Morphology poly networks

Siloxane containing interpenetrating networks (IPN) have also been synthesized and some properties were reported 59,354 356>. However, they have not received much attention. Preparation and characterization of IPNs based on PDMS-polystyrene 354), PDMS-poly(methyl methacrylate) 354), polysiloxane-epoxy systems 355) and PDMS-polyurethane 356) were described. These materials all displayed two-phase morphologies, but only minor improvements were obtained over the physical and mechanical properties of the parent materials. This may be due to the difficulties encountered in controlling the structure and morphology of these IPN systems. Siloxane modified polyamide, polyester, polyolefin and various polyurethane based IPN materials are commercially available 59). Incorporation of siloxanes into these systems was reported to increase the hydrolytic stability, surface release, electrical properties of the base polymers and also to reduce the surface wear and friction due to the lubricating action of PDMS chains 59). 

The variation of the domain sizes with crosslink density was recognized by Yeo et al. [28], investigating cross-poly(n-butyl acrylate)-inter-cross-polystyrene. Figure A shows the morphology of 50/50 compositions as a function of network I crosslinking level. The cellular structures are gradually transformed to finer, and more obviously cylindrical or worm-like shapes with increasing crosslink density. 

Figure 4. Transmission electron microscopy morphology of 50/50 cro55-poly( -butyl acrylate)-/ ler-croM-polystyrene IPNs as a function of network I cross-link density. (Reproduced with permission from ref. 18. Copyright 1982 Polymer Engineering and Science.)...

An additional porous polymer is poly(glycidyl methacrylate-ethyleneglycol dimethacrylate) (see Figure 2.46) that is synthesized by suspension polymerization in the presence of an inert porogen in the polymerization reaction, obtaining a material with an internal macroporous morphology characterized by an interconnected pore network, which permeates the extensively cross-linked polymer matrix [209],... 

Zhou P, Xu Q, Frisch HL (1994) Kinetics of simultaneous interpenetrating polymer networks of poly(dimethylsiloxane-urethane)/poly(methyl methacrylate) formation and studies of their phase morphology. Macromolecules 27(4) 938-946... 

Xiao H et al. (1990) The synthesis and morphology of semi-interpenetrating polymer networks based on polyurethane-poly(dimethylsiloxane) system. J Poly Sci Part A Poly Chem 28(3) 585-594... 

Several fundamental studies of morphology and glass transition temperatures of poly(urethane-seq-diene) networks have been published 144,211 216). Phase separation was characterized by electron microscopy. 

UV irradiation of poly(4-vinylbenzophenone) [poly(VBP)] in benzene solution, and in the presence of isopropanol as hydrogen donor, gives rise to a more complex picture [12,13]. Indeed, intra- and inter-molecular coupling reactions by the side-chain benzophenone ketyl radicals (K ) markedly change the macro-molecular morphology with the occurrence of cyclic and network structures as well as chain scission processes (Scheme 5). 

Conducting polymer blends based upon polyaniline (PANI) are a new class of materials in which the percolation threshold for the onset of electrical conductivity can be reduced to volume fractions well below that required for classical percolation (16% by volume for globular conducting objects dispersed in an insulating matrix in three dimensions) [277,278], The origin of this remarkably low threshold for the onset of electrical conductivity is the self-assembled network morphology of the PANI poly blends, which forms during the course of liquid-liquid phase separation [61],... 

Huelck, V. Thomas, D.A. Sperling, L.H. Interpenetrating polymer networks of poly(ethyl acrylate) and poly(styrene-co-methyl methacrylate). I. Morphology via electron microscopy and II. Physical and mechanical behavior. Macromolecules 1972, 5 (4), 340-348. 

A polyurethane (PU)/poly(n-butyl methacrylate) (PBMA) system has been selected for an investigation of the process of phase separation in immiscible polymer mixtures. Within this system, studies are made of the XX, lx, xl, and the 11 forms. In recognition of the incompatibility of PBMA with even the oligomeric soft segment precursor of the PU, no attempt was made to equalize the rates of formation of the component linear and network polymers. Rather, a slow PU formation process is conducted at room temperature in the presence of the PBMA precursors. At suitable times, a relatively rapid photopolymerization of the PBMA precursors is carried out in the medium of the slowly polymerizing PU. The expected result is a series of polymer mixtures essentially identical in component composition and differing experimentally only in the time between the onset of PU formation and the photoinitiation of the acrylic. This report focuses on the dynamic mechanical properties cf these materials and the morphologies seen by electron microscopy. 

Table III. Phase-Separation Process, Morphologies, and Properties for Neat or Modified Poly(cyanurate) Networks...

Figure S shows the ratio r1 1 / t, for H ZSM-b crystals of different morphology as a function of the amount of n-hexane coke deposited t.33.> poly-crystal line spherical particles and polyhedral crystals. Once again, two stages of coke iormation can be distinguished. The beginning of the second stage is virtually the same for all polyhedral crystals however, a distinct delay of this onset is to be seen with the poiycrystailine grain. This, experimental finding can be explained by the existence of the secondary pore system represented by the free space between the crystallites. Thus, an additional amount oi coke may be deposited on "neutral" spots outside tne zeolite channel network, causing a delay oi the onset oi the second period oi coke formation.

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