摘要:

AbstractThe nature and kinetics of phase separation processes of solutions of cellulose acetate (degree of substitution, 2.5) in mixtures of dioxane and water are studied by differential scanning calorimetry (DSC). The thermograms on heating show small endothermic effects, detectable only after prolonged aging below the phase separation temperature. Experiments in two regions of the ternary diagram are of interest for the description of the formation mechanism of asymmetric membranes viz., (1) at high polymer and high concentrations and low concentrations of nonsolvent (gelation); (2) at lower polymer concentrations of nonsolvent (liquid–liquid separation followed by gelation). Endothermic effects after prolonged aging are found at high polymer concentrations (≥40%). These results demonstrate that gelation is very slow in these systems. At lower concentrations of polymer and high concentrations of nonsolvent (up to 40%) a more rapid type of phase separation can be observed visually on cooling. The temperature where turbidity sets in (the cloud point) is independent of the rate of cooling. In DSC experiments no exothermic effect is found on cooling. Again, after aging an endothermic effect is present. The endothermic peak, which is situated below the cloud point, is probably a result of melting of the gelled concentrated ph

ISSN:0360-8905    

DOI:10.1002/polc.5070690103

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe thermal properties of several biopolymeric (DNA, RNAse, Folch‐Pi apoprotein)–water systems have been investigated by low‐temperature adiabatic differential scanning microcalorimetry. Determination of the heat change and temperature of fusion of the water and eutectic mixture allowed resolution of the various water states in native polymer solutions and before and after heat denaturation of the macromole

ISSN:0360-8905    

DOI:10.1002/polc.5070690104

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

年代:1981

数据来源: WILEY

摘要:

AbstractIt is established that the process of chromatin melting in tissues proceeds in one stage with the following transition parameters:T= 82°C, ΔT= 7°C, andQ= 24 cal/g DNA. The difference between the heats of melting for chromatin and DNA is 12 cal/g and corresponds to the melting of the secondary and tertiary structure of chromat

ISSN:0360-8905    

DOI:10.1002/polc.5070690105

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

年代:1981

数据来源: WILEY

摘要:

AbstractCalorimetric studies were carried out on partly dried yeast cells and some model substances supposed to afford the major binding sites in the yeast cells. The heat of vaporization and thawing as well as the water vapor sorption isotherm of yeast cells suggest that part of the cell water is somewhat bound to dry matter components and loses some of its responses observed when it is in bulk phase. Cell water down to 25% freezes and has the same value of differential heat of vaporization as in the bulk phase (10.5 kcal/mol). The contents of unfreezable water calculated from the heat of thawing obtained with yeast mannan, yeast RNA, bovine serum albumin (BSA), and the whole yeast cells are 43, 35, 30, and 25%, respectively. The calorimetric data obtained for yeast cells and their component molecules indicate that the magnitude of their interaction with water molecules are in the order of mannan, bovine serum albumin (BSA), and the whole yeast cells. The physical properties of water in yeast cells cannot be explained from those bound to their separate components. This may in part be due to some interactions between these molecules that change their binding properties with water molecules in yeast cells.

ISSN:0360-8905    

DOI:10.1002/polc.5070690106

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

年代:1981

数据来源: WILEY

摘要:

AbstractFor the ternary system water + RNase + KCl and equally for packed human erythrocytes the specific heat capacities were measured in the range from 282 to 353 K. It is shown that an expansion ofcpaccording to the McMillan–Mayer theory is helpful to the interpretation of the experimental data of the ternary system. Moreover, it will be shown that a first mathematical approximation forcpof human erythrocytes leads to an astonishing conformity with the experiment

ISSN:0360-8905    

DOI:10.1002/polc.5070690107

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

年代:1981

数据来源: WILEY

摘要:

AbstractStretching of poly(α‐amino acid) fibers or films as well as natural occurring protein fibers like wool is accompanied by heat effects due to conformation changes of the macromolecules and by orientation changes, sliding processes, etc. Such phenomena were studied by using a stretching calorimet

ISSN:0360-8905    

DOI:10.1002/polc.5070690108

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

年代:1981

数据来源: WILEY

摘要:

AbstractThis article investigates the influence of enzymatic and alkali‐salt treatment of the fibrillar collagen on the structure of the final products of dissolution with the help of the methods of infrared (IR) spectroscopy and differential thermal analysis. In addition we compared the products obtained by the two methods of treatment using two biochemical indices: content of ester bonds and hydroxyproline. One can conclude that enzymatic treatment is optimum for dissolution of the fibrillar collage

ISSN:0360-8905    

DOI:10.1002/polc.5070690109

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe protonation of some poly(amido amine)s has been studied in aqueous solution by potentiometric, calorimetric, and13C‐NMR methods. Only “apparent” constants were usually found in polymeric acids and bases; on the other hand, “sharp” basicity constants could be determined for the poly(amido amine)s studied. The logKvalues determined from13C‐NMR shifts versus pH agree well with those determined by potentiometric titrations. Also, the protonation enthalpies do not depend on the dissociation degree of polymeric bases, and this is a further proof of the peculiarity of this class of polymers. The trends of ΔH's and the conformations of polymers in solution are analyzed on the basis of theoretical

ISSN:0360-8905    

DOI:10.1002/polc.5070690110

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

年代:1981

数据来源: WILEY

摘要:

AbstractActivated anionic polymerization of ϵ‐caprolactam was investigated in the presence and absence of crown compounds by a suitable differential scanning calorimetry (DSC) technique. It was demonstrated that crown compounds influenced the heterogeneous character of polymerizationresulting PA 6 of higher crystalline proportion and higher average molecular weig

ISSN:0360-8905    

DOI:10.1002/polc.5070690111

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

年代:1981

数据来源: WILEY

摘要:

AbstractCourse and kinetics of the isothermal bulk polymerization of methyl acrylate, methyl methacrylate, and methyl‐2‐chloroacrylate at different temperatures were studied by differential scanning calorimetry. The initiator used was 2,2′‐azoisobutyronitrile. The polymerization was investigated without or in the presence of ZnCl2. The course of reactions, the heat of polymerization, the specific constants of polymerization rate, and the activation energy were det

ISSN:0360-8905    

DOI:10.1002/polc.5070690112

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

年代:1981

数据来源: WILEY