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| Format: | Artículo científico |
| Language: | en |
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Sociedad Mexicana de Física A.C.
2006
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| Online Access: | https://www.redalyc.org/articulo.oa?id=57065403 |
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Table of Contents:
- Second virial coefficient of a series of polysiloxanes: the effect of side groups and molecular weight J. A. Villegas J. Cervantes Física, Astronomía y Matemáticas gyration Polysiloxane molecular conformation radius expansion factor second virial coefficient This study reports the results of analyzing the second virial coefficient (A2) in a good solvent for a series of polysiloxane chains in whichthe pairs of substituents connected to the silicon are CH3, CH3;C2H5, C2H5; CH3, C6H13;CH3, C16H33;and CH3, C6H5:The effect ofthe side group and molecular weight on A2 was investigated using the Helical Wormlike (HW) chain model. A theoretical analysis ofthe interpenetration function (Ã) was carried out using a Two-Parameter (TP) scheme. The theoretical-experimental behaviour of A2ina series of polysiloxanes was investigated considering the effects of the type of substituent on the main chain, molecular conformation,and molecular weight. The results obtained were strongly dependent on the flexibility of the side groups and the molecular weight of thepolymer. Within the HW model and TP scheme, the A2 value for poly(dimethylsiloxane) (PDMS1 and PDMS2), poly(diethylsiloxane) andpoly(methylhexylsiloxane) agrees with the experimental results obtained through the coupled system (Gel Permeation Chromatography/LightScattering: GPC/LS). However, the A2 calculated for PDMS3, poly(methylhexadecylsiloxane) (PMHDS) and poly(methylphenylsiloxane)(PMPS) showed a significant difference from the experimental value. On the basis of the theory for the HW model, the deviation in PDMS3may be due to the effect of the end chains. For PMHDS and PMPS, the model used is outside of the coil limit (validity of TP model). InPMHDS the determination of the (RMSradius)2 value from the GPC/LS system is strongly influenced by the interaction between the bulkyside group and the main chain, which affects the calculation of A2. 2006 artículo científico 0035-001X https://www.redalyc.org/articulo.oa?id=57065403 en http://www.redalyc.org/revista.oa?id=570 Revista Mexicana de Física application/pdf Sociedad Mexicana de Física A.C. Revista Mexicana de Física (México) Num.6 Vol.52