Multi-step swelling

Much effort has been devoted to the development of a multi-step swelling polymerization technique using water as suspension medium [98]. This has resulted in polymers showing similar selectivities but slightly improved mass transfer characteristics compared with the corresponding monolithic polymers. Of particular rele-... 

Fig. 6 Schematic description of multi-step swelling and polymerisation...

Table 1 Two-step and multi-step swelling technique...

In the following years, many imprinted polymers were prepared by two- or multi-step swelling and polymerisation method using mostly EDMA as a crosslinker and various functional monomers interacting with the chosen template... 

Since the multi-step swelling and polymerisation method is time consuming, in 2005 Chen et al. [97] prepared uniformly sized MIP beads for separation of... 

In the synthesis of these macromolecular system, many parameters involved can affect the information associated with the binding sites, such as functional monomers/polymers, crosslinkers and solvents/porogens. Thus, both the feasibility of imprinting and the proper preparation conditions need exploration for the preparation of efficient imprinted materials (Liu Z. et al., 2010). It is important to state that MIP can be obtained in different formats, depending on the preparation method followed. To date, the most common polymerizations for preparing MIPs involve conventional solution, suspension, precipitation, multi-step swelling and emulsion core-shell. There are also other methods, such as aerosol or surface rearrangement of latex particles, but they are not used routinely (Puoci et al., 2011). 

The interactions and the compatibility between the template and monomers in a typical polymer matrix play an important role [41]. A number of different methods are used to prepare the imprinted nanomaterials, including bulk, suspension, multi-step swelling, mini-emulsion, core-shell and precipitation polymerizations [42]. 

These materials are swollen by solvents, but they do not dissolve. They form a gel. The amount of swelling depends on the density of cross-linking. If a difunctional monomer is added to a chain polymerization system, or a tri- or multi-functional monomer is used in step polymerization, then as the polymerization proceeds the probability of the chains coupling together increases and the reaction is characterized by a sudden enormous rise in viscosity. This is the gel point. If the polymerization is allowed to continue, then a thermoset polymer results. 

Multilayered polymer coatings Steps 1. Bioactive molecules is entrapped through multi-layered loaded-polymer coatings 2. Loading of encapsulating system into the polymer nanocomposite carrier system ++ Swelling control and polymer matrix degradation... 

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