Cross-linked polymers chemical applications

Because of their chemical and physical properties that allow their use in multiple applications, cross-linking polymers and polymeric gels prepared by different methods have been used extensively. 

Fundamental Aspects of the Chemical Applications of Cross-linked Polymers... 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

Albertsson and coworkers [240-244] carried out extensive research to develop polymers in which the polymer properties are altered for different applications. The predominant procedure is ring-opening polymerization which provides a way to achieve pure and well defined structures. They have utilized cyclic monomers such as lactones, anhydrides, carbonates, ether-lactones. The work involved the synthesis of monomers not commercially available, studies of polymerization to form homopolymers, random and block copolymers, development of cross-linked polymers and polymer blends, surface modification in some cases, and characterization of the materials formed. The characterization is carried out with respect to the chemical composition and both chemical and physical structures, the degradation behavior in vitro and in vivo, and in some cases the ability to release drug components from microspheres prepared from the polymers. 

Typical particle sizes of the resulting lattices are between 50 nm and 500 pm. Generally, the size distribution of the latex particles is broad [252], Lattices with a very narrow size distribution can be achieved by a short nucleation period followed by a long growth period in the absence of coagulation [250]. Because the polymerization takes place within the outer periphery (shell) of the particle, latex polymers with a core-shell structure can be prepared, the core consisting of a cross-linked polymer, surrounded by a shell of tethered linear non-cross-linked polymer of different chemical composition. Recent reviews deal with the preparation and application of these core-shell polymers [212,253]. 

Dendrimers are a unique class of hyperbranched polymers with well-defined size, shape, and chemical functionality and with properties not found in classical linear and cross-linked polymers. There have been significant developments in the last decade in many areas of dendrimer research, partly due to the commercial availability of dendrimers such as PAMAM, but also the result of the synthesis of several novel dendritic structures. Numerous pharmaceutical applications have been proposed for these hyperbranched polymers, and given the rate of current developments, it is envisaged that dendrimer-based formulations will appear in the next decade. 

Radiation cross-linking affects different characteristics of polymers like mechanical behaviour, chemical stability, thermal and flame resistance. Until now, radiation cross-linking is limited to only a few industrial applications cross-linking of rubber or polymers for tyres, cables, pipes (e.g. in under floor heating systems), and heat-shrinkable tubes. Nevertheless, there exist industrial facilities like electron accelerators and gamma plant. Some of these radiation sources are operated by research institutes. 

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