摘要:

Abstract(A‐B)n‐Block copolymers containing oligosaccharide blocks (A) and synthetic polymer blocks (B) coupled by amide linkages were synthesized. As starting material fully substituted cellulose and amylose derivatives with protecting groups of variable stability were used: triacetates, tricarbanilates and trimethyl ethers. The reaction steps were as follows: (i) trisubstituted oligosaccharides in the range of 2

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890901

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractSeveral series of thermotropic copolyesters with different spacers, containing the moieties of 1,4‐butanediol(4aor4b), 1,6‐hexanediol(6aor6b), bisphenol‐A(10a), bisphenol‐S(10b)or a telechelic polysulfone(12aor12b)were synthesized. The mesomorphic properties of the resulting copolyesters were examined by visual observation of stir‐opalescence and birefringence under a polarizing microscope. Copolyesters4a, 4b, 6aor6bwith mole fractions of mesogenic units over a broad extent (≥0,2) being thermotropic within wide mesomorphic temperature ranges, regardless of the spacers based on 1,4‐butanediol or 1,6‐hexanediol, have microstructures of block sequence distribution and do not retain liquid‐crystallinity if the mean lenghts of mesogenic segments are shorter than that of the triad with three phenyl rings. For the thermotropic copolyesters10a, 10b, 12aor12bthe minimum mole fraction of mesogenic units needed is not higher than 0,10, despite of the different varieties and lengths

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890902

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractDifunctional poly(dimethylsiloxane) (PDMS) macromonomers were synthesized. Emphasis was put on the synthesis of short PDMS chains exhibiting a narrow molecular weight distribution. This was achieved by the selection of an efficient initiator and under polymerization conditions such as to minimize reshuffling reactions. The macromonomers were subsequently obtained by deactivation of the living sites with an electrophilic unsaturation. Accurate characterization of the macromonomers (GPC, end‐group analysis) was performe

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890903

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA novel approach to the production of chiral, polymeric crown ethers incorporating D‐mannitol moieties was developed. Three optically active divinyl ethers(3, 6and9), derived from 1,3 : 4,6‐di‐O‐benzylidene‐, 1,2 : 5,6‐diisopropylidene‐ and 1,4 : 3,6‐dianhydro‐D‐mannitol(2, 5and8)were polymerized with cationic catalysts. The cyclopolymerization led to the chiral polymeric crown ethers4, 7and10consisting of only cyclic constitutional units. Both monomer9and polymer10, containing 1,4 : 3,6‐dianhydro‐D‐mannitol moieties are amphiphilic compounds. Polymer4with 1,3 : 4,6‐di‐O‐benzylidene‐D‐mannitol moieties was found to exhibit chiral recognition in favour of the (S)‐isomer of racemic ester salts of phenylglycine, phenylalanine, valine and methionine. The ability of chiral recognition, which was estimated as enantiomer distribution constants (EDC), is comparable to that of polymeric crown eth

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890904

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe oxidation of atactic poly(2‐methylthiirane) (PPS,M̄w≈ 1 – 2 · 105) to its corresponding sulfoxide (PPSO) is studied under a variety of experimental conditions:m‐chloroperbenzoic acid in homogeneous chloroform solution ( − 7°C) and hydrogen peroxide or bromine in an interfacial chloroform‐water system (20°C) lead to selective and quantitative oxidation under stoichiometric conditions with simultaneous chain degradation (M̄w(PPSO) ≈ 0,5 – 3 · 104). The high density of sulfoxide functions affords to the PPSO chain a number of specific properties such as: (a) solubility in dipolar protic (CH3OH, CHCHl3…) and aprotic (DMF, DMSO) solvents, the polymer coils being, however, strongly associated in aqueous solution, (b) strong polarity of the bulk polymer, as shown by an “apparent local dipole moment” of about 4,1 D, (c) poor thermal stability, degradation starting at about 130°C under nitrogen, with a weight loss of 50% at 160°C (apparent activat

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890905

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe syntheses and properties of a series of para‐linked aromatic homopolyesters with 2,2′‐dimethylbiphenylylene units are described. In the 2,2′‐dimethyl‐substituted biphenylylene unit the phenyl rings are forced into a non‐coplanar conformation, which decreases the interchain interactions. The combination of such a biphenylylene unit with a monosubstituted unit further reduces the regularity of the substituents along the polyester backbone. As a result, soluble and completely amorphous liquid‐crystalline (LC) aromatic polyesters with low phase transition temperatures are obtainable. Ternary solutions, consisting of a soluble aromatic LC polyester, a conventional randomly coiled thermoplastic and chloroform as solvent, can be used for the preparation of f

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890906

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractPreviously synthesized 2,3‐epoxypropyl esters were used to modify polymethacrylic and alginic acids. This way of synthesis led to polymers whose structure can be compared to that of polymers obtained from the reaction of acids with polymers bearing the same type of oxirane rings, the active molecule being linked to the polymer backbone through a glycerol spacer. As for the preceding studies, the reaction was investigated from a chemical and kinetical point of view with epoxypropyl esters of acetic acid and 1‐(4‐chlorobenzoyl)‐5‐methoxy‐2‐methyl‐3‐indolacetic ac

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890907

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractPolyetheresteramides (PEEA) on the basis of polyamide 12 and oligotetrahydrofuran (OTHF) may be referred to as intrinsically plasticized and intrinsically impact strength toughened thermoplastic elastomers. This is due to their special 4‐phase morphology consisting of two pure crystalline and two mixed amorphous phases, which was completely analysed by various TEM preparation techniques. PEEA containing more than 50% PA 12 hard segments exhibit a space filling dendritic superstructure of lamellar crystallized hard segments. In the range of 50 – 30% PA 12, the dendrites become more and more isolated, and below 30% PA 12 only single lamellae can be observed. The matrix in all PEEA is an amorphous, PA 12‐rich mixed phase (“OTHF‐plasticized PA 12”) located between the hard segment lamellae. An amorphous OTHF‐rich mixed phase is very finely dispersed in PEEA and acts as an intrinsically impact strength toughening modifier. Lamellar crystallized soft segments could be imaged by TEM in this dispersed phase, but only in PEEA products with a higher molecular OTHF and at sufficient low

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890908

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractLight scattering and viscometric measurements were performed for the system isooctane/poly(decyl methacrylate) of weight‐average molecular weightM̄w= 250 000 within the concentration regime of pair interaction between the macromolecules in the temperature range from 25°C to 100°C. In case of the intrinsic viscosities [η], the pressure was varied up to 3500 bar. Under isobaric conditions, the osmotic second virial coefficientsA2,the z‐average radii of gyrationrzand [η] pass through a maximum, the Huggins coefficientkHthrough a minimum, with variation of temperature. These extrema indicate a change in the heat of dilution from endothermal at low, to exothermal at high temperatureT. The calculation of the temperature dependence of the intrinsic viscosity [η] (T) for isochoric conditions does not yield a maximum, provided the pressure at the lowest temperature is chosen close to atmospheric pressure; it can, therefore, be concluded that the change in the sign of the enthalpy is in this case only due to the free volume of the system which increases markedly with increasingT.For pressures larger than ≈700 bar, maxima are always observed, no matter whether the temperature is changed isobarically or isochorically. All parameters under investigation are closely interdependent: A one‐to‐one correspondence exists between [η] andA2at 1 bar, andkHand [η] interrelate linea

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890909

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

Abstract29Si NMR spin‐lattice relaxation time (T1) measurements were performed with asymmetrically substituted oligomeric cyclosiloxanes (MeRSiO2/2)n(with R = phenyl,n= 3 and R = H,n= 4 – 6). Temperature‐ and field‐dependend measurements allow separation into different relaxation mechanisms. Based on these results, molecular correlation times τcwere calculated. The methyl‐H cycles were found to be more mobile than the methyl

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890910

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY