Size switches polymer/monomer

Keywords Constitutional changes Covalent changes Dynamic covalent chemistry Molecular machines Molecular motors Molecular switches Polymer/monomer switches Reversible polymers Size switches... 

Synthetic Molecular Machines and Polymer/ Monomer Size Switches that Operate Through Dynamic and Non-Dynamic Covalent Changes... 

Polymer/Monomer Size Switches Switching Between Small and Large Molecular Sizes... 

In the second part of this chapter are presented systems involving reversible and controlled conversions - through covalent changes - between relatively large (polymers) and small (monomers) molecules, which can be considered as size switches. 

Synthetic Molecular Machines and Polymer/Monomer Size Switches... 

A polymer/monomer (polymer/repeat-unit or polymer/macrocycle) switch may become of practical importance where a polymer decorated with certain groups has specific size-dependent properties that the monomeric units do not have. The modulation of the conversion between polymeric and monomeric (or macrocyclic) states would also result in the modulation of these properties. Moreover, such size switches, represented by polymerization/depolymerization processes that operate under the control of external events, are examples of environmentally-friendly recyclable polymers (reduction of waste treatment). As well, if the polymer has low solubility and the polymer/monomer switch can work in spite of this, then it becomes possible to reversibly generate a precipitating (solid) polymeric material from a liquid solution of monomer. 

The ability of the controller to handle process disturbances was examined by simulating abrupt variations in feed quality. This was simulated by increasing the concentration of inhibitor in the monomer from zero to 10 ppm. The variation in feed quality is a common problem in industrial practice and results from the deliberate addition of inhibitor to monomer to prevent premature polymerization. If monomer purification to remove inhibitor is not done (and it often is not in commercial operations), the switching of monomer feed tanks can produce undesirable and unexpected effects on the process outputs. In the open loop, the increase in inhibitor concentration from zero to 10 ppm causes a drop in the monomer conversion from 0.247 to 0.169. The particle size output also experiences a decline from 0.762 to 0.737. The reduction in polymerization rate is a direct result of the decreased initiator flux into the polymer particles, and the drop in particle size reflects the diminished... 

Nwabunma D, Kyu T (2(X)1) Phase behavior, photopolymerization and morphology development in mixtures of eutectic nematic liquid crystal and photocurable monomer. Polymer 42 801-806 Ohta S, hiasawa S, Yamaguchi Y (2012) Size control of phase-separated liquid crystal droplets in a polymer matrix based on the phase diagram. J Polym Sci Part B Polym Phys 50 863-869 Parab SS, Malik MK, Deshmukh RR (2012) Dielectric relaxation and electro-optical switching behavior of nematic liquid crystal dispersed in poly (methyl methacrylate). J NonCryst Solids 358 2713-2722... 

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