摘要:

Changes of specific rotation of protein irradiated with Co-60 gamma-rays were restored by some amino acids, such as mono-sodium 1-glutamate. Loss of this recovery effect in some amino acids by irradiation was studied by polarimetry and infrared spectometry. Optical rotation of protein-amino acid solutions increased with an increasing radiation dose given to the amino acids. Changes in optical rotation with irradiation may be due to the loss of the recovery effect of amino acids for the irradiated protein molecule. Changes in infrared spectra increased with an increasing radiation dose given to the amino acids. Such changes in infrared spectra with irradiation may be due to destruction of some radicals in the amino acid molecule.

ISSN:0022-233X    

DOI:10.1080/00222338108066440

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Organosilicone vapors [hexamethyldisiloxane (HMDSO), hexa-methyldisilazane (HMDSN), and hexamethylcyclotrisilazane (HMCTSN)] have been polymerized in a microwave plasma. The reaction kinetics, structure, and density of the plasma polymer films were studied as a function of substrate temperature (Ts) to 800°C, using metal or glass as the substrate.

ISSN:0022-233X    

DOI:10.1080/00222338108066441

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

This paper concerns an investigation of kinetic aspects of the synthesis and structure of α, ω-di(tert-chloro)-polyisobutylene (C1-PIB-C1). The molecular weight distribution function and dispersion ratioMw/Mncharacteristic for C1-PIB-C1 have been derived. In agreement with theory,Mw/Mn= 1.5 by experiment. An expression for the number-average degree of polymerization,Mn, has been deduced from the distribution function. Chain transfer studies based on this equation and its integrated form are presented. Chain transfer to monomer has been found to be negligible, and chain transfer to inifer was found to be a major process (CI= 0.3) determining molecular weight and terminal functionality of the polymer. Temperature and solvent polarity (within a modest range) do not affect chain transfer to inifer. NMR spectroscopy of low molecular weight Cl-PIB-C1 confirms the structure of the chain ends to be ∼CH2-C(CH3)2Cl. Number-average molecular weights (Mn's) determined by1H NMR spectroscopy and GPC were compared. The accuracy ofMn's calculated from GPC traces were confirmed by the more accurate and direct NMR method.

ISSN:0022-233X    

DOI:10.1080/00222338108066442

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The sparse literature on Albizia zygia (D. C.) Macbride is briefly reviewed. The nature of the gum particles when in aqueous suspension is discussed. The viscosity of the solutions increases with concentration, but at concentrations greater than 2% the solution gelled. At low concentration (i. e., below 1%) the solutions exhibit ideal Newtonian behavior but above this concentration the solutions exhibit non-Newtonian behavior. The gum behaves like gum ghatti and sodium alginate in its interaction with sodium chloride and magnesium chloride, the viscosity decreasing with increasing concentration of these electrolytes. For Albizia zygia Grade I variety, the viscosity increases with increasing magnesium chloride concentration, reaching a maximum and then falling off at higher magnesium chloride concentrations. The acid gum shows reserve acidity in its interaction with acids.

ISSN:0022-233X    

DOI:10.1080/00222338108066443

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A series of diamines was polycondensed with pyromellitic di-anhydride and 3, 3′, 4, 4′-benzophenone tetracarboxylic dianhydride using a two-step method to get thin, strong, and flexible polyimide films which were characterized by the variations of the substitution at the carbon atom connecting the two phenyl rings of the diamine moiety. The poly(amic acid) prepolymers obtained in the first step had inherent viscosities ranging from 0.9 to 1.60 and they were converted to polyimides by thermal cyclodehydration. All the polycondensation reactions were carried out in dimethyl acetamide under identical conditions. Thus 16 different polyimide polymers were synthesized and characterized by elemental analysis, IR spectroscopy, and viscosity measurements. Some other important properties, such as solubility, thermal stability, and electrical behavior, were also investigated. The alkyl chain length affected the flexibility of the resultant polyimide films greatly and the electrical properties slightly; however, thermal stability was decreased subsequently.

ISSN:0022-233X    

DOI:10.1080/00222338108066444

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Intrinsic viscosities of polystyrenes (PS), polymethyl meth-acrylates (PMMA), and their random copolymers have been determined at different temperatures to estimate chain flexibility of homopolymers and copolymers. The coefficients Ke, the chain flexibility descriptor, for PS decreases with increasing Mnand have positive values. For PMMA the Keincrease slightly with increasing Mnand have negative values. The Kevalues for S/MMA copolymers are all positive, showing that the chain flexibility in copolymers is predominantly influenced by styrene concentration. For PS the long-range parameter B and the excluded volume factor Z increase from 25 to 45°C and thereafter remain constant. The short-range parameter, A, for PS remains virtually unchanged with the change in temperature. For PMMA, the short-range, the long-range, and the excluded volume factors remain virtually constant between 25 and 65°C.

ISSN:0022-233X    

DOI:10.1080/00222338108066445

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The thermal decomposition and the glass transition temperature of poly(p-chlorostyrene) (PpCIS) were studied with a Model 2 differential scanning calorimeter (DSC). The undecom-posed and decomposed polymers were analyzed by gel permeation chromatography for molecular weight distributions and by DSC for changes in the polymer glass transition temperature. The decomposition of PpCIS under isothermal conditions during 50 min intervals at various temperatures or at a fixed temperature (320°C) but for different periods is characterized by the disappearance of increasing quantities of high molecular weight polymer and the appearance of low molecular weight products. Random scissions have been shown to break down the polymer chains which depolymerize into volatile products. Activation energy (72 kcal/mole) for the decomposition of PpCIS is lower than that (103 kcal/mole) for the decomposition of polystyrene.

ISSN:0022-233X    

DOI:10.1080/00222338108066446

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The thermal decomposition and the glass transition temperature of poly p-methoxystyrene (PpOMeS) were studied with a (DSC-2) differential scanning calorimeter. The undecomposed and decomposed polymers were analyzed by gel permeation chromatography for molecular weight distributions and by DSC-2 for changes in the polymer glass transition temperatures. Decomposition of PpOMeS under isothermal conditions during 50 min intervals at various temperatures or at a fixed temperature (320°C) during various intervals leads increasing quantities of high molecular weight material to yield low molecular weight products. Random scissions have been shown to break down the polymer chains which then volatilize via depolymeriza-tion. Activation energy for the decomposition of PpOMeS has been found to be less than that for the decomposition of polystyrene (PS). Variation of Tge(at q = l°K/min) withMnobeys the relation: Tge- (°K) = 386 - 4.67 × 105/Mn. The value of 386°K for the Tg∞ of PpOMeS is greater than the value (362°K) reported in the literature. A comparison of Tg∞ for PS (379°K) for poly p-methylstyrene (384°K) and for PpOMeS (386°K) reveals that the presence of p-CH3or p-OCH3groups neither influences the chain flexibility nor causes further steric hindrance than already exists in PS.

ISSN:0022-233X    

DOI:10.1080/00222338108066447

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Reactivity ratios of some p-substituted aniline-p-hydroxy-benzoic acid copolymerization systems have been determined by the linear graphical method of Kelen and Tüdös. It was found that the copolymerization parameters are affected by the nature of acidic functional groups present in the comonomers, and the sequence of reactivity of comonomers is found to be of the same order as that of their acid strengths.

ISSN:0022-233X    

DOI:10.1080/00222338108066448

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The reactivity ratios for the anionic copolymerization of N-carboxy anhydrides of O-acetyl-L-tyrosine and L-alanine have been determined to be 0.115 and 2.65, using the Fineman-Ross and Kelen-Tüdös, methods.

ISSN:0022-233X    

DOI:10.1080/00222338108066449

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor