IPN morphology

Even though TEM and SEM played major roles in the study of IPN morphological features, there are various shortcomings, such as staining artifacts, difficulties in sample preparation for very rubbery materials, and the two-dimensional viewing limit for the former. Recently, various scattering techniques have been applied to measure the phase dimensions of IPN s via statistical treatment. The principles of neutron scattering theory as applied to the phase separated materials have been described in a number of papers and review articles [33-36]. 

Turner JS, Cheng YL (2004) pH dependence of PDMS-PMAA IPN morphology and transport properties. J Membr Sci 240(1—2) 19—24... 

Variations in IPN morphology The following micrographs (Figures 2a-d) show full and semi IPNs, made from lightly and heavily cross-linked Solprene 416. 

Figure 8.30. Model of predicted latex IPN morphology, showing cellular structures, fine structures, and a shell-core morphology. (Sperling et aU 1972.)...

By combining the TEM and MTDSC techniques, a clearer understanding of the morphology of IPNs may be obtained. From TEM measurements, phase domain size and shape and connectivity can be determined. From MTDSC measurements, the weight fraction of interphase regions can be obtained. So, the relationships between mechanical properties and IPN morphology can now, in practice, be more comprehensively investigated. 

F. Vidal, C. Plesse, G. Palaprat, J. Juger, C. Gauthier, J.-M. Pelletier, K. MaseneUi-Varlot, C. Cheviot, D. Teyssie, Influence of the poly(ethylene oxide)/polybutadiene IPN morphology on the ionic conductivity of ionic liquid, European Polymer Journal, ISSN 0014-3057 49 (9) (September 2013) 2670-2679. http //dx.doi.Org/10.1016/j.eurpolymj.2013.05.020. 

Figure 2.3 shows six graft copolymer and IPN morphologies. " In each case, polybutadiene (or an SBR elastomer) served as polymer I, and polystyrene as polymer II. As described in Section 6.3, the unsaturated diene portion was stained with osmium tetroxide, in order to obtain the necessary contrast for these electron micrographs. 

Further electron micrographs will be found elsewhere in this book, particularly in Chapter 2. Certainly not all of the possible IPN morphologies have been discovered yet. While equation (6.36) describes the phase domain size in sequential IPNs, the correlation between synthetic detail and morphology is still in its infancy. Nonetheless, the experimentally known morphologies provide an important link between synthesis and properties. 

A. A. Donatelli, L. H. Sperling, and D. A. Thomas, Interpenetrating Polymer Networks Based on SBR/PS. 1. Control of Morphology by Level of Crosslinking, Macromolecules 9(4), 671 (1976). SBR/Polystyrene IPN. Morphology and crosslinking level. 

V. Huelck, D. A. Thomas, and L. H. Sperling, Interpenetrating Polymer Networks of Poly(ethyl acrylate) and Poly(styrene-co-methyl methacrylate). I. Morphology via Electron Microscopy, Macromolecules 5(4), 340 (1972). Polyacrylate/Polystyrene IPNs. Polymethacrylate/Polyacrylate IPNs. Morphology via electron microscopy. 

G. M. Yenwo, L. H. Sperling, J. A. Manson, and A. Conde, Castor Oil Based Interpenetrating Polymer Networks. III. Characterization and Morphology, in Chemistry and Properties of Crosslinked Polymers, S. S. Labana, ed.. Academic, New York (1977). Castor oil-urethane/PS IPNs. Morphology via electron microscopy. 

J. K. Yeo, Controlled Variation of Poly(n-Butyl Acrylate)/Polystyrene IPN Morphology and Behavior, Ph.D. thesis, Lehigh University, in preparation. 

The corresponding sequential IPN morphology of the same overall composition is shown in the lower left photo. In this case, a sheet of SBR was cross-linked, followed by swelling in styrene plus divinyl benzene and pol5mierizing in situ. The phase domains are of the order of 100 nm, with both phases exhibiting co-continuity. An increased cross-link level for the SBR results in a finer phase domain structure, as shown in the lower right of Figure 4. 

Phase Continuity in Sequentiai iPNs. The question has been repeatedly raised Do IPN morphologies really exhibit dual phase continuity Evidence for dual phase continuity in sequential IPNs was examined by Widmaier and Sperling (40,41). A series of sequential IPNs were prepared from poly(ra-butyl acrylate) and polystyrene. Two cross-linkers were used, divinyl benzene (DVB), which forms ordinary covalent cross-links, and aciyUc anhydride (AA), which forms labile crosslinks. The AA cross-links were cut by soaking the samples in a 10% aqueous ammonium hydroxide solution for about 12 hours. 

Kim et al. (43) studied the time-temperature-transformation (TTT), diagram (see Section 8.7.2) for the system poly(ether sulfone)-/nter-net-epoxy semi-II IPN see Figure 13.20. They identified five general steps in the development of IPN morphology in the figure ... 

Vidal F et al (2013) Influence of the poly(ethylene oxide)/polybutadiene IPN morphology on the ionic conductivity of ionic hquid. Eur Polym J 49(9) 2670-2679, Available at http //linkinghub. elsevier.eom/retrieve/pii/S0014305713002577. Accessed 30 Sept 2013 Wu Y et al (2006) Fast trilayer polypyrrole bending actuators for high speed applications. Synth Met 156(16-17) 1017-1022, Available at http //linkinghub.elsevier.com/retrieve/pii/ S0379677906001731. Accessed 12 Dec 2013... 

PEO/polybutadiene (PB) interpenetrating polymer networks (IPNs) have been prepared with l-ethyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide (EMITFSI) as an IL. Its ionic conductivity depends on the IPN morphology and can be as high as 2.5 x 10 S/cm at 30°C [4]. 

Vidal, R, Plesse, C., Palaprat, G., Juger, J., Gauthier, C., Pelletier, J.M., Masenelli-Varlot, K., Chevrot, C., Teyssie, D. 2013. Influence of the poly(ethylene oxide)/ polybutadiene IPN morphology on the ionic conductivity of ionic liquid. Euro. Polym.. 49 2670-2679. 

Morphological data showing that IPNs are highly heterogeneous structures allowed Sperling et aL [72-74] to propose the mechanism of IPN formation called nucleation and growth. A thermodynamic theory of IPN morphology has been developed in [74]. Its main assiunption is that there are two separate states of polymer I and polymer II separated one from another. In state 2, the... 

The review of IPN morphology was carried out by Sperling [16]. He states that for sequential IPNs the presence of cross-linked network I always guarantees that the gelation happens before the phase separation, because the gelation occurs before monomer II is added. If only polymer II is cross-linked, then phase separation precedes the gelation of polymer II. For semi-IPNs the morphology of polymer I may be continuous and of polymer II, discontinuous. For the full sequential IPNs the domains are always finely divided. 

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