摘要:

AbstractThe light‐stability of chlorinated poly(vinyl chloride) (PVCC) is investigated and the quantum yields of the major process involved are determined. By UV exposure, PVCC undergoes a fast dehydrochlorination process which develops ten times more efficiently than with poly(vinyl chloride) (PVC), leading to long chlorinated polyene sequences which are responsible for the rapid coloration of the irradiated polymer. Chain scission and crosslinking occur simultaneously, both in the presence and in the absence of oxygen, indicating that UV radiations are able to cleave the polymer chains. By reaction with polyenyl radicals, oxygen reduces slightly the efficiency of the dehydrochlorination, while promoting at the same time the formation of carbonyl and hydroperoxide groups in the polymer chain. The reasons of the high instability of PVCC against UV light are discussed and an overall reaction scheme is suggested to account for the various processes observed and their relative efficiencie

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830521

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractSedimentation coefficients,s0c, diffusion coefficients,Dc, and specific viscosities have been determined for eleven samples of commercial narrow‐molecular‐weight distribution polystyrenes Pressure Chemicals Co. and Waters Ass., 5 · 104g · mol−1

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830522

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractViscosity and preferential solvation measurements were carried out on maleic acid‐ethyl‐ and ‐butyl vinyl ether alternating copolymers (MA‐EVE and MA‐BVE, respectively) in watermethanol and water‐2‐chloroethanol mixtures. The conformational transition of MA‐BVE was found to be strongly related to the solvation of the polymer by 2‐chloroethanol. Comparison of experimental results on MA‐BVE, MA‐EVE, and poly(methacrylic acid) (PMA) in water‐2‐chloroethanol mixtures indicates that the behaviour of MA‐EVE is different from that of MA‐BVE and PMA because it does not undergo

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830523

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe molecular weight distribution (MWD) of a high polymer is calculated from a weakly perturbed Zimm‐plot of the classical light scattering on dilute solutions of Gaussian polymer coils (theta state). A typical Zimm‐plot is simulated corresponding to the measurements of high accuracy as would be obtained by using the laser photometer described by Hack and Meyerhoff. The accuracy as published by these authors for small dissymmetries is used. Two numerical methods for calculating the MWD are briefly described and tested, both using an empirical formula for the Laplace image of the calculated

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830524

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe molecular weight distribution (MWD) of a high polymer is calculated from a weakly perturbed Zimm‐plot of the classical light scattering on dilute solutions of Gaussian polymer coils (theta state). A typical Zimm‐plot is simulated corresponding to the measurements of high accuracy as would be obtained by using the laser photometer described by Hack and Meyerhoff. The accuracy as published by these authors for small dissymmetries is used. Two inversion procedures are described in detail and tested, both of them avoiding the use of an empirical formula for the Laplace image of the calculated MWD. A complete numerical analysis of the results is given. The results are compared with those of the previous pa

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830525

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe solid‐state conformation of copolymers of oxidizedL‐methionine [L‐Met(O)] withL‐methionine (L‐Met) and/orL‐alanine (L‐Ala) was studied by IR spectroscopy and circular dichroism (CD). The results from the IR spectra in the region of 900−330 cm−1are compared with data obtained by CD experiments. A film cast from the solution of a copolymer containingL‐Met(O) had a new trough between 205 and 210 nm in the solid‐state CD spectra and new IR absorption bands at 815 and 680 cm−1, while oxidizing the film of anL‐Met containing copolymer after casting did not induce a significant change in IR and CD spectra. It seems that the film cast from the solution of anL‐Met(O) containing copolymer exhibits the feature of a random coil as well as of an α‐helix. From the CD spectra of the film on immersion in water, it was deduced that the helix of the film became gradually disordered and hence t

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830526

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe electric dipole moments (per repeating unit) of cellulose acetate and tricarbanilate, and amylose acetate and tricarbanilate were determined in 1,4‐dioxane solution at 30°C. The parallel component of the moment to the chain contour was also estimated for samples of various molecular weights, and they were almost independent on molecular weight, indicating no excluded volume effect on the dipole moment. The persistence dipole moment, and monomer dipole component along the chain contour for cellulose derivatives were about 50% smaller than those for amylose derivatives. The relation between the dipole moment and the chain dimension is discussed for cellulose‐ and amylose derivat

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830527

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104seconds, indicating a slow physical process. Stress‐relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one‐component Maxwell mo

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830528

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY