Network phase-separated

The formation of one network proceeds much faster than the other. In this case, the first network is formed in a liquid medium of components for the second network. Phase separation may begin rather early and will not be hindered. The evolution of the first swollen network is possible. Liquid medium begins to form the second network later. As a result, IPN with a high degree of component segregation may appear. 

Pascault, J.P. (1995) Rubber-modified and thermoplastic-modified polymer networks -phase-separation process induced by polymerization and polycondensation. Macromol. Symp., 93, 43-51. 

Keywords Interpenetrating polymer networks Phase separation Interfacial region Segregation Heterogeneous structure... 

Chains of polybutadiene were trapped in the network formed by cooling a butadiene-styrene copolymer until phase separation occurred for the styrene, effectively crosslinking the copolymer. At 25°C the loss modulus shows a maximum which is associated with the free chains. This maximum occurst at the following frequencies for the indicated molecular weights of polybutadiene ... 

Consequently, interpenetrating phase-separated D/A network composites, i.e. bulk heterojunction , would appear to be ideal photovoltaic materials [5]. By controlling the morphology of the phase separation into an interpenetrating network, one can achieve a high interfacial area within a bulk material. Since any point in the composite is within a few nanometers of a D/A interface, such a composite is a bulk D/A heterojunction material. If the network in a device is bicontinuous, as shown in Figure 15-26, the collection efficiency can be equally efficient. 

Siloxane-(methyl methacrylate) networks showing high oxygen permeabilities were prepared by gamma-irradiation of tx,(o-methacryloyl terminated tetramethyl-disiloxanes and methyl methacrylate 325). Due to the utilization of very low molecular weight disiloxane modifier, no phase separation was observed in the networks produced. DSC studies showed only one Tg around 120 °C. These materials were evaluated... 

Typically IPNs exhibit some degree of phase separation in their structure depending on how miscible the component polymers are. However, because the networks are interconnected such phase separation can occur only to a limited extent, particularly by comparison with conventional polymer blends. Polymer blends necessarily have to be prepared from thermoplastics IPNs may include thermosets in their formulation. 

Wood and Hill consider that the role of fluoride in these glasses is uncertain. Phase-separation studies suggest that the structure of the glass might relate to the crystalline species formed, in which case a microcrystallite glass model is appropriate. But other evidence cited above on the structure-breaking role of fluoride is compatible with a random network model. 

In most cases phase separation can be overcome using a gelling additive. A gelling additive forms a fine network within the PCM and thereby builds small compartments which restrict phases with different density to separate on a macroscopic level (Figure 105). If the sample is then heated to a temperature... 

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