Retardation time spectra computed from complex compliance functions

Dominguez-Espinosa, Gustavo; Ginestar, D.; Sanchı́s, M. J.; Díaz‐Calleja, Ricardo; Riande, Evaristo

doi:10.1063/1.2970078

Cited by 8 publications

(12 citation statements)

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“…An alternative analysis of the R2 isotherms can be done in the time domain region, by transforming the complex permittivity to retardation spectra using a non linear regularization method [26,32,33]. We have fitted this set of spectra using a linear combination of two time-domain Havriliak Negami…”

Section: Resultsmentioning

confidence: 99%

“…where the constant N and the 'experimental' spectra (ln ) L τ were obtained from the complex permittivity, ( ) * ε ω , by means of the method described in the Reference [26]. The algorithm used implements the Tikhonov regularization method with a kernel that, besides the relaxational integral term, includes a conductivity contribution analogous to the σ term of Eq.…”

Section: Resultsmentioning

confidence: 99%

“…Due to the proximity of the calorimetric T g 's of PS and PMMA, the analysis of the data in the frequency domain (loss modulus vs. frequency curves) has not allowed to resolve the contributions of the two different dynamic modes found near the glass transition [23][24][25][26]. This is a problem frequently found in this type of systems.…”

Section: Introductionmentioning

confidence: 92%

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Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

et al. 2011

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The effect of the structure of copolymers (random, alternate or diblock) on their dynamics has been studied by dielectric spectroscopy. Six copolymers of styrene and methyl methacrylate (three diblocks, one alternate and two random) have been studied. The results show that the sub-T g transitions of the diblock samples can be described by one asymmetric Havriliak-Negami (HN) function, while two are necessary for the rest of the copolymers (β and γ relaxations). The characteristic times of the sub-T g relaxations show an Arrhenius temperature dependence and there is a strong coupling of the α and β relaxations at high temperatures. The deconvolution of the merging relaxations has been made in the framework of the Williams Ansatz set out in terms of Havriliak-Negami distributions. The γ relaxation may be assigned to the rotation of the methyl methacrylate group in a styrene-rich environment. The Molecular Dynamics simulations of a poly(methyl methacrylate) homopolymer and of the alternate copolymer are in qualitative agreement with the experimental results, although they predict smaller values for the activation energy of the sub-T g relaxations.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

et al. 2011

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“…Retardation spectra, obtained by means of numerical procedure describe in Ref. 28, for DCMMS in the temperature window 218-234 K, are shown in Fig. 3.…”

Section: B Dielectric Characterizationmentioning

confidence: 99%

Fractional Fokker–Planck equation approach for the interconversion between dielectric and mechanical measurements

Garcı́a-Bernabé

Sanchı́s

Díaz‐Calleja

et al. 2009

Journal of Applied Physics

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This work describes a model of interconversion between mechanical and dielectric measurement. A previous version of this model has been proposed in the hereafter called "previous paper" ͓Díaz-Calleja, et al.Phys. Rev. E 72, 051505 ͑2005͔͒, starting from a scaling relation between the translational and rotational viscosities present in a glass forming liquid near the glass transition temperature. Now, in order to improve the previous procedure, the following modifications have been made: ͑1͒ a definition of the rotational viscosity obtained from a fractional Fokker-Planck equation has been used, ͑2͒ the complex translational viscosity is taken as a non-Newtonian one, ͑3͒ a careful splitting of ␣ and ␤ relaxations is necessary, because the interconversión algorithm depends on the underlying molecular mechanism of each relaxation, and ͑4͒ the modulus and phase angle of complex viscosities were analyzed instead of real and imaginary parts of the complex viscosities. The proposed interconversion model, in the interval of frequencies 10 −2 -10 +5 Hz, shows that the obtained results are more accurate than those one obtained in the previous paper.

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“…In a previous work (Dominguez-Espinosa, et al, 2008), a procedure to carry out the transformation from the frequency domain to the time domain was published. Thus, the retardation loss spectra, ( ) L τ , can be evaluated from the experimental data of the dielectric permittivity function,…”

Section: Complex Systems Distribution Of the Relaxation Timesmentioning

confidence: 99%

A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis

Foj¹,

Belén²

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T h e s i s S u p e r v i s o r : P R O F . D r . M a r í a J e s ú s S a n c h i s S á n c h e z t o o b t a i n t h e d e g r e e o f D o c t o r o f P h i l o s o p h y a t t h e U n i v e r s i t a t P o l i t è c n i c a d e V a l è n c i a Prof. Dr. María Jesús Sanchis SánchezThe work presented in this thesis was carried out at the Universitat Politècnica de València and was financially supported by the Spanish Ministry of Economy and Competitiveness (Projects Nos. MAT2008-06725-C03-03 and MAT2012-33483)."Cuando quieres algo, todo el Universo conspira para que ACKNOWLEDGEMENTSTras estos años de trabajo, llega el momento de mostrar mi agradecimiento a todas las personas que me han acompañado y apoyado durante el desarrollo de mi tesis doctoral.En primer lugar, me gustaría expresar mi gratitud a mi directora de tesis María J.Sanchis por su inestimable ayuda durante todos estos años. Muchas gracias por confiar en mí, por darme esta oportunidad y por las incalculables horas invertidas tanto para el desarrollo de esta tesis como al mío propio.También me gustaría agradecer a mis estimadas compañeras Marta Carsí y Pilar Ortiz su ayuda y amistad en este largo recorrido que suponer realizar una tesis doctoral. He aprendido mucho de vosotras tanto científica como personalmente. En este punto, no puedo olvidarme de mi querida Aurora Alonso, que pese a no formar parte de nuestro grupo de investigación, me ha apoyado, aconsejado y dado su amistad durante todos estos años.Quiero mostrar mi agradecimiento a los profesores José M. García y Félix C. García ABSTRACTThe development of new and more complex polymeric materials involves challenging problems to basic sciences. The relationship between structure and molecular dynamics assumes great importance for the future development of novel technologies based on such polymers. Thus, the understanding of how small changes in the chemical structure affect the properties of the material is essential to progress in the technological and scientific area. An in-depth analysis of the molecular mobility leads to establish the structure-properties relationships. On this basis, the main aim of the present work is to study the molecular mobility of two different families of polymeric materials. For this purpose, the experimental techniques mainly used were Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS) (Chapter 3).The first family of polymers characterized was a series of chemically cross-linked copolymers composed by Vinylpyrrolidone (VP) and Butyl Acrylate (BA) monomers. The study was divided in two parts, which are collected in Chapter 4 and 5.In the first place, Chapter 4 contains the influence of the monomer molar ratio (XVP/YBA) on the copolymer properties. Thus, a Fourier Transform Infrared Spectroscopy (FTIR) analysis verified dipole-dipole interactions between amide groups. The influence of these interactions on several parameters related to the molecular mobility was evidenced by the DSC, DRS and Dynamic Mechanical Analysis (DMA) techni...

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Retardation time spectra computed from complex compliance functions

Cited by 8 publications

References 30 publications

Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

Fractional Fokker–Planck equation approach for the interconversion between dielectric and mechanical measurements

A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis

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