Discussions of The Faraday Society最新文献

{"title":"Fickian and non-Fickian diffusion in high polymer systems","authors":"G. Rehage, O. Ernst, J. Fuhrmann","doi":"10.1039/DF9704900208","DOIUrl":"https://doi.org/10.1039/DF9704900208","url":null,"abstract":"The normal and the anomalous diffusion in binary polymer solutions are considered. After a survey of the theory of diffusion it is demonstrated which criteria must be fulfilled so that the Fickian diffusion occurs. For transport between the solvent and a solution, or between two solutions, normal diffusion is found. Experimental results with polystyrene + solvent systems are given. With good solvents the diffusion coefficient increases strongly with increasing polymer concentration, passes through a maximum at medium concentrations and decreases by several decades at high polymer concentrations. This concentration dependence arises because the diffusion coefficient is not only a transport coefficient, but also contains a thermodynamic factor. With poor solvents, which show a phase separation of the polymer at low temperatures, the concentration dependence of the diffusion coefficient is even more complicated. With increasing concentration of polymer the diffusion coefficient first decreases, passes through a minimum and the increases again. In this case there is also a maximum at medium concentrations and a strong decrease at high polymer concentrations. The minimum for a binary system is located at the critical point of the system.Normally ln D is a linear function of 1/T. Deviations from the linear course can be explained by the temperature dependence of the thermodynamic factor.For anomalous diffusion the √t-relations are no longer valid, since the diffusion coefficient depends not only on concentration, but also explicitly on time. The anomalous diffusion is due to the fact that superimposed on the normal diffusion is another process. If a solvent penetrates into a glassy polymer, then relaxation processes are superimposed on the diffusion process. The polymer changes from the glassy state into a state of internal thermodynamic equilibrium. Experimentally the continuous range between the pure glassy polymer and the pure solvent can be divided into three parts of an open system. In the first and the third part only diffusion occurs, while in the second part diffusion and structural relaxation are superimposed.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"42 1","pages":"208-221"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79325240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultrasonic relaxation of rotational-isomeric equilibria in polymer solutions","authors":"H. Bauer, H. Hässler, M. Immendörfer","doi":"10.1039/DF9704900238","DOIUrl":"https://doi.org/10.1039/DF9704900238","url":null,"abstract":"The sound absorption per wavelength µ in solutions of polystyrene in benzene and carbon tetrachloride deviates from proportionality with frequency in the low MHz range. This could be accounted for with good agreement by an additional, Debye-shaped excess absorption. Various models for the relevant relaxation process are discussed; the most probable one is the thermal relaxation of a rotational-isomeric equilibrium within the polymer chain, consisting of a rotation of a single monomer unit. Under that assumption, from the temperature dependence of position and amount of the absorption maximum the following data of the rotational potential were calculated: separation of the equilibrium energies ΔH= 0.9 kcal/mol, activation energy ΔH12= 7.5 kcal/mol, frequency factor ν= 1.4 × 1012 s–1.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"57 1","pages":"238-243"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79255756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theory of the single chain","authors":"S. Edwards","doi":"10.1039/DF9704900043","DOIUrl":"https://doi.org/10.1039/DF9704900043","url":null,"abstract":"The theory of a polymer chain is discussed with special emphasis on the role of entanglements in the conformation and dynamics of a very long polymer.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"76 1","pages":"43-50"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83891682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fifteenth Spiers Memorial Lecture. Thermodynamics of polymer solutions","authors":"P. Flory","doi":"10.1039/DF9704900007","DOIUrl":"https://doi.org/10.1039/DF9704900007","url":null,"abstract":"","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"8 1","pages":"7-29"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84066601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coalescence of second phase particles in phase separation","authors":"R. Hopper, D. Uhlmann","doi":"10.1039/DF9705000166","DOIUrl":"https://doi.org/10.1039/DF9705000166","url":null,"abstract":"A model has been suggested by Haller and others for the development of interconnected submicrostructures in glasses which involves the nucleation, growth and coalescence of discrete second-phase particles. A theoretical objection has been raised to this model—viz., that interparticle interference effects limit diffusion controlled growth and prevent coalescence. The present paper discusses three mechanisms whereby coalescence may occur despite interference effects. These include heterogeneous nucleation between two particles; capillarity-induced volume diffusion; and diffusion driven by the variation with separation of the interfacial energy of two interfaces. Two theories of the latter variation are presented, a diffuse interface theory based on the variational method of Cahn and Hilliard, and a pair interaction, sharp-interface model. Both models predict a monotonic decrease in the interfacial energy as the separation decreases. Other aspects of coalescence as well as the alternative model of spinodal decomposition are briefly discussed. The results of various experiments attempting to distinguish between spinodal decomposition and nucleation-growth-coalescence are reviewed. It is concluded that the operative mechanism for the formation of interconnected submicrostructures in nearly all glass systems remains to be established.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"5 1","pages":"166-174"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89899699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Approximate molecular orbital calculations on metallo-organic complexes","authors":"I. H. Hillier, R. M. Canadine","doi":"10.1039/DF9694700027","DOIUrl":"https://doi.org/10.1039/DF9694700027","url":null,"abstract":"The results of approximate molecular orbital calculations on the metallo-organic complexes, palladium bis π-allyl, ferrocene, and dibenzene chromium are presented. The calculations include electron interaction and all valence electrons are considered. The bonding involves mainly the metal orbitals and the π orbitals of the hydrocarbon ligand. The results are compared with those of other workers and with experimental data.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"5 1","pages":"27-36"},"PeriodicalIF":0.0,"publicationDate":"1969-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80078554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of cobalt-carbon σ-bonds","authors":"Michael R. Green, Julian A C Smith, P. A. Tasker","doi":"10.1039/DF9694700172","DOIUrl":"https://doi.org/10.1039/DF9694700172","url":null,"abstract":"The properties of N,N′-bis-(o-aminobenzylidene)-1,2-diaminoethanato-cobalt(II) and nickel(II) and various derivatives are described. The formation of stable cobalt-carbon σ-bonds is discussed in terms of the energies of dz2 and dxy orbitals.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"25 1","pages":"172-177"},"PeriodicalIF":0.0,"publicationDate":"1969-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81606809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectroscopic study of the encaged molecule motion in some clathrates","authors":"P. Davies","doi":"10.1039/DF9694800181","DOIUrl":"https://doi.org/10.1039/DF9694800181","url":null,"abstract":"The far infra-red spectra of seven different gases trapped in the cages of β-quinol clathrates have been studied. Data are provided for N2, CO2, CO, HCl, HBr, SO2 and HCN in the frequency range 10–100 cm–1. For the chosen systems it has been possible to indicate (i) the degree to which quantization of the rotational states is maintained by polar guests in the clathrate and what displacement can be seen relative to free gas molecules, (ii) some factors governing the translational (“rattling”) mode of the guest molecule. The frequencies and relative intensities of quantized rotation, hindered rotation and “rattling” mode absorptions have been studied over a temperature range 4.2–300 K.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"51 1","pages":"181-191"},"PeriodicalIF":0.0,"publicationDate":"1969-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80729329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correlation between crystal structure and carbonyl-bond stretching vibrations of methyl benzene transition metal tricarbonyls","authors":"H. Buttery, G. Keeling, S. Kettle, I. Paul, P. J. Stamper","doi":"10.1039/DF9694700048","DOIUrl":"https://doi.org/10.1039/DF9694700048","url":null,"abstract":"The site and factor group approaches to the interpretation of solid state infra-red and Raman spectra of metal carbonyls are compared. A factor group analysis of seven arene chromium tri-carbonyls indicates that the effective symmetry of the vibrational repeating unit may be higher than that of the crystallographic point group.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"49 4 1","pages":"48-52"},"PeriodicalIF":0.0,"publicationDate":"1969-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76571483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lattice dynamics and restricted rotation in molecular crystals","authors":"P. Martin, S. Walmsley","doi":"10.1039/DF9694800049","DOIUrl":"https://doi.org/10.1039/DF9694800049","url":null,"abstract":"The problem of coupled rotors in molecular crystals is reviewed in the limits of low and high barrier to rotation. An approximate one-molecule potential is suggested. The phase properties of mixed crystals of para- and ortho-hydrogen are discussed using this model.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"24 1","pages":"49-53"},"PeriodicalIF":0.0,"publicationDate":"1969-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74356211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}