation times for the isolated single and correlated pair conformational transitions, respectively. Comparison of this parameter with that for other vinyl polymers showed that PHEG having planar peptide groups in the backbone belongs to polymer group with smaller values of 0 = 1. 0 = 1 was discussed in the relation to the distribution width of the correlation time. The spectral density function Jð!Þ has the exponent to the correlation time a as !Jð!Þ $ ð! a Þ 0:61 in the region of ! a < 0:2 which is close to the value of 0.5 from the DLM model.

mentioning

confidence: 56%

13C NMR Relaxation Study of Segmental Motion of Poly(Nε-hydroxyethyl L-glutamine) in Aqueous Solution

Uchino

Hiraoki

2004

Polym J

Self Cite

“…case and the previous case. 1 They became comparable to the steric hindrance effects of moderately bulky side chains.…”

Section: •mentioning

confidence: 98%

13C NMR Relaxation of Poly(acrylic acid) in Aqueous Solution. Effects of Charge Density on Local Chain Dynamics

Yamazaki

Noda

2000

Polym J

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A previous paper 1 studied the effects of electrostatic interactions on local chain dynamics by 13 C NMR relaxation using poly(2-vinylpyridine) (P2VP) in dioxaned8 and fully neutralized P2VP or poly(2-vinylpyridinium chloride) (P2VPC1) in D 2 0. All experimental data of main chain carbons were found in good agreement with the Dejean-Laupretre-Monnerie (OLM) model 2 modified from the Hall-Weber-Helfand model describing the main chain motions in terms of conformational transition 3 .4 by introducing libration motions of C-H vectors. The main chain motion of P2VPC1 was more restricted than those of P2VP owing to the electrostatic interactions.When the charge density increases beyond a critical value in polyelectrolytes, counterion condensation or ion-binding takes place so that the effective charge density becomes almost constant or electrostatic interactions are almost saturated. This is characteristic of polyelectrolytes, which plays an important role to determine physicochemical properties such as counterion activity, electric conductivity 5 and intrinsic viscosity. 6 In the previous work, 1 however, we were not able to study the effects of charge density because of the poor solubility of partially neutralized P2VP in D 2 0. We were not able to have definite conclusion on the activation energy of conformational transition because the solvents of P2VP and P2VPCI were different. To study these problems, poly(acrylic acid) (PAA) is considered a most suitable polyelectrolyte because the charge density can be easily varied by changing the degree of neutralization, IX and PAA is dissolved in water irrespective of a.In this work, we measured 13 C NMR relaxation such as spin-lattice relaxation time, T 1 , and nuclear Overhauser effect (NOE) of PAAs with different IX at two magnetic fields as a function of temperature and analyzed the data of main chains by the OLM model to study the effects of charge density on the local chain dynamics.EXPERIMENT AL AND DAT A ANALYSIS PAA purchased from Wako Pure Chemical Industries Ltd. was purified by passing its aqueous solution through a mixed ion-exchange resin column of Amberlite IR-120B and IRA-400 and some PAA solutions were partially neutralized by NaOH aqueous solution. The PAA solutions with IX= 0, 0.2, and 0.8 thus obtained were freeze-dried, followed by drying in vacuum and the dried samples were dissolved in D 2 0 purchased from Aldrich Chemical Co. The polymer concentrations were ca. IO wt¾. All sample solutions were degassed carefully and sealed in NMR sample tubes. The tacticity of PAA sample was found to be almost a tactic (rr = 31 %, mr=48%, and mm=21%, where rr, mr, and mm represent the triad sequences of meso (m) and racemo (r)) from the methine peak intensities of 13 C NMR spectra.7 Molecular weight of PAA (IX= 0) is ca. 1.2 x 104, determined from the intrinsic viscosity of poly(sodium acrylate) in IM NaCl aqueous solution. RESULTS AND DISCUSSIONFigures 1, 2, and 3 show temperature dependence of T 1 and NOE for methine carbons of PAAs with IX=0, 0.2, and 0.8, re...

¹³C NMR Relaxation Study of Segmental Motion of Poly(L-histidine) in Aqueous Solution

Uchino

Hiraoki

2004

Jpn. J. Appl. Phys.

Three theories connecting conditioning with material removal rates by the coefficient of friction are proposed and experimentally verified. The conditioning theory is employed to provide a specific prediction on how the number of active diamonds, cut rate, and cut furrow geometry affect pad surface abruptness. The same surface abruptness parameter was a factor in both the coefficient of friction and removal rate theories. The theory predicts a priori that friction and removal rate should decrease as the conditioned surface became less abrupt. Simple models of cut rate and active diamond count further indicate that abruptness should decrease with increasing conditioner load. Mitsubishi Materials Corporation conditioners with 60, 100, and 200 grit sizes are used to test the theory in an experiment in which conditioner load is varied from light to heavy. Polishing experiments and pad profilometry verified the main predictions of the theory.