Inverse IPNs

The synthesis of an IPN first requires a crosslinked polymer I, which may be either the elastomer or plastic component. In the first papers on IPN s, the elastomer was the first component. When the plastic was component I, the term inverse IPN was employed on an arbitrary basis. 

Figure 8.20. Study of phase continuity with the aid of mechanical models. Storage moduli at 25°C for PEAB/PS IPN s. (O) Normal IPN ( ) inverse IPN (A) blend ( ) graft. (Huelck et ai, 1972.)...

Assuming that the stained polymer (PEA) is the same, a positive-negative photographic inversion may be expected. Figure 6.15 presents a PS/PEA inverse IPN, which should be compared with Figure 6.2b. While a general inversion of phase structure is apparent, the cell walls of the inverse composition appear to be thicker and the fine structure at 100 A level appears to be within the cells, rather than in the cell walls. 

This hypothesis explains the minimum but not the large quantitative difference between normal IPN s on one hand and simultaneous and inverse IPN s on the other hand. 

Alternatively, VJiipi + ip2] = V m = sin(27ix) sin(27iy) cos(27iz), and cyclic pennutation of xyz gives ipt and ipn. The three symmetrized bases for T 25 are symmetric under inversion, as they should be. In a similar way, the bases forr15(TlM) are obtained by projecting oh 2,... 

Summary of Ring Notation. In summary, the addition of a zero, additive inverses, and coefficients allows for Laws One through Six to be followed. The polymer blend, graft, and IPN nomenclature scheme forms three rings, and the fact that the binary operation Om on R = (Pi, P2, P3,. . . , Pn) constitutes a group puts the system on an improved mathematical ground. Similar relationships can be developed for the other operations. 

If both 1 and 2 form networks, an IPN, designated as a full IPN, arises (26) as shown in Figure 6. This structure also has an inverse— that is, if 2 is synthesized first and then monomer 1 is swollen in and polymerized. A material may be considered an IPN rather than just a... 

The polymer assisted phase inversion (PAPI) variation of the phase Inversion process utilizes a solution consisting of a solvent and two physically compatible polymers to cast a dense film with a morphology known as an interpenetrating polymer network (IPN). 

Figure 6.2. Selected morphologies of IPNs based on SBR and polystyrene, SBR stained with osmium tetroxide. Upper left Commercial high-impact polystyrene. Upper right, Ostromislensky s material, with no phase inversion middle left, semi-IPN, SBR crosslinked middle right, semi-11 IPN, PS crosslinked lower left, full IPN lower right, full IPN, higher crosslinking in the SBR.

Phase diagrams for IPN Phase equilibria Phase inversion... 

When the IPN s are synthesized in inverse order, i.e., the plastic component first, the gross features are roughly inverted with respect to the normal preparations. Figure 8.6, showing a midrange PS/PEAB composition, should be compared to Figure 8.2. An important observation is that in both Figures 8.2 and 8.6 the first component forms the cell wall phase and the second component forms the cell contents phase. 

Figure 8.6. Electron micrograph of IPN 12 50.7 PS/49.3 PEAB. This structure is roughly the inverse of the structure shown in Figure 8.2. Note the greater continuity of the plastic phase in this case. (Huelck et al, 1972.)...

At this point, it is useful to recognize the concept of a semi-IPN. A semi-IPN may be defined as a graft copolymer in which one of the polymers is crosslinked and the other essentially is linear. Two semi-IPN s (one the inverse of the other) may be distinguished (1) a semi-IPN of the first kind, with polymer I in network form and polymer II linear and (2) a semi-IPN of the second kind, with polymer I linear and polymer II crosslinked. As further discussed by Sperling (1974c), many related systems contain one or both polymers in network form. 

Figure 8.29. DMS of poly(n-butyl acrylate)/poly-(ethyl methacrylate), PnBA/PEMA, latex 50/50 IPN and inverse composition. Dynamic mechanical spectroscopy at 110 Hz shows the two structures to be different. (A, A) 50 PnBA/50 PEMA (O, ) 50 PEMA/50 PnBA. (Sperling et al, 1972.)...

The elongation, as shown in Table III, shows a slight increase from 100% PU to 80% PU in the IPN s / indicating the exceptional toughness of this IPN. No increase occurs for the PDIPN s and the blends. A sharp drop in elongation takes place at 60% PU, which indicates that a phase inversion occurs around this composition. The Shore A and D hardnesses shown in Table IV show a rapid increase between 80% PU and 40% PU, which again indicates the phase inversion between 80% and 40% PU content. 

Koul, V., R. Mohamed, D. Kuckling, H.-J.P. Adler, and V. Choudhary. 2011. Interpenetrating polymer network (IPN) nanogels based on gelatin and poly(acrylic acid) by inverse miniemulsion technique synthesis and chaiactraization. Colloids and Surfaces B Biointerfaces 83(2) 204—213. 

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