摘要:

A commercial, branched polyethyleneimine was analyzed by13C-NMR. The chemical shift assignments for the eight principal peaks were compared to the calculated chemical shifts using an additivity relationship developed for low molecular weight acyclic aliphatic amines. The change in carbon chemical shift induced by H/D exchange at nearby nitrogens was examined for this polymer and low molecular weight model compounds. The direction and magnitude of the shift are determined by the number and proximity of exchangeable NH' and are described by a simple formula. The spin lattice relaxation times for the various methylenes indicate the usual decreasing mobility for units at chain ends, internal units, and units close to branch points in that order. The integrated spectrum, under equilibrium conditions, is not consistent with the reorted amine distribution, 1°:2°:3° = 1:2:1. Our results indicate 38k l°, 36% 2°, and 26% 3°.

ISSN:0022-233X    

DOI:10.1080/00222338508056641

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Catalysts of reduced and unreduced PdCl2with hydrazine hydrate deposited on polyaminochloroquinones or polyaminochlorohydroquinones were obtained. Polyaminochloroquinones were prepared by solution polycondensation of chloranil with benzidine in the presence of an acceptor, sodium acetate, for the resulting hydrochloric acid. Polyaminochlorohydroquinones were obtained by a reduction reaction of polyaminochloroquinones with 2,2′ -diphenyl hydrazine. The polymer catalysts were tested in the styrene hydro-genation reaction. The polymers and polymer catalysts were studied by IR spectroscopy.

ISSN:0022-233X    

DOI:10.1080/00222338508056642

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A nonconventional route for the manufacture of liquid or solid, one-step phenolic resins is discussed in this paper. Base-catalyzed condensation occurs in dispersed particles suspended in water as the continuous phase. Protective colloid type and concentration are major factors in determining particle size and, therefore, the ability to obtain either nonsettling dispersions or particulate solids that can be recovered and handled as powders. The technology is applicable to a variety of phenolic and aldehydic starting materials. In contrast to conventional manufacturing procedures, the current technology affords efficient process control and great latitude in selection of molecular weight, molecular weight distribution, and functionality.

ISSN:0022-233X    

DOI:10.1080/00222338508056643

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

It was established that linear polymers with quaternary ammonium groups are obtained by the reaction of chloromethylated polystyrene (CMPS) with hydroxyalkylic tertiary amines when the amines contain one or two hydroxyl groups, and that crosslinked polymers are obtained with aminoether groups when the amines have three hydroxyl groups, i.e., tris(2-hydroxyethy1)amine. The aminoether units appear by intramolecular rearrangement of quaternary ammonium structural units. Kinetic studies on the synthesis of polymers with quaternary ammonium groups from CMPS, poly(N,N-dimethylamino-ethylmethacrylate), and poly(N,N-dimethylaminopropylacrylamide), were performed. The main factors which influence the kinetics of reactions are steric hindrance of near neighboring groups, hydrophilic effect for hydroxyalkylamines and polymer-solvent interaction.

ISSN:0022-233X    

DOI:10.1080/00222338508056644

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The semicontinuous emulsion polymerization of vinyl acetate has been studied. Poly(vinyl alcohol) as a protective colloid and ethoxylated cetyl alcohol as a coemulsifier were used. The conversion and particle diameter were affected by the stirring speed and the coemulsifier distribution between initial reactor charge and continuously introduced monomer. The amount of unreacted monomer oscillates with time.

ISSN:0022-233X    

DOI:10.1080/00222338508056645

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The semicontinuous emulsion copolymerization of vinyl acetate: dibutyl maleate (60:40, vol/vol) was carried out at different co-emulsifier distributions between initial reactor charge and continuously introduced monomer. The overall conversion, the co-polymer particle size, and the properties of films obtained from emulsions were determined experimentally. Polyvinyl alcohol and cetyl alcohol ethoxylated with ethylene oxide (20 moll were used as protective colloid and coemulsifier, respectively. Experimental investigations have shown that the unreacted monomer concentration and the copolymer particle size oscillate with time. These oscillations are related to a tendency for limited particle flocculation.

ISSN:0022-233X    

DOI:10.1080/00222338508056646

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Copolymer structure has a marked effect on solution properties and thus behavioral characteristics of water-soluble copolymers utilized in enhanced oil recovery. The ability of random and graft copolymers to maintain large hydrodynamic volumes in dilute solutions in the presence of mono- and divalent electrolytes is critical for mobility control. The differences in viscosity behavior are described for a series of random and graft copolymers of acryl-amide with sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS), diacetone acrylamide (DAAM), and sodium acrylate (NaA) as a function of polymer microstructure, temperature, concentration, and added electrolytes. Copolymers of AM-NaAMPS show enhanced salt tolerance and phase stability over their AM-NaA counterparts with similar compositions and molecular weights. The AM-DAAM copolymers show unusual solution behavior with increases in viscosity in the presence of added salt.

ISSN:0022-233X    

DOI:10.1080/00222338508056647

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The morphology changes in polyethylene (PE) and polypropylene (PP) melts were studied by rheometrical and x-ray methods. The dependence of viscosity on temperature exhibits reproducible, characteristic inflections within given temperature ranges. Throughout the transition range the variation of viscosity of PE is slower than in adjacent regions. The temperature dependences of the position, height, and half-width of the x-ray amorphous peak also show inflections in the same temperature range as viscosity. However, while the position of the amorphous peak and therefore the distance between chains varies in the transition range slower than in adjacent regions, the half-width and height asSociated to short range order and molecular chain mobility, respectively, change faster in the transition range than outside it. This means that morphological transformations at the molecular chains level, occurring in the transition range, have to be assigned to an increase of the length of parallel packed chain segments, as well as to the faster decrease of the short range order. The variation of melt viscosity and melt density supports this interpretation. Similar results were obtained for PP melts.

ISSN:0022-233X    

DOI:10.1080/00222338508056648

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The activation energy and the threshold temperature of isomerization are determined for the cis-trans conversion of polyacetylene (26.5 kJ/mol and 236 K) and poly(phenyl acetylene) (42.5 kJ/mol and 373 K) in the solid state. Based on the low activation energy of conversion, a mechanism is proposed for the isomerization of cis-rich polyacetylene, which involves the delocalization of electrons in the first step followed by formation of trans geometries through their relocalization in the cisoidal form and rotation around single bonds to form stable transoidal sequences. No threshold temperature and activation energy could be defined in the case of poly(β-ethynyl naphthalene) where it is suggested that the driving force of isomerization lies in the constrained character of the cis-cisoidal helix.

ISSN:0022-233X    

DOI:10.1080/00222338508056649

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The use of nitroso derivatives in rubber compounds leads to a reinforcing effect with important practical implications. The mechanism of action of these promoters is explained on the basis of the theory according to which the reinforcing effect is due to the strain-crystallization process. This process is dependent on various factors, one of them being the presence of a network based on weak “rubber…carbon black” bonds. The properties of crude and cured blends on natural rubber, polyisoprene, and modified polyisoprene are compared. When nitroso derivatives are used, the active sites on the polymer chain are probably the nitroxyl radicals formed during the modification process. According to the mechanism proposed by the authors in previous papers, the formation of nitroxyl radicals is accompanied by changes of macromolecular characteristics which permit us to explain the reinforcement as well as the modification of viscoelastic and physical-mechanical properties of crude and cured compounds. On the basis of assumptions made on the whole set of reactions regaxding both polymer modification with nitroso derivatives and that of rubber compounds, one can explain not only some of the properties but also the conditions in which modification should be made in order to obtain an optimal reinforcing effect.

ISSN:0022-233X    

DOI:10.1080/00222338508056650

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor