摘要:

AbstractThe simplified necklace or the equivalent modified elastic dumb‐bell model with consideration of hydrodynamic interaction among the beads and its change with coil expansion was used for the calculation of the intrinsic stress tensor in laminar flow with transverse and parallel gradient as function of the conventional gradient\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}and the dimensionless gradient parameter β. The expansion of the Gaussian coil in flow first increases and then decreases the hydrodynamic interaction. As a consequence the intrinsic viscosity [η]trof sufficiently large macromolecules and the effective average hydrodynamic resistance coefficient Λ of the bead show first a decrease to a minimum and a subsequent gradually slower increase with the gradient. In laminar flow with parallel gradient this effect yields a deformational instability which may play some role in drag reduction of turbulent flow by polymer additives. Experimental evidence will have to conform or to refute these two interdependent phenomena. In the latter case, one suspects that the neglect of anisotropy of hydrodynamic interaction is the main cause of the unrealistic predictions of intrinsic hydrodynamic properties of polymer solut

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975131

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe polyethers poly(oxy‐1,3‐phenylene) (1), poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (2), poly(oxy‐2‐methyl‐6‐phenyl‐1,4‐phenylene) (3), poly(oxy‐2,6‐diphenyl‐1,4‐phenylene) (4), and poly(oxy‐2,5‐dimethoxy‐1,4‐phenylene) (5) were pyrolyzed in the direct inlet system of a mass spectrometer at temperatures between 563 K and 853 K. Statistical chain splitting is confirmed by the characteristic distribution of the thermal degradation products, namely monomers and oligomers. Chain splitting, leading primarily to radicals, is followed by fast stabilization reactions. Therefore, the pyro‐field ion mass spectra (PFIMS) show mainly fragments with hydroxy and phenyl end groups. In the polyethers2and3, the oxygen atom in ortho position lowers the strength of the bonds between the methyl side groups and the phenylene rings of the backbone. On fragmentation between monomeric units, one of the methyl groups at the point of chain break has the chance to change place to the newly established free end of the other fragment. In this way, fragments with both lack and surplus of a methyl group will be obtained. While the methoxy groups of5are easily split off, the overwhelming majority of the phenyl side groups in the polyethers3and4remain

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975132

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractDurch Messung der13C‐Spin‐Gitter‐Relaxationszeiten (T1) einzelner13C‐Kerne in Lösungen von statistischen und blockartigen Styrol/Butadien‐Copolymeren, Polystyrol und Polybutadien zeigt sich, daß die Segmentbewegung durch die Sequenzlängenverteilung beeinflußt wird. DieT1‐Werte der 1,4‐Butadienstruktureinheiten an Nahtstellen mit Styrolbzw. 1,2‐Butadieneinheiten unterscheiden sich von denT1‐Werten der 1,4‐Butadieneinheiten in Blocksequenzen. Zur13C‐Spin‐Gitter‐Relaxation tragen daher lokale, von der Struktur aufeinanderfolgender Monomerbausteine abhängige Konformationsänderungen bei. In den Styrol/Butadien‐Copolymeren erfolgt die Relaxation derortho‐Phenyl‐C‐Atome langsamer als diepara‐Phenyl‐Relaxation. Die wird gedeutet durch eine Rotationsbewegung der Phenylringe um die Achse, die durch die Bindung zwischen Phenyl und Kette gegeben ist. Die Rotation verläuft et

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975133

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractA normal vibration analysis has been carried out for crystallinesyndiotacticpoly(vinyl chloride) and its deuterated derivatives. This was based on a general valence force field derived from an analysis of the spectra of small secondary chloride molecules. The calculations permit a very satisfactory assignment to be made of the observed bands in the IR and Raman spectra, including the low frequency region.

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975134

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractIn den IR‐Spektren von 2‐substituierten Propen (1)‐Copolymeren des Typs (CH2C(CH3)R)(R = CH3, C6H5, CN, COOR) mit Styrol bzw. Acrylnitril wurde im Bereich 1250–1200cm−1eine intensive Absorption gefunden, die Aussagen über die Länge der 2‐substituierten Propylen‐Sequenzen gestattet. Die für das Erreichen der vollen Bandenintensität notwendige Sequenzlänge liegt bei ca. 5 Monomereinheiten. Die große Intensität weist auf Schwingungskopplung innerhalb einer bevorzugten Kettenkonformation (T+G′+T+G′+oder T+T+G′+G′+) (T =trans, G =gauche) hin, die durch das große Volumen der CH3‐ und R‐Gruppen stabilisiert wird. Bei kürzeren Sequenzlängen nimmt die Intensität der Bande, bei gleichzeitiger Verschiebung nach höheren Wellenzahlen, ab. Die Bande wird der CC(CH3)RC‐Gerüstschwingung zugeschrieben, wobei die Schwingungsart der isolierten Einheit etwa der n3(

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975135

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractSome solid‐state reactions which give rise to the formation of polymer crystals are discussed and the observation of the nascent polymer morphology is used as a guide‐line to learn about the reaction mechanism of solid‐state polymerizations. Examples for the following three different mechanisms are treated in detail: (a) crystallization succeeding polymerization, (b) simultaneous polymerization and crystallization, and (c) polymerization in solid solution.The nascent morphology of poly(alkylene)s obtained by Ziegler‐Natta catalysis is taken as an example forcrystallization succeeding polymerization. Another example is the cationic polymerization of 1,3,5‐trioxane from solution. In this case a thermodynamic equilibrium between the phases of the solid crystalline polymer and the dissolved monomer is approached; here, by breaking up chain folds and insertion of monomeric units, an increase in thickness of the crystals takes place, which finally leads to extended chain crystals by this transacetalization.The solid‐state polymerization of 1,3,5‐trioxane and 1,3,5,7‐tetroxane as induced by high‐energy radiation or catalysts is described as an example forsimultaneous polymerization and crystallization. Possible molecular models of the chain growth are developed on the basis of the morphological observations. Truly extended chain crystals of poly(oxymethylene), (POM), cannot be obtained generally from solid 1,3,5‐trioxane or 1,3,5,7‐tetroxane; the reason for this is either chain‐folding (density fluctuation along the fibre axis) or “twin”‐structure formation (orientation fluctuation). The nature and origin of the “twin”‐structure of POM from crystalline 1,3,5‐trioxane is discussed in detail.Topochemical polymerization of monomers with conjugated triple‐bonds is an example forpolymerization in solid solution. The polymer chains grow as isolated macromolecules within the monomer lattice. Since quantitative conversion can be reached in some cases without phase separation, this comprises a method to produce macroscopic, extended chain polymer single crystals, which so far

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975136

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractHermann Markpointed out in 1940H. Mark “Allgemeine Grundlagen der Hochpolymeren Chemie” Akad. Verl. Ges. Leipzig, S. 203 (1940).that up to then there did not exist a relevant method for the quantitative evaluation of the size and the lattice distortion of coherently scattering domains in a polymer. Until now usually one speaks of “crystalline” and “amorphous” domains within a polymer. The domains which scatter coherently are considered to be crystalline and it is out of consideration, that lattice distortions exist which are of fundamental interest in the understanding of the properties of polymers. It is the aim of this contribution to show that these distortions can be explained quantitatively by the theory of paracrystals. A series of misunderstandings are discussed which exist in the literature. Some results of the application of this theory to synthetic polymers are discussed which seem to be of fundament

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975137

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe change in the fraction crystallinity with time and elongation of syntheticcis‐1,4‐polyisoprene is studied through simultaneous measurement of birefringence and stress. Results are compared with values estimated from the decrease in stress arising from the crystallization. Various methods for calculating the crystallinity from the data are compared. This method proves to be a sensitive, convenient method for determination of crystallinity of such samp

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975138

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe elastic moduliEtof crystal lattices of polymers perpendicular to molecular chain axis are dependent on the intermolecular forces, and can be determined by an X‐ray diffraction method. At first, the assumption of “homogeneous stress distribution” used in the evaluation ofEtwas confirmed experimentally. TheEtvalues of a number of well known polymers were compared and discussed from the viewpoint of intermolecular forces. Hydrogen bonding and dipole forces increasedEt, whereas disorders in the crystal lattices and linear side chains decreasedEt. As a particular application ofEtit can be employed to discriminate whether a comonomer component of a copolymer can enter the crystal lattice o

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975139

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractDurch Zusatz von bestimmten organischen oder anorganischen Substanzen kann die Sphärolithgröße von Trioxan/Äthylenoxid‐Copolymeren verringert werden. Dies bewirkt nicht nur eine Erhöhung von Härte und Streckspannung, sondern führt auch zu einer Steigerung der Stoßfestigkeit. Aus lichtmikroskopischen Untersuchungen von Mikrotomschnitten aus vergleichbaren Bereichen von Spritzgußplatten sowie durch Löseversuche in γ‐Butyrolacton und durch Untersuchungen der ursprünglichen sowie der mit HCl‐Gas angeätzten und versilberten Bruchflächen wird die Hypothese gestützt, daß der Bruch beim Fallversuch überwiegend an den Sphärolithgrenzen erfolgt. Versuche mit in der Polymerschmelze gelösten Farbstoffen zeigen, daß eine Anreichung von niedermolekularen Zusätzen (Stabilisatoren, Pigmente) sowie von Oligomeren in den Bereich zwischen den einzelnen Sphärolithen erfolgen kann. Aus der Verfolgung des Sphärolithwachstums ergibt sich dagegen, daß keine Anreichung von äthylenoxidreichen Copolymerisaten an den Sphärolithgrenzen erfolgt. Die Anwesenheit der genannten niedermolekularen Substanzen an den Sphärolithgrenzen ist für die Ausbildung

ISSN:0025-116X    

DOI:10.1002/macp.1975.020011975140

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY