摘要:

AbstractPara‐linked aromatic polyhydrazides and poly(amide‐hydrazides) can be dissolved in sulfuric acid of about 100% concentration to form liquid–crystalline solutions, and if the solutions are not heated excessively, they are reasonably stable and can be spun into strong fibers. Similar results can be obtained in fluorosulfonic acid and its admixtures with sulfuric acid. Polyhydrazides and copolyhydrazides based on oxalyl, terephthaloyl, chloroterephthaloyl, and 2,5‐pyridinedioyl units and poly(amide–hydrazides) based in part on such intermediates as 4‐aminobenzhydrazide and terephthalic dihydrazide were examined for formation of optically anisotropic solutions. Polymers with high proportions of meta‐ and ortho‐linked ring units were highly soluble but did not yield liquid–crys

ISSN:0360-8905    

DOI:10.1002/polc.5070650103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractAromatic polyamides of the AB, AA–BB, and ordered copolyamide types plus aromatic hydrazide and amide–hydrazides were prepared via the phosphorylation reaction. The relationship of the molecular weight, as evidenced by the inherent viscosity values obtained, of the several polymers to the structural features and properties of the monomers used and the polymers obtained is discussed in detail. Some salient observations are that poor solubility of the rodlike polymers definitely appears to set limits to obtaining high molecular weight and strongly basic groups, e.g., —CO—NH—NH2, in monomers, prevent the attainment of high molecular weight because such groups coordinate more strongly with the phosphite complex than does the pyridine catalyst in the phosphorylation reaction. Fibers were spun from two aromatic polyamides prepared via the phosphorylation reaction. Excellent tensile properties were achieved for fiber from poly–p–benzamide (PPB) and the polyisophthalamide of 4, 4′‐methylenedianiline despite the relatively low molecular weight of these polymers (?7inh 1.6 and 1.1, respectively). The PPB fiber was spun from both isotropic and anisotropic spinning solutions. Fiber obtained from the anisotropic dope had moderately high tensile strengths (8–12 gpd) and remarkably high initial modulus values (435–745 gpd). These results indicate that polymers made by the phosphorylation route would give fibers with as high tensile properties as polymer made by the diacid chloride‐diamine polycondensation route providing that the inherent viscosities of polymer prepared by the former process could be increased to equal thos

ISSN:0360-8905    

DOI:10.1002/polc.5070650104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractAromatic polyamides are being extensively studied in our laboratories along the lines of synthesis, dilute solution viscosity and light scattering, concentrated solution optical and rheological measurements, and wet spinning of fibers. Several series of polymers have been synthesized, including those starting with chloro‐ and methyl‐substituted p‐phenylene diamine and also those starting with the monomer bisacid A2. Poly(chloro‐p‐phenylene terephthalamide) in dilute solution shows a marked hydrodynamic volume dependence on solvent when studied in DMA–5% LiCl versus H2SO4At higher concentration, optical characterization shows that liquid crystal formation in the quiescent state corresponds to changes observed in the rheological behavior for Kevlar–H2SO4solutions; these observations include a yield stress and the inversion of the order ofG/G' = tan 5. Fibers produced by wet spinning and subsequently studied in cross section via SEM have revealed that material continuity is easily attained with Kevlar‐H2SO4spinning dopes under a variety of proces

ISSN:0360-8905    

DOI:10.1002/polc.5070650105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe reaction product ofm‐cresol and phosphorus pentoxide has been shown by31P‐nmr to consist of an equimolar mixture of mono‐ and di‐m‐cresyl phosphate. A mixture of pure di‐m‐cresyl phosphate andm‐cresol is an excellent polymerization medium for the preparation of polyquinolines via the Friedländer reaction, giving higher‐molecular‐weight polymers than can be obtained from the crude reaction ofm‐cresol and phosphorus pentoxide. Spin‐lattice relaxation timesT1have been used to relate the chain mobility of the polymers in solution to the glass transition tempe

ISSN:0360-8905    

DOI:10.1002/polc.5070650106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractRigid‐chain polyacenaphthylene (PAcN) was synthesized by a novel emulsion polymerization method that besides water and the sodium oleate emulsifier consisted of a water‐soluble initiator, K2S2O8, and the water‐insoluble (at the polymerization temperature 50°), crystalline monomer acenaphthylene. The molecular weight of the emulsion PAcN was 150, 000 by gel permeation chromatography (gpc). With the exception of a C13nuclear magnetic resonance study, the PAcN was characterized in the bulk state by infrared spectroscopy and x‐ray and electron diffraction. The C13nmr spectrum in solution suggests a macromolecular association. The infrared spectra indicate that the PAcN can be either paracrystalline or amorphous. An amorphous infrared band at 670 cm−1was identified. The emulsion PAcN is predominantly threo‐disyndiotactic, and it is possible, therefore, to have a mesophase of nematic type in the bulk state. The paracrystallinity or ordered structure of PAcN is supported by wide‐angle x‐ray and electron diff

ISSN:0360-8905    

DOI:10.1002/polc.5070650107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe polymerization of phenylacetylene initiated by ferric acetylacetonate and triethylaluminum was studied over the temperature range −30°−70°, in bulk as well as in the presence of diluents, and over a range of catalyst compositions and concentrations. The product consisted of four major fractions: crystalline polymer of molecular weight about 7000 and a very narrow molecular‐weight distribution (MWD), (fraction I); somewhat lower‐molecular‐weight amorphous polymer with a broader MWD (fraction II); linear oligomer (fraction III); and the asymmetric cyclic triphenyl‐benzene (fraction IV). The average degree of polymerization, of fraction I (65–70) is independent of all polymerization variables, that is, temperature from −30° to 70°C, the presence or absence of diluent (tetralin or benzene), and catalyst concentration and composition. The MWD is narrow with M̄w/M̄nequal to 1.05 or less. The results suggest that thermodynamic rather than kinetic factors limit the size of the polymer. A possible

ISSN:0360-8905    

DOI:10.1002/polc.5070650108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractCrystals of poly(5, 7–dodecadiinediol‐1, 12–bisphenylurethane) are monoclinic, P2/1a. The crystal structure has been determined and refined by full matrix least‐squares analysis of diffractometrically measured intensities. The finalRindex is 0.081 (719 observed reflections). Intramolecular hydrogen bonding, a strong contribution of electron delocalization in the polymer backbone, and unusual C—C bond lengths in the side chain are observed. Polymerized crystals of o,o′‐bisphenyl glutarate diacetylene crystallize in a C2/c monoclinic space group. The x‐ray refinement reveals a solid solution of the monomer and polymer. It was determined that the only movement that occurs during polymerization is in the diacetylene rod (a rotation of 33°) and in adjacent phenyl groups (a rotation of 19° and a swing of 6°) and all other atomic positions in the side group remain essentially the same. An infrared investigation and the final refined atomic coordinates with their standard deviations indicate the BPG crystal was polymerized to an extent of 35%. The finalRindex is 0.075 (902 observed reflections). Again a strong contribution of electron delocalization in the polymer ba

ISSN:0360-8905    

DOI:10.1002/polc.5070650109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractSome applications of depolarized light‐scattering spectroscopy to the study of rigid macromol‐ ecules in solution are described. The depolarized light‐scattering method can be used to obtain ro‐ tational diffusion coefficients and static and dynamic correlation factors of rigid macromolecules. In molecules exhibiting some flexibility, intramolecular conformational relaxation times may also be obtained. Dynamic polarized light‐scattering measurements give the orientation averaged translational diffusion coefficient. With the Perrin relations for spheroids, the rotational and translational diffusion coefficients may be combined to yield the macromolecular solution dimensions. In addition, changes in rigidity and shape of rigid macromolecules may be observed by measuring changes in the depolarized spectrum. For instance, the total depolarized intensity and relaxation time usually decrease when a helical molecule is denatured to a flexible form. The rotational diffusion coefficients obtained by light scattering may also be combined with relaxation times obtained by other techniques such as nuclear magnetic relaxation to draw inferences about molecular rigidity and loca

ISSN:0360-8905    

DOI:10.1002/polc.5070650110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractWe present a primitive model that describes a cooperative helix‐coil liquid–crystal phase transition. Consider a solution of macromolecules that individually undergo a helix‐coil “transition” as a function of some external parameter such as temperature or pH. At some given value of the parameter, the chain is composed of a statistical distribution of rigid (helical) segments and flexible coiled segments. We then suppose that there exists an intermolecular Maier‐Saupe type of quadrupole‐quadrupole interaction between the rigid sections that derives from excluded volume and van der Waals forces. In terms of a mean‐field approximation, we investigate the possible phase transitions as a function of polymer concentration. In particular, we show that the intermolecular coupling may lead to a first‐order transition in which the macromolecules make a transition from a nearly coiled to a nearly rigid conformation accompanied by the simultaneous development of a long‐range nematic type of liquid‐crystallin

ISSN:0360-8905    

DOI:10.1002/polc.5070650111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe helical polyamino acids exhibit a two‐component temperature‐composition phase diagram that corresponds well in overall appearance to the Flory prediction for rigid, impenetrable rods. The phase diagram may be characterized as a narrow, typically 1–2%, biphasic region separating the disordered (isotropic) state from the ordered (liquid–crystalline) state, connected to a wide biphasic region in which nearly pure polymer is in equilibrium with nearly pure solvent. Initial studies have been undertaken to deduce the kinetics of formation of the ordered phase, both when the thermodynamically stable state is the ordered state, as well as when it is in an ordered‐disordered biphasic state. The time course of the formation of the ordered phase at different temperatures is reminiscent of analogous studies on polymer crystallization, describable by a nucleation and growth mechanism. Formation of the ordered phase when the final state is the narow biphasic state appears also to follow a nucleation‐growth mechanism. However, when the final state is the wide biphasic region, the morphology of the final state is that of an optically clear, self‐supporting gel, even at very low concentrations (as low as 0.03 wt %). The reasons for and nature of the gel state are believed to be a kinetic phenomenon. The shape of the phase diagram is such that the temperature range of thermodynamic metastability is small and phase separation occurs in the thermodynamically unstable region. In the unstable region the zero activation‐energy spinodal decomposition mechanism dominates the kinetics of phase separation, leading to bicontinuous interconnected phases that have little possibility or driving force to rearrange further. The polymer network structure is proposed to be a bulk thermodynamic phase, characterized by bundles or sheets of polymer between branch points, rather than individual chains as in the usual polymer network. Rheological, electron microscope, and light‐scattering data are presented that support this view. The possibility of other stiff‐chain polymers forming a network structure for similar r

ISSN:0360-8905    

DOI:10.1002/polc.5070650112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY