摘要:

The radiation-induced polymerization of zinc chloride-acrylonitrile (AN) complexes, both the amorphous ZnCl2-AN (1:l) type and the crystalline (1:2) type, was carried out at 30 and -35°C. The rate of polymerization of the 1:1 type exceeds that of the 1:2 type not only in bulk but also in their benzene (BZ) solution, which seems to be attributable to the difference in the relative concentration of ZnCl2to AN rather than to difference in their phases. The addition of a small amount of water to both type complexes results in an increase in the rate of polymerization. In the BZ solution of the 1:2 type complex (Zncl2:AN:BZ = 1:2:2), the addition of water, methanol, and acetic acid increases the rate of polymerization, and the apparent G value of initiation increases with the added amount of water. The findings indicate considerable contribution of the added ligands coordinated to zinc cation to formation of initiating species on irradiation. The bromine atom number NBrper polymer chain was measured by means of radioactivation analysis for polymers obtained from the polymerization of ZnBr2-AN complexes. NBrof 0.20 for both 1:1 and 1:2 types suggests a minor contribution of the initiation by addition of the bromine radical to monomer molecules. In the BZ solution of complexes of the 1:2 type, the NBrof 0.19 was reduced to 0.13 upon addition of water (0.2 mole ratio), which indicates some contribution of water to formation of initiating species. The result is in accord with the estimation based on the rate increase.

ISSN:0022-233X    

DOI:10.1080/00222337808081018

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Copolymers obtained by the condensation of p-bromoaniline, formaldehyde, and p-cresol have been separated into five fractions by a fractional precipitation method. Some of these copolymers showed characteristic titration curves in non-aqueous media. The titration curves indicated a series of breaks which bear integral relations to each other. These features have been interpreted in terms of homoconjugation, intramolecular hydrogen bonding, and composition of the copolymers.

ISSN:0022-233X    

DOI:10.1080/00222337808081019

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

As a modification and improvement of Slocombe's and O'Driscoll's terpolymerization patterns, a new graphical representation of terpolymer systems has been proposed. The suggested patterns retain all the information necessary to describe ternary systems, including also those related to their azeotropic behavior. The main advantage of the proposed representation is its similarity to the accustomed binary representation: the sides of the composition triangles depict the behavior of the corresponding binary systems.

ISSN:0022-233X    

DOI:10.1080/00222337808081020

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Natural abundance15N-NMR spectra of ten different sequence polymers containing taurine, γ-aminopropanesulfonic acid, or sulfanilic acid as well as various aminocarboxylic acids were measured in trifluoroacetic acid. Strong neighboring residue effects and a relationship between chemical shift and chain length of the ω-amino acyl residues are observed and discussed. Isomeric sequences of first and second order like (Tau-γ-Abu)n, and (γ-Aps-β-Ala)nor (Tau-Gly-β-Ala)n, and (Tau-β-Ala-Gly)n, show different spectra. The deprotonation of the sulfonamide groups in alkaline solution results in a downfield shift as well as a substantial decrease in signal intensity.

ISSN:0022-233X    

DOI:10.1080/00222337808081021

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Barium methacrylate monohydrate, Ba2+[CH2˭C(CH3)COO−]2·H2O, may be readily polymerized in the crystalline state by γ-irradiation. However, except under special conditions, there is negligible polymer produced when anhydrous barium methacrylate is exposed to γ-irradiation. The differences in polymer iz-ability are considered in relation to the detailed spatial arrangements of the methacrylate molecules and molecular mobility assimiated with development of disorder.

ISSN:0022-233X    

DOI:10.1080/00222337808081022

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Nuclear magnetic resonance (NMR) studies on poly a-methyl-styrene prepared at high temperatures (>25°C) and having multimodal gel permeation chromatographic (GPC) molecular weight distributions built up of components D + A and B + C showed that their propagation reactions follow Bernoullian statistics, the Pmvalue being in the range of 0.34 to 0.45 for the former and 0.26 for the latter component. The NMR analyses of polymers prepared at lower temperatures (5 to 25° C) and having unimodal GPC molecular weight distributions also showed the presence of component D + A whose propagation followed Bernoullian statistics but with lower (0.25 to 0.35) Pmvalue. On further lowering the polymerization temperatures to -25 or -78°C, the reaction continued to yield component D + A; however, the propagation reaction did not correspond to Bernoullian but a first-order Markov statistics. The propagation reaction responsible for the formation of component B + C, on the other hand, always obeyed Bernoullian propagation with Pmof about 0.26. This suggests that the formation of component D + A results from a reaction mechanism which is different from that of B + C.

ISSN:0022-233X    

DOI:10.1080/00222337808081023

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Kinetic studies on the decomposition of poly-p-isopropyl-α-methylstyrene samples with molecular weights ranging from 1.2 × 104to 6.9 × 105were carried out with the differential thermogravimetric technique. Changes in molecular weight distributions, at different temperatures, were studied by gel-permeation chromatography. The results show that the mechanism responsible for the decomposition is that of depolymerization. The order of the reaction was found to be one. The activation energy for the decomposition of polymer samples of series S (which are less branched in structure) decreases with increasing molecular weight. For the more branched samples of series F, the activation energy remains essentially constant with increasing molecular weight. For identical molecular weights, samples of series F require a a lower activation energy than do samples of series S. The proportions of the three steric forms, viz., isotactic, hetero-tactic, and syndiotactic, in the polymer, both before and after thermal treatments, did not change, suggesting that stereoregularity has no apparent effect on the decomposition of poly-p-isopropyl-α-methylstyrene.

ISSN:0022-233X    

DOI:10.1080/00222337808081024

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Kinetic studies on the decomposition of poly-α-methylstyrene samples with molecular weights ranging from 3.7 × 103to to 2.0 × 105have been carried out with the differential thermo-gravimetric technique. Changes in molecular weight distributions with decomposition, at different temperatures, have been studied by gel-permeation chromatography. A depolymeriza-tion mechanism was shown to be responsible for the decomposition phenomenon. The order of reaction for this depolymerization reaction was found to be one. The values of the activation energy for samples of different molecular weights showed no specific trends; however, it would appear that polymers with relatively higher molecular weights have lower activation energies of decomposition. The proportions of the three steric forms, viz., isotactic, heterotactic, and syndiotactic, in the polymer before and after thermal treatments did not change, suggesting that stereoregularity has no apparent effect on the decomposition of poly-α-methylstyrene.

ISSN:0022-233X    

DOI:10.1080/00222337808081025

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Glass transition temperature (Tg) studies on poly-p-isopropyl-α-methylstyrene havingMnvalues ranging from 5 × 103to 1.53 × 105were carried out with the DSC-2 differential scanning calorimeter. The variation of Tge(at q = l°K/min) withMnobeys the relation, Tge(°K) = 422–3.6 × 105/M. A comparison of Tg∞values for polystyrene (379°K), poly-α-methylstyrene (453°K), and poly-p-isopropyl-α-methylstyrene (422°K) reveals that although the addition of an α-methyl group in polystyrene increases its Tg∞from 379 to 453°K due to steric hindrance, the addition of the p-isopropyl group in poly-α-methylstyrene lowers it from 453 to 422°K due to reduced chain stiffness and smaller interchain steric hindrance. Poly-p-isopropyl-α-methylstyrene samples having similarMnbut different Tgvalues are shown to possess different structures. The effect of polydispersity on Tgis also stressed.

ISSN:0022-233X    

DOI:10.1080/00222337808081026

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Glass transition temperature (Tg) studies on poly-α-methylstyrene havingMnvalues ranging from 2.9 × 103to 7.0 × 104were carried out with the DSC-2 differential scangng calorimeter. The variation of Tge(at q = l°K/min) withMnobeys the relation, Tge(°K) = 453–3.1 × 105Mn. The enthalpy change ΔH observed near the glass transition temperature drops to zero for zero annealing time and zero extrapolated heating rate conditions, suggesting that it is not necessary to postulate a first order transition to account for energy absorption. Operating with longer annealing periods or low heating rates yields similar trends as far as the AH values are concerned. Tgextrapolated to zero ΔH for zero extrapolated heat-ing rate conditions was found to increase with increasing annealing time.

ISSN:0022-233X    

DOI:10.1080/00222337808081027

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor