摘要:

AbstractThe13C NMR spectra of methylstyrenes and methoxystyrenes and their polymers prepared with radical initiators, a Ziegler catalyst, or a cationic catalyst were measured. The spectra of the polymers were assigned by the chemical shifts of the monomers and gated‐decoupling method. The absorption of the aromatic C1carbon of each polymer, which varied by the polymerization conditions, was assigned in terms of a pentad sequence assuming that the Bernoullian statistics holds for the polymerization of ring substituted styrenes. The stereoregularities calculated from C1carbon absorptions were compared with those of polystyrenes obtained unter the same polymerization conditions. In the radical polymerization ofortho‐derivatives, where the substituent locates near the polymer backbone, high syndiotactic polymers (Pr= 0,80 − 0,83) were prepared. The effect of the substituent inpara‐derivatives did not appear. On the other hand, random polymers were generally fromed by cationic polymerization regardless of the position and the type of the subs

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830111

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe stereoregularity of poly(methoxystyrene)s was determined from the absorption of the aromatic C1carbon assuming a first‐order Markov statistics holds for the polymerization as well as polystyrenes. The stereoregularity of poly(p‐methoxystyrene)s prepared by sodium, potassium, or rubidium cations as catalysts in THF hardly varied and syndiotactic‐rich polymers were obtained, whereas a random polymer was formed with cesium‐naphthalene. In the polymerization ofp‐methoxystyrene in toluene, syndiotactic‐rich polymers were obtained with butyllithium and random polymers were prepared by sodium or potassium cations as catalysts. The stereoregularity of poly(o‐methoxystyrene)s prepared by sodium or potassium cations in tetrahydrofuran changed with the polymerization temperatures, and highly syndiotactic polymers were formed at−78°C. The structure of poly(o‐methoxystyrene)s obtained in toluene, markedly depended on the initiators; that is, with increasing the size of the ionic radius of the counterions, the isotacticity of the polymers decreased. The mechanism of the polymerization and the substituent effect of the stereoregula

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830112

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe stereoregularity of the polymers of ortho‐, meta‐, and para‐methylstyrenes prepared with various anionic catalysts was determined by means of13C NMR spectroscopy. The substituent effect on the stereoregularity was discussed comparing with that of polystyrenes obtained under the same polymerization conditions. Syndiotactic‐rich poly(methylstyrene)s were prepared with butyllithium in toluene and the syndiotacticity increased in the order of para‐, meta‐, and ortho‐derivatives. Although the structure of the polymers prepared with sodium‐naphthalene (Na‐naph.) in THF did not change with the position of the substituent, in toluene, however, the methyl group at ortho‐position influences the stereoregularity. The trend of the stereoregularity of the polymers produced by potassium‐naphthalene was almost the same as that of poly(methylstyrene)s prepared by Na‐naph. Nearly random polymers were obtained with the

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830113

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPolymerization of 1‐(4‐pyridyl)‐1,3‐butadiene (PyBu) initiated by 2,2′‐azoisobutyronitrile (AIBN) or butyllithium (BuLi) was studied. Radical polymerization gave poly(PyBu) of low molecular weight, soluble in chloroform, tetrahydrofuran, or methanol. PyBu was polymerized by BuLi more rapidly than by AIBN, but the produced polyanion was not living. IR and1H NMR spectra of poly(PyBu) indicate the presence oftrans‐1,4‐andtrans‐3,4‐units. The content oftrans‐1,4‐units was found to be 75 mole‐% (for radical polymerization) or 90 mole‐% (for anionic polymerization). From radical copolymerization with styrene the following reactivity ratios resulted:r1(PyBu) = 7,21,r2(styrene) = 0,12;Q= 6, 1 ande= −0,42 (for PyBu). Reaction of PyBu with ethyl bromide in benzene at 30°C produced a polyelectrolyte, as observed

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830114

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

Abstractα,ω‐Dimethoxycarbonyl substituted polyenes were synthesized by co‐metathesis between 1,5‐cyclooctadiene (1) and dimethyl 3‐hexenedioate (2) by use of the catalytic system WCl6/Sn(CH3)4. The ability of2for co‐metathesis with1was proved by determination of the distribution of low molecular weight products in terms of reaction time and2/1mole ratio. For these studies, high values of2/1ratios (0,5–4) were chosen in order to obtain lowest molecular weight co‐metathesis products (3b–3e). Metathesis involved preferentially the double bonds in the neighbourhood of the ester groups. At lower values of the2/1ratio (0,012–0,061) α,ω‐difunctional prepolymer

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830115

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe1H NMR spectra of poly(methyl acrylate‐d1) +CHDCH(COOCH3)+nwere measured ino‐dichlorobenzene and CDCl3in the temperature range between − 20 and 145°C. Trans and gauche coupling constant were determined from the temperature dependence of the geminal coupling constants, neglecting g' conformers. It was estimated that the proportion of trans conformer is 1,5 to 1,9 times that of the gauche conformer in this temperatu

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830116

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe intrinsic viscosities of a Gaussian chain with and without hydrodynamic interaction preaveraging and with the identification of the centre of gravity of the Gaussian coil with the chain center were calculated using Tsuda's theory. It appears that the value of the Flory constant is more affected by approximations used in the derivation of Tsuda's theory than by preaveraging of hydrodynamic interaction. Svetlov's theory was used in the calculation of the ratio of intrinsic flow birefringence to intrinsic viscosity. For unpreaveraged hydrodynamic interaction this quantity is lower by some 15–20% than for a free‐draining c

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830117

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractHomopolymers of 2,3‐epoxypropyl methacrylate with various molecular masses were prepared by solution polymerization with 2,2′‐azoisobutyronitrile as initiator. The effect of polymerization conditions on the molecular parameters (weight‐ and number‐average molecular massesMWandMnintrinsic viscosity [η]) and the tacticity of the resulting poly (2,3‐epoxypropyl methacrylate)s was investigated. For unfractionated polymers, the constants of the Mark‐Houwink equation for 1,4‐dioxane and tetrahydrofuran were determined. Gel permeation chromatography was tested as a tool for the determination of

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830118

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe presence of the α‐methyl group in the alternating methyl methacrylate‐styrene copolymer produces a remarkable difference in its13C NMR spectra as compared with the spectra of the alternating methyl acrylate‐styrene copolymer; cotacticity‐dependent splittings occur only in the former spectrum. A theoretical interpretation was attempted for this characteristic spectral variation in terms of the calculated time‐averaged chemical shifts for carbons in the dyads constituting the alternating copolymers. Each (meso or racemic) dyad sequence is considered to exist in several conformational states which are mutually exchanging rapidly and the probabilities of which are determined by a statistical mechanical procedure. The calculation of cotacticity‐dependent chemical shifts is conducted for the side chain carbonyl, aromatic C1and methoxyl carbons as well as for some main chain carbons to give good agreement with the observed peak splittings, especially with respect to the side chain carbons. In accordance with the reported assignment, the calculated differences in shielding factors between meso and racemic dyads for the side chain carbons of poly(methyl methacrylate‐alt‐styrene) are positive, i.e. the meso or isotactic peak appears at higher field than the racemic or syndiotactic peak. Furthermore, the resulting values are relatively large (≈0,63 ppm) in conformity with the experiment. The calculation for the carbons in poly(methyl acrylate‐alt‐styrene) gives a very small shielding difference (−0,04 to 0,06 ppm) by the dyad cotacticity, being consistent with the observation, i. e. ab

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830119

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractTacticity‐dependent splittings observed in1H and13C NMR spectra of poly(methyl methacrylate) are elucidated by a theoretical procedure which consists of conformational analysis of the polymer chain and shielding calculation. The conformation is analyzed by the statistical mechanical method combined with the force field energy calculation on the dyad sequence models. As significant shielding factors, diamagnetic, anisotropic, and electrostatic terms are taken into account for the chemical shifts of1H NMR, while paramagnetic, diamagnetic, and anistropic terms are considered for13C NMR. The calculation is used to assing the α‐methyl proton, methoxyl proton, methylene proton, quaternary carbon, methylene carbon, α‐methyl carbon, carbonyl carbon, and methoxyl carbon peaks split due to dyad and triad cotacticities. The results are generally consistent with the observed spectra. Especially, the calculated splitting widths are in quantitative agreement with the observed splittings of the methoxyl and α‐methyl protons resonances as well as of the carbonyl and α‐methyl carbons resonances. Effects of temperature and stereoregularity on the spectra are a

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830120

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY