摘要:

AbstractStudies of the effects of ring substituents in aromatic amineN‐oxide or amine modifiers on Ziegler‐type propylene polymerization catalyst performance are reported. Among sterically hindered amines orN‐oxides, theo,o‐dimethyl substituted derivatives provide the best stereospecificity with little loss in activity. On the other hand,m‐ orp‐substituted derivatives with electron‐withdrawing substituents were found to activate the catalyst, producing higher yields relative to the unmodified (TiCl3‐Al alkyl) catalyst system. The inductive and steric effects introduced by the modifiers in the catalyst system are discussed. Aromatic amineN‐oxides generally produce less active catalyst systems relative to their parent amines, owing presumably to a redox reaction between the N—

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830511

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

Abstractp‐Trimethylsilylstyrene was found to be polymerisable anionically. When the reaction is carried out at low temperature in THF as solvent the polymer—poly(p‐trimethylsilylstyrene)—is obtained in a quantitative yield and exhibits a low polydispersity. The glass transition temperature, viscosity‐molecular weight relationships, and1H and13C NMR spectra were investigated in order to compare the influence of the trimethylsilyl group located at the benzene nucleus with respect to polystyrene and some otherp‐subtituted polystyrenes. The presence of the trimethylsilyl group in para position of the aromatic nucleus results in an increase of the rigidity of the polymer chain and in an increase of the glass transition

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830512

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe microstructure of poly(α‐acetoxystyrene), prepared from α‐acetoxystyrene by bulk thermal polymerization, was studied by1H and13C NMR spectroscopy. Anomalies observed in the NMR spectra could be ascribed to fragmentations with formation of benzoxy and acetoxy radicals followed by re‐initiation. The thermal degradation of the polymer, resulting in the formation of polyphenylacetylene, rules out certain types of transfer. α‐Acetoxystyrene was copolymerized with styrene or substituted styrenes and the NMR study (1H and13C) was limited to α‐acetoxystyrene. The composition of the copolymer could be ascertained by means of the resonances of the quaternary carbons of the aromatic cycle. The copolymers were characterized by viscometry, GPC, and thermal degradation. Their compositions, except that of poly(α‐acetoxystyrene‐co‐styrene) were determined b

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830513

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe thermal degradation of polydisperse polystyrene samples with mol. wts. (M̄n) between 60000 and 22000 has been investigated at different temperatures under oxygen free conditions. Product analysis has been carried out by GPC. The experimental degradation could be simulated by a model consisting of scission and depolymerization. The dynamical behaviour of this model is expressed in a matrix from. The ratio of scission and depolymerization is constant for all polymers and different temperatures during degradation. Therefore, a master curve could be evaluated, which gives a general relation between the decrease of mol. wt. and the mass of volatiles. Finally a radical chain mechanism has been proposed in a lumped form which is consistent with the kinetic model and the experimental results

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830514

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractDielectric measurements were made in the frequency range from 30 Hz to 3 MHz for a series of the solutions of poly(2‐methylpent‐1‐ene sulfone) (PMPS) having two different molecular weights in benzene at 30°C. The unperturbed chain molecular dimension was estimated from dielectric relaxation time at the critical polymer contents,Ccr. This value of the unperturbed dimension was much higher than that from the intrinsic viscosity measurement. The dielectric motion atCcrinvolves simultaneous co‐operative reorientations of about three spheres. The number of the spheres of reorientation may be related to the flexibility of the molecular chain of the polymer. The ratio of two effective volumes of the polymer obtained from the unperturbed chain molecular dimension and from the dielectric relaxation time, τmagreed with that of the two effective volumes obtained from theKvalue in Onogi's treatment and from th

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830515

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

Abstractp‐Isopropylstyrene was homopolymerized or copolymerized with styrene using AIBN as initiator in benzene at 50°C. The resulting polymers were easily oxidized by oxygen to produce polymers having hydroperoxy groups. The oxidized polymer was found to have considerably different solubility from the original polymer. Kinetic evaluation of the oxidation reactions of poly(p‐isopropylstyrene) showed that the tertiary hydrogen of the isopropyl group present at the pendant aromatic ring was more susceptible to the oxidation reaction than the main chain methine hydrogen. The rate constants of these two oxidation reactions were found to be 4,0 · 10−4mol−1/2· l1/2· sAutoxidation reactions of polystyrene derivatives1/2and 2,5 · 10−4mol−1/2· l1/2· s−1/2, respectively. These values were much smaller than that for the tertiary hydrogen atom of the isopropyl group of cumene (3,21 · 10−3mol−1/2· l1/2· s−1/2, at 68°C), a low m

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830516

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe adsorption of trimethylammonium glycol chitosan iodide (TGCI) on Dowex CCR‐2 resin was investigated at different pH values and resin weights. The concentration of Na+or Ca2+ions, released by the ion exchange reaction with TGCI, was measured by inductively coupled plasma spectroscopy. It was found that the amount of the released ions is comparable to that of the absorbed TGCI. This indicates that the salt‐linkage formation of carboxylate ions of the exchanger with ⊕N(CH3)3‐groups in TGCI follows a stoichiometric relationship. This result is discussed in connection with the form of the polymer layer adsorbed on the solid

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830517

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPoly(2‐vinylnaphthalene) and poly(2‐tert‐butyl‐6‐vinylnaphthalene) having small fractions of 2‐vinylanthracene were prepared to examine the effect of bulkytert‐butyl groups on the intramolecular singlet energy transfer from naphthalene to anthracene chromophore. The steric interactions of thetert‐butyl groups were found not only to reduce excimer formation and thereby increase the donor lifetime, but to suppress energy migration through the donor chromophores, giving a significant reduction of the overall tran

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830518

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe electro‐optical properties of liquid crystalline polymers with polar mesogenic units in the side chain were investigated. It could be shown, that in an electric field, they show all effects known from low molecular weight liquid crystals, e.g. the Freedericksz‐transition, the DAP‐effect, the formation of William's domain, and the dynamic scattering. The optical response times are slightly longer than for low molecular weight liquid crystals, but in some cases at higher temperatures as short as 200 ms. By comparison of different polymers and some corresponding liquid crystalline monomers, it is found that: (1) the difference between the measuring temperature and the glass transition temperature mainly determines the optical response times, (2) the fixation of mesogenic groups to a polymer main chain via spacers influences the threshold voltage. Low values are found for long spacers. These results allow a discussion of the influence of polymer fixation of the mesogenic groups on their liquid crystalline properties, pointing to a partial decoupling of the motions of main chains and side c

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830519

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPhotochromic measurements are reported on the decay of the coloured form of 1′,3′,3′‐trimethyl‐6‐nitro[2H‐(1)‐benzospiropyran‐2,2′‐indoline] dispersed in poly(methyl methacrylate) and poly(ethyl methacrylate) matrices. Polarized light was used to photoselect molecules in specific orientations, and the data are analysed in terms of a free volume distribution controlling the kinetic matrix effect. A time correlation function is obtained which characterizes both the rotation and the isomeriz

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830520

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY