The effect of cross-linking on the molecular dynamics of the segmental and β Johari–Goldstein processes in polyvinylpyrrolidone-based copolymers
The effect of the cross-link density on the molecular dynamics of copolymers composed of vinylpyrrolidone (VP) and butyl acrylate (BA) was studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). A single glass transition was detected by DSC measurements. T...
| Authors: | , , , , , |
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| Format: | article |
| Publication Date: | 2015 |
| Country: | España |
| Institution: | Universitat Politècnica de València (UPV) |
| Repository: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Language: | English |
| OAI Identifier: | oai:riunet.upv.es:10251/64685 |
| Online Access: | https://riunet.upv.es/handle/10251/64685 |
| Access Level: | Open access |
| Keyword: | MAQUINAS Y MOTORES TERMICOS TERMODINAMICA APLICADA (UPV) |
| Summary: | The effect of the cross-link density on the molecular dynamics of copolymers composed of vinylpyrrolidone (VP) and butyl acrylate (BA) was studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). A single glass transition was detected by DSC measurements. The dielectric spectra exhibit conductive processes and three dipolar relaxations labeled as a, b and g in the decreasing order of temperatures. The cross-linker content affects both a and b processes, but the fastest g process is relatively unaffected. An increase of cross-linking produces a typical effect on the a process dynamics: (i) the glass transition temperature is increased, (ii) the dispersion is broadened, (iii) its strength is decreased and (iv) the relaxation times are increased. However, the b process, which possesses typical features of a pure Johari Goldstein relaxation, unexpectedly loses the intermolecular character for the highest cross-linker content. |
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