PROTON MAGNETIC RESONANCE LINE WIDTH AS A FUNCTION OF POLYMER TACTICITY

1966 ◽  
Vol 44 (2) ◽  
pp. 153-156 ◽  
Author(s):  
S. Brownstein ◽  
D. M. Wiles
Keyword(s):  
Magnetic Resonance ◽  
Methyl Methacrylate ◽  
Proton Magnetic Resonance ◽  
Chloroform Solution ◽  
Spin Coupling ◽  
Solution Viscosity ◽  
Dilute Solution ◽  
Poly Methyl Methacrylate ◽  
Resonance Line Width ◽  
Polymer Tacticity

The high resolution proton magnetic resonance spectra of five samples of poly(methyl methacrylate) in chloroform solution have been measured with 100 Mc/s equipment. The widths of the absorption lines arising from the protons of the α-methyl and the methoxyl groups have been compared. The widths are greater when the polymer is predominantly syndiotactic than when it is predominantly isotactic. It is concluded that isotactic samples have the more extended conformation in chloroform solution. An analogy with dilute solution viscosity measurements is outlined in support of this conclusion. Differences between the widths of the lines of the methylene protons in a completely isotactic poly(methyl methacrylate) sample are attributed to long range spin coupling.

scholarly journals Processing parameters for electrospinning poly(methyl methacrylate) (PMMA)/titanium isopropoxide composite in a pump-free setup

2018 ◽  
Vol 1 ◽  
pp. 27
Author(s):  
Leah Nyangasi ◽  
Dickson Andala ◽  
Charles Onindo ◽  
Alphonse Wanyonyi ◽  
Josphine Chepngetich
Keyword(s):  
Methyl Methacrylate ◽  
Polymer Solution ◽  
Solution Concentration ◽  
Titanium Isopropoxide ◽  
Processing Parameters ◽  
Solution Viscosity ◽  
Poly Methyl Methacrylate ◽  
Size And Morphology ◽  
Set Up ◽  
Almost All

Background: Electrospinning is a technique for producing nanofibers, useful in many fields of nanotechnology. The size and morphology of the nanofibers obtained depends on the polymer solution properties, the parameters of the equipment and the conditions of the surrounding. In almost all reported electrospinning set ups, a pump ,which regulates the flow of the polymer solution, has been included as one of the requirements. In this study, the effects of solution concentration, viscosity, voltage and the distance from the tip of the syringe to the aluminum collector on the morphology and diameters of poly(methyl methacrylate)(PMMA) fibers were investigated, using a pump-free electrospinning set up. Methods: Varied PMMA concentration (50 -120 mg/mL), voltage (10-18 kV) and distance (5 – 18 cm) of electrospinning were studied and the optimum electrospinning conditions identified.  PMMA/ titanium isopropoxide solution of ratio 1:2 was prepared, electrospun at optimized conditions (15 kV, 18 cm, Dichloromethane/Dimethylformamide 60:40) and the fibers obtained analyzed using a scanning electron microscope. Results: Solutions of PMMA whose concentrations were less than 50 mg/mL, produced beads on fibers, whereas those at ~ 100 mg/mL formed the best bead-free fibers of diameter 350±50 nm. The results showed a direct dependence of fiber diameter on the solution viscosity. Fibers of larger diameters were obtained when the distance from the tip of the syringe to the aluminum collector and voltage were increased but at higher distances (>18 kV) fewer fibers were collected. When the voltage was steadily increased, the fibers broadened and the diameters were non-uniform due to splaying and splitting. Increasing the distance between the pipette-tip and the collector from 10 to 18 cm resulted in reduced electric field which in turn yielded fewer fibers. Conclusions: The results obtained in a pump free set-up were comparable to those eletrospun in the presence of a pump.

Proton magnetic resonance spectra of paraxylylene-methylmethacrylate copolymer in chloroform solution

1962 ◽  
Vol 62 (173) ◽  
pp. S9-S10 ◽  
Author(s):  
Atsuo Nishioka ◽  
Yoshinori Kato ◽  
Hisao Mitsuoka
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chloroform Solution ◽  
Magnetic Resonance Spectra

Proton magnetic resonance spectra of some benzo[b]thiophens. An investigation of substituent effects in a heteroaromatic system

1968 ◽  
Vol 21 (7) ◽  
pp. 1853 ◽  
Author(s):  
B Caddy ◽  
M Martin-Smith ◽  
RK Norris ◽  
ST Reid ◽  
S Sternhell
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Spin Coupling ◽  
Heteroaromatic System ◽  
Spin Spin Coupling ◽  
Magnetic Resonance Spectra

N.m.r. data for 19 5-substituted and 13 polysubstituted benzo[b]thiophens are tabulated. The influence of the substituents at C5 on the chemical shifts of H4 and H6 is discussed. Long-range interproton spin-spin coupling between H3 and H7, and between H2 and H6, is general in benzo[b]thiophens. The vicinal coupling J6,7 in 5-substituted benzo[b]thiophens varies directly and linearly with the electronegativity of the substituents at C5.

A proton magnetic resonance determination of the small rotational barriers about the C—Si bond in phenyl derivatives of chloro and methyl silanes

1977 ◽  
Vol 55 (3) ◽  
pp. 557-561 ◽  
Author(s):  
William J. E. Parr ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of ◽  
Low Energy Conformations

The long-range spin–spin coupling constants between protons bonded to silicon and ring protons in C6H5SiH3, C6H5SiH2Cl, C6H5SiH2CH3, C6H5SiHCl2, and C6H5SiH(CH3)2 are determined from the proton magnetic resonance spectra of benzene solutions. A hindered rotor treatment of the barrier to internal rotation about the C—Si bond, in conjunction with the coupling constants over six bonds, allows the deduction of the low-energy conformations for C6H5SiH(CH3)2 and for C6H5SiHCl2, as well as of barriers of 1.0 ± 0.2 kcal/mol. The approach becomes less reliable for C6H5SiH2CH3 and for C6H5SiH2Cl and, particularly for the latter compound, the derived barrier is very likely an upper limit only. Ab initio molecular orbital calculations of the conformational energies are reported for C6H5SiH3, C6H5SiH2Cl, and for C6H5SiHCl2.

Nuclear magnetic resonance studies of ionomers. 5. Spectra of poly (methyl methacrylate-co-4-vinyl pyridine), poly (methyl methacrylate-co-2-methyl-5-vinyl pyridine), and their quaternized derivatives

1987 ◽  
Vol 65 (8) ◽  
pp. 1873-1881 ◽  
Author(s):  
Almeria Natansohn ◽  
Adi Eisenberg
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Methyl Methacrylate ◽  
Pyridine Ring ◽  
Main Chain ◽  
Structural Units ◽  
Poly Methyl Methacrylate ◽  
Nuclear Magnetic Resonance Spectra ◽  
Vinyl Pyridine ◽  
Nuclear Magnetic

Proton and carbon nuclear magnetic resonance spectra in solution of poly (methyl methacrylate-co-4-vinyl pyridine), poly(methyl methacrylate-co-2-methyl-5-vinyl pyridine), and of their derivatives obtained by quaternization with methyl iodide are presented. The vinyl pyridine structural units content of the samples is ca. 10%. In different solvents, the spectra provide information about the sequence distribution and configuration of the copolymers. A "coisotactic" alternating addition, defined as the probability of finding a methoxy group and a pyridine ring neighboring each other on the same side of the main chain, can be estimated as about 0.5 in both cases. This information arises from the splitting of the aromatic and of the methoxy signals (both in proton and carbon spectra). As expected, quaternization does not affect the copolymer configuration. Heteronuclear-correlated two-dimensional spectra can help in assigning the spectra.

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