摘要:

AbstractIt is found that the chromatic and characteristic polynomials of a graph are reconstructible. This result is obtained by a process of reconstruction applied to partial results already in the literature.

ISSN:0007-1641    

DOI:10.1002/pi.4980090302

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe contribution of neutron scattering to polymer science is reviewed. A summary is given of the theory of neutron scattering followed by a review of the literature. Particular emphasis is placed on the use of small angle neutron scattering to observe the conformation of polymer chains in bulk polymers and concentrated polymer solutions and on quasi elastic neutron scattering to measure the dynamics of polymer chains.

ISSN:0007-1641    

DOI:10.1002/pi.4980090303

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractFrom published HEdata for 10 n‐alkane solutions in benzene at 25°C, the three parameters of the author's solution theory have been calculated. The values obtained agree quite well with εΔ = 3068 J/mole, K = 1, and rσ= 0.2 + 0.2 nc= 0.1 nH. The problems involved in the extension of these results to higher oligomers of polymethylene and to other solutions of chain molecules are briefly disc

ISSN:0007-1641    

DOI:10.1002/pi.4980090304

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractIn Simple Flory‐Huggins solvent‐polymer systems liquid three‐phase separation occurs via a homogeneous double plait point. The conditions for three‐phase separation in a system consisting of a solvent and two polydisperse polymer homologues are given.It is shown that in a simple Flory‐Huggins solvent‐polymer system four and more phase separation cannot occur.General conditions for a multicritical poin

ISSN:0007-1641    

DOI:10.1002/pi.4980090305

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractPreferential solvation in quasiternary systems composed ofp‐xylene (pXY), 1,2‐dibromo‐1, 1‐difluoroethane (DBFE) and styrene (ST)‐methyl methacrylate (MMA) copolymers of varying architecture and composition was studied by two ultracentrifugation methods: sedimentation equilibrium in a density gradient and conventional sedimentation equilibrium. The preferential solvation parameters were estimated for the systems containing alternating, statistical and block copolymers as well as polymethyl methacrylate (PMMA) and polystyrene (PST). Virtually no solvation was observed by PST, while significant solvation of DBFE to MMA units took place. For alternating and statistical copolymers the solvation parameter is approximately the composition average of those of PST and PMMA, although a slight but distinct difference between those of the alternating and statistical copolymers was observed. However, in block copolymers of either PST‐PMMA or PMMA‐PST‐PMMA type of high PST content, it appears that the solvation of DBFE to PMMA‐blocks is suppressed by the prese

ISSN:0007-1641    

DOI:10.1002/pi.4980090306

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe thermodynamic properties of the system polystyrene‐ethylcyclohexane (temperature 70°C) were examined between 57 and 80°C for weight fractions of the polymer 0‐0.16. Scholte's light scattering method was used for this purpose. The results are presented in the form of the temperature and concentration dependence of the interaction parameter of the Flory‐Huggins equation. The interaction function thus obtained has been tested by comparing calculated and experimental spinodals. The given system has been compared with a pseudoideal solution in order to discuss the pronounced concentration dependence of the interaction parameter and its dependence on molecular

ISSN:0007-1641    

DOI:10.1002/pi.4980090307

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractCloud‐point curves in mixtures of short‐chain polymers often have irregular shapes, showing shoulders or two maxima. Limits of the thermodynamic stability as measured by Pulse Induced Critical Scattering also appear to be bimodal in such cases. A possible explanation of this phenomenon might be that the constituent molecules influence each other's chain flexibility, the more flexible chains becoming less flexible upon addition of stiffer ones, andvice versa. Such a feature is incorporatedi.a.in Huggins' new theory in which orientational entropy correction terms relate the average randomness of orientation of a segment with respect to the preceding one in the chain to the surroundings of the segm

ISSN:0007-1641    

DOI:10.1002/pi.4980090308

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe intensity of light scattered from dilute solutions of mixtures of two nonidentical polymers in a single solvent was measured. The parameter A24characterising the thermo‐dynamic interaction of two nonidentical polymer molecules in solution was calculated for several systems polymer 2 ‐ polymer 4 ‐ solvent. For chemically strongly different polymers, A24is independent of molecular weights of the polymers and probably also of solvent. A24is related to the compatibility of both polymers and decreases contrary to expectation with increasing chemical difference between polymers 2

ISSN:0007-1641    

DOI:10.1002/pi.4980090309

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractLight scattering measurements were carried out on several standard polystyrenes and their binary mixtures in benzene and in 2‐butanone. Their second virial coefficients, B2, were determined as a function of the polymer composition. It was revealed that for some pairs of mixtures whose components differ greatly in size, a minimum in B2is observed, whereas a maximum is expected theoretically. The reasons for this phenomenon are discussed and interpreted in terms of the characteristics of the samples in solution and by considering the non‐negligible contribution of the attractive for

ISSN:0007-1641    

DOI:10.1002/pi.4980090310

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe polymer topomorphism concept previously treated in terms of crystalline topomorphism only is reconsidered on the basis of thermodynamic dualism following from T. Hill's thermodynamics of small systems.1This leads to substantial generalisations extending to ‘amorphous’ topomorphism as well. Thus we can treat, in a physically rigorous manner the problems of inherent ‘thermodynamic dissymmetry’ of the melting‐crystallisation on behaviour of flexible chain polymers and of their phase dualism. The latter involves W. Kuhn's statistical elements (segments) as ‘supermolecules’ belonging both to small systems (macromolecules) and to the large one (the whole amorphous polymeric sample) the latter being a superposition of interpenetrating statistical coils which in their turn are accumulated in subsystems, or groups, having equal degrees of coiling β. It is essential that the β distribution and the corresponding conformational entropy distribution is the same as Maxwell's distribution for kinetic energy in the theory of gases. This equivalence of two distributions of essential thermodynamic parameters is not a mere formal coincidence but reflects the dualistic behaviour of segments which must be treated as ‘gas molecules’ within a given coil and as molecules of a liquid when the large system is considered. It follows immediately that many essential properties of amorphous polymers and melts (including their crystallisation behaviour) must be due to the superposition of gas‐like and liquid‐like properties of segments, and that some important properties of the large system are due exclusively to contributions from the small systems.This general approach is used to investigate the behaviour of polymer melts under high pressure. In accord with the Le Chatelier's principle, increasing pressure changes the gas‐likeness to the liquid‐likeness and the liquid‐likeness to some type of ordering (crystalline or liquid crystalline if the former state is impossible due to the lack of tacticity). The small systems can become liquid‐like due to supercoiling or touncoiling, and it is shown that the latter case is energetically much more favourable. Solely due to this uncoiling the large system undergoes a transition into a nematic state followed (if the chain configuration is appropriate) by an extended chain crystallisation.In this instant the effects of pressure are the same as effects of melt extension prior to crystallisation. In both cases a critical value β = β* appears when further spontaneous uncoiling occurs. The phase transition of the whole system at crytical values of β is a typical ‘behavioural’ transition in Prigogine's3sense being a bifurcation in a non‐equilibrium state, leading to the change of mode of crystalline growth. However, even in static and close to macroscopic equilibrium conditions a similar bifurcation may occur due to the fact that the above mentioned groups may be far from equilibrium (depending on their particular β values). Again the crystalline topomorphism results, the growth of extended chain crystals proceeding by the mechanism of ‘order through fluctuations’.Finally, a remark is made on a possibility of developing a theory of crystallisation and melting of polymers leading directly to the above mentioned ‘thermodynamic dissymmetry’ and based on s

ISSN:0007-1641    

DOI:10.1002/pi.4980090311

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY