Networks, interpenetrating

It has been noted above that phase separation in thermoplastics is a common occurrence when two or more polymers are mixed and that miscibility is the uncommon event. This is exploited in toughening of thermosets by elastomers when phase separation occurs during the reaction that leads to three-dimensional network formation. If macroscopic phase separation is not desired then it is possible to achieve a different microscopic morphology and in some cases maintain some features of miscibility 

The topology of interpenetration is, at present, a still poorly explored field of chemical topology [59]. Batten and Robson [2] have treated this phenomenon through the analysis of a number of different real cases, and have introduced a currently accepted nomenclature on this subject. 

The classification is based on recognizing the dimensionality (ID, 2D, 3D), the connectivity of the nodes and the topology of the individual interpenetrating motifs, the degree of interpenetration and the possible modes of interpenetration. The last point, the less known, is concerned with the relative disposition of the individual motifs in the three-dimensional space and the consequent mutual 

Distinct modes of interpenetration for 2D layers [2] and dia nets [60] have been discussed. 

According to the concepts introduced in Fig. 1.3.10 we can have three types of interpenetrating nets based on the dimensionality (ID, 2D and 3D). 

Class I (Translational) The individual nets are exclusively related by translations. The degree of interpenetration Z corresponds to the translational degree of interpenetration Zt. There are two distinct subclasses (la and lb) depending on the 

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Pig. 1. Interpenetrating network morphology of thermoplastic elastomer where A = the crystalline domain, B = the junction of crystalline lamellae, and... 

Interpenetrating networks of DMPPO and polymers such as polystyrene, polybutadiene, poly(urethane acrylate), and poly(methyl methacrylate) have been prepared by cross-linking solutions of DMPPO containing bromomethyl groups with ethylenediamine in the presence of the other polymer (68). 

The component with the lower viscosity tends to encapsulate the more viscous (or more elastic) component (207) during mixing, because this reduces the rate of energy dissipation. Thus the viscosities may be used to offset the effect of the proportions of the components to control which phase is continuous (2,209). Frequently, there is an intermediate situation where a cocontinuous or interpenetrating network of phases can be generated by careflil control of composition, microrheology, and processing conditions. Rubbery thermoplastic blends have been produced by this route (212). 

Coagents ate often used with peroxides to increase the state of cure. Some coagents, such as polybutadiene or multifimctional methacrylates, are used at high levels to form polymer grafts or interpenetrating networks. Other coagents such as triaHyl cyanurate, triaHyl trimelHtate, and y /i -phenjiene bismaleimide are used at low levels to reduce the tendency of the polymer to degrade by chain scission. 

SiHcone PSAs are blends or interpenetrating networks (IPNs) composed of a tackifyiag MQ resia cured ia a cross-linked poly(siloxane) aetwork. 

Interpenetrating networks have been made by co-curing polychloroprene with copolymers of 1-chloro-1,3-butadiene [627-22-5]. The 1-chloro-1,3-butadiene serves as a cure site monomer, providing a cure site similar to that already in polychloroprene. The butadiene copolymer with 1-chloro-1,3-butadiene (44) and an octyl acrylate copolymer (45) improved the low temperature brittieness of polychloroprene. The acrylate also improved oil resistance and heat resistance. 

During the hardening of PMF-resins no co-condensation occurs in the hardened state two independent interpenetrating networks exist [58]. Indications for a co-condensation via methylene bridges between the phenolic nucleus and the amido group of the melamine had been found by H-NMR only in model reactions between phenolmethylols and melamine. 

Interpenetrating network polymer. In a separate study, it was shown that cardanol-formaldehyde resins foiTn semi-interpenetrating networks with polymethylmethacrylate (PMMA). Although interpenetration of CF... 

Another area of recent interest is covulcanization in block copolymers, thermoplastic rubbers, and elasto-plastic blends by developing an interpenetrating network (IPN). A classical example for IPN formation is in polyurethane elastomer blended acrylic copolymers [7]. 

Other methods of blending include (1) fine powder mixing, and (2) monomer as a solvent for other components of the blend, followed by polymerization for making an interpenetrating network (IPN) [15]. 

The organofunctional group (R) in the coupling agent causes the reaction with the polymer. This could be a copolymerization and/or the formation of an interpenetrating network. This curing reaction of a silane-treated substrate enhances the wetting by the resin (Table 9). 

The chapter is organized as follows the second section will discuss the photophysics of conjugated polymer/fullerene composites as a standard model for a charge-generating layer in plastic solar cells. Pristine polymer devices will be discussed in the third section while bilayer and interpenetrating network devices are presented in Sections 4 and 5. Section 6 contains some remarks on large area plastic solar cells and Section 7 conclusions. 

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. 

The classic objective of alloying and blending is to find two or more polymers whose mixture will have synergistic property improvements (Fig. 6-8). Among the techniques used to combine dissimilar polymers are cross-linking to form what are called interpenetrating networks (IPNs), and grafting, to improve the compatibility of the plastics. 

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