摘要:

AbstractInterfacial condensation polymerization of bischloroformates of bisphenol A with bisphenol A results in the formation of cyclic aromatic polycarbonates of high molecular weight. Products made by this technique show a significant reduction (up to 95%) in their end group content. Also, in comparison to molecular weights determined by light scattering, these products show markedly lower molecular weights by solution viscocity measurements and by applying the Mark‐Houwink equation for linear polycarbonates. The existence of high molecular weight cyclic polycarbonates is confirmed by a controlled saponification reaction using piperidine as a basic compound. The saponification reaction causes nearly no change in the number average molecular weight of the polymer and causes an increase in the number of end groups of up to 2 end groups per molecule. The observed increase in the intrinsic viscosity data is similar to what would be expected from linear polycarbonates. It is shown that cyclic polycarbonates with molecular weights exceeding 100 000 are easily obtaine

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810111

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe preparations of 2,4‐bis(4‐bromophenyl)pentane (1b) and 2,4,6‐tris(4‐bromophenyl)heptane (2b) are described. The study of the different isomers of1band2bby13C NMR allows a comparison of the various configurational sequences of these compounds in terms of their chemical shifts. Methyl, methylene, and aromatic C1carbons of1band2bcould be deduced from the values obtained from corresponding polystyrene model compounds by a mere translation. From the aromatic C1chemical shifts it was possible to propose an assignment of the corresponding triads of poly(4‐brom

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810112

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe spontaneous thermal polymerization of methyl methacrylate (MMA) is accompanied by the production of serveral oligomers among which a linear unsaturated dimerH‐1(dimethyl 1‐hexene‐2,5‐dicarboxylate) is predominant. The reaction kinetics of this dimer formation was investigated in bulk and in solution. The temperature dependence of the second order dimerization constant was determined as\documentclass{article}\pagestyle{empty}\begin{document}$$ \log _{\rm e} k_{{\rm H} ‐ 1} = 13,11 ‐ \frac{{107,2{\rm }{{{\rm kJ}} \mathord{\left/ {\vphantom {{{\rm kJ}} {{\rm mol}}}} \right. \kern‐\nulldelimiterspace} {{\rm mol}}}}}{{RT}} $$\end{document}Reaction mechanisms for the thermal dimer formation of MMA are di

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810113

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractUsing a bifunctional initiator such as the tetrameric dianion of α‐methylstyrene for the anionic polymerization of methyl methacrylate the rate constant is found to increase with conversion approaching that observed with a monofunctional initiator while the tacticity of the polymers obtained changes from that of an almost ideally atactic to a highly syndiotactic polymer. The results are explained by the assumption of an intramolecular association of the two terminal ion pairs yielding a new active species and gradually dissociating with increasing degree of polymerization of the chain. Using a polymeric dianion of α‐methylstyrene as an initiator the association phenomenon is not obs

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810114

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

Abstract13C NMR has been used to study the helix‐coil transition induced in polypeptides by trifluoroacetic acid. An attempt is made to separate the influences of conformational change and direct solvent interaction. For poly(γ‐methyl‐L‐glutamate), interactions between trifluoroacetic acid and the ester group of the side chain occur in the helical region. Poly(L‐norvaline) and poly(L‐norleucine) are in the form of “partially distorted helical conformation”. Conformational change and the interaction between trifluoroacetic acid and the peptide group which accompany the helix‐coil transition, affect the chemical shift difference up to Cδor Cβof poly(L‐norvaline) and poly(L‐norleucine), On the contrary, in the case of polyglutamates and polyaspartate, these effects are minor for the carbons in the ester portion. The chemical shift differences of these polypeptides can be well interpreted qualitatively by the results for some butyrates, poly(L‐norvalin

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810115

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe origin of the chemical shift differences of carbons in polypeptides which accompany the helix‐coil transition has been investigated by using oligopeptides, benzyloxycarbonyl‐γ‐ethyl‐L‐glutamyl‐diethyl‐L‐glutamate and benzyloxycarbonyl‐di‐(γ‐ethyl‐L‐glutamyl)‐diethyl‐L‐glutamate, as models of the backbone of polypeptides. Structures of aggregates in deuterated chloroform were proposed for these oligopeptides on the basis of concentration dependence and temperature dependence of the chemical shifts of protons and carbons, and spin‐lattice relaxation times. Antiparallel and/or parallel “in‐register” structures for extended forms and “out‐of‐register” network of extended forms are coexisting in deuterated chloroform solution for these oligopeptides. From the shift for the carbons of the oligopeptides induced by organic acids, it was in ferred that down‐field shifts are induced at α and amide carbons in polypeptides by organic acids. By comparing the induced shift of the carbons in the peptides with the chemical shift differences of the carbons in polypeptides which accompany the helix‐coil transitions, it was found that the conformational changes play a predominant role in the origin of the chemical shift differences of the carbons in polypeptides which accompany the helix‐coil transitions, it was found that the conformational changes play a predominnant role in the orgin of the chemical shift d

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810116

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractIn order to clarify the arrangement of sulfated poly(vinyl alcohol) (PVS) chains about the α‐helical poly(L‐lysine) (PLL) chain in the previously reported complexes of PLL/46 mole‐% sulfated poly(vinyl alcohol) (PVS‐46) and PLL/PVS‐95, induced circular dichroism was studied on PLL/PVS/acridine orange (AO) complexes in acidic aqueous solution. A positive ellipticity, [θ], of ca. 3 400 deg·cm2·dmol−1at 465 am and small negative values of [θ] at 435 and 510 nm indicated a right‐handed super helical arrangement of AO molecules about the right‐handed α‐helix of PLL, where PVS chains were intercalated. The amount of AO molecules responsible for the induced CD was estimated as low as a few mole‐%. Taking into consideration the arrangement of ε‐amino groups of the right‐handed α‐helical PLL and the distance among the neighboring ε‐amino groups on the radial projection of the helix, the PVS chain segments could be arranged both in the right‐handed and in the left‐handed superhelices about the right‐handed α‐helix of PLL. In cases of the PLL/PVS‐25/AO and PLL/PVS‐30/AO complexes, no induced CD and a quite weak CD were obtained, resp., being consistent with random coil conformation of PLL in the PLL/PVS

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810117

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractOptically active copolymers of (−)3‐menthyl acrylate (MtA) and (−)3‐menthyl methacrylate (MtMA) with styrene (St) of different compositions were prepared by radical initiation. The reactivity ratios were determined by the least square evaluation of the Kelen‐Tüdös parameters. Substantially alternating copolymers by donor‐acceptor complex polymerization and the corresponding model compounds were also prepared. Spectroscopic and chiroptical properties of these copolymers and models were studied. The possible mechanisms of the generation of the induced dissymmetry of the longest wavelength π → π*electronic transition of the aromatic chromophore of St co‐

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810118

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe gaschromatographic retention behaviour of a series of solutes with potential hydrogen bonding activity has been studied, using polyethylene, poly(ethylene‐vinyl acetate), poly(vinyl acetate), and poly(ethylene glycol) as stationary phases. Measurements were performed at various temperatures above the melting point and/or glass transition temperature of the polymers and the slopes of the lnV 0gversus 1/T‐functions (whereV 0gis the specific retention volume) were used to calculate partial molar heats of solution (ΔHs). Correspondingly, the temperature dependence of the activity coefficient can be used to calculate partial molar heats of mixing (ΔH̄1infin;) of the solute at infinite dilution in the polymer. Based on a “homomorph” concept with the inherent assumption of additive group contributions to the total interaction energy, hydrogen bonding energies of polymer‐solute systems could be separated using polyethylene on one hand and appropriate model solutes on the other hand as ref

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810119

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractUsing a set of laboratory poly(acrylamide) samples in the molecular weight region M̄w= 5.105to M̄w= 6.106the following relations have been established, the polymer concentration c given in g/cm3:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {[\eta ] = 4,9 \cdot 10^{ ‐ 3} \bar M_{\rm w}^{{\rm 0,8}} } \hfill & {\rm,} \hfill & {{\rm solvent: H}_{\rm 2} {\rm O, temp}{\rm .: 298 K}} \hfill \\ {[\eta ] = 7,19 \cdot 10^{ ‐ 3} \bar M_{\rm w}^{{\rm 0,77}} } \hfill & {\rm,} \hfill & {{\rm solvent: 0,5 M aqueous NaCl, temp}{\rm .: 298 K}} \hfill \\ {[\eta ] = 1,36 \cdot 10^{ ‐ 1} \bar M_{\rm w}^{{\rm 0,54}} } \hfill & {\rm,} \hfill & {{\rm solvent: ethylene glycol, temp}{\rm .: 298 K}} \hfill \\ {s_0 = 0,9 \cdot 10^{ ‐ 1} \bar M_{\rm w}^{{\rm 0,32}} } \hfill & {\rm,} \hfill & {{\rm solvent: 0,5 M aqueous NaCl, temp}{\rm .: 293 K}} \hfill \\ \end{array} $$\end{document}([η], intrinsic viscosity;s0, sedimentation constant) Mainly based on light scattering experiments a more detailed description on molecular dimensions and solution structure of PAAm/H2O and PAAm/ethylene glycol systems is given. In both systems the relationa= 3v− 1 (aandvbeing the exponents of the intrinsic viscosity — and root‐means‐square end‐to‐end distance — molecular weight

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810120

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY