摘要:

AbstractOptically active isotactic polychloral was prepared in which the optical activity comes exclusively from molecular asymmetry (i.e., helical conformation). Molecular asymmetry requires a high conformational energy barrier for the polymer backbone, and an asymmetric initiator to induce a predominance of one helical screw‐sense. Polychloral meets the criteria. Asymmetric initiators used to obtain optically active polychloral include tetramethyl ammonium (+)‐ or (−)‐0‐acetylmandelate, tetramethylammonium (+)‐ or (−)‐0‐methylmandelate, the lithiumalkoxides of methyl (+)‐ or (−)‐mandelate, lithium cholesten‐3β‐oxide, lithium cholestan‐3β‐oxide, and lithium (+)‐ or (−)‐2‐octanoxide. Using the above initiators at 0.5 mol %, a maximum specific rotation of [α] D25= 5000 was obtained for polychloral. Erro

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985102

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractPoly(N‐acyl ethylenimine) of various molecular weights was synthesized by the cationic ring‐opening polymerization of 2‐H‐2‐oxazoline and 2‐methyl‐2‐oxazoline. Acid hydrolysis afforded the linear poly(ethylenimine) which was used in the following grafting reactions. Vapor pressure osmometry, gel permeation chromatography and viscosity measurements were used to characterize the polymers synthesized. Potassium 2‐(cytos‐l‐yl) propanoate and potassium 3‐(cytos‐l‐yl) butanoate were synthesized in good yield from thenucleic acid base. These cytosyl pendant groups were grafted onto the poly(ethylenimine) using 4‐chloro‐1‐(4‐chlorobenzenesulfonyl) benzotriazole, 90% graft, and norborn‐5‐ene‐2,3‐carboximido diphenyl phosphate, 70% graft. Grafting of thet‐butoxycarbonyl andn‐butoxycarbonyl protected cytosyl pendant groups resulted in a 47% graft. Hypochromicity studies indicated an ordered structure at the local level. The secondary structure is a base‐stacked conformation. Light scattering results gave insight into the tertiary structure of the macromolecule. The polymer exists in solution as stiff chains, rod‐like in nature. Continuous mixing experiments were carried out with polyribonucleotides. The Job plots indicated increased level of ordered conformation with either an increase in the molecular weight or an increase of the base to base distance in the analog. Enhancement in the base‐stacked conformation was higher in the polyinosinic ac

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985103

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThree topics on molecular design of functional polymers having amino groups will be discussed. The first topic is on the synthesis of functional isoprene oligomers with one amino end group. The best condition for the synthesis is to seed a small amount of the amino‐ended oligomer into a reaction system where isoprene was polymerized with lithium diisopropylamide as initiator. The highly active behavior of the amino‐ended oligomer as chain transfer agent was ascribed to a “macromolecular effect”. The second topic is concerned with a study on the soluble poly(1,4‐divinylbenzene) which was formed by polymerizing 1,4‐divinylbenzene with lithium diisopropylamide in the presence of excess diisopropylamine in THF. Structural analyses with 400MHz1H NMR and 25 MHz13C NMR showed that there were 2 or 3 branchings per 100 monomeric units along the main chain. Population of the triad tacticities suggested the steric course of polymerization to proceed according to the Bernoulli statistics with respect to diad placements,mandr. Third topic is on a polyamine macromer which was prepared by allowinganethylenediamine homologue, N,N′‐diethylethylene‐diamine (DEDA), to react with 1,4‐divinylbenzene in the presence of lithium diisopropylamide as catalyst. Results on syntheses and properties of polystyrene‐polyamine (SA) and poly(2‐hydroxyethyl methacrylate)‐polyamine (HA) graft copolymers will be presented with the emphasis on

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985104

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper deals with the ability of macromonomers to undergo polymerization and copolymerization with vinylic or acrylic comonomers.Polymacromonomers have been made by free radical or by anionic polymerization techniques. The species formed are branched, and characterized by high segment densities, which imply that their molecular dimensions are smaller than those of linear homologues of the same molecular weight.The free radical copolymerization of various types of macromonomers with low molecular weight comonomers was investigated kinetically. The graft copolymers obtained are homogeneous in composition, as it could be anticipated from the mole ratio of macromonomer to monomer used. Special emphasis was given to amphiphilic species, made of hydrophilic grafts attached to a hydrophobic backbone. These copolymers exhibit a strong tendency to form stable emulsions.

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985105

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe following applications of polymers carrying fluorescent labels are described: (1) Intramolecular excimer formation was used to show that conformational transitions take place at similar rates in polymer backbones and in analogous small molecules. (2) Nonradiative energy transfer between donor and acceptor labeled molecules was used to characterize polymer compatibility, chain entanglement in solution and the self‐diffusion of polymers. (3) The solvent dependence of the emission characteristics of the dansyl groups was used to study the equilibrium and kinetics of the association of dansyl‐labeled poly(acrylic acid) with polyoxyethyl

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985106

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractAbsorption spectra of poly(N‐vinyl‐carbazole) and related polymers in the excited singlet, triplet, cationic, and anionic states were measured by nanosecond and picosecond laser photolysis methods and compared with those of model bichromophoric compounds. Absorption spectral shape of the excited singlet and cationic states is a function of polymer structure and sensitive to relative geometrical structure of two carbazolyl groups. The excited singlet species in poly(N‐vinylcarbazole) are the sandwich excimer, the excited dimer with the partial overlap structure between two chromophores, and the so‐called second excimer. The formation process of the sandwich excimer consists of an instantaneous rise and a slow one with a time‐constant of a few hundred ps. The absorption spectrum of poly(N‐vinylcarbazole) cation can be reproduced by a superposition of absorption bands of the sandwich dimer cation, the dimer cation with the partial overlap, and the dimer cation with the open form. On the other hand, absorption spectra of the triplet and anionic polymers are similar to those of the corresponding monomer model compound, showing a very weak interchromophoric interaction. All these results indicate that electronic excitation and charge in these polymers are not delocalized over several chromophores but trapped in some monomer and dimer sites. Dynamic behavior such as conformational change, intersystem crossing, photochemical formation yield of ion radicals, and their decay kinetics was also studie

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985107

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe basic phenomena of fluorescence and fluorescence anisotropy decay (FAD) are briefly presented. The FAD technique is first applied to polybutadiene labelled with anthracene in the middle of the chain and embedded in a matrix of unlabelled polybutadiene; experiments are performed in the temperature range −50°C‐ +80°C. It is shown that the experimental data can be very well accounted for using the orientation autocorrelation function proposed by Hall and Helfand (6) for polymer chains. Studies performed on 9,10‐dialkylanthracene probes (with various lengths of the alkyl substituents) molecularly dispersed in a polybutadiene matrix, have shown that the dynamic behavior of the 9,10‐dihexadecylanthracene probe is very close to that of the labelled polybutadiene chain. This indicates that the 1‐dimension diffusion of orientation correlation along the chain, observed by FAD on labelled polybutadiene in bulk, involve rather short chain portions (about 6 monomer units). Furthermore, the temperature dependence of the correlation times of both anthracene labelled chains and anthracene probes with long alkyl substituents, is in agreement with the WLF equation used to describe the glass‐transition phenomena. Thus, these local reorientation processes observed in FAD correspond to segmental motions of polybutadiene chains which are involved in the macroscopic phenomenon of the gla

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985108

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe influence of Lewis bases on the stereospecificity and productivity of catalytic systems of the type MgCl2/TiCl4/AlR3as well as on microtacticity and molecular weight of the polymer fractions has been systematically investigated using propylene as monomer.The results are in keeping with the hypothesis that beside non stereospecific centers two types of stereospecific catalytic centers exist, in one of which the Lewis base is present.The centers can be classified according to their Lewis acidity, the more acidic centers yielding polymers with lower molecular weight and tacticity. The structure of the Lewis bases is of paramount importance in determining the stereospecificity of the catalytic systems and can be used as a probe to investigate the structure of the different catalytic centers.

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985109

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThis lecture summarizes some of our recent results about reactions with synthetic polymers. By cationic ring‐opening polymerization of 4H, 7H‐1,3‐dioxepin a linear polyacetal containing one C‐C‐double bond per repeating unit is obtained. Copolymerization of this monomer with trioxane or dioxolane is possible. Various addition reactions can be carried out with these unsaturated polyacetals, polymeric epoxides being of special interest. Some other unsaturated cycloacetals are briefly mentioned. Amide moieties in linear polyamides can be modified by different reactions. Preparation and properties of poly‐N‐chloroamides and poly‐N‐trifluoroacetyl‐amides are described. By reaction of metalated polyamides with alkyl halides poly‐N‐alkylamides are available. Anionic grafting reactions can also be carried out. Reduction of the amide groups leads to the formation of polyminoalkylenes. By topochemical polymerization of esters of 10,12‐docosadiyne‐1, 22‐diol soluble polydiacetylenes are obtained. These polymers react in homogeneous solution with SbCl5or FeCl3. Furthermore the hydrolysis of the ester groups and

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985110

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractWater‐soluble nonstoichiometric polyelectrolyte complexes (NPEC) are formed as a result of interaction of opposite charged polyelectrolytes used in nonequivalent ratios. One of the most important properties of NPEC is their ability to participate in intermacromolecular exchange and substitution reactions in aqueous solutions. The kinetics of exchange and substitution reactions has been studied by the method of luminescence quenching. It has been found that such reactions proceed by the contact mechanism and that addition of low molecular electrolytes to the reaction mixtures results in a dramatic increase in the rates of the reactions. The kinetics of the reactions is well described by the equation q = 1‐exp(‐ kt∝) (here q is the degree of conversion and ∝<1), deduced under the assumption that exchange and substitution occur by the nucleation mechanism and the development of nuclei is inhibited in time. The studied reactions represent a new class of interpolymer reactions and they can be very important, in particular, for understanding the mechanism of functioning of biologically important macromolecules and for the interpretation of the physiological activity of polyele

ISSN:0025-116X    

DOI:10.1002/macp.1985.020131985111

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY