摘要:

Graft copolymerization of MMA onto nylon 6 fiber by UV radiation was studied at 70°C using various water alcoholic systems: water-methanol, water-ethanol, and water-n-propanol. The effects of monomer concentration, time, and the medium were investigated. The graft yield is greatly enhanced by increasing the monomer concentration and reaction time. The extent of grafting is affected by the medium of grafting and is in the following order: water-methanol > water-ethanol > water-n-propanol.

ISSN:0022-233X    

DOI:10.1080/00222338208062407

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The kinetics of the cationic polymerization of 1-β-cyanoethyl aziridine initiated 3-hydroxy- 1-propane sulfonic acid sultone and methyl tosylate have been studied. The course of polymerization involved the propagation stage and termination reaction due to the reaction between the growing chain and imino groups in the polymer chain. The propagation constants and termination constants were obtained. The enthalpies of activation for the propagation and termination reactions are ΔHp* = 12.9 kcal/mol and ΔHt* = 12.4 kcal/mol, and the entropies of activation are ΔSp* = -31 cal/deg·mol and ΔSt* = -39 cal/deg·mol. Otherwise, the polymerization initiated with methyl tosylate involved an early stage which was initiated very quickly.

ISSN:0022-233X    

DOI:10.1080/00222338208062408

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The graft polymerization of styrene onto chitin powder, and chitosan powder and film initiated by γ-ray irradiation was carried out at 30°C. The graft polymerization was found to proceed predominantly in the presence of water, and the degree of grafting increased with an increase in the radiation dose. From ESR spectroscopy it was noted that the free radicals generated both in chitin and in chitosan were stable enough at ambient temperature. Styrene-grafted chitin and chitosan powders thus obtained showed less swelling in water, and chitosan after graft polymerization was insoluble in dilute acids. Graft polymerization of other vinyl monomers was also studied.

ISSN:0022-233X    

DOI:10.1080/00222338208062409

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The chemical group contribution technique, based on the principle of additivity of molar refraction and polarization constants for groups in a molecule, has been used for determining the solubility parameters of acrylamide series polymers. The solubility parameter for a polymer is calculated through its components by using the contributions of chemical groups reported in the literature with the resultant values found to compare favorably. It is also noticed that the δ-values decrease with an increase in molar volume.

ISSN:0022-233X    

DOI:10.1080/00222338208062410

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Ultrasonic degradations of hydroxypropyl cellulose (HPC) have been carried out in water, ethanol, and tetrahydrofuran (THF) solutions. In the HPC-water system, cavitation intensity did not increase linearly with ultrasound intensity because of a lower threshold of ultrasonic intensity below which cavitation does not occur. At 27°C the rate of degradation in the three solvents followed the order water > ethanol > THF which is not in line with their characteristic impedance values. The rate of degradation for 20 kHz, 70 W ultrasound intensity was found to increase with a decrease in solution volumes, concentration of HPC, and temperature. Increased rate of degradation at lower temperatures supports the concept based on sonoluminescence experiments that it is the cavitation in a polymer solution that is responsible for ultrasonic degradations and the dissolved polymer molecules do not act as cavitation nuclei. Increased surface tension and density of the solvent are thought to be responsible for improved cavitation at low temperatures. Infrared spectroscopy and x-ray analysis of HPC subjected to ultrasonic treatments remained unchanged, suggesting that there were no chemical or structural (e.g., degree of order) changes on irradiation. The decreases in molecular weights on irradiation arise due to random chain scission whereas similar decreases in Huggins coefficients can be attributed to physical changes (decrease in molecular weight or branching) in the degraded HPC samples.

ISSN:0022-233X    

DOI:10.1080/00222338208062411

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper concerns the preparation and characterization of a new graft copolymer comprising polychloroprene backbone and polyisobutylene branches which carry tertiary chlorine termini. Synthesis involved the grafting of isobutylene from polychloroprene by the use of BCI3coinitiator in methylene chloride solvent in the -12 to -78°C range. Conditions have been defined for efficient and convenient graft copolymerizations. Carefully purified grafts (selective solvent extraction) were characterized by a battery of analytical techniques including1H-NMR spectroscopy and GPC. Agreement between calculated and experimental graftMn's indicate absence of disturbing side reactions, i.e., backbone degradation and cross-linking, during synthesis. The presence of tertiary chlorine endgroups has been demonstrated by thermal dehydrochlorination studies. Branch molecular weight, molecular weight distribution, and frequency have been obtained by selective oxidative destruction of the polychloroprene backbone followed by surviving branch analysis. A graft prepared at -20°Carried ∼5 polyisobutylene branches ofMn= 5000 each.

ISSN:0022-233X    

DOI:10.1080/00222338208062412

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The polymerization of 2-hydroxy-4-(2,3-epoxypropoxy)benzophenone catalyzed by tin(IV) chloride in a solution of chloroform and dichloromethane was investigated by adiabatic calorimetry, and the photostabilizing efficiency of the product of the polymerization in polypropylene fibers was estimated. The kinetic study has shown that the amount of catalyst rapidly decreases during the reaction, the time decrease in the concentration of active centers involves their rapid deactivation, and an oligomer with a low degree of polymerization arises. No distinct destruction of the 2-hydroxybenzophenone structures appears during the cationic polymerization as indicated by the UV spectra and the results of measurements of the photostabilizing efficiency. In comparison with 2-hydroxy-4-n-octyloxybenzophenone, the higher molecular stabilizer thus prepared exhibits lower extractibility from polypropylene fibers with ligroin.

ISSN:0022-233X    

DOI:10.1080/00222338208062413

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The stereoregularity of polystyrenes obtained with complex bases and salt complex bases in various solvents was determined by13C-NMR spectroscopy. Polystyrenes produced by complex bases are mostly syndiotactic and obey Bernoullian statistics.

ISSN:0022-233X    

DOI:10.1080/00222338208062414

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Poly-Schiff-base ligand (SBSAL-DDM) is synthesized by condensing bis-salicylaldehyde 5,5′-sulfone with 4,4′-diaminodiphenyl methane. The polychelates of Cu(II), Ni(II), Co(II), and Mn(II) with poly-Schiff base have been isolated and analyzed. The analytical data agree with 1:1 metal-ligand stoichiometry. The polychelates are studied in terms of electrical, thermal, spectral, and magnetic properties. A probable structure has been proposed for the above polymers.

ISSN:0022-233X    

DOI:10.1080/00222338208062415

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Concepts of the synthesis of shell topological compounds, which consist of a guest molecule (or molecules) trapped by a host molecule with a spacial, egg shell-like structure are discussed. Generally, both constructing the shell molecule in the presence of a guest molecule and constructing the guest molecule in the presence of the shell (host) are ways to “shell” topological compounds. The preparation of shell molecules may consist of the completion of “preshell” molecules or of obtaining cascade branched oligomers and polymers. Cyclodextrins and substances like triquinance are considered to play a role in preshell molecules. Shell molecules may also be obtained by polyreaction of a monomer of the XRYntype, which results in a cascade branched molecule of shell structure (spherical form). When the polyreaction is continued, the cascade branched molecule becomes a “cast” one. It is theoretically possible to enclose a guest molecule inside the shell during the cascade branching process if there is a good solvent (of high expansion coefficient value) in respect to the growing branches. A spacially developed molecule of both “empty” and “cast” structure may be obtained also by the known “step by step” cascade branching process which involves, for instance, a repeated cyanoethylation-reduction reaction.

ISSN:0022-233X    

DOI:10.1080/00222338208062416

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor