Control of morphology

Most IPNs and related materials investigated to date show phase separation. The phases, however, vary in amount, size, shape, sharpness of their interfaces, and degree of continuity. These aspects together constitute the morphology of the material, and the multitude of possible variations in the morphology controls many of the material properties. 

Some aspects of morphology can be observed directly by transmission electron microscopy of stained and ultramicrotomed thin sections. The most successful staining method, developed by Kato, makes use of osmium tetroxide, which attacks the double bonds in diene type polymers. The OSO4 staining technique can also be used with other active groups, such as polyurethanes.Many saturated or nonreactive polymers are not easily studied by transmission electron microscopy, unfortunately, because they cannot be stained. Other aspects of morphology, such as phase continuity and interface characteristics, are best determined by combining chemical and dynamic mechanical spectroscopy methods with electron microscopy. 

Some of the factors that control the morphology of IPNs are now reasonably clear they include chemical compatibility of the polymers, interfacial tension, crosslink densities of the networks, polymerization method, and the IPN composition. While these factors may be interrelated, they can often be varied independently. Their effects are summarized here. 

A degree of compatibility between polymers may be brought about by IPN formation, because the two polymers are interlocked in a three-dimensional structure imposed by the synthetic method. Phase separation 

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Synthesis of solid state materials using surfactant molecules as template has been extensively used in this decade. Among the advantages of the use of amphiphilic molecules, the self-assembling property of the surfactants can provide an effective method for synthesising ceramic and composite materials with interesting characteristics, such as nanoscale control of morphology, and nano or mesopore structure with narrow and controllable size distribution [1-5]. 

Steneck, R.S. and Adey, W.H., The role of environment in control of morphology in Lithophyllum congestum, a Caribbean algal ridge builder, Botanica Marina, 19, 197, 1976. 

Given R.K. and Wilkinson B.H. (1985a) Kinetic control of morphology composition and mineralogy of abiotic sedimentary carbonates. J. Sediment. Petrol. 55, 109-119. 

Control of Morphology in Mesoporous and Mesostructured Hybrid Materials... 

Knaub P, Camberlin Y (1988) Gerard JF, New reactive polymer blends based on poly(urethane ureas) (PUR) and polydisperse poly(dimethylsiloxane) (PDMS) control of morphology using a PUR-b-PDMS block copolymer. Polymer 29(8) 1365-1377... 

The Transition from Ductile to Brittle Behavior of a Semicrystalline Polyester by Control of Morphology... 

The interplay of orientation and crystallisation leads to a wide range of super-molecular structures or morphologies. Each different morphology represents to the user a different compromise in physical properties, so that characterisation and control of morphology becomes very important for the efficient application of polymeric materials. 

Herricks, T., Chen, J. and Xia, Y. (2004). Polyol synthesis of platinum nanoparticles Control of morphology with sodium nitrate. Nano Lett. 4 2367-2371. 

The control of morphology in mesoporous materials is thought to be governed by kinetic effects as the self-assembly of surfactant molecules and nucleation processes... 

Donatelli, A.A. Sperling, L.H. Thomas, D.A. Interpenetrating polymer networks based on SBR/PS. 1. Control of morphology by level of crosslinking and 2. Influence of synthetic detail and morphology on mechanical behavior. Macromolecules 1976, 9 (4), 671, 676. 

Davey, R.J., L.A. Polywka, and S.J. Maginn (1991). The control of morphology by additives molecular recognition, kinetics and technology. In Advances in Industrial Crystallization, J. Garside, R.J. Davey, and A.G. Jones (eds.). Butterworth-Heinemann, Oxford, 150-165. 

A broader set of operating parameters than in conventional methods leads to better control of morphology and particle size. 

S. Chattopadhyay, X. L. Li, and P. W. Bohn, In-plane control of morphology and tunable photoluminescence in porous silicon produced by metal-assisted electroless chemical etching, J. Appl. Phys. 91, 6134-6140 (2002). 

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